The Response of the Vascular Beds to Sodium Bicarbonate in Patients During Normothermic Bypass

Objectives: Cardiopulmonary bypass (CPB) provides a unique circumstance to study the effects of drugs on the systemic vasculature. Thus, this study was designed to evaluate the effects of sodium bicarbonate on the systemic circulation during CPB in humans.Design: Randomized, double-blind study.Setting: Tertiary care university hospital.Participants: Patients presenting for coronary artery bypass graft surgery with CPB.Interventions: In this double-blind study, 22 consecutive adult patients of both sexes undergoing cardiac surgery were randomized into 2 groups. After establishing CPB and cardioplegia, patients in group 1 (n = 11) received saline (0.9%) (1.2 mL/kg), and group 2 received sodium bicarbonate (SB) (7%) (1.2 mL/kg). The blood level in the cardiotomy reservoir, pump flow, and mean arterial pressure were measured for 25 minutes.Measurements and Main Results: The SB-treated patients (group 2) showed significantly greater (p < 0.05) decreases in cardiotomy reservoir blood volume (336 ± 186 mL) than the saline-treated (140 ± 97 mL) patients. The mean arterial pressure in group 2 patients significantly (p < 0.05) increased (from 49 ± 11.9 to 65 ± 5.3 mmHg) more than in the saline group (from 50 ± 6.8 to 57 ± 9.2 mmHg) after 20 minutes. The decrease in reservoir volume significantly (p < 0.05) and inversely correlated (r = −0.61) with the acidotic state of the patients before SB.Conclusions: This study found a biphasic response to SB on the systemic circulation during CPB. Early dilation of venous capacitance vessels occurred followed by arteriolar constriction over the 20-minute study interval.