Electrolyte Imbalances

Sodium (Na+)

• Function:
  • Main extracellular fluid cation.
  • Maintains extracellular fluid concentration.
  • Primary determinant of extracellular osmolality.
  • Transmits nerve and muscle impulses.
• Hyponatremia (Low Sodium)
  • Causes:
    • Thiazide diuretics.
    • Adrenal gland insufficiency.
    • Drinking too much water.
    • Edema.
    • Kidney failure.
    • Heart failure.
  • Consequences:
    • Lethargy.
    • Confusion.
    • Diminished reflexes.
    • Fatigue.
    • Nausea.
    • Vomiting.
    • Seizures.
    • Coma.
    • Orthostatic hypotension and tachycardia (if hypovolemic).
    • Pitting edema (if hypervolemic).
  • Mechanism:
    • Cells are in a hypotonic solution.
    • Cells gain water, swell, and no longer function well.
• Hypernatremia (High Sodium)
  • Causes:
    • Drinking too little water.
    • Excessive sweating.
    • Loop diuretics.
    • Diabetes insipidus and mellitus.
    • Vomiting.
    • Diarrhea.
    • Burns.
    • Hyperaldosteronism.
    • Drinking seawater.
  • Consequences:
    • Irritability.
    • Confusion.
    • Seizure.
    • Coma.
    • Hypotension.
    • Tachycardia.
    • Weakness.
  • Mechanism:
    • Cells are in a hypertonic solution.
    • Cells lose water, crenate, and no longer function well.

Potassium (K+)

• Function:
  • Major intracellular cation.
  • Helps maintain intracellular osmolality.
  • Main determinant of resting membrane potential.
• Hypokalemia (Low Potassium)
  • Causes:
    • Starvation.
    • Diuretics.
    • Vomiting.
    • Diarrhea.
    • Excessive sweating.
    • Hyperaldosteronism.
  • Consequences:
    • Weakness.
    • Hyporeflexia.
    • Paresthesia.
    • Dysrhythmias.
    • Cardiac arrest.
  • Mechanism:
    • Low potassium causes hyperpolarization of cells.
    • Makes it harder to produce action potentials, including in the heart.
• Hyperkalemia (High Potassium)
  • Causes:
    • Kidney disease.
    • Adrenal insufficiency.
    • ACE inhibitors.
    • Dehydration.
    • Excessive potassium supplements.
    • Diuresis.
  • Consequences:
    • Confusion.
    • Numbness.
    • Weakness.
    • Flaccid paralysis.
    • Dysrhythmias.
    • Cardiac arrest.
  • Mechanism:
    • High potassium depolarizes cells.
    • Making repolarization difficult or impossible, including in the heart.

Chloride (Cl-)

• Function:
  • Main extracellular anion.
  • Helps maintain extracellular osmolality.
  • Associated directly with sodium and inversely with bicarbonate.
• Hypochloremia (Low Chloride)
  • Causes:
    • Loop diuretics.
    • Vomiting.
  • Consequence:
    • Not many symptoms due to hypochloremia alone, but symptoms due to associated disorders - irritability, hyperreflexia, cramping
• Hyperchloremia (High Chloride)
  • Causes:
    • Dehydration.
    • Sweating.
    • Diarrhea.
    • Kidney failure.
    • Diuretics.
    • Excessive intake of NaCl.
    • Diabetes insipidus.
  • Consequences:
    • Not many symptoms due to hyperchloremia alone, but symptoms due to associated disorders - lethargy, reduced consciousness, weakness, edema, tachypnea, hypertension, tachycardia

Calcium (Ca2+)

• Function:
  • Affects action potentials.
  • Triggers muscle contraction.
  • Activates some enzymes.
  • Cell signaling.
• Hypocalcemia (Low Calcium)
  • Causes:
    • Hypoparathyroidism.
    • Eating disorders.
    • Osteoporosis treatment.
    • Kidney failure.
    • Vit D deficiency.
    • Alkalosis.
  • Consequences:
    • Confusion.
    • Irritability.
    • Seizures.
    • Dysrhythmias.
    • Fatigue.
    • Paresthesia.
    • Hyperreflexia.
    • Muscle cramps.
  • Mechanism:
    • Neuromuscular - calcium usually inhibits some V-gated sodium channels, raising the threshold for depolarization. When \text{Ca}^{2+} is low, sodium channels reach threshold more easily, and neurons and muscles fire action potentials more easily
    • Alkalosis – blood \text{H}^+ and \text{Ca}^{2+} compete for albumin carriers. As blood \text{H}^+ decreases, more albumin binding sites are freed up, \text{Ca}^{2+} binds, and less \text{Ca}^{2+} is available
• Hypercalcemia (High Calcium)
  • Causes:
    • Hyperparathyroidism.
    • Cancer.
    • Immobility.
    • Severe dehydration.
    • Excessive supplements
  • Consequences:
    • Dysrhythmias.
    • Asystole.
    • Coma.
    • Lethargy.
    • Weakness.
    • Diminished reflexes.
    • Nausea.
    • Vomiting.
  • Mechanism:
    • \text{Ca}^{2+} usually inhibits some V-gated sodium channels, raising the threshold for depolarization. When \text{Ca}^{2+} is high, sodium channels are farther from threshold, and neurons and muscles fire fewer action potentials

Electrolytes

• Electrolytes are compounds that dissociate into ions and can conduct electric charge.
• Several electrolytes play important roles in the body, such as maintaining osmolality and resting membrane potential, cell signaling, and permitting proper conduction of action potentials.
• The major electrolytes in the body are sodium (\text{Na}^+), potassium (\text{K}^+), calcium (\text{Ca}^{2+}), chloride (\text{Cl}^-), phosphate (\text{PO}_4^{3-}), and magnesium (\text{Mg}^{2+}).
• Health care practitioners must understand electrolyte balance because it is critical to patient health and indicates whether a patient can function normally and/or function safely.