Effects of calcium chloride on grafted internal mammary artery flow after cardiopulmonary bypass

Abstract

Objective: To examine the effects of calcium chloride (CaCl 2) administration on blood flow through the grafted left internal mammary artery (IMA) after cardiopulmonary bypass (CPB). Design: Single-arm prospective study. Setting: University-affiliated hospital operating room. Participants: Twenty adult patients scheduled for coronary artery bypass graft surgery with IMA graft. Interventions: IMA flow was measured noninvasively with a laser Doppler flow probe placed around the IMA, and measurements were recorded for 10 seconds and averaged. After separation from CPB under stable hemodynamics, baseline IMA flow was measured. CaCl 2, 15 mg/kg, was administered intravenously over 1 minute. Blood pressure, left atrial pressure, heart rate, and IMA flow were then measured at 1, 5, and 10 minutes. Coronary perfusion pressure and IMA vascular resistance were calculated. Measurements and Main Results: After CaCl 2 administration, IMA blood flow significantly decreased from baseline at 1,5, and 10 minutes (from 28 ± 9 mL/min to 19 ± 8 mL/min, 22 ± 6 mL/min, and 25 ± 4 mL/min), with gradual return toward baseline over time. Blood pressure, coronary perfusion pressure, and IMA vascular resistance significantly increased at 1 and 5 minutes after CaCl 2. Left atrial pressure and heart rate remained unchanged. No systolic regional wall motion abnormalities were detected on transesophageal echocardiography. Conclusions: CaCl 2, administered as a bolus dose after separation from CPB, transiently but significantly reduces IMA flow and can potentially trigger vasospasm, increasing the risk for myocardial ischemia or infarction in susceptible patients. Further studies are needed to determine whether this effect also occurs with nitrosodilators or phosphodiesterase inhibitors.