Increasing mean arterial blood pressure has no effect on jugular venous oxygen saturation in insulin-dependent patients during tepid cardiopulmonary bypass

Preexisting diabetes mellitus is one of the major factors related to adverse postoperative neurological disorders after cardiac surgery. In previous reports, we found that diabetic patients more often experienced cerebral desaturation than nondiabetic patients during normothermic cardiopulmonary bypass (CPB). The purpose of this study was to examine the effects of increasing mean arterial blood pressure (MAP) by the administration of phenylephrine on internal jugular venous oxygen hemoglobin saturation (SjVo(2)) during tepid CPB in diabetic patients. We studied 20 diabetic patients scheduled for elective coronary artery bypass graft surgery and, as a control, 20 age-matched nondiabetic patients. After the induction of anesthesia, a fiberoptic oximetry catheter was inserted into the right jugular bulb to monitor Sjvo(2), After measuring the baseline partial pressure of the arterial and jugular venous blood gases and cardiovascular hemodynamic values, MAP was increased by the repeated administration of a 10-mug bolus of phenylephrine until it reached 100% of baseline values. There was a significant difference in Sjvo(2), value between the Diabetic and Control groups after the administration of phenylephrine (Diabetic group, 56% +/- 6%; Control group: 60% +/- 4%) (P < 0.05). There was a significant difference in the arterial-jugular oxygen content difference value between the Diabetic and Control groups after the administration of phenylephrine (diabetic group, 4.9% +/- 0.6%; Control group, 45% +/- 0.4%) (P < 0.05). We subdivided the Diabetic group into three groups (Diet Therapy group [n = 4], Glibenclamide group [n = 10], and Insulin-Dependent group [n = 6]). There was a significant difference in the mean slopes of Sjvo(2), versus cerebral perfusion pressure for increasing cerebral perfusion pressure between the Insulin-Dependent group and the other groups (Dunnett test: P = 0.04). Increasing MAP had no effects on the Sjvo(2), value in insulin-dependent patients during tepid CPB.