The effect of diabetes on the interrelationship between jugular venous oxygen saturation responsiveness to phenylephrine infusion and cerebrovascular carbon dioxide reactivity.

In this study, we examined whether cerebrovascular carbon dioxide (CO(2)) reactivity was related to the response of jugular venous oxygen saturation (SjvO(2)) to phenylephrine infusion in diabetic patients during cardiopulmonary bypass. Forty diabetic patients scheduled for coronary artery bypass graft surgery were studied, and 40 age-matched nondiabetic cardiopulmonary bypass patients served as controls. Cerebrovascular CO(2) reactivity was measured continuously using transcranial Doppler. Mean arterial blood pressure (MAP) was increased by repeated phenylephrine infusion until reaching 100% of baseline values. There was a significant difference in absolute CO(2) reactivity between the diabetic and control groups (controls, 2.8 +/- 0.7 cm. s(-1). mm Hg(-1); diabetics, 2.2 +/- 1.1 cm. s(-1). mm Hg(-1); P = 0.02). Among the diabetics, absolute CO(2) reactivity in insulin-dependent patients was less than that in noninsulin-dependent patients (diet therapy group, 3.2 +/- 0.7; glibenclamide group, 2.6 +/- 0.7; insulin-dependent group, 1.0 +/- 0.7; P < 0.01). There was a correlation between absolute CO(2) reactivity and the mean slope of SjvO(2) versus MAP for increasing MAP (r = 0.54; P < 0.0001). In conclusion, we found that the interrelationship between SjvO(2) responsiveness to phenylephrine infusion and cerebrovascular CO(2) reactivity, as well as impaired cerebrovascular autoregulation, were associated with previous hyperglycemia.