Isoflurane decreases the cortisol response to cardiopulmonary bypass

Eighteen patients with normal left ventricular function scheduled for elective myocardial revascularization were anesthetized with fentanyl (52-58 micrograms/kg). At the beginning of hypothermic cardiopulmonary bypass (CPB) they were assigned to a control (C) group (n = 6) that did not receive further anesthesia, or to a group given either 1% isoflurane (n = 6) or 2% isoflurane (n = 6). Blood samples for measurement of total plasma cortisol concentrations were obtained before, during, and after CPB. Hemodynamic measurements before and after CPB were not different among groups. Patients in group C required higher infusion rates of sodium nitroprusside (P less than or equal to 0.05) and patients given 2% isoflurane received more phenylephrine (P less than or equal to 0.05) to keep mean arterial pressure at 50 +/- 10 mm Hg during CPB. Isoflurane caused a dose-related decrease in total plasma cortisol concentrations during and after CPB. We conclude that increased depth of anesthesia attenuates the cortisol (stress) response to cardiopulmonary bypass.