Assessment of recovery in patients undergoing intravenous conscious sedation using bispectral analysis

Purpose: The Bispectral Index (BIS) has been recently shown to objectively predict the level of sedation in patients undergoing conscious sedation. It was the goal of this study to directly compare the recovery profile of pat ients where the BIS was used to monitor sedation with a control group where the monitor was not used. Patients and Methods: Forty patients undergoing third molar extractions und er intravenous conscious sedation were randomly assigned to 2 groups. In bo th groups, induction of sedation was performed using a standard dose of fen tanyl (1.5 mug/kg) and midazolam (0.05 mg/kg). Propofol was then given in 1 0 to 20 mg boluses until a clinically desirable sedation level was achieved . In 1 group, the BIS was then monitored continually during surgery using a microcomputer (Aspect-1050 Monitor, Aspect Co, Natick, MA) and recorded at 5-minute intervals. The anesthetist (N.A.S.) provided additional propofol boluses to maintain a BIS level of 70 to 80. In the other group, the BIS se nsor was applied, but the monitor was not used. In this group, the sedation was modified, and additional propofol was given based solely on the anesth etist's subjective assessment of the desired level of sedation (Observer's Assessment of Alertness/Sedation [OAA/S] scale level 2 to 3). Additional bo luses of I mg of midazolam were given during the procedure if patients requ ired repeated boluses of propofol at less than 5-minute intervals to mainta in the desired sedation level (BIS level of 70 to 80 or OAA/S level of 2 to 3). These additional midazolam boluses, as well as the time of the last se dative dose (propofol or midazolam) were recorded to study the effect of th ese factors on recovery. Results: Of the 40 patients initially included in the study, 1 subject in t he BIS-monitored group was excluded due to the loss of intravenous access a t initiation of the case. For the remaining 33 subjects, 19 were assessed o bjectively using the BIS monitor, whereas 20 were assessed subjectively usi ng the OAA/S scale. The BIS cases were slightly longer in duration than the OAA/S cases, lasting an average of 26 minutes versus 22 minutes. This diff erence was statistically nonsignificant (P = .19). Less propofol was used i n the BIS cases, with an average of 98 mg for BIS cases versus 106 mg for O AA/S cases (P = .59). The total dose in mg/kg/min was significantly less in the BIS group (0.054 mg/kg/min) than in the OAA/S group (0.074 mg/kg/min; P = .0082). There was no significant difference in the amount of midazolam administered after induction between the 2 groups (P = .60). The surgeon, w ho was blinded to whether the monitor was used, ranked the third molar extr actions more difficult in the BIS group (P = .05). However, patients in the BIS group were on average more cooperative, with better maintenance of mus cle tone. The difference in these parameters were nonsignificant (P = .15 a nd .092, respectively).