Patterns of postoperative systemic vascular resistance in a randomized trial of conventional on-pump versus off-pump coronary artery bypass graft surgery

Background Off-pump coronary artery bypass grafting (OPCAB) is associated with a less intense systemic inflammatory response according to biochemical markers. We studied systemic vascular resistance (SVR) as a physiologic response to systemic inflammatory response to determine any differences between OPCAB and on-pump coronary artery bypass grafting (ONCAB) in a prospective randomized trial. Methods One hundred consecutive patients were randomized to OPCAB or ONCAB, 50 in each group. Antifibrinolytics and steroids were not used. All protocols were identical except for cardiopulmonary bypass. Temperature, SVR index, cardiac index, and blood pressure were measured continuously for the first 24 hours postoperatively. All patients were reviewed at 30 days. Results There was no 30-day mortality, no stroke, and no acute renal failure. Mean temperature peaked at 37.5°C at 12 hours ( p = 0.700 between groups). Mean SVR index fell to 1,900 dyne·cm −5 ·m −2 at 12 to 18 hours; 42% of OPCAB and 32% of ONCAB patients developed very low SVR index ( −5 ·m −2 ). The incidence of high SVR (>2,500 dyne·cm −5 ·m −2 ) fell from 20% to 2% by 12 to 18 hours. The extent and pattern of SVR index responses were similar in both groups ( p = 0.840). Mean cardiac index peaked at 3.0 L·min −1 ·m −2 , 12 to 18 hours postoperatively ( p = 0.815 between groups); 84% of OPCAB and 90% of ONCAB had cardiac index greater than 2.2 L·min −1 ·m −2 at all times. Only 10% of patients required vasopressors. Blood pressure responses were also similar ( p = 0.314). Conclusions The incidence of low SVR, and patterns of SVR changes were similar in ONCAB and OPCAB, and were clinically unimportant as few patients required vasopressor support. Cardiac outputs and clinical outcomes were excellent in both groups.