Effects of calcium infusion on function and vascular resistance in children after cardiopulmonary bypass

Calcium has important roles in systolic, diastolic, and peripheral vascular functions of the cardiovascular system. Infusion of calcium in experimental animals results in improved cardiac index (CI) and diastolic filling characteristics. However, calcium infusion increases systemic vascular resistance (SVRI) in animals made hypercalcemic. A clinically recognized phenomenon is the improvement in arterial blood pressure (ABP) that occurs with the infusion of calcium in children with presumed depressed cardiac function after cardiopulmonary bypass (CPB). We designed a study to determine if the increased ABP is the result of improved CI or is associated with raised SVRI. Hypothesis: Infusion of calcium in children after cardiac surgery with CPB results in improved ABP from increased CI, rather than raised SVRI. Methods: Following CPB, evaluation of cardiac and peripheral vascular functions were made before (Pre-Ca) and after (Post-Ca) infusion of 10 mg/kg calcium over 30 min.. M mode and Doppler measures were made using transthoracic echocardiography. CI was determined using Simpson's Method. SVRI was calculated from recorded central venous pressures and ABP. Results: Ten children were studied and completed measures made in 7. Serum ionized Ca was unchanged (1.23 and 1.31 mmol/L, pre- and post-Ca, NS). ABP rose in all patients after calcium infusion. Median increase in CI was 25%; although CI fell in 2 subjects. Median change in SVRI was 8%. SVRI rose in the 2 subjects with concomitant fall in CI. Isovolumic relaxation times, peak E and A wave velocities, and E/A ratios were unchanged. Conclusions: Infusion of a single dose of calcium to normocalcemic children raised CI, without change in diastolic function. However in 2 patients, calcium infusion also resulted in raised SVRI and diminishment of CI.