TITLE: BISPECTRAL INDEX (BIS) ANALYSIS OF ANESTHESIA DEPTH AND ANESTHETIC REQUIREMENTS DURING PARTIAL HEPATECTOMY AND LIVER TRANSPLANTATION

AUTHORS: Piotr K. Janicki, MD, PhD, Mike Higgins, MD, MPH, Russ Weitman, BSc, Garry Walker, MD, Leopoldo Rodriguez, MD, Charles Beattie, MD
AFFILIATION: Vanderbilt University Hospital, Nashville, TN.

INTRODUCTION: Liver transplantation (LT) is associated with increased post-operative levels of opioid peptides and patients after LT experience less pain and require less analgesic, compared with control patients undergoing partial hepatectomy (PH).^1,2 The comparison of anesthetic requirements during the intraoperative period has never been investigated. To answer this question we performed the study with the following goals 1: To evaluate and compare baseline BIS readings before induction and during anesthesia for LT and PH; 2. To determine if the sufficient anesthesia depth (quantified by BIS) requires different amounts of delivered anesthetics in LT and PH groups.
METHODS: Twenty patients undergoing LT (N=10) and PH ( N=10) were enrolled into the IRB approved study. Five minutes of BIS baseline recordings were obtained before induction. After standard premedication (midazolam and fentanyl) and induction (thiopental, succinylcholine) anesthesia was maintained with isoflurane and non-depolarizing muscle relaxants. The level of anesthesia was adjusted to BIS index between 40-55 by increas- ing isoflurane concentration and/or repeated boluses of fentanyl during the whole intraoperative period. BIS and hemodynamic data were continuously captured (20 sec intervals) by the PC- based computer system for the analysis of pre-and post-induction BIS average values, corresponding average end-tidal concentration of isoflurane and correlation analysis of BIS vs end-tidal isoflurane concentration.
RESULTS: No statistically significant differences (p=0.05) in the baseline (pre-induction) BIS values were observed in the LT and PH groups (90.2 ± 4.5 vs 94.5 ± 5.2). The average post- induction BIS values for the intraoperative period did not differ significantly between PH and LT groups (42.4 ± 6.7 and 45.2 ± 8.9 respectively, p=0.05). The average end-tidal concentration of isoflurane for the intraoperative period was similar in both groups (0.61 ± 0.04 in PH group and 0.65 ± 0.08 in LT group, p=0.05 by t test). Although the average total dose of fentanyl used during the intraoperative period was higher in the PH group (1. 4 ± 0.6 mg) when compared to the LT group (1.1 mg ± 0.5 mg), this difference did not reach significance level (p=0.05 by t test).
CONCLUSIONS: Despite the presence of end-stage liver disease and various degree of liver encephalopathy in LT patients, no differences in the average pre-induction and post- induction BIS readings, average intraoperative end-tidal isoflurane concentration and the total dose of fentanyl used during the case were observed between LT and PH groups. It might be concluded therefore that the anesthetic requirements (as judged by BIS recordings and anesthetic dose comparison) were not different in PH and LT groups.
REFERENCES:

1. Acta Anesthesiol Scand 1996, 40, 1161.

2. Transplantation 1997, 63, 1423.