Key Concepts: Fluids and Electrolytes

Cell Membrane Transport

• Homeostasis: Balance of fluids and solutes in the body.
• Transport Processes:
  • Diffusion:
    • Simple Diffusion: Passive; molecules move from high to low concentration (e.g., oxygen, carbon dioxide).
    • Facilitated Diffusion: Passive; uses helper proteins for larger, charged molecules (e.g., glucose, ions).
  • Active Transport: Movement against concentration gradient using ATP.
  • Osmosis: Movement of water through a semi-permeable membrane from low to high solute concentration; passive.
  • Hydrostatic Pressure: Pushes water across capillary walls.
  • Oncotic Pressure (Colloidal Osmotic Pressure): Pulls water into capillaries, influenced by albumin.

Hormones and Fluid Regulation

• Renin-Angiotensin-Aldosterone System (RAAS):
  • Activated by low blood pressure.
  • Increases blood pressure by retaining water and sodium.
• Thirst Mechanism: Responds to high blood osmolality.
• Hormones:
  • ADH (Antidiuretic Hormone): Prevents diuresis, retains water.
  • Aldosterone: Retains sodium and water, excretes potassium.
  • Natriuretic Peptides (ANP, BNP): Counteracts RAAS, preventing fluid overload.

Lab Values

• Complete Blood Count (CBC): RBCs, WBCs, Platelets.
• Arterial Blood Gases (ABGs): Acid-base status.
• Metabolic Panels: Electrolytes, renal function, liver enzymes.
• Coagulation Levels: PT, INR, APTT.
• Lipid Panels: Cardiovascular risk.
• Drug Levels: For drugs with narrow therapeutic ranges.

Electrolyte Imbalances

• Sodium (Na+): Normal: 135-145 mEq/L
  • Hyponatremia: Seizures, cramps, lethargy.
  • Hypernatremia: Thirst, restlessness, dry mouth.
• Potassium (K+): Normal: 3.5-5 mEq/L
  • Hypokalemia: Weakness, arrhythmias.
  • Hyperkalemia: Muscle weakness, cardiac changes.
• Calcium (Ca2+): Normal: 8.5-10.5 mg/dL
  • Hypocalcemia: Tetany, muscle spasms.
  • Hypercalcemia: Weakness, kidney stones.
• Magnesium (Mg2+): Normal: 1.5-2.5 mg/dL
  • Hypomagnesemia: Muscle cramps, seizures.
  • Hypermagnesemia: Lethargy, diminished reflexes.

IV Fluid Types

• Isotonic Solutions: 0.9% Normal Saline, Lactated Ringers.
• Hypotonic Solutions: Used for cellular dehydration.
• Hypertonic Solutions: Used for severe hyponatremia or cerebral edema.

Fluid Volume Imbalances

• Hypervolemia (Fluid Overload):
  • Caused by excessive fluid intake, heart failure.
  • Symptoms: Edema, high blood pressure, pulmonary edema.
• Hypovolemia (Fluid Deficit):
  • Causes: Vomiting, diarrhea, excessive sweating.
  • Symptoms: Dry skin, low blood pressure, tachycardia.

Hypovolemic Shock

• Causes: Blood loss, severe dehydration.
• Stages: Class 1 (asymptomatic) to Class 4 (severe shock).
• Treatment: Fluid replacement, control bleeding.

Nursing Interventions

• Monitor: Vital signs, intake/output, daily weights.
• Administer: IV fluids, diuretics as needed.
• Educate: Patient and family on fluid restrictions, signs of imbalance.

Lab Monitoring

• Regularly check electrolytes levels, renal function, and fluid balance indicators.

These notes cover the essentials of fluid and electrolyte management, including hormonal regulation, imbalances, IV fluid types, and relevant nursing interventions. They provide a fundamental understanding necessary for clinical practice and exams related to this topic.