Symptomatic hypokalemia

Specialty: Endocrine and metabolic.

• symptomatic low plasma potassium
• hypokalemia of endocrine origin
• hypokalemic neuromuscular weakness

Why it occurs

• Primary hyperaldosteronism or Conn syndrome (aldosterone-producing adenoma or bilateral adrenal hyperplasia that promotes excessive sodium reabsorption and active secretion of potassium and hydrogen ions in the cortical collecting duct)
• Cushing syndrome (extreme excess of cortisol exceeds the inactivation capacity of the 11-beta-HSD2 enzyme and saturates the mineralocorticoid receptors, causing massive kaliuresis)
• Renal tubular acidosis type 1 distal or type 2 proximal (potassium loss due to dysfunction in bicarbonate management or proton secretion)
• Gitelman or Bartter syndrome (congenital salt-wasting tubulopathies with stimulation of the renin-aldosterone axis and severe kaliuresis)
• Recovery phase of diabetic ketoacidosis (insulin therapy rapidly introduces potassium to the intracellular space, unmasking or aggravating pre-existing hypokalemia)

Initial workup

Basal serum potassium (typically symptomatic below 3.0 mEq/L); arterial blood gas to evaluate the acid-base balance (metabolic alkalosis leads to mineralocorticoid excess, metabolic acidosis to renal tubular acidosis); potassium in 24-hour urine or potassium/creatinine ratio in isolated urine sample; plasma renin activity (PRA) and plasma aldosterone concentration (CAP) to rule out primary hyperaldosteronism; urinary free cortisol; and continuous 12-lead electrocardiogram.

Standard management

• Potassium chloride — intravenous administration at doses of 10-20 mEq/hour through a peripheral or central line diluted exclusively in 0.9% physiological saline solution under continuous cardiac monitoring, reserved for potassium less than 2.5 mEq/L or presence of arrhythmias or paralysis; never administer as a direct bolus
• Potassium gluconate syrup or extended-release potassium chloride tablets — oral replacement in stable mild to moderate cases without neuromuscular compromise
• Spironolactone — competitive aldosterone receptor antagonist, indicated to correct kaliuresis and control hypertension in primary hyperaldosteronism, at doses of 25-100 mg/day
• Amiloride — potassium-sparing diuretic that blocks the epithelial sodium channel ENaC in the collecting duct, useful if there is intolerance to spironolactone or in specific tubular syndromes