General anesthesia occurs frequently in elderly patients during propofol-based sedation and spinal anesthesia

Study Objective: To test the hypothesis that sedation in elderly patients is often electrophysiologically equivalent to general anesthesia (GA). Design: Prospective, observational study. Setting: Operating room of a university medical center. Patients: 40 elderly patients (>= 65 yrs of age) undergoing hip fracture repair with spinal anesthesia and propofol-based sedation. Interventions: In the routine practice group (RP; n = 15), propofol sedation was administered per the usual routine of the anesthesiologist. In the targeted sedation group (TS; n = 25), sedation was titrated to an observer's assessment of alertness/sedation (OAA/S) score of 4 (ie, lethargic in response to name called) to 5 (ie, awake and alert). Measurements: Both patient groups underwent processed electroencephalographic monitoring using bispectral index (BIS) intraoperatively. BIS levels were compared between groups to determine amount of surgical time spent in GA (BIS 60). Main Results: In the RP group, subjects spent 32.2% of surgical time at BIS levels consistent with GA. Although averaged BIS values during surgery increased from (mean +/- SD) 71 16 to 88 9 (P < 0.001), GA was still observed during 5% of surgical time in the TS group. Overall, 13 of 15 (87%) RP group patients and 11 of 25 (44%) TS group patients (P < 0.010) experienced some period of GA. Conclusions: BIS levels consistent with GA occur frequently in elderly patients during propofol-based sedation for spinal anesthesia. Altering routine practice such that sedation is titrated to a targeted clinically-determined sedation level reduces but does not eliminate this incidence. (C) 2010 Elsevier Inc. All rights reserved.