BACKGROUND: Arm withdrawal movements are often observed on the administration of rocuronium. This study used the BIS to predict the depth of sedation and the prevention of withdrawal movements.

METHODS: With the approval of the institutional review board and the informed consent of the subjects, sixty patients, with ASA physical stati of 1 to 2, were randomized into four groups. After the induction of anesthesia using 0.5 mg/kg of thiopental sodium, each group received 0.6 mg/kg of rocuronium when their BIS values were 85 (Group I), 75 (Group II), 65 (Group III), or 55 (Group IV). The blood pressure, heart rate, BIS value at the time of loss of eyelash reflex, incidence of withdrawal movement and grade, and the correlation between the BIS value and loss of eyelash reflex were observed.

RESULTS: No difference were observed in the incidence of withdrawal movement and grade between the four groups. The correlation coefficients of the BIS value and time of loss of eyelash reflex were both 0.33 (P<0.05).

CONCLUSIONS: It may be impossible to rely solely on the BIS value to insure patients reach a deep anesthetic state after induction of anesthesia with thiopental. The withdrawal movement on injection of rocuronium can not be prevented with BIS monitoring.