Effects of Hypothermic Cardiopulmonary Bypass on Bispectral Analysis

Kwon, Jae Young; Lee, Hyun Jung; Kim, Chul Hong; Kim, Hae Kyu; Baik, Seong Wan; Kim, Inn Se

Abstract

BACKGROUND: Patient awareness is a particular problem in cardiac anesthesia with cardiopulmonary bypass (CPB). Transformed electroencephalogram monitors, such as the Bispectral index (BIS) monitor, has been advocated as a tool that may reduce the incidence of unexpected intraoperative recall. The authors studied the effects of hypothermia during CPB on the BIS score and the BIS can be a useful monitor to measure anesthetic depth and requirement during hypothermic CPB.
METHODS
Eighteen consenting volunteers scheduled for an elective cardiac surgery were studied. Volunteers were randomly allocated to one of two groups. All patients were given propofol by a target controlled infusion system, Diprifusor, with fentanyl (0.6 ug/kg/min). In group A, before and during CPB propofol was infused at a predetermined target plasma concentration (2.0 ug/ml), the BIS score and temperature were monitored. In group B, before and during CPB, to maintain the BIS score at 30 40 units, changing propofol plasma concentrations and temperature were monitored. Then we asked patients about intraoperative awareness.
RESULTS
In group A, compared with before the start of CPB, the BIS score was decreased by the temperature (P < 0.05) during CPB (5 min, 10 min, 20 min, 30 min after the start of CPB) and after the stop of CPB. In group B, compared with before the start of CPB, the required propofol plasma concentration was decreased by the temperature during CPB (P < 0.05). In addition, no one experienced awareness during surgery.
CONCLUSIONS
The BIS score was decreased by a decline in temperature during the hypothermic CPB, and bispectral analysis can be a relative indicator of anesthetic requirement and the hypnotic state under this conception.