Hypokalemia is defined as a serum potassium level <3.5 mEq/L. Moderate hypokalemia is defined as serum potassium levels of 2.5 to 3 mEq/L and severe hypokalemia defined as a serum potassium level <2.5 mEq/L. The ratio of intracellular to extracellular potassium determines, in part, the cellular membrane potential. Therefore small changes in the extracellular potassium level can have large effects on the function of the cardiovascular and neuromuscular systems.
Hypokalemia is most commonly due to urinary or GI losses. A fall in serum potassium from 4.0 to 3.0 mEq/L represents an approximate loss of 200 to 400 mEq of potassium. However, these estimates do not always apply to patients with transcellular potassium redistribution. Clinical manifestations of hypokalemia are typically seen only if the serum potassium is <3.0 mEq/L.
Common acute manifestations are muscle weakness and ECG changes. More prolonged and profound hypokalemia may cause rhabdomyolysis, renal abnormalities, and cardiac arrhythmias.
The rapidity and method of potassium repletion depends on the:
severity of hypokalemia
presence of associated conditions
presence or absence of signs and symptoms
expectation of continued losses.
Obtaining an ECG is recommended for all patients with hypokalemia. Frequent monitoring of the serum potassium concentration is also recommended to ensure appropriate repletion and to avoid hyperkalemia.
- Severe diarrhea
- Laxative and bowel cleansing agent use
- Bulimia nervosa
- Anorexia nervosa
- Diabetic ketoacidosis
- Hyperosmolar hyperglycemic state
- Primary aldosteronism
- Exercising in a hot climate
- Stress response in critical illness
- Villous adenoma
- Ileal loop/conduit with ureteric implants
- Dialysis or plasmapheresis
- Apparent mineralocorticoid excess
- Cushing syndrome
- Central diabetes insipidus (DI)
- Hypokalemic periodic paralysis
- Congenital adrenal hyperplasia due to 11-beta-hydroxylase deficiency
- Renal tubular acidosis (RTA)
- Bartter syndrome
- Gitelman syndrome
- Liddle syndrome
- Renal disease associated with Sjögren syndrome
- Renal disease associated with lupus nephropathy
- Eczema involving a large surface area
- Psoriasis involving a large surface area
- Cystic fibrosis (CF)
- Primary (often psychogenic) polydipsia
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