The Effect of Epidural Bupivacaine on BIS Levels in the Awake Phase and on the Maintenance Doses of Propofol and Fentanyl During General Anesthesia

Background: Simultaneous administration of epidural local anesthetic agents (LA) and general anesthetics (intravenous or inhaled) is a common procedure in patients undergoing major operations. The effects of epidural anesthesia during combined general-epidural anesthesia on the alertness level (CGEA) in the awake phase and the doses of anesthetics have been reported. Objectives: The present study was designed to determine the effects of epidural bupivacaine on the alertness level measured by bispectral index (BIS) in the awake phase and the maintenance doses of propofol and fentanyl during general anesthesia for vascular operation on the lower limb. Patients and methods: A double-blinded randomized clinical trial was conducted on patients awaiting vascular surgery on lower extremities in a teaching hospital from October 2007 to October 2008. During the epidural anesthesia, the control group received 0.9% NS while 0.125% bupivacaine was injected in the case group via the epidural route. No sedative drug was utilized for epidural catheter placement. The BIS measurement was performed in both groups during the awake phase, before performing epidural anesthesia, and 10 minutes after epidural injection at 1-min intervals for 15 min. After induction of general anesthesia in both groups, anesthesia maintenance was established using the infusion of propofol with the aim of keeping the BIS level between 40 and 50 throughout the anesthesia. At the end of the study period, maintenance dose requirements of propofol and fentanyl were measured. Results: Thirty-two patients were enrolled in the study. There was no difference in BIS levels of the two groups in the awake phase. There was a significant difference between the propofol and fentanyl requirements of the two groups. Conclusions: Performing CGEA using bupivacaine was reported to reduce propofol and fentanyl doses required to maintain BIS levels between 40 and 50 considerably.