Effects of penehyclidine hydrochloride on the propofol dose requirement and Bispectral Index for loss of consciousness.

Penehyclidine hydrochloride (PH), a new anticholinerigic drug associated with few cardiovascular side effects, was used widely as premedication in China. There is no information on the pharmacodynamic interaction between PH and anesthetics for loss of consciousness (LOC). This study was designed to determine the effects of premedicated PH on the propofol dose requirement for LOC and Bispectral Index (BIS) during target-controlled infusion (TCI) of propofol. Forty patients were randomly allocated to 1 of 2 groups to receive PH (Group PH) or normal saline (Group NS). TCI propofol was administered 30 min after PH or normal saline was given. During study period, BIS value, mean arterial pressure (MAP), heart rate (HR) and the Observer's Assessment of Alertness/Sedation (OAA/S) rating scale were recorded. Predicted effect-site propofol concentrations (Ce) and the total propofol dose were recorded when end-point was achieved. The time to reach end point was also noted. The time to reach LOC was shorter in Group PH than Group NS (p < 0.05). The predicted propofol Ce and consumption based on body weight of each patient were lower in Group PH than Group NS (p < 0.05). BIS values were not significantly changed before propofol infusion, and decreased gradually as propofol Ce increased and were not significantly different when LOC was reached between two groups (p > 0.05). We conclude that premedicated PH reduces the propofol Ce and dose requirement for LOC, but has no effect on BIS.