Thiopental as an adjunct to hypothermia for EEG suppression in infants prior to circulatory arrest

Fifteen infants were studied to evaluate the effect of profound hypothermia (16°C to 18°C) and hypothermia plus thiopental on the electroencephalogram (EEG) prior to circulatory arrest. Mean patient age and weight were 5.5 ± 1.2 months and 4.9 ± 0.3 kg, respectively. After core cooling on cardiopulmonary bypass (CPB), all patients received thiopental, 8 mg/kg, 5 minutes prior to circulatory arrest. Satisfactory EEG recordings were obtained for 9 patients, and serum thiopental concentration was measured in 12 patients. Hypothermia (mean venous return temperature, 17.8°C ± 1.6°C) alone was associated with persistent cerebral electrical activity in 8 of 9 patients (89%). The addition of thiopental, 8 mg/kg, produced an isoelectric EEG in 6 of these 8 patients (75%). Mean circulatory arrest duration was 44 ± 4 minutes. EEG activity resumed after reinstitution of CPB in all patients. Serum thiopental concentration at the end of CPB was negligible. It is concluded that hypothermia alone often may not produce EEG isoelectricity, and that the associated cerebral metabolic activity may be suppressed by adjunctive use of thiopental.