Pharmacology Revision: Management of Na+ Disorders

Sodium Disorders

• Normal serum Na+ level: 135-145 mEq/L
• Normal serum osmolality: 280–295 mosm/kg

Hyponatremia

• Causes:
  • Hypotonic hyponatremia
  • Isotonic hyponatremia
  • Hypertonic hyponatremia
  • Hyperproteinemia
  • Hyperglycemia
  • Lipidemia
  • Azotemia
  • Alcohol intoxication
• Treatment of severe hyponatremia (< 120 mEq/L):
  • Hypertonic saline (3%)
  • Rate of correction: 6-10 mEq/L in the 1st 24h, ≤18 mEq/L in 48h
  • Do not overcorrect Na+ levels to avoid osmotic demyelination
• Treatment of chronic asymptomatic hyponatremia:
  • Hypotonic fluids and sodium restriction
  • Demeclocycline and V2 receptor antagonists
  • Loop diuretics

Hypernatremia

• Causes:
  • Hypovolemic hypernatremia
  • Isovolemic hypernatremia
  • Hypervolemic hypernatremia
  • Inadequate water intake
  • Excess water loss
  • Diabetes insipidus
  • Conns syndrome
• Treatment:
  • Hypovolemic hypernatremia: isotonic saline
  • Isovolemic hypernatremia: hypotonic fluids (D5W) and free-water administration
  • Hypervolemic hypernatremia: diuretics
  • Target serum Na+ level: 145 mEq/L/h

Calcium Homeostasis

• Normal serum Ca2+ level: 8.5-10.2 mg/dL
• Corrected calcium in hypoalbuminemia: Corrected calcium (mg/dL) = measured total Ca (mg/dL) + 0.8 (4.0 - serum albumin [g/dL])

Hypercalcemia

• Treatment:
  • Mild hypercalcemia: adequate hydration and treating the cause
  • Moderate hypercalcemia: may not require immediate treatment
  • Severe hypercalcemia: fluids, glucocorticoids, calcitonin, bisphosphonates, and hemodialysis

Hypocalcemia

• No mention in the provided text

Potassium Disorders

• Normal serum K+ level: 3.5-5 mEq/L

Hyperkalemia

• Treatment:
  1. IV Ca2+ (in severe cases)
  2. Increasing K+ movement into cells: glucose-insulin infusion, β2 agonist nebulizer, and IV NaHCO3
  3. Removal of K+ from the body: loop diuretics, cation-exchange resins, and dialysis

Magnesium Homeostasis

• Normal serum Mg2+ level: 1.5-2.5 mEq/L
• Mechanisms of action: natural physiologic competitive antagonist of Ca2+ at L-type Ca2+ channels, NMDA receptor antagonist, and muscle relaxation
• Indications:
  • Hypomagnesemia associated with MI and diabetic coma
  • Refractory hypokalemia
  • Torsades de pointes and digitalis-induced arrhythmias
  • Seizures in preeclampsia
  • Adjuvant in anesthesia
• Adverse effects:
  • Diarrhea
  • Drowsiness
  • Hypotension
  • Asystole (rapid IV)
  • Teratogenic (fetal skeletal abnormalities)

Chronic Kidney Disease (CKD)

• Management aims:
  • Delaying the progression
  • Treating manifestations
  • Prevention of ARF
• Delaying the progression:
  1. Management of underlying cause
  2. Blood pressure control
  3. Glycemic control
  4. Reduction of proteinuria
• Treating manifestations:
  1. Edema with diuretics
  2. Ca2+/PO4 disturbances and renal osteodystrophy
  3. Anemia
  4. Hyperkalemia with cation exchange resins
  5. Acidosis with Na HCO3 capsules