Describe the mechanism of actions and duration of effect of drugs used to lower potassium in hyperkalaemia.
A good answer to this question required the collation of knowledge from broad range of
areas, ie drug activity. Marks were divided between each of the following: 8.4%NaHCO3-,insulin/glucose, K+ exchange resin, frusemide/loop diuretics, Beta2 agonists and K+ free
fluid rehydration/dilution. Candidates often overlooked the fact that only loop diuretics and
K+ exchange resins lower total body K+ content, whilst the others induce an intracellular K+
shift which is not sustained and do not directly result in body elimination of K+. Intravenous
fluid rehydration lowers total body K+ if there is a resulting diuresis.
Most candidates just passed this question. Common omissions included NaHCO3, loop
diuretics and beta 2 agonists. No candidate mentioned rehydration/dilution. Calcium does not
lower serum potassium.