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Hypokalemia is defined as a serum potassium concentration <3.5 mEq/L (normal range, 3.5 to 5.0 mEq/L).
- Mild hypokalemia (serum potassium 3.0 to 3.5 mEq/L)
- Moderate hypokalemia (serum potassium 2.5 to 3.0 mEq/L)
- Severe hypokalemia (serum potassium <2.5 mEq/L)
Predominant sex: male = female
- Electrolyte abnormality is commonly encountered in clinical practice and in the elderly (1).
- Found in >20% of hospitalized patients (when defined as potassium <3.6 mEq/L)
- Higher incidence (5–20%) in individuals with eating disorders
- >10% of inpatients with alcoholism
- Higher incidence in patients with AIDS
- Higher incidence in patients receiving diuretics
- 12–18% in patients with CKD
- Associated risk after bariatric surgery
Etiology and Pathophysiology
Most common causes:
- Decreased intake: deficient diet in alcoholics and elderly; anorexia nervosa
- GI loss: vomiting, diarrhea, nasogastric tubes, laxative abuse, fistulas, villous adenoma, ureterosigmoidostomy, malabsorption, chemotherapy, radiation enteropathy, bulimia
- Intracellular shift of potassium: metabolic alkalosis, insulin excess, β-adrenergic catecholamine excess (acute stress, β2-agonists), hypokalemic periodic paralysis, intoxications (theophylline, caffeine, barium, toluene)
- Renal potassium loss
- Drugs: diuretics (especially loop and thiazides), amphotericin B, aminoglycosides
- Mineralocorticoid excess states: primary hyperaldosteronism; secondary hyperaldosteronism (congestive heart failure [CHF], cirrhosis, nephrotic syndrome, malignant hypertension, renin-producing tumors); renovascular hypertension; Bartter syndrome; Gitelman syndrome; congenital adrenogenital syndromes; exogenous mineralocorticoids (glycyrrhizic acid in licorice, carbenoxolone, steroids in nasal sprays); Liddle syndrome; vasculitis
- Osmotic diuresis (e.g., poorly controlled diabetes)
- Renal tubular acidosis (type I and II)
- Magnesium depletion
- Glucocorticoid excess states: Cushing syndrome, exogenous steroids, ectopic adrenocorticotrophic hormone production, II-β-hydroxysteroid dehydrogenase deficiency, refeeding syndrome
Some rare, familial disorders can cause hypokalemia.
- Familial hypokalemic periodic paralysis: hypokalemia after a high-carbohydrate or high-sodium meal or after exercise
- Congenital adrenogenital syndromes
- Liddle syndrome: increases K+ secretion
- Familial interstitial nephritis
When initiating a diuretic, especially loop and thiazide diuretics, advise patients to increase their dietary potassium intake (see “Diet”).