Overview
This lecture covers the main fluid and electrolyte imbalances nurses must recognize, including their causes, normal lab ranges, and characteristic signs and symptoms.
Body Fluid and Electrolyte Basics
- Body water makes up about 70% of total body weight and is essential for transporting nutrients and oxygen.
- Electrolytes, substances that conduct electrical signals, include sodium, potassium, chloride, calcium, phosphate, and magnesium.
- Electrolytes regulate muscle contraction, nerve impulses, fluid balance (osmosis), bone health, and acid-base balance.
Regulation and Causes of Imbalances
- Electrolytes are gained from food and drinks and absorbed in the gut.
- Kidneys filter blood, adjusting electrolyte levels, and excrete excess in urine.
- Renal dysfunction, diuretics, fluid loss (vomiting, diarrhea, burns, NG suction), hormone disorders, and certain medications can cause imbalances.
Sodium (Na+)
- Normal range: 135–145 mEq/L.
- Hyponatremia (<135): causes include diuretics, GI loss, excess water (SIADH, CHF), and Addison’s disease.
- Signs (SALT LOSS): Seizures, abdominal cramp, lethargy, tendon reflex decrease, loss of urine/appetite, orthostatic hypotension, shallow respiration, muscle spasm.
- Hypernatremia (>145): causes include Cushing’s, Conn’s, hypertonic fluids, dehydration, DI, burns, excess intake.
- Signs (FRIED): Fatigue, restlessness, increased reflexes, extreme thirst, decreased urine, dry skin/mouth.
Chloride (Cl-)
- Normal range: 95–105 mEq/L.
- Follows sodium; maintains acid-base balance and digestion.
- Hypochloremia: causes—GI loss, diuretics, burns, CF, fluid overload, SIADH, metabolic alkalosis.
- Symptoms: Dehydration, tachycardia, low BP, fever, lethargy.
- Hyperchloremia: causes—too much Na+, dehydration, low bicarb, Conn’s, corticosteroids, acidosis.
- Symptoms: Similar to hypernatremia/acidosis.
Potassium (K+)
- Normal range: 3.5–5 mEq/L.
- Main intracellular cation; essential for muscle/nerve function.
- Hypokalemia: causes—loop diuretics, corticosteroids, insulin, GI loss, starvation.
- Signs (7 L’s): Lethargy, low respirations, lethal arrhythmias, lots of urine, leg cramps, limp muscles, low BP/HR.
- Hyperkalemia: causes—cell/tissue damage, Addison’s, renal failure, K+-sparing diuretics, ACE inhibitors, NSAIDs.
- Signs (MURDER): Muscle weakness, urine low/none, respiratory failure, decreased cardiac contractility, early twitching, rhythm changes (tall T waves).
Calcium (Ca2+)
- Normal range: 8.5–10.5 mg/dL.
- Needed for bone/teeth, nerve/muscle activity, clotting.
- Hypocalcemia: causes—parathyroid issues, low intake, low vitamin D, CKD, meds.
- Signs (CRAMPS): Convulsions, hyperactive reflexes, arrhythmias (prolonged QT), muscle spasms, positive Trousseau’s/Chvostek’s, paresthesia.
- Hypercalcemia: causes—overactive parathyroid, excess vitamin D/calcium, bone mets, thiazides, lithium.
- Signs (WEAK): Weak muscles, EKG changes (short QT), absent reflexes, abdominal distension, kidney stones.
Magnesium (Mg2+)
- Normal range: 1.5–2.5 mg/dL.
- Important for ATP function, muscle/nerve, BP, and with Na+/K+ pump.
- Hypomagnesemia: causes—poor intake, malabsorption, PPIs, alcoholism, low Ca/K+.
- Signs (TWITCH): Trousseau’s/Chvostek’s, weakness, increased reflexes, torsades, tetany, low Ca/K+, hypertension.
- Hypermagnesemia: causes—overcorrection, preeclampsia treatment, renal failure.
- Signs (LETHARGIC): Lethargy, EKG changes, tendon reflex absence, hypotension, arrhythmia, flushing, N/V, impaired breathing, confusion.
Phosphate (PO4^3-)
- Normal range: 2.5–4.5 mg/dL.
- Functions in bones/teeth, energy, regulated by parathyroid and vitamin D.
- Hypophosphatemia: causes—antacids, starvation/refeeding, overactive parathyroid, low vitamin D.
- Signs (BONE): Bone pain, osteomalacia, neuro changes, erythrocyte destruction.
- Hyperphosphatemia: causes—laxatives, renal failure, too much vitamin D, rhabdomyolysis, hypoparathyroid.
- Symptoms: Similar to hypocalcemia (convulsions, reflexes, arrhythmias, spasms, itching, positive signs).
Key Terms & Definitions
- Electrolyte — ions in body fluids that regulate electrical and physiological functions.
- Osmosis — movement of water across a membrane to balance solute concentration.
- SIADH — syndrome with excess ADH causing water retention and dilutional hyponatremia.
- Trousseau’s sign — hand/finger spasm with BP cuff inflation, suggests hypocalcemia.
- Chvostek’s sign — facial muscle twitching when tapped, seen in hypocalcemia.
- Tetany — muscle cramps/twitches from low calcium or magnesium.
- Rhabdomyolysis — muscle breakdown releasing electrolytes into blood.
Action Items / Next Steps
- Review the individual electrolyte imbalance playlists for focused nursing interventions and treatments.
- Complete the free quiz to test understanding of fluid and electrolyte concepts.