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 conservati ve surgery: breast cancer removal with axillary lymph node dissection), and to compare the action of clonidine with that of preanesthetic oral diazepa m, 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: SO breast cancer patients scheduled for surgery. Interventions: Patients were randomized to one of four treatment groups (pl acebo, clonidine 75 mu g, or 150 mu g of clonidine, al 10 mg of diazepam we re orally administered 60 min before induction of anesthesia); n = 20 per g roup. 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 (O-2): nitrous oxide (N2O) (30:70) with a continuous infusion of propofol. The propofol infusion was started at 10 mg/kg/h for 20 minutes, then decreased to 8 mg/hg/h, and 6 mg/kg/h thereafter, and the rate of infusion was adjusted to obtain adequate anesthesia (maintaining he modynamic parameters within 20 % of that prior to premedication). Fentanyl 0.2 mg (each 0.1 mg was given for intubation and axillary lymph node dissec tion, respectively) was administered. Measurements and Main Results: Preanesthetic oral clonidine (150 mu g) and diazepam (10 mg) Induced anxiolysis without sedation. The total requirement (the mean infusion rates) of propofol in placebo, clonidine 75 mu g; cloni dine 150 mu g; 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 $5 1.0 +/- 3.8, $45.5 +/- 3.2, $33.5 +/- 2.3, and $50.5 +/- 4.4, respectively. Conclusions: Preanesthetic oral clonidine (150 mu g) but not diazepam (10 m g) reduced the total requirement of propofol while stabilizing hemodynamic parameters. In addition, 150 mu g of oral clonidine attenuates the hemodyna mic responses associated with tracheal intubation. (C) 1998 by Elsevier Sci ence Inc.