Nitric oxide activity in patients undergoing cardiopulmonary bypass

Abstract

It is well known that cardiopulmonary bypass (CPB) causes major hemodynamic and physiologic disturbances. These may be alleviated by replacing conventional nonpulsatile perfusion with pulsatile flow, which under normothermic conditions results in a lower peripheral vascular resistance, associated with lower plasma angiotensin II and vasopressin levels, t, 2 It is also known that release of the endogenous vasodilator nitric oxide (NO) is sensitive to flow pulsatility, 3' 4 a mechanism that may contribute to the improved peripheral hemodynamics associated with pulsatile perfusion. We therefore tested the hypothesis that higher NO activity is associated with pulsatile flow than with nonpulsatile flow during and immediately after normothermic CPB. We also investigated whether hypothermic CPB modulated any observed differences.Twenty-four patients without diabetes who were undergoing elective CPB (2.4 L-min -1. m -2) for coronary artery bypass grafting were randomly assigned to four groups: 37 ° C with pulsatile flow, 37 ° C with nonpulsatile flow, 28 ° C with pulsatile flow, and 28 ° C with nonpulsatile flow (n = 6 per group). There were no differences among the groups with respect to age (mean for 24 patients of 59.3 years), number of arteries grafted (median for all groups of 3), crossclamp time (mean for 24 patients of 33.9 minutes), or smoking habits. The same anesthetic regimen (methohexitone, fentanyl, midazolam, and enflurane) was employed for all subjects. Preoperative use of /3-blockers, calcium antagonists, oral nitrates, and aspirin did not differ among the groups; any nitrate medications were discontinued at least 12 hours before operation and were not recommenced until after our investigation. In each patient, arterial blood pressure, cardiac output (by thermal dilution), and gastric mucosal blood flow (by laser Doppler velocimetry) were measured, and peripheral vascular resistance was calculated. Sampling of peripheral venous blood for plasma nitrite plus nitrate (index of NO activity) was achieved at the following time points: 45 minutes after induction of anesthesia (time point A, baseline); 10 minutes (B) and 20 minutes (C) after commencement of CPB; 10 minutes after release of the aortic crossclamp (D); and 10 minutes (E) and 30 minutes (F) after CPB was discontinued. Plasma nitrite plus

Pulsatile flow during cardiopulmonary bypass preserves postoperative microcirculatory perfusion irrespective of systemic hemodynamics

“…The beneficial effects of pulsatile flow on microcirculatory perfusion are in agreement with findings by others who showed that pulsatility reduced markers of endothelial damage and improved gastric mucosal oxygenation and tonometry (24,28). Here we confirm these findings by direct measurements of microcirculatory perfusion.…”

“…A recent crossover study by Elbers et al (10) showed no difference in microcirculatory perfusion after 10 min of either pulsatile or nonpulsatile CPB, but their conclusions were limited by the study design. In contrast, laser-Doppler flow or gastric tonometry measurements indirectly indicated that pulsatility may preserve microvascular perfusion (13,24,28). At similar mean arterial pressures, pulsatile flow was associated with a 10 -15% more energy equivalent pressure than nonpulsatile flow (37), which has previously been suggested to be a prerequisite to overcome the critical capillary closing pressure (43).…”

Preservation of Endothelium Nitric Oxide Release by Pulsatile Flow Cardiopulmonary Bypass When Compared With Continuous Flow

“…In the majority, different perfusion modes are given to the same subject following one another, but this change in perfusion modality affects other mechanisms involved in NO release (11)(12)(13), and consequently alters NO release measurement. Moreover, only few studies concern the analysis of human patients undergoing cardiac surgery (14)(15)(16).…”

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

“…Balligand et al recently published a complete review about this phenomenon. 4 Many studies concerning ex vivo analyses of released NO 4,5 or in vivo studies on animals or humans who underwent CPB under different perfusion modalities 4,[6][7][8][9][10] can be found in the literature. However, despite the large number of ex vivo or animal studies, only a few papers deal with human patients undergoing cardiac surgery.…”