[Total intravenous anesthesia with continuous infusion of midazolam--study on plasma levels of midazolam and catecholamines].

: Total intravenous anesthesia was performed with continuous infusion of midazolam and bolus injection of fentanyl. A bolus injection of midazolam 0.3 mg.kg-1 was followed by an infusion regimen with an initial infusion rate of 0.68 mg.kg-1.hr-1 for 15 min followed by a maintenance infusion of 0.125 mg.kg-1.hr-1 and infusion was stopped at about 30 min before the end of operation. Fentanyl and pancuronium were injected as required. Nicardipine was given for intraoperative hypertension. Plasma concentrations of epinephrine and norepinephrine decreased significantly at 10 min after induction, but increased significantly during operation. Therefore, this anesthetic method was considered not to be so deep. Plasma concentrations of midazolam were higher than 200 ng.ml-1 during operation. After discontinuation of midazolam infusion, its concentration decreased quickly, and the elimination half life of midazolam was 1.675 +/- 0.2807 hr. The value was not so large as we had anticipated. Total intravenous anesthesia with continuous infusion of midazolam and bolus injection of fentanyl is thought to produce light anesthesia. Plasma concentration of midazolam decreased quickly.