A 9-year-old child with tumor lysis syndrome has serum potassium of 6.9 mEq/L. Along with calcium gluconate and insulin-dextrose, nebulized salbutamol is administered. By what mechanism does salbutamol lower serum potassium?
- A It binds potassium in the gut lumen and promotes fecal excretion
- B It stimulates beta-2 receptors and drives potassium from the extracellular to the intracellular compartment ✓
- C It increases glomerular filtration and enhances renal potassium secretion
- D It exchanges sodium for potassium across the distal tubular epithelium
Correct answer: B. It stimulates beta-2 receptors and drives potassium from the extracellular to the intracellular compartment
Explanation
Beta-2 agonist stimulation activates the Na-K ATPase pump, shifting potassium into cells within 15 to 30 minutes and lowering serum levels by roughly 0.5 to 1 mEq/L. It is therefore a temporizing measure, not definitive elimination. Option D describes the action of cation-exchange resins such as sodium polystyrene sulfonate, and option C describes loop diuretics, neither of which acts rapidly enough for emergency control.
Reference: Katzung's Basic and Clinical Pharmacology, 16th ed.
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