THE IMPACT OF EEG-BISPECTRAL INDEX MONITORING ON DRUG USAGE AND RECOVERY DURING AMBULATORY ANESTHESIA

Abstract

S51 INTRODUCTION: The Bispectral Index (BIS) is a processed EEG parameter that has been validated as a measure of the sedative-hypnotic effects of anesthetic drugs. Controlled studies have shown that BIS use facilitates the administration of intravenous and inhaled anesthetics, resulting in decreased propofol use and improved recovery. [1,2] These studies, however, involved only limited number of patients and included a specific requirement to titrate the sedative-hypnotic drug according to a predetermined target BIS values. The impact of BIS monitoring on drug usage in routine clinical practice remains to be confirmed. Therefore, we evaluated the effect of BIS monitoring on propofol use and on patient recovery during standard ambulatory anesthesia. METHODS: Following IRB approval, the hospital records of 1043 patients who had undergone orthopedic surgery under general anesthesia at our outpatient surgical facility during a 45 month period were reviewed. Patient demographic, anesthesia and recovery data were obtained for two groups of patients, namely, those treated during a 30 month period "Prior to BIS use", and those treated during the 15 month period of "BIS use". Anesthesia providers received only a standard instruction in the use of BIS (A-1050, Aspect Medical, Inc.). Patient management was according to routine clinical practice. After premedication with midazolam, 1-2 mg i.v., anesthesia was induced with 2-2.5 mg/kg propofol and maintained with a variable rate infusion of propofol supplemented with sufentanil, 2.5-5 [micro sign] g boluses, as needed, and 65% nitrous oxide in oxygen. Data on neuromuscular blocking and reversal agents were not included. Data were analyzed using Student t-and Chi-square tests, as appropriate. P values < 0.05 were considered statistically significant (*). Data are presented as mean +/- SD. RESULTS: There were no significant demographic differences between the two study groups (Table 1). All procedures were conducted by the same small group of surgeons and anesthesia provides. A difference in propofol use was not evident in the grand total propofol dose. However, the introduction of BIS monitoring was associated with a significant reduction in the normalized total propofol dose (total propofol dose divided by weight and case duration), (p<0.001). Likewise, there was a reduction in the average maintenance rate of propofol during the anesthesia maintenance period of 8.9 [micro sign] g/kg/min (p<0.001). There was a small but significant increase in the average intraoperative opioid dosage (p<0.001). The difference in recovery times was minimal but the incidence of postoperative nausea and vomiting (PONV) was reduced (p<0.01).Table 1DISCUSSION: These results suggest that BIS has a significant impact on the use of anesthetic drugs in routine clinical practice. Titration of propofol using BIS resulted in decreased maintenance rates. The reduction in propofol use for the "average" case in this study was approximately 77 mg/case. Contrary to previous reports, [1] we found an increase in the use of intraoperative opioids. This may relate to the ability to maintain "lighter" planes of anesthesia with BIS. Thus, in addition to its influence on the amount of hypnotics used, BIS monitoring also affects the choice of drugs during outpatient anesthesia.