Wakefulness during cesarean section after anesthetic induction with ketamine, thiopental, or ketamine and thiopental combined.

Thirty-six pregnant women (ASA class I or II) at term who underwent general anesthesia and cesarean section received either ketamine, 1 mg/kg (n = 12); thiopental, 4 mg/kg (n = 13); or a combination of ketamine, 0.5 mg/kg, and thiopental, 2 mg/kg (n = 11). A blood pressure cuff inflated to 250 mm Hg isolated one arm from the effects of succinylcholine so that awareness during anesthesia could be assessed by asking the patient to move her hand. Although only one patient receiving ketamine responded to commands during anesthesia, 46% of patients receiving either thiopental or the combination responded to commands intraoperatively. No patient hallucinated, the incidence of dreams was low (11%), and no postoperative dysphoria was noted. Three patients (8%) had postoperative recall of intraoperative awareness; one had received thiopental and two the combination. Maternal intraoperative cardiovascular responses among the groups were similar, as were umbilical blood gas values, newborn Apgar scores, and neonatal neurobehavioral test scores at 4 and 24 hr. Ketamine more effectively blocked maternal responsiveness to commands and strong stimuli during the first few minutes after anesthetic induction for cesarean section than did thiopental or a combination of thiopental and ketamine, each at a lower dose.