Nitric oxide production is more prominent in off-pump than in on-pump coronary artery bypass surgery

Abstract

The aim of our study was to elucidate the extent to which cardiopulmonary bypass contributes to endogenous nitric oxide (NO) production in patients undergoing coronary artery bypass grafts (CABG). One-hundred-and-sixteen patients undergoing elective CABG with (on-pump, n=66) and without cardiopulmonary bypass (off-pump, n=50) were included. Urinary nitrite/nitrate (NOx) excretion was measured as an index of endogenous NO production during the first two postoperative days. Haemodynamic profiles, serum CK-MB and C-reactive protein (CRP) concentrations were measured after the operation. There was no significant difference in urinary NOx/creatinine (Cr) excretion on day one post CABG. The mean urinary NOx/Cr excretion ratio significantly (P <0.01) decreased from days one to two in the on-pump group, but not in the off-pump group. The mean urinary NOx/Cr excretion ratio was significantly (P < 0.01) higher in the off-pump group (0.51 ± 0.26 μmol/mg) than in the on-pump group (0.38 ± 0.20 μmol/ mg) on day two. The mean serum CRP concentration was also significantly (P <0.01) higher in the off-pump group than in the on-pump group on day two. There was no significant difference in the mean cardiac index or the mean systemic vascular resistance index between the two groups after surgery. The mean serum CK-MB concentration was significantly (P<0.05) lower in the off-pump group than in the on-pump group on days one and two. These findings suggest that endogenous NO production is stimulated by a surgical inflammatory response and that the cardio-pulmonary bypass procedure per se is not the inciting stimulus for NO production in patients undergoing CABG.