PIII-5Relationship between modified observer’s assessment of alertness/sedation (OAA/S) scale, bispectral index, and propofol effect-site concentration in the regional anesthesia

Abstract

BACKGROUND Appropriate sedation during regional anesthesia of elderly patients is required to avoid psychological discomfort and severe anxiety. We investigated whether the relationship between OAA/S, bispectral (BIS) index, and propofol effect-site concentration is useful for maintaining the adequate sedation of elderly patients under regional anesthesia. METHODS In 30 elderly patients who were scheduled transurethral resection surgery, we measured BIS and started infusion of propofol with the target controlled infusion method to sedate the patients after regional anesthesia. We assessed also OAA/S and elevated propofol effect-site concentration by 0.3 μg/ml every 5 minutes. At each score of OAA/S scale, effect-site concentration, BIS, and vital signs were measured. RESULTS At the OAA/S score 5, the BIS was 97.2 ± 1.1. At the OAA/S score 4, the BIS was 84.3 ± 4.6 and effect-site concentation was 0.8 ± 0.3 μg/ml. At the OAA/S score 3, the BIS 78.4 ± 4.3 and effect-site concentration 1.2 ± 0.3, resp. At the OAA/S score 2, the BIS 73.2 ± 5.9 and effect-site concentration 1.5 ± 0.4, resp. The OAA/S scale had a good relationship with BIS and effect-site concentration (Pearson correlation coefficient (r): 0.973 and −0.968, resp.). BIS also showed a good correlation with effect-site concentration (r: −1.0). CONCLUSIONS Our results suggest that BIS index is a good monitoring tool to evaluate the propofol sedation level during the regional anesthesia of elderly patients without complications of deep sedation. Clinical Pharmacology & Therapeutics (2005) 79, P58–P58; doi: 10.1016/j.clpt.2005.12.213