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Hypokalemia is defined as a serum potassium concentration <3.5 mEq/L (normal range, 3.5–5 mEq/L).
Predominant sex: Male = FemaleIncidence
- Electrolyte abnormality is commonly encountered in clinical practice (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
- Associated risk after bariatric surgery
Some rare, familial disorders 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”).
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, B2 agonists ), hypokalemic periodic paralysis, intoxications (theophylline, caffeine, barium, toluene)
- Renal potassium loss:
- Drugs: Diuretics (especially loop and thiazides), amphotericin B, aminoglycosides (3,4,5)
- 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
- Glucocorticoid-excess states: Cushing syndrome, exogenous steroids, ectopic adrenocorticotrophic hormone (ACTH) production, II B hydroxysteroid dehydrogenase deficiency.
- Renal tubular acidosis (type I and II):
- Magnesium depletion
- Thyrotoxic hypokalemic paralysis
- Osmotic diuresis (e.g., poorly controlled diabetes)
Commonly Associated Conditions
Acute GI illnesses with severe vomiting or diarrhea