Q&A Medicine>>>>>Nephrology
Question 5#

A 68-year-old man presents to the hospital with nausea, vomiting, muscle weakness, and palpitations. He has a history of ischemic cardiomyopathy and takes lisinopril, carvedilol, simvastatin, and aspirin. He recently started taking spironolactone due to an increase in heart failure symptoms. There are no recent changes in his diet, and he denies any chest pain or shortness of breath. His screening chemistry panel is shown below.

Which of the following treatments is LEAST beneficial in the acute setting?

a. Insulin
b. Calcium gluconate
c. Sodium polystyrene sulfonate
d. Furosemide

Correct Answer is C


: Sodium polystyrene sulfonate. This patient presents with symptoms and laboratory confirmation of hyperkalemia, which is likely caused by the recent addition of spironolactone to his medication regimen. Spironolactone inhibits aldosterone’s actions on the distal convoluted tubule of the nephron, which normally upregulates apical sodium channels and increases the activity of the sodium–potassium ATPase. The potential consequence is a rise in serum potassium concentration. ACE inhibitors have the effect of reducing the production of aldosterone, and therefore have a similar effect.

Sodium polystyrene sulfonate (kayexalate) is a cation exchange resin that increases potassium excretion in the GI tract and effectively removes potassium from the body; however, it takes hours to work and is the least beneficial in the acute setting. (B) The most rapid acting treatment of hyperkalemia is calcium gluconate, which acts within minutes to transiently stabilize cardiac membranes in order to prevent the fatal arrhythmogenic complications of hyperkalemia. (A) Insulin is used for its effect of increasing the activity of the sodium–potassium ATPase, driving potassium into cells. It should be given with sugar to prevent hypoglycemia. It is important to note that both calcium and insulin are important in the acute treatment but do not reduce total body potassium; they are “temporizing” measures. Sodium polystyrene sulfonate, furosemide, and hemodialysis are the only options that will reduce total body potassium. (D) Furosemide is a loop diuretic that causes potassium excretion in the urine, and takes roughly 30 minutes to work. Other options for the treatment of hyperkalemia include β2 agonists (e.g., albuterol) and bicarbonate.