Preservation of endothelium nitric oxide release during beating heart surgery with respect to continuous flow cardiopulmonary bypass

Abstract

A correlation between perfusion modality and vascular dilation induced by endothelial nitric oxide (NO) release has been pointed out in the literature; nevertheless, only a few studies deal with the analysis of patients treated by cardiac surgery. The aim of this work is to analyze endothelial NO release in patients undergoing cardiac surgery under continuous flow cardiopulmonary bypass (CPB) or pulsatile perfusion. Pulsatile devices approved for clinical CPB do not accurately reproduce the physiological flow waveform provided by the left ventricle while, on the other hand, it is important to analyze pulsatile perfusion under both physiological flow waveform and pulsatile flow CPB. Physiological pulsatile perfusion (supplied by the left ventricle) was examined in this study. A total of 16 patients undergoing cardiac surgery were enrolled in the study and divided into two groups: 8 patients were put on continuous flow CPB while the others underwent beating heart surgery. Venous blood samples were withdrawn to quantify endothelial NO release through its bioactive forms in blood. Plasma was used for the chemiluminescent detection of nitrite (NO2—) and nitrate (NO3—), and the cellular component for electron spin resonance detection of nitrosylhemoglobin. Significant reduction in the intraoperative concentration with respect to the preoperative was observed only in the continuous group for both NO2— and NOx (NO2— + NO3—) concentration (p=0.003 and p=0.016, respectively). A significant difference in the intraoperative nitrite concentration was also observed between the groups (p=0.006). Nitrosylhemoglobin concentration, although not instrumentally detectable, resulted as negligible with respect to the other NO metabolites. Despite the small number of patients belonging to each group, this significant reduction of NO2— concentration under continuous flow CPB revealed a strong dependence on endothelial NO release and plasma nitrite concentration on perfusion modality.