The effects of preanesthetic oral clonidine on total requirement of propofol for general anesthesia.

STUDY OBJECTIVE To investigate the effects of preanesthetic oral clonidine on total propofol requirement for uniform minor surgery (breast conservative surgery: breast cancer removal with axillary lymph node dissection), and to compare the action of clonidine with that of preanesthetic oral diazepam, a commonly used benzodiazepine. DESIGN Randomized double-blinded study. SETTING Operating room ASA physical status I and II room and recovery room of the cancer center. PATIENTS 80 breast cancer patients scheduled for surgery. INTERVENTIONS Patients were randomized to one of four treatment groups (placebo, clonidine 75 micrograms, or 150 micrograms of clonidine, or 10 mg of diazepam were orally administered 60 min before induction of anesthesia); n = 20 per group. After evaluating the sedation and anxiety levels of patients using a visual analog scale, anesthesia was induced with propofol (1.5 mg/kg), and maintained with oxygen (O2): nitrous oxide (N2O) (30:70) with a continuous infusion of propofol. The propofol infusion was started at 10 mg/kg/h for 10 minutes, then decreased to 8 mg/kg/h, and 6 mg/kg/h thereafter, and the rate of infusion was adjusted to obtain adequate anesthesia (maintaining hemodynamic parameters within 20% of that prior to premedication). Fentanyl 0.2 mg (each 0.1 mg was given for intubation and axillary lymph node dissection, respectively) was administered. MEASUREMENTS AND MAIN RESULTS Preanesthetic oral clonidine (150 micrograms) and diazepam (10 mg) induced anxiolysis without sedation. The total requirement (the mean infusion rates) of propofol in placebo, clonidine 75 micrograms, clonidine 150 micrograms, and 10 mg of diazepam groups were 841 +/- 70 (9.0 +/- 0.3), 720 +/- 63 (7.1 +/- 0.4), 491 +/- 39 (5.6 +/- 0.2), and 829 +/- 77 mg (7.9 +/- 0.4 mg/kg/h), respectively. The cost of propofol in these groups was $51.0 +/- 3.8, $45.5 +/- 3.2, $33.5 +/- 2.3, and $50.5 +/- 4.4, respectively. CONCLUSIONS Preanesthetic oral clonidine (150 micrograms) but not diazepam (10 mg) reduced the total requirement of propofol while stabilizing hemodynamic parameters. In addition, 150 micrograms of oral clonidine attenuates the hemodynamic responses associated with tracheal intubation.