Ionized calcium concentration and cardiovascular function after cardiopulmonary bypass.

Patients who required cardiopulmonary bypass were studied to determine the postoperative incidence of hypocalcemia and to quantify the effects of intravenous (IV) calcium chloride on ionized calcium (Ca++) concentration in blood and on cardiac function. Patients either received no calcium chloride postoperatively (control), or received it as an intermittent IV bolus (5 mg/kg) or as a constant infusion (0.5 mg/kg/min) whenever Ca++ concentration was less than 1.8 mEq/L. Hemodynamic profiles were determined every 15 minutes during the first two postoperative hours. Regardless of Ca++ concentration and therapy, cardiac indices, stroke indices, and vascular resistances of all patients never differed significantly. No variable changed consistently, other than Ca++ concentration, in those patients receiving calcium chloride. We conclude that postoperative hypocalcemia occurs frequently after cardiopulmonary bypass surgery, but not to the degree that would be expected to cause cardiovascular depression, and is readily corrected with IV calcium chloride. Myocardial depression occurred in all patients, but likely resulted from other causes.