Arousal with iv epinephrine depends on the depth of anesthesia

Purpose: To investigate whether the depth of anesthesia affects the change in the bispectral index (BIS) caused by iv epinephrine during propofol anesthesia. Methods: Forty women undergoing elective lower abdominal surgery received a propofol target controlled infusion (TCI) to maintain a modified Observer's Assessment of Alertness/Sedation (OAA/S) score of 2 (sedation period). Subsequently anesthesia was induced with propofol TCI 5 μg·mL^-1 and rocuronium 0.9 mg·kg^-1, and propofol continued so as to maintain general anesthesia at a BIS of 50 (general anesthesia period). Intravenous epinephrine at a dose of 10 μg·5 mL^-1 in normal saline (epinephrine group, n = 20) or normal saline 5 mL (control group, n = 20) was administered during both periods. The BIS, mean arterial pressure (MAP) and heart rate (HR) were measured immediately before, and one, two, three, four, six, eight, and ten minutes after injection. The modified OAA/S scale was evaluated during the sedation period. Results: There was no significant change in the modified OAA/S scale, BIS, or hemodynamic variables compared to preinjection values during either sedation or general anesthesia in the control group. Intravenous epinephrine increased the BIS and modified OAA/S scale during sedation, but there was no increase in BIS during general anesthesia. Increases in HR and MAP were observed during both periods after iv epinephrine. Conclusion: Intravenous epinephrine 10 μg resulted in an arousal effect and an increase in BIS during sedation, but did not change the BIS during general anesthesia. These results suggest that the arousal effect of iv epinephrine during propofol anesthesia depends on anesthetic depth.