Hypothermia Plus Thiopental:

Abstract

Duration of EEG suppression was compared in 3 groups of patients undergoing hypothermic cardiopulmonary bypass (CPB) at 25-30.degree. C under halothane-N2O anesthesia. Group 1 (8) received 3 doses of thiopental (8 mg/kg, i.v.): for induction of anesthesia; immediately after the institution of CPB; and just after emergence from CPB. Group 2 (5) received no thiopental. Group 3 (4) received thiopental, 8 mg/kg administered i.v., during CPB only. An unexpectedly prolonged duration of EEG suppression (26.1 min) was noticed in group 1 patients with thiopental and hypothermia in combination, as compared with 4.8 min of suppression in group 2 patients during hypothermic CPB without thiopental. To rule out a possible cumulative effect of thiopental administration, group 3 patients were studied. With only a single dose of thiopental, administered during CPB, 29.3 min of EEG suppression was noticed. Mild cardiovascular depression occurred with thiopental administration during induction of anesthesia, whereas mild-to-moderate depression was associated with thiopental administration following emergence from CPB. Thiopental and hypothermia, when administered in combination in modest doses during CPB, result in profound depression of cerebral electrical activity and presumably cerebral metabolism.