WARMING DURING CARDIOPULMONARY BYPASS IS ASSOCIATED WITH JUGULAR BULB DESATURATION

The objective of this study was to characterize cerebral venous effluent during normothermic nonpulsatile cardiopulmonary bypass. Thirty-one (23%) of 133 patients met desaturation criteria (defined as jugular bulb venous oxygen saturation less-than-or-equal-to 50% or jugular bulb venous oxygen tension less-than-or-equal-to 25 mm Hg) during normothermic cardiopulmonary bypass (after hypothermic cardiopulmonary bypass at 27-degrees to 28-degrees-C). Cerebral blood flow, calculated using xenon 133 clearance methodology, was significantly (p < 0.005) higher in the saturated group (33.7 +/- 10.3 mL . 100 g-1 . min-1) than in the desaturated group (26.2 +/- 6.9 mL . 100 g-1 . min-1), whereas the cerebral metabolic rate for oxygen was significantly lower (p < 0.005) in the saturated group (1.28 +/- 0.39 mL . 100 g-1 . min-1) than in the desaturated group (1.52 +/- 0.36 mL . 100 g-1 . min-1) at normothermia. The arteriovenous oxygen difference at normothermia was lower in the saturated group (3.92 +/- 1.12 mL/dL) than in the desaturated group (5.97 +/- 1.05 mL/dL). Neuropsychological testing was performed in 74 of the 133 patients preoperatively and on day 7 postoperatively. There was a general decline in mean scores of all tests postoperatively in both groups with no significant difference between the groups. We conclude that cerebral venous desaturation represents a global imbalance in cerebral oxygen supply-demand that occurs during normothermic cardiopulmonary bypass and may represent transient cerebral ischemia. These episodes, however, are not associated with impared neuropsychological test performance as compared with the performance of patients with no evidence of desaturation.