A 43-year-old woman develops acute renal failure following an emergency resection of a leaking abdominal aoic aneurysm. One week after surgery, the following laboratory values are obtained: Serum electrolytes (mEq/L): Na + 127, K+ 5.9, Cl - 92, HCO3 - 15 Blood urea nitrogen: 82 mg/dL Serum creatinine: 6.7 mg/dL The patient has gained 4 kg since surgery and is mildly dyspneic at rest. Eight hours after these values are repoed, the following electrocardiogram is obtained. Which of the following is the most appropriate initial treatment in the management of this patient?

The electrocardiogram demonstrates changes that are essentially diagnostic of severe hyperkalemia. Correct treatment for the affected patient includes discontinuation of exogenous sources of potassium, administration of a source of calcium ions (which will immediately oppose the myocardial effects of potassium), and administration of sodium bicarbonate (which, by producing a mild alkalosis, will shift potassium into cells); each will temporarily reduce serum potassium concentration. Infusion of glucose and insulin would also effect a temporary transcellular shift of potassium. However, these maneuvers are only temporarily effective; definitive treatment calls for removal of potassium from the body. The sodium-potassium exchange resin sodium polystyrene sulfonate (Kayexalate) would accomplish this removal, but over a period of hours and at the price of adding a sodium ion for each potassium ion that is removed. Hemodialysis or peritoneal dialysis is probably required for this patient, since these procedures also rectify the other consequences of acute renal failure, but they would not be the first line of therapy, given the acute need to reduce the potassium level. Both lidocaine and digoxin would be not only ineffective but contraindicated, since they would fuher depress the myocardial conduction system.