Standard blood flow rates of cardiopulmonary bypass are adequate in awake on-pump cardiac surgery☆

Abstract

Standard blood flow rates for cardiopulmonary bypass have been assumed to be the same for awake cardiac surgery with thoracic epidural anesthesia (TEA) as for general anesthesia. However, compared with general anesthesia, awake cardiac surgery with epidural anesthesia may be associated with higher oxygen consumption and may result in lactic acidosis when standard blood flow rates were used. The aim of our study was to investigate if standard blood flow rates are adequate in awake cardiac surgery. Forty-five patients undergoing elective on-pump cardiac surgery were assigned to receive either epidural (Group TEA, n=15), combined (Group TEA-GA, n=15) or general (Group GA, n=15) anesthesia. To monitor the adequacy of standard blood flow rates, arterial lactate, acid base parameters, and central venous and jugular bulb saturation were measured at six time points (before, during, and after the surgery) in all groups. Blood flow rates were adjusted when needed. No lactic acidosis has developed in any group (p=NS). TEA as compared with TEA-GA and GA groups had lower central venous (67±4%, 75±11%, and 72±13%, respectively, p<0.05) and jugular bulb oxygen saturations during cardiopulmonary bypass (60±7%, 68±9%, and 75±12%, respectively, p<0.05) during the post-cardiopulmonary bypass period. The TEA group as compared with the TEA-GA and GA groups also had mild hypercapnic respiratory acidosis (56±10, 42±8, and 37±4 mmHg, respectively, p<0.05) and mild decrease of arterial oxygen saturation (93±4%, 97±2%, and 96±1%, respectively, p<0.05) at the end of surgery without any clinical consequences. Thus, no additional blood flow rates adjustments in any study group and no ventilatory support in TEA group were required. Under careful monitoring, the use of standard blood flow rates is adequate for patients undergoing awake on-pump normothermic cardiac surgery.