Blood The fluid that circulates through the heart, arteries, capillaries, and veins, carrying nutriment and oxygen to the body cells. It consists of plasma, its liquid component, plus three major solid components: erythrocytes (red blood cells [RBCs], leukocytes (white blood cells or WBCs), and platelets. Colloids Protein substances that increase the colloid oncotic pressure. Colloid oncotic pressure Another name for oncotic pressure. It is a form of osmotic pressure exerted by protein in blood plasma that tends to pull water into the circulatory system. Crystalloids Substances in a solution that diffuse through a semipermeable membrane. Dehydration Excessive loss of water from the body tissues. It is accompanied by an imbalance in the concentrations of electrolytes, particularly sodium, potassium, and chloride. Edema The abnormal accumulation of fluid in interstitial spaces. Extracellular fluid (ECF) That portion of the body fluid comprising the interstitial fluid and intravascular fluid. Gradient A difference in the concentration of a substance on two sides of a permeable barrier. Homeostasis The tendency of a cell or organism to maintain equilibrium by regulating its internal environment and adjusting its physiologic processes. Hyperkalemia An abnormally high potassium concentration in the blood, most often the result of defective renal excretion but also caused by excessive dietary potassium or certain drugs, such as potassium-sparing diuretics or angiotensin-converting enzyme (ACE) inhibitors and other causes such as acidosis. Hypernatremia An abnormally high sodium concentration in the blood; may be due to defective renal excretion but is more commonly caused by excessive dietary sodium or replacement therapy or the loss of water. Hypokalemia A condition in which there is an inadequate amount of potassium in the bloodstream; possible causes include diarrhea, diuretic use, and others. Hyponatremia A condition in which there is an inadequate amount of sodium in the bloodstream, caused by inadequate excretion of water or by excessive water intake. Interstitial fluid (ISF) The extracellular fluid that fills in the spaces between most of the cells of the body. Intracellular fluid (ICF) The fluid located within cell membranes throughout most of the body. It contains dissolved solutes that are essential to maintaining electrolyte balance and healthy metabolism. Intravascular fluid (IVF) The fluid inside blood vessels. Isotonic Having the same concentration of solutes as another solution and hence exerting the same osmotic pressure as that solution, such as an isotonic saline solution that contains an amount of salt equal to that found in the intracellular and extracellular fluid. Osmotic pressure The pressure produced by a solution necessary to prevent the osmotic passage of solvent into it when the solution and solvent are separated by a semipermeable membrane. Plasma The watery, straw-colored fluid component of lymph and blood in which the leukocytes, erythrocytes, and platelets are suspended. Serum The clear, cell-free portion of the blood from which fibrinogen has been separated during the clotting process, as typically carried out with a laboratory sample. Solute A substance that is dissolved in another substance. Transcellular fluid The fluid that is contained within specialized body compartments such as cerebrospinal, pleural, and synovial cavities. Drug Profiles albumin, p. 463 conivaptan, p. 467 dextran, p. 463 fresh frozen plasma, p. 464 packed red blood cells, p. 464 potassium, p. 466 sodium chloride, pp. 461, 467 sodium polystyrene sulfonate (potassium exchange resin), p. 466 High-Alert Drugs hypertonic saline solution, p. 467 potassium, p. 466 Overview Fluid and electrolyte management is one of the cornerstones of patient care. Most disease processes, tissue injuries, and surgical procedures greatly influence the physiologic status of fluids and electrolytes in the body. Body fluids provide transportation of nutrients to cells and carry waste products away from cells. Understanding fluid and electrolyte management requires knowledge of the extent and composition of the various body fluid compartments. Approximately 60% of the adult human body weight is composed of water. This is referred to as the total body water (TBW). The percent of body water is higher in infants and lower in older adults. Both populations are more sensitive to fluid imbalances than the adult. Total body water is distributed in two main compartments: intracellular fluid (ICF) and extracellular fluid (ECF). Extracellular fluid is further divided into interstitial fluid (ISF) and intravascular fluid (IVF). This distribution is illustrated in Fig. 29.1.
FIG. 29.1 Distribution of total body water (TBW). ECF, Extracellular fluid; ICF, intracellular fluid; ISF, interstitial fluid; IVF, intravascular volume. Fluid contained within the cells is called ICF, and it contains solutes such as electrolytes and glucose. ECF is the fluid outside the cells. Its function is to transport nutrients to cells and transport waste products away from cells. ECF is further broken down into intravascular fluid (contained within blood vessels) and interstitial fluid (surrounding the cell). Intravascular refers to the volume of blood in the circulatory system and contains protein-rich plasma and large amounts of albumin. In contrast, ISF contains little or no protein. ISF is further broken down to transcellular fluid, which is contained within specialized body compartments such as the synovial, cerebrospinal, and pleural cavities. Water within the body is critical, not only because of its vast quantity but also because it serves as a solvent to dissolve solutes and acts as a medium for metabolic reactions. Throughout the body, water is freely exchanged among all fluid compartments and is retained in a relatively constant amount. Internal control mechanisms responsible for maintaining fluid balance include thirst, antidiuretic hormone (ADH), and aldosterone. Movement into and out of cells is carried out through the following processes: diffusion, filtration, active transport, and osmosis. The goal of fluid and electrolyte balance is to maintain homeostasis, where fluid intake is equal to fluid output. Fluid intake comes from liquids, solid foods, intravenous fluid, or parenteral fluid. Fluid loss (output) comes primarily from the kidney and also can be from emesis or feces. Insensible losses (those that cannot be measured) come from the skin, lungs, and gastrointestinal tract. Other measurable loss can be from fistulas, drains, or gastrointestinal suction. All measurable sources of intake and output are important to document in the hospitalized patient. A sudden change in weight is a strong indicator of fluid balance. If the amount of water gained exceeds the amount of water lost, the end result is overhydration. Such fluid excesses often accumulate in interstitial spaces, such as in the pericardial sac, joint capsules, and lower extremities. This is referred to as edema. In contrast, if the quantity of water lost exceeds that gained, a water deficit, or dehydration, occurs. Death often occurs when 20% to 25% of TBW is lost. Dehydration leads to a disturbance in the balance between the amount of fluid in the extracellular compartment and that in the intracellular compartment. Sodium is the principle extracellular electrolyte and plays a primary role in maintaining water concentration. In the initial stages of dehydration, water is lost first from the extracellular compartments. The amount of further fluid losses, changes to colloid oncotic pressure, or both, determine the type of clinical dehydration that develops (Table 29.1). Clinical conditions that can result in dehydration and fluid loss, and the symptoms of dehydration and fluid loss, are presented in Table 29.2. When fluid that has been lost must be replaced, there are three categories of agents that can be used to accomplish this: crystalloids, colloids, and blood products. The clinical situation dictates which category of agents is most appropriate. TABLE 29.1
Types of Dehydration Type of Dehydration Characteristics Hypertonic Occurs when water loss is greater than sodium loss, which results in a concentration of solutes outside the cells and causes the fluid inside the cells to move to the extracellular space, thus dehydrating the cells. Example: Elevated temperature resulting in perspiration. Hypotonic Occurs when sodium loss is greater than water loss, which results in higher concentrations of solute inside the cells and causes fluid to be pulled from outside the cells (plasma and interstitial spaces) into the cells. Examples: Renal insufficiency and inadequate aldosterone secretion. Isotonic Caused by a loss of both sodium and water from the body, which results in a decrease in the volume of extracellular fluid. Examples: Diarrhea and vomiting. TABLE 29.2
Conditions Leading to Fluid Loss or Dehydration and Associated Corresponding Symptoms a Condition Associated Symptoms Bleeding Tachycardia and hypotension Bowel obstruction Reduced perspiration and mucous secretions Diarrhea Reduced urine output (oliguria) Fever Dry skin and mucous membranes Vomiting Reduced lacrimal (tears) and salivary secretions a There may be overlap involving more than one of the symptoms depending on the patient’s specific condition.
Tonicity and osmolality are similar terms that are often used interchangeably, but they are not exactly the same, chemically speaking. Osmolality is used in reference to body fluids and is the concentration of particles in a solution. Normal osmolality of body fluids is between 290 and 310 mOsm/kg. Tonicity is used in reference to intravenous fluids and is the measurement of the concentration of intravenous fluids as compared with the osmolality of body fluids. Tonicity also can be defined as the measure of osmotic pressure. The tonicity of intravenous solutions can be considered isotonic, hypotonic, or hypertonic. Isotonic means that the osmotic pressures inside and outside of the blood cell are the same. Hypotonic means that the solution outside the cell has a lower osmotic pressure than inside the cell. Hypertonic means the solution outside the blood cell has a higher osmotic pressure than inside the cell. Giving an isotonic solution such as normal saline (0.9% NaCl) or lactated Ringer’s solution causes no net fluid movement. Administering a hypotonic solution (0.45% NaCl) causes fluid to move out of the vein and into the tissues and cells. Injecting a hypertonic solution (3% NaCl) causes fluid to move from the ISF into the veins. This is depicted in Fig. 29.2.
FIG. 29.2 A depiction of what happens when red blood cells are exposed to different fluids. Isotonic solutions cause no net fluid movement. Hypertonic solutions cause water to move out of the cells and can cause the cells to shrink. Hypotonic solutions cause water to move into the cells, which can cause them to burst. Acid-base balance is also important to normal bodily functions and is regulated by the respiratory system and the kidney. An acid is a substance that can donate or release hydrogen ions, such as carbonic acid or hydrochloric acid. A base is a substance that can accept hydrogen ions, such as bicarbonate. The pH is a measure of the degree of acidosis and alkalinity and is inversely related to hydrogen ion concentration. For example, when hydrogen ion concentration increases, the pH decreases and leads to acidity. As the hydrogen ion concentration decreases, the pH increases, leading to more alkalinity. With the normal pH ranging from 7.35 to 7.45, acidosis occurs when pH falls below 7.35. Conversely, alkalosis occurs when the pH rises above 7.45. Regulation of the acid-base balance requires healthy functioning of the respiratory and renal systems. The respiratory system compensates for metabolic problems and pH imbalances by regulation of carbon dioxide. In acidosis, CO2 can be exhaled to try to normalize the lower pH; in alkalosis, CO2 will be retained by the respiratory system to try to elevate the pH. The kidney also compensates by reabsorbing and generating bicarbonate and excreting hydrogen ions in acidosis to normalize the low pH. Conversely, the kidney can excrete bicarbonate and retain hydrogen ions to normalize the high pH seen with alkalosis. The influence of the respiratory system is determined by an arterial blood gas (ABG) test. The influence of the body on acid-base balance is determined by a blood test, which measures total body CO2 and is usually represented as HCO3. Both are used in determining and treating acid-base disorders. Detailed determination and treatment of acid-base balance is complex and beyond the scope of this textbook. Certain drugs, such as the diuretic acetazolamide (see Chapter 28) and sodium bicarbonate (tablets or injection), can be used to correct metabolic acid-base disturbances. Crystalloids Crystalloids are fluids given by intravenous injection that supply water and sodium to maintain the osmotic gradient between the extravascular and intravascular compartments. Their plasma volume–expanding capacity is related to their sodium concentration. Serum is a term closely related to plasma. The most commonly used crystalloids are normal saline (0.9% NaCl) and lactated Ringer’s solution. Mechanism of Action and Drug Effects Crystalloid solutions contain fluids and electrolytes that are normally found in the body. They do not contain proteins (colloids), which are necessary to maintain the colloid oncotic pressure and prevent water from leaving the plasma compartment. In fact, the administration of large quantities of crystalloid solutions for fluid resuscitation decreases the colloid oncotic pressure, because of a dilutional effect. Crystalloids are distributed faster into the interstitial and intracellular compartments than colloids. This makes crystalloids better for treating dehydration than for expanding the plasma volume alone. Indications Crystalloid solutions are most commonly used as maintenance fluids. They are used to compensate for insensible fluid losses, to replace fluids, and to manage specific fluid and electrolyte disturbances. Crystalloids also promote urinary flow. They are much less expensive than colloids and blood products. In addition, there is no risk for viral transmission or anaphylaxis and no alteration in the coagulation profile associated with their use, unlike with blood products. The choice of whether to use a crystalloid or a colloid depends on the severity of the condition. Common indications for either crystalloid or colloid replacement therapy include acute liver failure, burns, cardiopulmonary bypass surgery, hypoproteinemia, renal dialysis, and shock. Contraindications to the use of crystalloids include known drug allergy to a specific product and hypervolemia and may include severe electrolyte disturbance, depending on the type of crystalloid used. Adverse Effects Crystalloids are a very safe and effective means of replacing needed fluid. They do, however, have some unwanted effects. Because they contain no large particles, such as proteins, they do not stay within the blood vessels and can leak out of the plasma into the tissues and cells. This may result in edema anywhere in the body. Peripheral edema and pulmonary edema are two common examples. Crystalloids also dilute the proteins that are in the plasma, which further reduces the colloid oncotic pressure. To be effective, large volumes (liters of fluid) are usually required. As a result, prolonged infusions may cause fluid overload. Another disadvantage of crystalloids is that their effects are relatively short-lived. Interactions Interactions with crystalloid solutions are rare because they are very similar if not identical to normal physiologic substances. Dosage The dose of crystalloids is determined by the specific condition being treated. Drug Profile The most commonly used crystalloid solutions are normal saline (0.9% NaCl) and lactated Ringer’s solution. Sodium chloride is also discussed briefly in the section on electrolytes and in the Nursing Process section under electrolytes. sodium chloride Sodium chloride (NaCl) is available in several concentrations, the most common being 0.9%. This is the physiologically normal concentration of sodium chloride (isotonic), and it is referred to as normal saline (NS). Concentrations considered hypotonic are 0.45% (“half-normal”) and 0.25% (“quarter-normal”). Hypertonic saline (a high-alert solution) is available in 3% and 5% solutions. These solutions have different indications and are used in different situations, depending on how urgently fluid volume restoration is needed and/or the extent of the sodium loss. Normal saline contains 154 mEq of sodium per liter. Sodium chloride is a physiologic electrolyte that is present throughout the body’s water. Thus there are no hypersensitivity reactions to it. It is safe to administer it during any stage of pregnancy, but it is contraindicated in patients with hypernatremia and/or hyperchloremia. Hypertonic saline injections (3% and 5%) are contraindicated in the presence of increased, normal, or only slightly decreased sodium concentrations. Hypertonic saline is considered a high-risk drug because deaths have occurred when it is infused inappropriately. Correcting sodium too rapidly with hypertonic saline can lead to osmotic demyelination syndrome, which is potentially fatal. Conversely, infusing very low hypotonic saline (0.25% NaCl) is not recommended because it can cause hemolysis of the red blood cells. Sodium chloride is also available as a 650-mg tablet. The dose of sodium chloride administered depends on the clinical situation. Generally speaking, the amount of 0.9% NaCl that is needed to increase intravascular or plasma volume by 1000 mL is 5000 to 6000 mL. By contrast, the amount of albumin, which is a colloid solution (discussed later), needed to increase intravascular volume by the same 1000 mL is only 500 mL. Table 29.3 provides other examples. Colloids Colloids are substances that increase the colloid oncotic pressure and move fluid from the interstitial compartment to the plasma compartment by pulling the fluid into the blood vessels. Normally, this task is performed by the three blood proteins: albumin, globulin, and fibrinogen. The total body protein level needs to be in the range of 7.4 g/dL. If this level falls below 5.3 g/dL, fluid shifts out of blood vessels into the tissues. When this happens, colloid replacement therapy is used to reverse this process by increasing the colloid oncotic pressure. Colloid oncotic pressure decreases with age and malnutrition. Commonly used colloids include albumin, dextran, and hetastarch. Information on the composition of these colloids can be found in Table 29.4. TABLE 29.3
Crystalloids and Colloids: Dosing Guidelines Crystalloids and Colloids 0.9% Saline 3% Saline a 5% Colloid b 25% Colloid c To Raise Plasma Volume by 1L, Administer 5–6L 1.5–2L 1L 0.5L Compartment to Which Fluid Is Distributed Plasma 25% 25% 100% 200%–300% Interstitial space 75% 75% 0 Decreased fluid levels Intracellular space 0 0 0 Decreased fluid levels a Hypertonic saline is a high-alert drug and should not be given faster than 100mL/hr for short periods. Frequent monitoring of serum levels is required.
b Iso-oncotic solutions such as 5% albumin, and hetastarch.
c Hyperoncotic solutions such as 25% albumin.
TABLE 29.4
Commonly Used Colloids Product Composition (mEq/L) Volume (mL) Cost a Na Cl Dextran 40 b 154 154 500 2 Hetastarch 154 154 500 5 5% Albumin 145 145 500 10 25% Albumin 145 145 100 10 Cl, Chloride; Na, sodium.
a Relative cost compared with the cost of dextran 40.
b Dextran is available in NaCl, which has 154 mEq/L of both Na and Cl. It is also available in 5% dextrose in water, which contains no Na or Cl.
Mechanism of Action and Drug Effects The mechanism of action of colloids is related to their ability to increase the colloid oncotic pressure. Because the colloids cannot pass into the extravascular space, there is a higher concentration of colloid solutes (solid particles) inside the blood vessels (intravascular space) than outside the blood vessels. Fluid moves from the extravascular space into the blood vessels in an attempt to make the blood isotonic. See Fig. 29.3. As such, colloids increase the blood volume, and they are sometimes called plasma expanders. They also make up part of the total plasma volume. Colloids increase the colloid oncotic pressure and move fluid from outside the blood vessels to inside the blood vessels. They can maintain the colloid oncotic pressure for several hours. They are naturally occurring products and consist of proteins (albumin), carbohydrates (dextrans or starches), fats (lipid emulsion), and animal collagen (gelatin). Usually they contain a combination of both small and large particles. The small particles are eliminated quickly and promote diuresis and perfusion of the kidneys; the larger particles maintain the plasma volume. Albumin is the one exception in that it contains particles that are all the same size.
FIG. 29.3 Colloid osmotic pressure (oncotic pressure). As shown, the colloids inside the blood vessel are too large to pass through the vessel wall. The resulting oncotic pressure exerted by the colloids draws fluid from the surrounding tissues and other extravascular spaces into the blood vessels and also keeps fluid inside the blood vessel. Indications Colloids are used to treat a wide variety of conditions, including shock and burns, or whenever the patient requires plasma volume expansion. Clinically, colloids are superior to crystalloids because of their ability to maintain the plasma volume for a longer time. However, colloids are significantly more expensive and are more likely to promote bleeding. Colloids are less likely than crystalloids to cause edema because of the larger volumes of crystalloids needed to achieve the desired clinical effect. Crystalloids are better than colloids for emergency short-term plasma volume expansion. Contraindications Contraindications to the use of colloids include known drug allergy to a specific product and hypervolemia and may include severe electrolyte disturbance. Adverse Effects Colloids are relatively safe agents, although there are some disadvantages to their use. They have no oxygen-carrying ability and contain no clotting factors, unlike blood products. Because of this, they can alter the coagulation system through a dilutional effect, which results in impaired coagulation and possibly bleeding. Rarely, dextran therapy causes anaphylaxis or renal failure. Interactions No drug interactions occur with colloids. Dosages For dosage information on colloids, see Table 29.3. Drug Profiles The specific colloid used for replacement therapy varies from institution to institution. The three most commonly used are 5% albumin, dextran 40, and hetastarch. They all have a very rapid onset of action and a long duration of action. They are metabolized in the liver and excreted by the kidneys. Albumin is the one exception; it is metabolized by the reticuloendothelial system and excreted by the kidneys and the intestines. Hetastarch is a synthetic colloid with properties similar to those of albumin and dextran. albumin Albumin is a natural protein that is normally produced by the liver. It is responsible for generating approximately 70% of the colloid oncotic pressure. Human albumin is a sterile solution of serum albumin that is prepared from pooled blood, plasma, serum, or placentas obtained from healthy human donors. It is pasteurized to destroy any contaminants. Unfortunately, because it is derived from human donors, the supply is limited, which causes it to be extremely expensive. Albumin is contraindicated in patients with a known hypersensitivity to it and in those with heart failure, severe anemia, or renal insufficiency. Albumin is available only in parenteral form in concentrations of 5% and 25%. It is classified as a pregnancy category C drug. See Table 29.3 for dosing guidelines. Pharmacokinetics: Albumin Route Onset of Action Peak Plasma Concentration Elimination Half-Life Duration of Action IV Less than 1min Unknown 16hr Less than 24hr dextran Dextran is a solution of glucose. It is available as dextran 40 and has a molecular weight similar to that of albumin. It has actions similar to those of human albumin in that it expands the plasma volume by drawing fluid from the interstitial space to the intravascular space. Dextran is contraindicated in patients with a known hypersensitivity to it and in those with heart failure, renal insufficiency, and extreme dehydration. It is available only in parenteral form mixed in either a 5% dextrose solution or a 0.9% NaCl solution. It is classified as a pregnancy category C drug. See Table 29.3 for dosing guidelines. Pharmacokinetics: Dextran Route Onset of Action Peak Plasma Concentration Elimination Half-Life Duration of Action IV 5min Unknown 2–6hr 4–6hr Blood Products Blood products can be thought of as biologic drugs. They augment the plasma volume. Red blood cell (RBC)-containing products can also improve tissue oxygenation. Blood products are significantly more expensive than crystalloids and colloids and are less available because they are natural products and require human donors. They are most often indicated when a patient has lost 25% or more blood volume. Mechanism of Action and Drug Effects The mechanism of action of blood products is related to their ability to increase the colloid oncotic pressure, and hence the plasma volume. They do so in the same manner as colloids and hypertonic crystalloids, by pulling fluid from the extravascular space to the intravascular space. Because of this they are also considered plasma expanders. RBC products also have the ability to carry oxygen. They can maintain the colloid oncotic pressure for several hours to days. Because they come from human donors, they have all the benefits (and hazards) that human blood products have. They are administered when a person’s body is deficient in these products. Indications Blood products are used to treat a wide variety of clinical conditions, and the blood product used depends on the specific indication. The available blood products and the specific conditions they are used to treat are listed in Table 29.5. Contraindications There are no absolute contraindications to the use of blood products. However, because there is a risk for transfer of infectious disease, although remote, their use needs to be based on careful clinical evaluation of the patient’s condition. Adverse Effects Blood products can produce undesirable effects, some potentially serious. Because these products come from other humans, they can be incompatible with the recipient’s immune system. These incompatibilities are tested for before their administration by determining the respective blood types of the donor and recipient and by performing cross-matching tests to screen for incompatibility between selected blood proteins. This helps reduce the likelihood that the recipient will reject the blood product, which would precipitate transfusion reactions and anaphylaxis. These products can also transmit pathogens (hepatitis and human immunodeficiency virus [HIV]) from the donor to the recipient. Various preparation techniques are now used to reduce the risk for pathogen transmission, and these have resulted in a drastic reduction in the incidence of such problems. TABLE 29.5
Blood Products: Indications Blood Product Indication Cryoprecipitate and PPF To manage acute bleeding (over 50% blood loss slowly or 20% rapidly) FFP To increase clotting factor levels PRBCs To increase oxygen-carrying capacity in patients with anemia, in patients with substantial hemoglobin deficits, and in patients who have lost up to 25% of their total blood volume Whole blood Same as for PRBCs, except that whole blood is more beneficial in cases of extreme (over 25%) loss of blood volume because whole blood also contains plasma and plasma proteins, the chief osmotic component, which help draw fluid back into blood vessels from surrounding tissues FFP, Fresh frozen plasma; PPF, plasma protein fraction; PRBCs, packed red blood cells.
Interactions As with crystalloids and colloids, blood products are very similar if not identical to normal physiologic substances; therefore they are involved in very few interactions. Calcium and aspirin, which normally affect coagulation, may interact with these substances when infused in the body in much the same way that they interact with the body’s own blood components. Blood must not be administered with any solution other than normal saline. Clinical Pearl Blood products can be administered with normal saline ONLY. Dosages Table 29.6 provides dosage information on blood products. Drug Profiles Packed red blood cells (PRBCs) and fresh frozen plasma (FFP) are among the most commonly used blood products. All of the blood products are derived from pooled blood from human donors. Other less commonly used, but still important, blood products are whole blood, plasma protein fraction, cryoprecipitate, and platelets. packed red blood cells PRBCs are obtained by the centrifugation of whole blood and the separation of RBCs from plasma and the other cellular elements. The advantage of PRBCs is that their oxygen-carrying capacity is better than that of the other blood products, and they are less likely to cause cardiac fluid overload. Their disadvantages include high cost, limited shelf life, and fluctuating availability, as well as their ability to transmit viruses, trigger allergic reactions, and cause bleeding abnormalities. The suggested guidelines for use are given in Table 29.6. fresh frozen plasma FFP is obtained by centrifuging whole blood and thereby removing the cellular elements. The resulting plasma is then frozen. FFP is not recommended for routine fluid resuscitation, but it may be used as an adjunct to massive blood transfusion in the treatment of patients with underlying coagulation disorders. The plasma-expanding capability of FFP is similar to that of dextran but slightly less than that of hetastarch. The disadvantage of FFP use is that it can transmit pathogens. The suggested guidelines for use are given in Table 29.6. TABLE 29.6
Suggested Guidelines for Blood Products: Management of Bleeding Amount of Blood Loss Fluid of Choice 20% or less (slow loss) Crystalloids 20%–50% (slow loss) Nonprotein plasma expanders (dextran and hetastarch) Over 50% (slow loss) or 20% (acutely) Whole blood or PRBCs, and/or PPF and FFP 80% or more As above, but for every 5 units of blood given, administer 1–2 units of FFP and 1–2 units of platelets to prevent the hemodilution of clotting factors and bleeding FFP, Fresh frozen plasma; PPF, plasma protein fraction; PRBCs, packed red blood cells.
Physiology of Electrolyte Balance Electrolytes are solutes that work in conjunction with fluids to keep the body in balance. They are measured in milliequivalent (mEq) units. Electrolytes are either positively charged (cations) or negatively charged (anions). The positively charged cations include sodium (Na+), potassium (K+), calcium (Ca++), and magnesium (Mg++). The negatively charged anions include chloride (Cl − ), phosphate (PO4 − ), and bicarbonate (HCO3 − ). Electrolytes are involved in nerve impulse transmission, muscle contraction, regulation of water distribution, blood clotting, enzyme reactions, and acid-base balance. Sodium (Na+) and chloride (Cl − ) are the principal electrolytes in the extracellular fluid, whereas potassium (K+) is the major electrolyte in the intracellular fluid. Other important electrolytes are calcium, magnesium, and phosphorus. Electrolytes are controlled by the renin-angiotensin-aldosterone system, ADH system, and sympathetic nervous system. When these neuroendocrine systems are out of balance, adverse electrolyte imbalances commonly result. Patients who receive diuretics (see Chapter 28) are at risk for electrolyte abnormalities. Potassium Potassium is the most abundant electrolyte inside cells (the intracellular fluid), where the normal concentration is approximately 150 mEq/L. Approximately 95% of the potassium in the body is intracellular. In contrast, the amount of potassium outside the cells in the plasma ranges from 3.5 to 5 mEq/L. The ratio of intracellular to extracellular potassium is important. Small changes in the extracellular potassium level can lead to serious unwanted effects on the neuromuscular and cardiovascular systems. Potassium is obtained from a variety of foods, the most common being fruit and juices, vegetables, fish, and meats. The average daily diet usually provides 35 to 100 mEq of potassium, which is well above the required daily amount. Excess dietary potassium is usually excreted by the kidneys in the urine. Hypokalemia (a deficiency of potassium) is defined as a serum potassium level of less than 3.5 mEq/L. Hypokalemia can result from decreased intake, shifting of potassium into cells, increased renal excretion, and other losses such as diarrhea, vomiting, or tube drainage. Certain medications can also cause hypokalemia, including diuretics, steroids, beta blockers, and aminoglycoside antibiotics. Early symptoms of hypokalemia include hypotension, lethargy, mental confusion, muscle weakness, and nausea. Late symptoms of hypokalemia include cardiac irregularities, neuropathies, and paralytic ileus. A low serum potassium level can increase the toxicity associated with digoxin, which can precipitate serious ventricular dysrhythmias. Treatment involves both identifying and treating the cause and restoring the serum potassium levels to normal (>3.5 mEq/L). For mild hypokalemia, the consumption of potassium-rich foods is usually sufficient. Clinically significant hypokalemia requires the oral or parenteral administration of a potassium supplement. Hyperkalemia is the term for an excessive serum potassium level and is defined as a serum potassium level exceeding 5.5 mEq/L. Hyperkalemia can result from increased potassium intake, reduced renal excretion of potassium or redistribution of potassium from the intracellular to the extracellular compartment after burns, or rhabdomyolysis. Symptoms of hyperkalemia include generalized fatigue, weakness, paresthesia, palpitations, and paralysis. Clinical manifestations of hyperkalemia are generally related to the heart. Severe hyperkalemia (>7 mEq/L) can precipitate ventricular fibrillation and cardiac arrest. Mechanism of Action and Drug Effects The importance of potassium as the primary intracellular electrolyte is highlighted by the number of life-sustaining physiologic functions in which it is involved. Muscle contraction, the transmission of nerve impulses, and the regulation of heartbeats (the pacemaker function of the heart) are just a few of these functions. Potassium is also essential for the maintenance of acid-base balance, isotonicity, and the electrodynamic characteristics of the cell. It plays a role in many enzymatic reactions, and it is an essential component in gastric secretion, renal function, tissue synthesis, and carbohydrate metabolism. Indications Potassium replacement therapy is indicated in the treatment or prevention of potassium depletion. Potassium salts commonly used for this purpose include potassium chloride, potassium phosphate, and potassium acetate. The chloride is required to correct the hypochloremia (low level of chloride in the blood) that commonly accompanies potassium deficiency, and the phosphate is used to correct hypophosphatemia. The acetate salt may be used to raise the blood pH in acidotic conditions. Contraindications Contraindications to potassium replacement products include known allergy to a specific drug product, hyperkalemia from any cause, severe renal disease, acute dehydration, untreated Addison disease, severe hemolytic disease, and conditions involving extensive tissue breakdown (e.g., multiple trauma, severe burns). Adverse Effects The adverse effects of oral potassium are primarily limited to the gastrointestinal tract, including diarrhea, nausea, and vomiting. More significant effects include gastrointestinal bleeding and ulceration. The parenteral administration of potassium usually produces pain at the injection site. Cases of phlebitis have been associated with intravenous administration. The generally accepted maximum concentration for peripheral infusion is 20 to 40 mEq/L and up to 60 mEq/L for a central line. Excessive administration of potassium salts can lead to hyperkalemia and toxic effects. If intravenous potassium is administered too rapidly, cardiac arrest may occur. Intravenous potassium must not be given faster than 10 mEq/hr to patients who are not on cardiac monitors. For critically ill patients on cardiac monitors, rates of 20 mEq/hr or more may be used. Clinical Pearl Intravenous potassium can be given no faster than 10 mEq/hr in unmonitored patients. Toxicity and Management of Overdose The toxic effects of potassium are the result of hyperkalemia. Symptoms include muscle weakness, paresthesia, paralysis, cardiac rhythm irregularities that can result in ventricular fibrillation, and cardiac arrest. The treatment instituted depends on the degree of the hyperkalemia and ranges from reversal of life-threatening problems to simple dietary restrictions. In the event of severe hyperkalemia, the intravenous administration of dextrose and insulin, sodium bicarbonate, and calcium gluconate or chloride is often required. These drugs correct severe hyperkalemia by causing a rapid intracellular shift of potassium ions, which reduces the serum potassium concentration. Such interventions are often followed with orally or rectally administered sodium polystyrene sulfonate (Kayexalate) or hemodialysis to eliminate the extra potassium from the body. Less critical levels can be reduced with dietary restrictions. Interactions Concurrent use of potassium-sparing diuretics and ACE inhibitors can produce a hyperkalemic state. Concurrent use of non–potassium-sparing diuretics, amphotericin B, and mineralocorticoids can produce a hypokalemic state. Dosages Fluid and electrolyte therapy involves replacing any deficits or losses and/or providing maintenance levels for specific patient requirements. Accordingly, specific dosage amounts of fluids or electrolytes depend on several clinical factors, including the following: • Specific patient losses • Efficacy of patient physiologic systems involved in fluid and electrolyte metabolism, especially adrenal, cardiovascular, and kidney functions • Current drug therapy for pathologic conditions that complicate the amount and duration of replacement • Selection of oral or parenteral replacement formulations Suggested dosage guidelines for potassium with subsequent adjustments are 10 to 20 mEq administered orally several times a day or parenteral administration of 30 to 60 mEq every 24 hours. Drug Profiles potassium Potassium supplements are administered either to prevent or to treat potassium depletion. The acetate, bicarbonate, chloride, citrate, and gluconate salts of potassium are available for oral administration, including tablets, solutions, elixirs, and powders for solution. The parenteral salt forms of potassium for intravenous administration are acetate, chloride, and phosphate. The dosage of potassium supplements is usually expressed in milliequivalents of potassium and depends on the requirements of the individual patient. Different salt forms of potassium deliver varying milliequivalent amounts of potassium. It is classified as a pregnancy category A drug. Intravenous potassium is identified as a high-alert drug because of the serious toxicity that can occur when potassium is given intravenously. Pharmacokinetics: Potassium Route Onset of Action Peak Plasma Concentration Elimination Half-Life Duration of Action IV Immediate Rapid Variable Variable sodium polystyrene sulfonate (potassium exchange resin) Sodium polystyrene sulfonate (Kayexalate) is known as a cation exchange resin and is used to treat hyperkalemia. It is usually administered orally by nasogastric tube or as an enema. It works in the intestine, where potassium ions from the body are exchanged for sodium ions in the resin. Although the drug effects in each case are unpredictable, approximately 1 mEq of potassium is lost from the body per gram of resin administered. It can cause disturbances in electrolytes other than potassium, such as calcium and magnesium. For this reason, patients’ electrolytes are closely monitored during treatment with sodium polystyrene sulfonate. In 2011, the US Food and Drug Administration (FDA) required safety labeling changes to state that cases of intestinal or colonic necrosis and other serious gastrointestinal adverse events (bleeding, ischemic colitis, perforation) had been reported. Kayexalate should not be used in patients who do not have normal bowel function and should be discontinued in patients who develop constipation. It should not be used concurrently with sorbitol. Concurrent use of sorbitol with Kayexalate has been implicated in cases of intestinal colonic necrosis. This condition may be fatal. Other adverse effects include hypernatremia, hypokalemia, hypocalcemia, hypomagnesemia, nausea, and vomiting. Drug interactions include antacids and laxatives, which should be avoided. It is typically dosed in multiples of 15 to 30 g until the desired effect on serum potassium occurs. Onset of action varies from 2 to 12 hours and is generally faster with the oral route than with rectal administration. It is available in 15 g/60 mL suspensions and in a powder for reconstitution. It is classified as a pregnancy category C drug. Patiromer (Veltassa) is a new oral drug indicated for hyperkalemia. It is a nonabsorbed cation exchange polymer that increases fecal potassium excretion and ultimately reduces serum potassium levels. Patiromer has a delayed onset of action, and thus it should not be used as an emergency treatment for life-threatening hyperkalemia. Patiromer has a black box warning regarding the decreased absorption of many oral medications. Other oral drugs need to be given 6 hours before or 6 hours after patiromer. No other drug interactions have been identified. Adverse effects include hypomagnesemia, hypokalemia, constipation, diarrhea, and nausea. Patiromer should be given with food and must be diluted before administering. Sodium Zirconium Cyclosilicate (Lokelma) is another option to treat hyperkalemia. It is available orally and is not to be used for emergency treatment of hyperkalemia because it has a delayed onset of action. Sodium Sodium is the counterpart of potassium, in that potassium is the principal cation inside cells, whereas sodium is the principal cation outside cells. The normal concentration of sodium outside cells is 135 to 145 mEq/L, and it is maintained through the dietary intake of sodium in the form of sodium chloride, which is obtained from salt, fish, meats, and other foods flavored, seasoned, or preserved with salt. Serum sodium concentration and serum osmolarity are maintained under tight control involving thirst, secretion of ADH, and renal mechanisms. Hyponatremia is a condition of sodium loss or deficiency and occurs when the serum levels decrease to less than 135 mEq/L. It is manifested by lethargy, hypotension, stomach cramps, vomiting, diarrhea, and seizures. There are three types of hyponatremia, which can be categorized as follows: • Hypovolemic hyponatremia (when the TBW is decreased, but the total sodium is decreased to a greater extent) • Euvolemic hyponatremia (when the TBW is increased, but the total sodium remains normal) • Hypervolemic hyponatremia (when the total sodium is increased, but the TBW is increased to a greater extent) Causes of hyponatremia include pneumonia, central nervous system infection, trauma, cancer, congestive heart failure, liver failure, medications, poor dietary intake, excessive perspiration, prolonged diarrhea or vomiting, renal disorders, hypothyroidism, or adrenal insufficiency. Medications known to cause hyponatremia include diuretics, carbamazepine, amiodarone, and selective serotonin reuptake inhibitors. The syndrome of inappropriate antidiuretic hormone is another common cause of hyponatremia. Symptoms of hyponatremia include anorexia, confusion, lethargy, agitation, headache, and/or seizures. Hypernatremia is the condition of sodium excess and occurs when the serum levels of sodium exceed 145 mEq/L. Hypernatremia generally indicates that there is a relative deficit of TBW in relation to total body sodium. Causes of hypernatremia include water depletion, shifting of water into cells, or sodium overload. Hypernatremia causes cellular dehydration and can cause a multitude of symptoms including muscle cramps, headache, lethargy, seizures, coma, and possible intracranial hemorrhage. Severe neurologic symptoms can occur as a result of shifts of water from the brain’s intracellular to extracellular spaces. Mechanism of Action and Drug Effects Sodium is the major cation in extracellular fluid and is involved in the control of water distribution, fluid and electrolyte balance, and osmotic pressure of body fluids. Sodium also participates along with both chloride and bicarbonate in the regulation of acid-base balance. Chloride, the major extracellular anion (negatively charged substance), closely complements the physiologic action of sodium. Indications Sodium is primarily administered for the treatment or prevention of sodium depletion. Sodium chloride is the primary salt used for this purpose. Mild hyponatremia is usually treated with oral administration of sodium chloride tablets and/or fluid restriction. Pronounced sodium depletion is treated with intravenous normal saline or lactated Ringer’s solution. These drugs were discussed earlier. Hypertonic saline (3% NaCl) is sometimes used to correct severe hyponatremia. It is considered a high-alert drug because giving it too rapidly or in too high a dose can cause a syndrome known as central pontine myelinolysis, also known as osmotic demyelination syndrome. This can cause irreversible brainstem damage. A new class of drugs for the treatment of euvolemic (normal fluid volume) hyponatremia is the dual arginine vasopressin (AVP) V1A and V2 receptor antagonists. These drugs are conivaptan (Vaprisol) and tolvaptan (Samsca). This class of drugs is often referred to as vaptans. Specific information on conivaptan is listed under its drug profile. Contraindications The only usual contraindications to the use of sodium replacement products are known drug allergy to a specific product and hypernatremia. Adverse Effects The oral administration of sodium chloride can cause gastric upset consisting of nausea, vomiting, and cramps. Venous phlebitis can be a consequence of its parenteral administration. Interactions Sodium is not known to interact significantly with any drugs with the exception of the antibiotic called quinupristin/dalfopristin (Synercid). Dosages Fluid and electrolyte therapy involves replacing any deficit losses and/or providing maintenance levels for specific patient requirements. Accordingly, specific dosage amounts vary based on the patient’s situation. Drug Profiles sodium chloride Sodium chloride is primarily used as a replacement electrolyte for the prevention of or treatment of sodium loss. It is also used as a diluent for the infusion of compatible drugs and in the assessment of kidney function after a fluid challenge. Sodium chloride is contraindicated in patients who are hypersensitive to it. It is available in many intravenous preparations and in oral form as 650-mg tablets. It is classified as a pregnancy category C drug. Pharmacokinetics: Sodium Chloride Route Onset of Action Peak Plasma Concentration Elimination Half-Life Duration of Action IV Immediate Rapid Unknown Variable conivaptan Conivaptan (Vaprisol) is a nonpeptide dual-AVP, V1A and V2 receptor antagonist. It inhibits the effects of arginine vasopressin, also known as antidiuretic hormone (ADH), in the kidney. It is specifically indicated for the treatment of hospitalized patients with euvolemic hyponatremia, or low serum sodium levels at normal water volumes. Conivaptan is available for intravenous infusion. Adverse events associated with the use of conivaptan may include infusion site reactions (e.g., phlebitis, pain), thirst, headache, hypokalemia, vomiting, diarrhea, and polyuria. Closely monitor serum sodium levels during treatment, because overly rapid increases in serum sodium levels have been associated with potentially permanent adverse events, including osmotic demyelination syndrome. Several potential drug-drug interactions have been identified. Conivaptan is metabolized by the hepatic enzyme CYP3A4; coadministration of drugs that inhibit this enzyme (including but not limited to ketoconazole, itraconazole, clarithromycin, ritonavir, and indinavir) may increase serum levels. Tolvaptan (Samsca) is an oral version of conivaptan. It is available in 15- and 30-mg tablets. Tolvaptan has a black box warning stating that the patient must be in a hospital where sodium levels can be closely monitored when starting therapy. Pharmacokinetics: Conivaptan Route Onset of Action Peak Plasma Concentration Elimination Half-Life Duration of Action IV Immediate Rapid 6.7–8.6hr 12hr after infusion is stopped Nursing Process Assessment There are multiple indications for fluid and electrolyte replacement that demand close assessment of the patient’s needs. Any medications or solutions ordered must be given exactly as prescribed and without substitution. However, never take the prescriber’s order at face value without confirming the accuracy and safety of the medication order against authoritative resources (e.g., current drug reference guides, Physician’s Desk Reference, nursing pharmacology textbook, manufacturer’s drug insert). Remember that you are responsible for making sure that the drug therapy administration process—beginning with the assessment phase of the nursing process through to evaluation—is accurate, safe, and meets professional standards of care. Before administering a fluid and/or electrolyte solution, complete a thorough physical assessment as well as a review of the medications/solutions prescribed. With isotonic solutions, such as 0.9% NaCl or lactated Ringer’s solution, there is no net fluid movement from the vein into the tissues/cells. These isotonic solutions (e.g., 0.9% NaCl [NS] and lactated Ringer’s solution) are customarily used to augment extracellular volume in patients experiencing blood loss and/or severe vomiting. Isotonic NaCl is used as the diluting fluid for blood transfusions because D 5 W results in hemolysis of RBCs (in transfusions). Parenterally administered hydrating and hypotonic solutions, such as 0.45% NaCl, are indicated for the prevention and/or treatment of dehydration. When giving these fluids, there is movement of fluid from the vein into the tissues and cells. Hypertonic solutions (e.g., 3% or 5% NaCl and D 10 W) result in movement of fluids from the ISF into the veins and used for replacement of fluids and electrolytes in specific situations (see pharmacology discussion). Because of the potential risks related to the use of these solutions, they are rarely administered outside of the hospital setting. After verifying all prescriber orders and checking for accuracy and completeness (as with all drugs), the solution or product, patient, and intravenous site must be assessed (if applicable). Assess the following for infusion infusion of fluids and/or electrolytes: the solution to be infused, infusion equipment, infusion rate of the solution, concentration of the parenteral solution, and compatibilities as well as the mathematical calculations and laboratory values (e.g., serum sodium, chloride, and potassium levels). Specific assessment of the patient needs to focus on gathering information about the patient’s medical history, including diseases of the gastrointestinal, renal, cardiac, and/or hepatic systems. Obtain a medication history, including a list of prescription drugs, over-the-counter medications, supplements, and herbals. Additionally, take a dietary history, including specific dietary habits and recall of all foods consumed during the previous 24 hours. Assess fluid volume and electrolyte status through laboratory testing, as prescribed, and measurement of urinary specific gravity, vital signs, intake, and output. Because the skin and mucous membranes reflect a patient’s hydration status, be sure to assess skin turgor and/or rebound elasticity of skin over the top of the hand and other areas over the body. Document the findings as “immediate” or “delayed” rebound. Count the number of seconds that the patient’s skin stays in the “pinched-up” position, with normal return being immediately or within 3 to 5 seconds. Potassium’s normal range in the serum is 3.5 to 5 mEq/L. Serum potassium levels below 3.5 mEq/L, or hypokalemia, may result in a variety of problems, such as cardiac irregularities and muscle weakness. Early symptoms of hypokalemia include hypotension, lethargy, mental confusion, muscle weakness, and nausea. Late symptoms of hypokalemia include cardiac irregularities, neuropathies, and paralytic ileus. Avoid potassium supplementation, or use with extreme caution in patients taking ACE inhibitors or potassium-sparing diuretics (e.g., spironolactone). These drugs are associated with adverse effects of hyperkalemia and, if given with potassium supplementation, could worsen hyperkalemia and possibly result in severe cardiac dysrhythmias. Other concerns regarding potassium-related contraindications include severe renal disease, untreated Addison disease, severe tissue trauma, and acute dehydration. Because oral potassium supplements are irritants and may be ulcerogenic, perform a thorough gastrointestinal tract assessment. If oral potassium supplementation is prescribed and the patient has a history of ulcers or gastrointestinal bleeding, contact the prescriber for further instructions because oral potassium dosage forms may exacerbate these conditions. For identification and treatment of hyperkalemia, the normal range of potassium is established at 3.5 to 5 mEq/L. Realize that potassium levels of 5.3 mEq/L may be identified as abnormally high by some laboratories, whereas other laboratories may categorize 5.0 mEq/L as being abnormally high. Be sure to check institutional policy and laboratory guidelines for normal ranges and report any elevations (or decreases) in serum potassium. Symptoms of hyperkalemia include fatigue, weakness, paresthesia, palpitations, and paralysis. A serum level exceeding 5.5 mEq/L is considered, by most sources, to be toxic and dangerous to the patient. Report this laboratory value to the prescriber immediately. With close monitoring of patients, the dangerous effects of hyperkalemia (i.e., cardiac dysrhythmias) and other potentially life-threatening complications may be identified early, treated appropriately, and/or prevented. Venous access is an important issue with parenteral potassium supplementation because the vein may be irritated with infiltration or if the solution has not been mixed thoroughly before infusion. The following are some important considerations regarding assessment of peripheral veins for the purpose of access to administer intravenous potassium, sodium, fluid, and any other type of medication: (1) Assess the overall condition of the veins before selecting a site. (2) Try to use the most distal veins first. (3) Know the purpose of administering potassium and other electrolytes. (4) Calculate and set the rate, as ordered, for the infusion. (5) Know the anticipated duration of therapy. (6) Know the restrictions imposed by the patient’s history. For example, in postmastectomy patients with lymph node dissection, the affected arm must not be used. The affected arm of a patient with a stroke is to be avoided, as well. Limb circulation may be inadequate in these situations and lead to edema and other complications if used as a venous access site. Sodium is another electrolyte that is an ingredient in various intravenous replacement solutions. Hyponatremia, or serum sodium level below 135 mEq/L, if not resolved with dietary and/ Safety: Laboratory Values Related to Drug Therapy Serum Potassium Laboratory Test Normal Ranges Rationale for Assessment Serum potassium 3.5–5mEq/L The main function of potassium is the regulation of water and electrolyte content in the cell. A decrease is generally considered to be a level less than 3.5mEq/L. A serum level less than 3.5mEq/L is known as hypokalemia, and a small decrease in potassium levels may have profound effects with lethargy, muscle weakness, hypotension, and cardiac dysrhythmias. A serum potassium level greater than 5mEq/L is known as hyperkalemia and is manifested by muscle weakness, paresthesia, paralysis, and cardiac rhythm abnormalities. or oral intake, may need to be treated with parenteral infusions. Signs and symptoms of hyponatremia include lethargy, hypotension, stomach cramps, vomiting, and diarrhea. Carefully assess venous access sites because of possible irritation of the vein and subsequent phlebitis. If replacement to correct hyponatremic states is overzealous, the result may be hypernatremia with fluid overload, edema, and dyspnea. Assess baseline vital signs. Continually monitor vital signs, hydration status of the skin and mucous membranes and baseline level of consciousness. Contraindications to sodium replacement include elevated serum sodium levels, congestive heart failure, edema, and hypertension. Hypernatremia also requires careful assessment. Manifestations of hypernatremia include red, flushed skin; dry, sticky mucous membranes; increased thirst; temperature elevation; water retention (edema); hypertension; and decreased or absent urination. Identifying any precipitating events, medical concerns, and risk-prone patient situations is important in finding early treatment solutions. The individuals at most risk for hypernatremia include older adults, those with renal and cardiovascular diseases, patients who are receiving sodium supplements or excessive sodium intake and those with decreased fluid intake. Assess for cautions, contraindications, and drug interactions. When administering albumin and other colloids (e.g., dextran), assess for cautions, contraindications, and drug interactions. Contraindications include patients with heart failure, severe anemia, and renal insufficiency. The rationale is that these products cause fluids to shift from interstitial to intravascular spaces. This places more strain on the patient’s cardiac and respiratory systems. Assess the patient’s hematocrit, hemoglobin levels, and serum protein levels. Assess the patient’s blood pressure, pulse rate, respiratory status, and intake and output. Document and report any abnormal assessment findings (e.g., dyspnea, edema) immediately. Fluid infusions may also include the administration of blood or blood components. Obtain a thorough history regarding any transfusions received previously and the patient’s response. Report any history of adverse reactions to blood transfusions or problems with PRBCs and/or FFP to the prescriber and document the nature of these reactions. Assess the status of venous access areas. Monitor the patient’s hematocrit, hemoglobin, white blood cells (WBCs), RBCs, platelets, and clotting factors. Note baseline vital signs, blood pressure, pulse rate, respiratory rate, and temperature before infusing blood or blood products. Even the general appearance of the patient, energy levels, ability to carry out activities of daily living, and color of extremities are important to note. Assess for any potential drug interactions, specifically aspirin and calcium, because these may potentially alter clotting. During the infusion of blood components, assess continually for the occurrence of fever and/or hematuria (blood in the urine). Both of these findings are indicative of a reaction requiring immediate medical attention. In summary, safety and being cautious are top priorities when patients receive any drug; fluid and electrolyte replacement drugs are no exception. Deficient and/or excess fluid and electrolyte levels may pose tremendous risks to patients. A thorough assessment is critical to patient safety. In addition, because so many patients receive therapies in the home setting, there is even more accountability and responsibility for performing skillful and thorough assessment before, during, and after therapy. Human Need Statements
© Dundanim. M.S., an 85-year-old retired engineer, seems somewhat confused when his daughter comes home from work. She takes him to the emergency department, where his blood pressure is 90/62 his heart rate is 114 and his skin is dry but cool. His daughter says that he seems “much weaker” than usual, and he is unable to answer questions clearly. His daughter reports that he has “lost his appetite” lately and has not taken in much food or drink. The nurse starts an IV infusion of 0.9% sodium chloride (NS) at 100 mL/hr via a gravity drip infusion.
FIG. 29.1 Distribution of total body water (TBW). ECF, Extracellular fluid; ICF, intracellular fluid; ISF, interstitial fluid; IVF, intravascular volume. Fluid contained within the cells is called ICF, and it contains solutes such as electrolytes and glucose. ECF is the fluid outside the cells. Its function is to transport nutrients to cells and transport waste products away from cells. ECF is further broken down into intravascular fluid (contained within blood vessels) and interstitial fluid (surrounding the cell). Intravascular refers to the volume of blood in the circulatory system and contains protein-rich plasma and large amounts of albumin. In contrast, ISF contains little or no protein. ISF is further broken down to transcellular fluid, which is contained within specialized body compartments such as the synovial, cerebrospinal, and pleural cavities. Water within the body is critical, not only because of its vast quantity but also because it serves as a solvent to dissolve solutes and acts as a medium for metabolic reactions. Throughout the body, water is freely exchanged among all fluid compartments and is retained in a relatively constant amount. Internal control mechanisms responsible for maintaining fluid balance include thirst, antidiuretic hormone (ADH), and aldosterone. Movement into and out of cells is carried out through the following processes: diffusion, filtration, active transport, and osmosis. The goal of fluid and electrolyte balance is to maintain homeostasis, where fluid intake is equal to fluid output. Fluid intake comes from liquids, solid foods, intravenous fluid, or parenteral fluid. Fluid loss (output) comes primarily from the kidney and also can be from emesis or feces. Insensible losses (those that cannot be measured) come from the skin, lungs, and gastrointestinal tract. Other measurable loss can be from fistulas, drains, or gastrointestinal suction. All measurable sources of intake and output are important to document in the hospitalized patient. A sudden change in weight is a strong indicator of fluid balance. If the amount of water gained exceeds the amount of water lost, the end result is overhydration. Such fluid excesses often accumulate in interstitial spaces, such as in the pericardial sac, joint capsules, and lower extremities. This is referred to as edema. In contrast, if the quantity of water lost exceeds that gained, a water deficit, or dehydration, occurs. Death often occurs when 20% to 25% of TBW is lost. Dehydration leads to a disturbance in the balance between the amount of fluid in the extracellular compartment and that in the intracellular compartment. Sodium is the principle extracellular electrolyte and plays a primary role in maintaining water concentration. In the initial stages of dehydration, water is lost first from the extracellular compartments. The amount of further fluid losses, changes to colloid oncotic pressure, or both, determine the type of clinical dehydration that develops (Table 29.1). Clinical conditions that can result in dehydration and fluid loss, and the symptoms of dehydration and fluid loss, are presented in Table 29.2. When fluid that has been lost must be replaced, there are three categories of agents that can be used to accomplish this: crystalloids, colloids, and blood products. The clinical situation dictates which category of agents is most appropriate. TABLE 29.1
Types of Dehydration Type of Dehydration Characteristics Hypertonic Occurs when water loss is greater than sodium loss, which results in a concentration of solutes outside the cells and causes the fluid inside the cells to move to the extracellular space, thus dehydrating the cells. Example: Elevated temperature resulting in perspiration. Hypotonic Occurs when sodium loss is greater than water loss, which results in higher concentrations of solute inside the cells and causes fluid to be pulled from outside the cells (plasma and interstitial spaces) into the cells. Examples: Renal insufficiency and inadequate aldosterone secretion. Isotonic Caused by a loss of both sodium and water from the body, which results in a decrease in the volume of extracellular fluid. Examples: Diarrhea and vomiting. TABLE 29.2
Conditions Leading to Fluid Loss or Dehydration and Associated Corresponding Symptoms a Condition Associated Symptoms Bleeding Tachycardia and hypotension Bowel obstruction Reduced perspiration and mucous secretions Diarrhea Reduced urine output (oliguria) Fever Dry skin and mucous membranes Vomiting Reduced lacrimal (tears) and salivary secretions a There may be overlap involving more than one of the symptoms depending on the patient’s specific condition.
Tonicity and osmolality are similar terms that are often used interchangeably, but they are not exactly the same, chemically speaking. Osmolality is used in reference to body fluids and is the concentration of particles in a solution. Normal osmolality of body fluids is between 290 and 310 mOsm/kg. Tonicity is used in reference to intravenous fluids and is the measurement of the concentration of intravenous fluids as compared with the osmolality of body fluids. Tonicity also can be defined as the measure of osmotic pressure. The tonicity of intravenous solutions can be considered isotonic, hypotonic, or hypertonic. Isotonic means that the osmotic pressures inside and outside of the blood cell are the same. Hypotonic means that the solution outside the cell has a lower osmotic pressure than inside the cell. Hypertonic means the solution outside the blood cell has a higher osmotic pressure than inside the cell. Giving an isotonic solution such as normal saline (0.9% NaCl) or lactated Ringer’s solution causes no net fluid movement. Administering a hypotonic solution (0.45% NaCl) causes fluid to move out of the vein and into the tissues and cells. Injecting a hypertonic solution (3% NaCl) causes fluid to move from the ISF into the veins. This is depicted in Fig. 29.2.
FIG. 29.2 A depiction of what happens when red blood cells are exposed to different fluids. Isotonic solutions cause no net fluid movement. Hypertonic solutions cause water to move out of the cells and can cause the cells to shrink. Hypotonic solutions cause water to move into the cells, which can cause them to burst. Acid-base balance is also important to normal bodily functions and is regulated by the respiratory system and the kidney. An acid is a substance that can donate or release hydrogen ions, such as carbonic acid or hydrochloric acid. A base is a substance that can accept hydrogen ions, such as bicarbonate. The pH is a measure of the degree of acidosis and alkalinity and is inversely related to hydrogen ion concentration. For example, when hydrogen ion concentration increases, the pH decreases and leads to acidity. As the hydrogen ion concentration decreases, the pH increases, leading to more alkalinity. With the normal pH ranging from 7.35 to 7.45, acidosis occurs when pH falls below 7.35. Conversely, alkalosis occurs when the pH rises above 7.45. Regulation of the acid-base balance requires healthy functioning of the respiratory and renal systems. The respiratory system compensates for metabolic problems and pH imbalances by regulation of carbon dioxide. In acidosis, CO2 can be exhaled to try to normalize the lower pH; in alkalosis, CO2 will be retained by the respiratory system to try to elevate the pH. The kidney also compensates by reabsorbing and generating bicarbonate and excreting hydrogen ions in acidosis to normalize the low pH. Conversely, the kidney can excrete bicarbonate and retain hydrogen ions to normalize the high pH seen with alkalosis. The influence of the respiratory system is determined by an arterial blood gas (ABG) test. The influence of the body on acid-base balance is determined by a blood test, which measures total body CO2 and is usually represented as HCO3. Both are used in determining and treating acid-base disorders. Detailed determination and treatment of acid-base balance is complex and beyond the scope of this textbook. Certain drugs, such as the diuretic acetazolamide (see Chapter 28) and sodium bicarbonate (tablets or injection), can be used to correct metabolic acid-base disturbances. Crystalloids Crystalloids are fluids given by intravenous injection that supply water and sodium to maintain the osmotic gradient between the extravascular and intravascular compartments. Their plasma volume–expanding capacity is related to their sodium concentration. Serum is a term closely related to plasma. The most commonly used crystalloids are normal saline (0.9% NaCl) and lactated Ringer’s solution. Mechanism of Action and Drug Effects Crystalloid solutions contain fluids and electrolytes that are normally found in the body. They do not contain proteins (colloids), which are necessary to maintain the colloid oncotic pressure and prevent water from leaving the plasma compartment. In fact, the administration of large quantities of crystalloid solutions for fluid resuscitation decreases the colloid oncotic pressure, because of a dilutional effect. Crystalloids are distributed faster into the interstitial and intracellular compartments than colloids. This makes crystalloids better for treating dehydration than for expanding the plasma volume alone. Indications Crystalloid solutions are most commonly used as maintenance fluids. They are used to compensate for insensible fluid losses, to replace fluids, and to manage specific fluid and electrolyte disturbances. Crystalloids also promote urinary flow. They are much less expensive than colloids and blood products. In addition, there is no risk for viral transmission or anaphylaxis and no alteration in the coagulation profile associated with their use, unlike with blood products. The choice of whether to use a crystalloid or a colloid depends on the severity of the condition. Common indications for either crystalloid or colloid replacement therapy include acute liver failure, burns, cardiopulmonary bypass surgery, hypoproteinemia, renal dialysis, and shock. Contraindications to the use of crystalloids include known drug allergy to a specific product and hypervolemia and may include severe electrolyte disturbance, depending on the type of crystalloid used. Adverse Effects Crystalloids are a very safe and effective means of replacing needed fluid. They do, however, have some unwanted effects. Because they contain no large particles, such as proteins, they do not stay within the blood vessels and can leak out of the plasma into the tissues and cells. This may result in edema anywhere in the body. Peripheral edema and pulmonary edema are two common examples. Crystalloids also dilute the proteins that are in the plasma, which further reduces the colloid oncotic pressure. To be effective, large volumes (liters of fluid) are usually required. As a result, prolonged infusions may cause fluid overload. Another disadvantage of crystalloids is that their effects are relatively short-lived. Interactions Interactions with crystalloid solutions are rare because they are very similar if not identical to normal physiologic substances. Dosage The dose of crystalloids is determined by the specific condition being treated. Drug Profile The most commonly used crystalloid solutions are normal saline (0.9% NaCl) and lactated Ringer’s solution. Sodium chloride is also discussed briefly in the section on electrolytes and in the Nursing Process section under electrolytes. sodium chloride Sodium chloride (NaCl) is available in several concentrations, the most common being 0.9%. This is the physiologically normal concentration of sodium chloride (isotonic), and it is referred to as normal saline (NS). Concentrations considered hypotonic are 0.45% (“half-normal”) and 0.25% (“quarter-normal”). Hypertonic saline (a high-alert solution) is available in 3% and 5% solutions. These solutions have different indications and are used in different situations, depending on how urgently fluid volume restoration is needed and/or the extent of the sodium loss. Normal saline contains 154 mEq of sodium per liter. Sodium chloride is a physiologic electrolyte that is present throughout the body’s water. Thus there are no hypersensitivity reactions to it. It is safe to administer it during any stage of pregnancy, but it is contraindicated in patients with hypernatremia and/or hyperchloremia. Hypertonic saline injections (3% and 5%) are contraindicated in the presence of increased, normal, or only slightly decreased sodium concentrations. Hypertonic saline is considered a high-risk drug because deaths have occurred when it is infused inappropriately. Correcting sodium too rapidly with hypertonic saline can lead to osmotic demyelination syndrome, which is potentially fatal. Conversely, infusing very low hypotonic saline (0.25% NaCl) is not recommended because it can cause hemolysis of the red blood cells. Sodium chloride is also available as a 650-mg tablet. The dose of sodium chloride administered depends on the clinical situation. Generally speaking, the amount of 0.9% NaCl that is needed to increase intravascular or plasma volume by 1000 mL is 5000 to 6000 mL. By contrast, the amount of albumin, which is a colloid solution (discussed later), needed to increase intravascular volume by the same 1000 mL is only 500 mL. Table 29.3 provides other examples. Colloids Colloids are substances that increase the colloid oncotic pressure and move fluid from the interstitial compartment to the plasma compartment by pulling the fluid into the blood vessels. Normally, this task is performed by the three blood proteins: albumin, globulin, and fibrinogen. The total body protein level needs to be in the range of 7.4 g/dL. If this level falls below 5.3 g/dL, fluid shifts out of blood vessels into the tissues. When this happens, colloid replacement therapy is used to reverse this process by increasing the colloid oncotic pressure. Colloid oncotic pressure decreases with age and malnutrition. Commonly used colloids include albumin, dextran, and hetastarch. Information on the composition of these colloids can be found in Table 29.4. TABLE 29.3
Crystalloids and Colloids: Dosing Guidelines Crystalloids and Colloids 0.9% Saline 3% Saline a 5% Colloid b 25% Colloid c To Raise Plasma Volume by 1L, Administer 5–6L 1.5–2L 1L 0.5L Compartment to Which Fluid Is Distributed Plasma 25% 25% 100% 200%–300% Interstitial space 75% 75% 0 Decreased fluid levels Intracellular space 0 0 0 Decreased fluid levels a Hypertonic saline is a high-alert drug and should not be given faster than 100mL/hr for short periods. Frequent monitoring of serum levels is required.
b Iso-oncotic solutions such as 5% albumin, and hetastarch.
c Hyperoncotic solutions such as 25% albumin.
TABLE 29.4
Commonly Used Colloids Product Composition (mEq/L) Volume (mL) Cost a Na Cl Dextran 40 b 154 154 500 2 Hetastarch 154 154 500 5 5% Albumin 145 145 500 10 25% Albumin 145 145 100 10 Cl, Chloride; Na, sodium.
a Relative cost compared with the cost of dextran 40.
b Dextran is available in NaCl, which has 154 mEq/L of both Na and Cl. It is also available in 5% dextrose in water, which contains no Na or Cl.
Mechanism of Action and Drug Effects The mechanism of action of colloids is related to their ability to increase the colloid oncotic pressure. Because the colloids cannot pass into the extravascular space, there is a higher concentration of colloid solutes (solid particles) inside the blood vessels (intravascular space) than outside the blood vessels. Fluid moves from the extravascular space into the blood vessels in an attempt to make the blood isotonic. See Fig. 29.3. As such, colloids increase the blood volume, and they are sometimes called plasma expanders. They also make up part of the total plasma volume. Colloids increase the colloid oncotic pressure and move fluid from outside the blood vessels to inside the blood vessels. They can maintain the colloid oncotic pressure for several hours. They are naturally occurring products and consist of proteins (albumin), carbohydrates (dextrans or starches), fats (lipid emulsion), and animal collagen (gelatin). Usually they contain a combination of both small and large particles. The small particles are eliminated quickly and promote diuresis and perfusion of the kidneys; the larger particles maintain the plasma volume. Albumin is the one exception in that it contains particles that are all the same size.
FIG. 29.3 Colloid osmotic pressure (oncotic pressure). As shown, the colloids inside the blood vessel are too large to pass through the vessel wall. The resulting oncotic pressure exerted by the colloids draws fluid from the surrounding tissues and other extravascular spaces into the blood vessels and also keeps fluid inside the blood vessel. Indications Colloids are used to treat a wide variety of conditions, including shock and burns, or whenever the patient requires plasma volume expansion. Clinically, colloids are superior to crystalloids because of their ability to maintain the plasma volume for a longer time. However, colloids are significantly more expensive and are more likely to promote bleeding. Colloids are less likely than crystalloids to cause edema because of the larger volumes of crystalloids needed to achieve the desired clinical effect. Crystalloids are better than colloids for emergency short-term plasma volume expansion. Contraindications Contraindications to the use of colloids include known drug allergy to a specific product and hypervolemia and may include severe electrolyte disturbance. Adverse Effects Colloids are relatively safe agents, although there are some disadvantages to their use. They have no oxygen-carrying ability and contain no clotting factors, unlike blood products. Because of this, they can alter the coagulation system through a dilutional effect, which results in impaired coagulation and possibly bleeding. Rarely, dextran therapy causes anaphylaxis or renal failure. Interactions No drug interactions occur with colloids. Dosages For dosage information on colloids, see Table 29.3. Drug Profiles The specific colloid used for replacement therapy varies from institution to institution. The three most commonly used are 5% albumin, dextran 40, and hetastarch. They all have a very rapid onset of action and a long duration of action. They are metabolized in the liver and excreted by the kidneys. Albumin is the one exception; it is metabolized by the reticuloendothelial system and excreted by the kidneys and the intestines. Hetastarch is a synthetic colloid with properties similar to those of albumin and dextran. albumin Albumin is a natural protein that is normally produced by the liver. It is responsible for generating approximately 70% of the colloid oncotic pressure. Human albumin is a sterile solution of serum albumin that is prepared from pooled blood, plasma, serum, or placentas obtained from healthy human donors. It is pasteurized to destroy any contaminants. Unfortunately, because it is derived from human donors, the supply is limited, which causes it to be extremely expensive. Albumin is contraindicated in patients with a known hypersensitivity to it and in those with heart failure, severe anemia, or renal insufficiency. Albumin is available only in parenteral form in concentrations of 5% and 25%. It is classified as a pregnancy category C drug. See Table 29.3 for dosing guidelines. Pharmacokinetics: Albumin Route Onset of Action Peak Plasma Concentration Elimination Half-Life Duration of Action IV Less than 1min Unknown 16hr Less than 24hr dextran Dextran is a solution of glucose. It is available as dextran 40 and has a molecular weight similar to that of albumin. It has actions similar to those of human albumin in that it expands the plasma volume by drawing fluid from the interstitial space to the intravascular space. Dextran is contraindicated in patients with a known hypersensitivity to it and in those with heart failure, renal insufficiency, and extreme dehydration. It is available only in parenteral form mixed in either a 5% dextrose solution or a 0.9% NaCl solution. It is classified as a pregnancy category C drug. See Table 29.3 for dosing guidelines. Pharmacokinetics: Dextran Route Onset of Action Peak Plasma Concentration Elimination Half-Life Duration of Action IV 5min Unknown 2–6hr 4–6hr Blood Products Blood products can be thought of as biologic drugs. They augment the plasma volume. Red blood cell (RBC)-containing products can also improve tissue oxygenation. Blood products are significantly more expensive than crystalloids and colloids and are less available because they are natural products and require human donors. They are most often indicated when a patient has lost 25% or more blood volume. Mechanism of Action and Drug Effects The mechanism of action of blood products is related to their ability to increase the colloid oncotic pressure, and hence the plasma volume. They do so in the same manner as colloids and hypertonic crystalloids, by pulling fluid from the extravascular space to the intravascular space. Because of this they are also considered plasma expanders. RBC products also have the ability to carry oxygen. They can maintain the colloid oncotic pressure for several hours to days. Because they come from human donors, they have all the benefits (and hazards) that human blood products have. They are administered when a person’s body is deficient in these products. Indications Blood products are used to treat a wide variety of clinical conditions, and the blood product used depends on the specific indication. The available blood products and the specific conditions they are used to treat are listed in Table 29.5. Contraindications There are no absolute contraindications to the use of blood products. However, because there is a risk for transfer of infectious disease, although remote, their use needs to be based on careful clinical evaluation of the patient’s condition. Adverse Effects Blood products can produce undesirable effects, some potentially serious. Because these products come from other humans, they can be incompatible with the recipient’s immune system. These incompatibilities are tested for before their administration by determining the respective blood types of the donor and recipient and by performing cross-matching tests to screen for incompatibility between selected blood proteins. This helps reduce the likelihood that the recipient will reject the blood product, which would precipitate transfusion reactions and anaphylaxis. These products can also transmit pathogens (hepatitis and human immunodeficiency virus [HIV]) from the donor to the recipient. Various preparation techniques are now used to reduce the risk for pathogen transmission, and these have resulted in a drastic reduction in the incidence of such problems. TABLE 29.5
Blood Products: Indications Blood Product Indication Cryoprecipitate and PPF To manage acute bleeding (over 50% blood loss slowly or 20% rapidly) FFP To increase clotting factor levels PRBCs To increase oxygen-carrying capacity in patients with anemia, in patients with substantial hemoglobin deficits, and in patients who have lost up to 25% of their total blood volume Whole blood Same as for PRBCs, except that whole blood is more beneficial in cases of extreme (over 25%) loss of blood volume because whole blood also contains plasma and plasma proteins, the chief osmotic component, which help draw fluid back into blood vessels from surrounding tissues FFP, Fresh frozen plasma; PPF, plasma protein fraction; PRBCs, packed red blood cells.
Interactions As with crystalloids and colloids, blood products are very similar if not identical to normal physiologic substances; therefore they are involved in very few interactions. Calcium and aspirin, which normally affect coagulation, may interact with these substances when infused in the body in much the same way that they interact with the body’s own blood components. Blood must not be administered with any solution other than normal saline. Clinical Pearl Blood products can be administered with normal saline ONLY. Dosages Table 29.6 provides dosage information on blood products. Drug Profiles Packed red blood cells (PRBCs) and fresh frozen plasma (FFP) are among the most commonly used blood products. All of the blood products are derived from pooled blood from human donors. Other less commonly used, but still important, blood products are whole blood, plasma protein fraction, cryoprecipitate, and platelets. packed red blood cells PRBCs are obtained by the centrifugation of whole blood and the separation of RBCs from plasma and the other cellular elements. The advantage of PRBCs is that their oxygen-carrying capacity is better than that of the other blood products, and they are less likely to cause cardiac fluid overload. Their disadvantages include high cost, limited shelf life, and fluctuating availability, as well as their ability to transmit viruses, trigger allergic reactions, and cause bleeding abnormalities. The suggested guidelines for use are given in Table 29.6. fresh frozen plasma FFP is obtained by centrifuging whole blood and thereby removing the cellular elements. The resulting plasma is then frozen. FFP is not recommended for routine fluid resuscitation, but it may be used as an adjunct to massive blood transfusion in the treatment of patients with underlying coagulation disorders. The plasma-expanding capability of FFP is similar to that of dextran but slightly less than that of hetastarch. The disadvantage of FFP use is that it can transmit pathogens. The suggested guidelines for use are given in Table 29.6. TABLE 29.6
Suggested Guidelines for Blood Products: Management of Bleeding Amount of Blood Loss Fluid of Choice 20% or less (slow loss) Crystalloids 20%–50% (slow loss) Nonprotein plasma expanders (dextran and hetastarch) Over 50% (slow loss) or 20% (acutely) Whole blood or PRBCs, and/or PPF and FFP 80% or more As above, but for every 5 units of blood given, administer 1–2 units of FFP and 1–2 units of platelets to prevent the hemodilution of clotting factors and bleeding FFP, Fresh frozen plasma; PPF, plasma protein fraction; PRBCs, packed red blood cells.
Physiology of Electrolyte Balance Electrolytes are solutes that work in conjunction with fluids to keep the body in balance. They are measured in milliequivalent (mEq) units. Electrolytes are either positively charged (cations) or negatively charged (anions). The positively charged cations include sodium (Na+), potassium (K+), calcium (Ca++), and magnesium (Mg++). The negatively charged anions include chloride (Cl − ), phosphate (PO4 − ), and bicarbonate (HCO3 − ). Electrolytes are involved in nerve impulse transmission, muscle contraction, regulation of water distribution, blood clotting, enzyme reactions, and acid-base balance. Sodium (Na+) and chloride (Cl − ) are the principal electrolytes in the extracellular fluid, whereas potassium (K+) is the major electrolyte in the intracellular fluid. Other important electrolytes are calcium, magnesium, and phosphorus. Electrolytes are controlled by the renin-angiotensin-aldosterone system, ADH system, and sympathetic nervous system. When these neuroendocrine systems are out of balance, adverse electrolyte imbalances commonly result. Patients who receive diuretics (see Chapter 28) are at risk for electrolyte abnormalities. Potassium Potassium is the most abundant electrolyte inside cells (the intracellular fluid), where the normal concentration is approximately 150 mEq/L. Approximately 95% of the potassium in the body is intracellular. In contrast, the amount of potassium outside the cells in the plasma ranges from 3.5 to 5 mEq/L. The ratio of intracellular to extracellular potassium is important. Small changes in the extracellular potassium level can lead to serious unwanted effects on the neuromuscular and cardiovascular systems. Potassium is obtained from a variety of foods, the most common being fruit and juices, vegetables, fish, and meats. The average daily diet usually provides 35 to 100 mEq of potassium, which is well above the required daily amount. Excess dietary potassium is usually excreted by the kidneys in the urine. Hypokalemia (a deficiency of potassium) is defined as a serum potassium level of less than 3.5 mEq/L. Hypokalemia can result from decreased intake, shifting of potassium into cells, increased renal excretion, and other losses such as diarrhea, vomiting, or tube drainage. Certain medications can also cause hypokalemia, including diuretics, steroids, beta blockers, and aminoglycoside antibiotics. Early symptoms of hypokalemia include hypotension, lethargy, mental confusion, muscle weakness, and nausea. Late symptoms of hypokalemia include cardiac irregularities, neuropathies, and paralytic ileus. A low serum potassium level can increase the toxicity associated with digoxin, which can precipitate serious ventricular dysrhythmias. Treatment involves both identifying and treating the cause and restoring the serum potassium levels to normal (>3.5 mEq/L). For mild hypokalemia, the consumption of potassium-rich foods is usually sufficient. Clinically significant hypokalemia requires the oral or parenteral administration of a potassium supplement. Hyperkalemia is the term for an excessive serum potassium level and is defined as a serum potassium level exceeding 5.5 mEq/L. Hyperkalemia can result from increased potassium intake, reduced renal excretion of potassium or redistribution of potassium from the intracellular to the extracellular compartment after burns, or rhabdomyolysis. Symptoms of hyperkalemia include generalized fatigue, weakness, paresthesia, palpitations, and paralysis. Clinical manifestations of hyperkalemia are generally related to the heart. Severe hyperkalemia (>7 mEq/L) can precipitate ventricular fibrillation and cardiac arrest. Mechanism of Action and Drug Effects The importance of potassium as the primary intracellular electrolyte is highlighted by the number of life-sustaining physiologic functions in which it is involved. Muscle contraction, the transmission of nerve impulses, and the regulation of heartbeats (the pacemaker function of the heart) are just a few of these functions. Potassium is also essential for the maintenance of acid-base balance, isotonicity, and the electrodynamic characteristics of the cell. It plays a role in many enzymatic reactions, and it is an essential component in gastric secretion, renal function, tissue synthesis, and carbohydrate metabolism. Indications Potassium replacement therapy is indicated in the treatment or prevention of potassium depletion. Potassium salts commonly used for this purpose include potassium chloride, potassium phosphate, and potassium acetate. The chloride is required to correct the hypochloremia (low level of chloride in the blood) that commonly accompanies potassium deficiency, and the phosphate is used to correct hypophosphatemia. The acetate salt may be used to raise the blood pH in acidotic conditions. Contraindications Contraindications to potassium replacement products include known allergy to a specific drug product, hyperkalemia from any cause, severe renal disease, acute dehydration, untreated Addison disease, severe hemolytic disease, and conditions involving extensive tissue breakdown (e.g., multiple trauma, severe burns). Adverse Effects The adverse effects of oral potassium are primarily limited to the gastrointestinal tract, including diarrhea, nausea, and vomiting. More significant effects include gastrointestinal bleeding and ulceration. The parenteral administration of potassium usually produces pain at the injection site. Cases of phlebitis have been associated with intravenous administration. The generally accepted maximum concentration for peripheral infusion is 20 to 40 mEq/L and up to 60 mEq/L for a central line. Excessive administration of potassium salts can lead to hyperkalemia and toxic effects. If intravenous potassium is administered too rapidly, cardiac arrest may occur. Intravenous potassium must not be given faster than 10 mEq/hr to patients who are not on cardiac monitors. For critically ill patients on cardiac monitors, rates of 20 mEq/hr or more may be used. Clinical Pearl Intravenous potassium can be given no faster than 10 mEq/hr in unmonitored patients. Toxicity and Management of Overdose The toxic effects of potassium are the result of hyperkalemia. Symptoms include muscle weakness, paresthesia, paralysis, cardiac rhythm irregularities that can result in ventricular fibrillation, and cardiac arrest. The treatment instituted depends on the degree of the hyperkalemia and ranges from reversal of life-threatening problems to simple dietary restrictions. In the event of severe hyperkalemia, the intravenous administration of dextrose and insulin, sodium bicarbonate, and calcium gluconate or chloride is often required. These drugs correct severe hyperkalemia by causing a rapid intracellular shift of potassium ions, which reduces the serum potassium concentration. Such interventions are often followed with orally or rectally administered sodium polystyrene sulfonate (Kayexalate) or hemodialysis to eliminate the extra potassium from the body. Less critical levels can be reduced with dietary restrictions. Interactions Concurrent use of potassium-sparing diuretics and ACE inhibitors can produce a hyperkalemic state. Concurrent use of non–potassium-sparing diuretics, amphotericin B, and mineralocorticoids can produce a hypokalemic state. Dosages Fluid and electrolyte therapy involves replacing any deficits or losses and/or providing maintenance levels for specific patient requirements. Accordingly, specific dosage amounts of fluids or electrolytes depend on several clinical factors, including the following: • Specific patient losses • Efficacy of patient physiologic systems involved in fluid and electrolyte metabolism, especially adrenal, cardiovascular, and kidney functions • Current drug therapy for pathologic conditions that complicate the amount and duration of replacement • Selection of oral or parenteral replacement formulations Suggested dosage guidelines for potassium with subsequent adjustments are 10 to 20 mEq administered orally several times a day or parenteral administration of 30 to 60 mEq every 24 hours. Drug Profiles potassium Potassium supplements are administered either to prevent or to treat potassium depletion. The acetate, bicarbonate, chloride, citrate, and gluconate salts of potassium are available for oral administration, including tablets, solutions, elixirs, and powders for solution. The parenteral salt forms of potassium for intravenous administration are acetate, chloride, and phosphate. The dosage of potassium supplements is usually expressed in milliequivalents of potassium and depends on the requirements of the individual patient. Different salt forms of potassium deliver varying milliequivalent amounts of potassium. It is classified as a pregnancy category A drug. Intravenous potassium is identified as a high-alert drug because of the serious toxicity that can occur when potassium is given intravenously. Pharmacokinetics: Potassium Route Onset of Action Peak Plasma Concentration Elimination Half-Life Duration of Action IV Immediate Rapid Variable Variable sodium polystyrene sulfonate (potassium exchange resin) Sodium polystyrene sulfonate (Kayexalate) is known as a cation exchange resin and is used to treat hyperkalemia. It is usually administered orally by nasogastric tube or as an enema. It works in the intestine, where potassium ions from the body are exchanged for sodium ions in the resin. Although the drug effects in each case are unpredictable, approximately 1 mEq of potassium is lost from the body per gram of resin administered. It can cause disturbances in electrolytes other than potassium, such as calcium and magnesium. For this reason, patients’ electrolytes are closely monitored during treatment with sodium polystyrene sulfonate. In 2011, the US Food and Drug Administration (FDA) required safety labeling changes to state that cases of intestinal or colonic necrosis and other serious gastrointestinal adverse events (bleeding, ischemic colitis, perforation) had been reported. Kayexalate should not be used in patients who do not have normal bowel function and should be discontinued in patients who develop constipation. It should not be used concurrently with sorbitol. Concurrent use of sorbitol with Kayexalate has been implicated in cases of intestinal colonic necrosis. This condition may be fatal. Other adverse effects include hypernatremia, hypokalemia, hypocalcemia, hypomagnesemia, nausea, and vomiting. Drug interactions include antacids and laxatives, which should be avoided. It is typically dosed in multiples of 15 to 30 g until the desired effect on serum potassium occurs. Onset of action varies from 2 to 12 hours and is generally faster with the oral route than with rectal administration. It is available in 15 g/60 mL suspensions and in a powder for reconstitution. It is classified as a pregnancy category C drug. Patiromer (Veltassa) is a new oral drug indicated for hyperkalemia. It is a nonabsorbed cation exchange polymer that increases fecal potassium excretion and ultimately reduces serum potassium levels. Patiromer has a delayed onset of action, and thus it should not be used as an emergency treatment for life-threatening hyperkalemia. Patiromer has a black box warning regarding the decreased absorption of many oral medications. Other oral drugs need to be given 6 hours before or 6 hours after patiromer. No other drug interactions have been identified. Adverse effects include hypomagnesemia, hypokalemia, constipation, diarrhea, and nausea. Patiromer should be given with food and must be diluted before administering. Sodium Zirconium Cyclosilicate (Lokelma) is another option to treat hyperkalemia. It is available orally and is not to be used for emergency treatment of hyperkalemia because it has a delayed onset of action. Sodium Sodium is the counterpart of potassium, in that potassium is the principal cation inside cells, whereas sodium is the principal cation outside cells. The normal concentration of sodium outside cells is 135 to 145 mEq/L, and it is maintained through the dietary intake of sodium in the form of sodium chloride, which is obtained from salt, fish, meats, and other foods flavored, seasoned, or preserved with salt. Serum sodium concentration and serum osmolarity are maintained under tight control involving thirst, secretion of ADH, and renal mechanisms. Hyponatremia is a condition of sodium loss or deficiency and occurs when the serum levels decrease to less than 135 mEq/L. It is manifested by lethargy, hypotension, stomach cramps, vomiting, diarrhea, and seizures. There are three types of hyponatremia, which can be categorized as follows: • Hypovolemic hyponatremia (when the TBW is decreased, but the total sodium is decreased to a greater extent) • Euvolemic hyponatremia (when the TBW is increased, but the total sodium remains normal) • Hypervolemic hyponatremia (when the total sodium is increased, but the TBW is increased to a greater extent) Causes of hyponatremia include pneumonia, central nervous system infection, trauma, cancer, congestive heart failure, liver failure, medications, poor dietary intake, excessive perspiration, prolonged diarrhea or vomiting, renal disorders, hypothyroidism, or adrenal insufficiency. Medications known to cause hyponatremia include diuretics, carbamazepine, amiodarone, and selective serotonin reuptake inhibitors. The syndrome of inappropriate antidiuretic hormone is another common cause of hyponatremia. Symptoms of hyponatremia include anorexia, confusion, lethargy, agitation, headache, and/or seizures. Hypernatremia is the condition of sodium excess and occurs when the serum levels of sodium exceed 145 mEq/L. Hypernatremia generally indicates that there is a relative deficit of TBW in relation to total body sodium. Causes of hypernatremia include water depletion, shifting of water into cells, or sodium overload. Hypernatremia causes cellular dehydration and can cause a multitude of symptoms including muscle cramps, headache, lethargy, seizures, coma, and possible intracranial hemorrhage. Severe neurologic symptoms can occur as a result of shifts of water from the brain’s intracellular to extracellular spaces. Mechanism of Action and Drug Effects Sodium is the major cation in extracellular fluid and is involved in the control of water distribution, fluid and electrolyte balance, and osmotic pressure of body fluids. Sodium also participates along with both chloride and bicarbonate in the regulation of acid-base balance. Chloride, the major extracellular anion (negatively charged substance), closely complements the physiologic action of sodium. Indications Sodium is primarily administered for the treatment or prevention of sodium depletion. Sodium chloride is the primary salt used for this purpose. Mild hyponatremia is usually treated with oral administration of sodium chloride tablets and/or fluid restriction. Pronounced sodium depletion is treated with intravenous normal saline or lactated Ringer’s solution. These drugs were discussed earlier. Hypertonic saline (3% NaCl) is sometimes used to correct severe hyponatremia. It is considered a high-alert drug because giving it too rapidly or in too high a dose can cause a syndrome known as central pontine myelinolysis, also known as osmotic demyelination syndrome. This can cause irreversible brainstem damage. A new class of drugs for the treatment of euvolemic (normal fluid volume) hyponatremia is the dual arginine vasopressin (AVP) V1A and V2 receptor antagonists. These drugs are conivaptan (Vaprisol) and tolvaptan (Samsca). This class of drugs is often referred to as vaptans. Specific information on conivaptan is listed under its drug profile. Contraindications The only usual contraindications to the use of sodium replacement products are known drug allergy to a specific product and hypernatremia. Adverse Effects The oral administration of sodium chloride can cause gastric upset consisting of nausea, vomiting, and cramps. Venous phlebitis can be a consequence of its parenteral administration. Interactions Sodium is not known to interact significantly with any drugs with the exception of the antibiotic called quinupristin/dalfopristin (Synercid). Dosages Fluid and electrolyte therapy involves replacing any deficit losses and/or providing maintenance levels for specific patient requirements. Accordingly, specific dosage amounts vary based on the patient’s situation. Drug Profiles sodium chloride Sodium chloride is primarily used as a replacement electrolyte for the prevention of or treatment of sodium loss. It is also used as a diluent for the infusion of compatible drugs and in the assessment of kidney function after a fluid challenge. Sodium chloride is contraindicated in patients who are hypersensitive to it. It is available in many intravenous preparations and in oral form as 650-mg tablets. It is classified as a pregnancy category C drug. Pharmacokinetics: Sodium Chloride Route Onset of Action Peak Plasma Concentration Elimination Half-Life Duration of Action IV Immediate Rapid Unknown Variable conivaptan Conivaptan (Vaprisol) is a nonpeptide dual-AVP, V1A and V2 receptor antagonist. It inhibits the effects of arginine vasopressin, also known as antidiuretic hormone (ADH), in the kidney. It is specifically indicated for the treatment of hospitalized patients with euvolemic hyponatremia, or low serum sodium levels at normal water volumes. Conivaptan is available for intravenous infusion. Adverse events associated with the use of conivaptan may include infusion site reactions (e.g., phlebitis, pain), thirst, headache, hypokalemia, vomiting, diarrhea, and polyuria. Closely monitor serum sodium levels during treatment, because overly rapid increases in serum sodium levels have been associated with potentially permanent adverse events, including osmotic demyelination syndrome. Several potential drug-drug interactions have been identified. Conivaptan is metabolized by the hepatic enzyme CYP3A4; coadministration of drugs that inhibit this enzyme (including but not limited to ketoconazole, itraconazole, clarithromycin, ritonavir, and indinavir) may increase serum levels. Tolvaptan (Samsca) is an oral version of conivaptan. It is available in 15- and 30-mg tablets. Tolvaptan has a black box warning stating that the patient must be in a hospital where sodium levels can be closely monitored when starting therapy. Pharmacokinetics: Conivaptan Route Onset of Action Peak Plasma Concentration Elimination Half-Life Duration of Action IV Immediate Rapid 6.7–8.6hr 12hr after infusion is stopped Nursing Process Assessment There are multiple indications for fluid and electrolyte replacement that demand close assessment of the patient’s needs. Any medications or solutions ordered must be given exactly as prescribed and without substitution. However, never take the prescriber’s order at face value without confirming the accuracy and safety of the medication order against authoritative resources (e.g., current drug reference guides, Physician’s Desk Reference, nursing pharmacology textbook, manufacturer’s drug insert). Remember that you are responsible for making sure that the drug therapy administration process—beginning with the assessment phase of the nursing process through to evaluation—is accurate, safe, and meets professional standards of care. Before administering a fluid and/or electrolyte solution, complete a thorough physical assessment as well as a review of the medications/solutions prescribed. With isotonic solutions, such as 0.9% NaCl or lactated Ringer’s solution, there is no net fluid movement from the vein into the tissues/cells. These isotonic solutions (e.g., 0.9% NaCl [NS] and lactated Ringer’s solution) are customarily used to augment extracellular volume in patients experiencing blood loss and/or severe vomiting. Isotonic NaCl is used as the diluting fluid for blood transfusions because D 5 W results in hemolysis of RBCs (in transfusions). Parenterally administered hydrating and hypotonic solutions, such as 0.45% NaCl, are indicated for the prevention and/or treatment of dehydration. When giving these fluids, there is movement of fluid from the vein into the tissues and cells. Hypertonic solutions (e.g., 3% or 5% NaCl and D 10 W) result in movement of fluids from the ISF into the veins and used for replacement of fluids and electrolytes in specific situations (see pharmacology discussion). Because of the potential risks related to the use of these solutions, they are rarely administered outside of the hospital setting. After verifying all prescriber orders and checking for accuracy and completeness (as with all drugs), the solution or product, patient, and intravenous site must be assessed (if applicable). Assess the following for infusion infusion of fluids and/or electrolytes: the solution to be infused, infusion equipment, infusion rate of the solution, concentration of the parenteral solution, and compatibilities as well as the mathematical calculations and laboratory values (e.g., serum sodium, chloride, and potassium levels). Specific assessment of the patient needs to focus on gathering information about the patient’s medical history, including diseases of the gastrointestinal, renal, cardiac, and/or hepatic systems. Obtain a medication history, including a list of prescription drugs, over-the-counter medications, supplements, and herbals. Additionally, take a dietary history, including specific dietary habits and recall of all foods consumed during the previous 24 hours. Assess fluid volume and electrolyte status through laboratory testing, as prescribed, and measurement of urinary specific gravity, vital signs, intake, and output. Because the skin and mucous membranes reflect a patient’s hydration status, be sure to assess skin turgor and/or rebound elasticity of skin over the top of the hand and other areas over the body. Document the findings as “immediate” or “delayed” rebound. Count the number of seconds that the patient’s skin stays in the “pinched-up” position, with normal return being immediately or within 3 to 5 seconds. Potassium’s normal range in the serum is 3.5 to 5 mEq/L. Serum potassium levels below 3.5 mEq/L, or hypokalemia, may result in a variety of problems, such as cardiac irregularities and muscle weakness. Early symptoms of hypokalemia include hypotension, lethargy, mental confusion, muscle weakness, and nausea. Late symptoms of hypokalemia include cardiac irregularities, neuropathies, and paralytic ileus. Avoid potassium supplementation, or use with extreme caution in patients taking ACE inhibitors or potassium-sparing diuretics (e.g., spironolactone). These drugs are associated with adverse effects of hyperkalemia and, if given with potassium supplementation, could worsen hyperkalemia and possibly result in severe cardiac dysrhythmias. Other concerns regarding potassium-related contraindications include severe renal disease, untreated Addison disease, severe tissue trauma, and acute dehydration. Because oral potassium supplements are irritants and may be ulcerogenic, perform a thorough gastrointestinal tract assessment. If oral potassium supplementation is prescribed and the patient has a history of ulcers or gastrointestinal bleeding, contact the prescriber for further instructions because oral potassium dosage forms may exacerbate these conditions. For identification and treatment of hyperkalemia, the normal range of potassium is established at 3.5 to 5 mEq/L. Realize that potassium levels of 5.3 mEq/L may be identified as abnormally high by some laboratories, whereas other laboratories may categorize 5.0 mEq/L as being abnormally high. Be sure to check institutional policy and laboratory guidelines for normal ranges and report any elevations (or decreases) in serum potassium. Symptoms of hyperkalemia include fatigue, weakness, paresthesia, palpitations, and paralysis. A serum level exceeding 5.5 mEq/L is considered, by most sources, to be toxic and dangerous to the patient. Report this laboratory value to the prescriber immediately. With close monitoring of patients, the dangerous effects of hyperkalemia (i.e., cardiac dysrhythmias) and other potentially life-threatening complications may be identified early, treated appropriately, and/or prevented. Venous access is an important issue with parenteral potassium supplementation because the vein may be irritated with infiltration or if the solution has not been mixed thoroughly before infusion. The following are some important considerations regarding assessment of peripheral veins for the purpose of access to administer intravenous potassium, sodium, fluid, and any other type of medication: (1) Assess the overall condition of the veins before selecting a site. (2) Try to use the most distal veins first. (3) Know the purpose of administering potassium and other electrolytes. (4) Calculate and set the rate, as ordered, for the infusion. (5) Know the anticipated duration of therapy. (6) Know the restrictions imposed by the patient’s history. For example, in postmastectomy patients with lymph node dissection, the affected arm must not be used. The affected arm of a patient with a stroke is to be avoided, as well. Limb circulation may be inadequate in these situations and lead to edema and other complications if used as a venous access site. Sodium is another electrolyte that is an ingredient in various intravenous replacement solutions. Hyponatremia, or serum sodium level below 135 mEq/L, if not resolved with dietary and/ Safety: Laboratory Values Related to Drug Therapy Serum Potassium Laboratory Test Normal Ranges Rationale for Assessment Serum potassium 3.5–5mEq/L The main function of potassium is the regulation of water and electrolyte content in the cell. A decrease is generally considered to be a level less than 3.5mEq/L. A serum level less than 3.5mEq/L is known as hypokalemia, and a small decrease in potassium levels may have profound effects with lethargy, muscle weakness, hypotension, and cardiac dysrhythmias. A serum potassium level greater than 5mEq/L is known as hyperkalemia and is manifested by muscle weakness, paresthesia, paralysis, and cardiac rhythm abnormalities. or oral intake, may need to be treated with parenteral infusions. Signs and symptoms of hyponatremia include lethargy, hypotension, stomach cramps, vomiting, and diarrhea. Carefully assess venous access sites because of possible irritation of the vein and subsequent phlebitis. If replacement to correct hyponatremic states is overzealous, the result may be hypernatremia with fluid overload, edema, and dyspnea. Assess baseline vital signs. Continually monitor vital signs, hydration status of the skin and mucous membranes and baseline level of consciousness. Contraindications to sodium replacement include elevated serum sodium levels, congestive heart failure, edema, and hypertension. Hypernatremia also requires careful assessment. Manifestations of hypernatremia include red, flushed skin; dry, sticky mucous membranes; increased thirst; temperature elevation; water retention (edema); hypertension; and decreased or absent urination. Identifying any precipitating events, medical concerns, and risk-prone patient situations is important in finding early treatment solutions. The individuals at most risk for hypernatremia include older adults, those with renal and cardiovascular diseases, patients who are receiving sodium supplements or excessive sodium intake and those with decreased fluid intake. Assess for cautions, contraindications, and drug interactions. When administering albumin and other colloids (e.g., dextran), assess for cautions, contraindications, and drug interactions. Contraindications include patients with heart failure, severe anemia, and renal insufficiency. The rationale is that these products cause fluids to shift from interstitial to intravascular spaces. This places more strain on the patient’s cardiac and respiratory systems. Assess the patient’s hematocrit, hemoglobin levels, and serum protein levels. Assess the patient’s blood pressure, pulse rate, respiratory status, and intake and output. Document and report any abnormal assessment findings (e.g., dyspnea, edema) immediately. Fluid infusions may also include the administration of blood or blood components. Obtain a thorough history regarding any transfusions received previously and the patient’s response. Report any history of adverse reactions to blood transfusions or problems with PRBCs and/or FFP to the prescriber and document the nature of these reactions. Assess the status of venous access areas. Monitor the patient’s hematocrit, hemoglobin, white blood cells (WBCs), RBCs, platelets, and clotting factors. Note baseline vital signs, blood pressure, pulse rate, respiratory rate, and temperature before infusing blood or blood products. Even the general appearance of the patient, energy levels, ability to carry out activities of daily living, and color of extremities are important to note. Assess for any potential drug interactions, specifically aspirin and calcium, because these may potentially alter clotting. During the infusion of blood components, assess continually for the occurrence of fever and/or hematuria (blood in the urine). Both of these findings are indicative of a reaction requiring immediate medical attention. In summary, safety and being cautious are top priorities when patients receive any drug; fluid and electrolyte replacement drugs are no exception. Deficient and/or excess fluid and electrolyte levels may pose tremendous risks to patients. A thorough assessment is critical to patient safety. In addition, because so many patients receive therapies in the home setting, there is even more accountability and responsibility for performing skillful and thorough assessment before, during, and after therapy. Human Need Statements
© Dundanim. M.S., an 85-year-old retired engineer, seems somewhat confused when his daughter comes home from work. She takes him to the emergency department, where his blood pressure is 90/62 his heart rate is 114 and his skin is dry but cool. His daughter says that he seems “much weaker” than usual, and he is unable to answer questions clearly. His daughter reports that he has “lost his appetite” lately and has not taken in much food or drink. The nurse starts an IV infusion of 0.9% sodium chloride (NS) at 100 mL/hr via a gravity drip infusion.