A pharmacokinetically designed etomidate infusion regimen for hypnosis.

An etomidate infusion regimen for hypnosis as part of balanced, totally intravenous anesthesia was designed to maintain plasma etomidate concentrations above the awakening concentration of 300 ng/ml while avoiding dose-related side effects. The etomidate infusion regimen of 0.1 mg/kg/min for 3 min, 0.02 mg/kg/min for 27 min, and 0.01 mg/kg/min for the remainder of the anesthesia was used together with intravenous bolus doses of fentanyl, droperidol, and pancuronium. This was evaluated in 11 patients and the kinetics of etomidate were reexamined. The anesthetic technique seemed clinically satisfactory for the infusion periods of 30-109 min. The average time and plasma concentration at the end of the infusion was 59.5 min and 583 ng/ml, at awakening was 9.3 min and 307 ng/ml, and at alertness was 19.5 min and 227 ng/ml. The main difference between the kinetics observed in the present study and those of previous studies is in the elimination clearance. The average plasma elimination clearance of the present study was 1210 ml/min and the whole-blood clearance was estimated to be 1357 ml/min, giving an apparent hepatic extraction ratio of approximately 0.90. The negative correlation of patient mass and elimination clearance normalized for body mass suggests that the terminal infusion should not be adjusted to body mass.