Midazolam-fentanyl anesthesia for major surgery. Plasma levels of midazolam during prolonged total intravenous anesthesia

Abstract

The water-soluble benzodiazepine midazolam was used along with fentanyl and pancuronium in a totally intravenous anesthetic technique for hysterectomies. Midazolam was given as a 0.3 mg X kg-1 bolus dose followed by constant rate infusion of 0.25 mg X kg-1 X h-1. Plasma midazolam concentrations were measured during the anesthesia. The technique provided excellent conditions for surgery, with pulse rate and blood pressure under good control and without any recall of the peri-operative period. A disadvantage was early respiratory depression, which necessitated administration of naloxone to make extubation possible. This was attributed to the proportionally large amount of fentanyl used. Drowsiness during the first postoperative hours was also pronounced.