Which therapy acutely lowers serum potassium by shifting potassium into cells?

• A. Kayexalate
• B. Insulin + Dextrose
• C. IV Calcium Gluconate
• D. Hemodialysis

Answer: (B)

Shifting potassium into cells is the quickest way to acutely lower serum potassium. Insulin, given with glucose, activates Na+/K+-ATPase, which pumps potassium from the extracellular space into cells. This rapidly reduces serum K within minutes to an hour and lasts several hours, which is why it’s the go-to acute measure in hyperkalemia.

Kayexalate works by binding potassium in the gut to remove it in stool, but this has a slower onset and does not prompt an intracellular shift. Calcium gluconate helps stabilize cardiac membranes and reduce arrhythmia risk, but it does not lower the potassium level itself. Hemodialysis removes potassium from the blood directly, which lowers levels quickly as well, but the mechanism is elimination, not shifting potassium into cells.