Fluid and electrolyte imbalances after cardiac surgery

Patients having cardiac surgery experience a myriad of fluid and electrolyte disorders. Cardiopulmonary bypass (CPB) can cause multiple physiologic alterations, including electrolyte disturbances, acid-base imbalances, atelectasis, diminished pulmonary compliance, hemolysis, and thromboembolism. Cardioplegic solutions and induced hypothermia impose alterations in potassium metabolism and pH. The stress of surgery increases catecholamine circulation and augments antidiuretic hormone release, both of which affect fluid and electrolyte equilibrium. Dilution of the circulating blood volume from pump perfusate and volume resuscitation with crystalloid and colloid solutions produce fluid, electrolyte, and hemostatic disorders. Nonpulsatile flow produced by CPB can alter renal function. This article describes the metabolic alterations that are iatrogenically produced by cardiac surgery and the nursing and medical therapies aimed at correcting such alterations.