Etomidate versus thiopental for induction of anesthesia

Hemodynamic changes and side effects of anesthesia induction with etomidate or thiopental were evaluated in 83 ASA class I or II patients. Patients were randomly assigned to one of 12 groups according to pretreatment drug (fentanyl, 100 micrograms, or normal saline intravenously), induction agent (etomidate, 0.4 mg/kg, or thiopental, 4 mg/kg), and maintenance anesthetic technique (isoflurane-oxygen, isoflurane-nitrous oxide-oxygen, or fentanyl-nitrous oxide-oxygen). The purpose of this experiment, of factorial design, was to evaluate the combined effects of two or more experimental variables used simultaneously and to observe interaction effects. There were significant increases in heart rate in all groups, especially after tracheal intubation. These increases were attenuated but not eliminated by fentanyl pretreatment. Systolic arterial blood pressure increased significantly after intubation and was not affected either by fentanyl pretreatment or by the induction agent. Patients in whom anesthesia was induced with etomidate had a greater incidence of pain on injection and myoclonus and a lesser incidence of apnea than patients in whom anesthesia was induced with thiopental. Fentanyl pretreatment significantly decreased the incidence of pain on injection and myoclonus, but it increased the incidence of apnea when anesthesia was induced with etomidate. The incidence of postoperative nausea and vomiting was similar after thiopental and etomidate and was unaffected by fentanyl pretreatment. (ABSTRACT TRUNCATED AT 250 WORDS)