hyponatremia

• related: Nephrology, hypernatremia
• tags: #nephrology

Causes

Thiazide Induced

This patient's symptoms are most likely due to hyponatremia; an occasional, but possibly fatal complication of thiazide diuretics.  Thiazide-induced hyponatremia usually occurs within 1-2 weeks after starting the drug, more commonly in older woman with low body mass index.  One study showed that 36% of patients had a plasma sodium < 130 mEq/L and patients > age 70 had a 3.9 times higher risk of developing hyponatremia.  Thiazide diuretics cause hyponatremia by increasing sodium and potassium excretion in the cortical distal tubule and increasing medullary water reabsorption.  The concentrated urine leads to ADH-induced water retention, which further dilutes the serum and worsens the hyponatremia.  Although they work in the loop of Henle to decrease sodium reabsorption and increase excretion, loop diuretics have a lower incidence of hyponatremia because they impair medullary water reabsorption and make the medulla less responsive to ADH-induced water retention.

Patients with thiazide-induced hyponatremia usually appear clinically euvolemic but can present with dizzy spells, lethargy, malaise, vomiting, associated significant hypokalemia, and metabolic alkalosis.  Treatment involves stopping the diuretic, replacing potassium, and giving normal saline for evidence of volume depletion.  Hypertonic saline is reserved for patients with marked symptomatic hyponatremia.

Treatment

• correct 4-6 in 24 hours
• 126-135: correct K, water restriction?
• 120-125: 1L/day fluid restriction, stop diuretics, correct hypokalemia
• <120: water restriction, albumin, correct hypokalemia