Oral clonidine premedication reduces induction dose and prolongs awakening time from propofol-nitrous oxide anesthesia

Purpose: To evaluate whether oral clonidine premedication affects the induction dose of propofol and awakening time from epidural and propofol anesthesia. Methods: Thirty-nine female patients (ASA I or II) were randomly allocated to receive 5 mu g.kg(-1) clonidine po or no clonidine 90 min before induction of anesthesia. After epidural anesthesia was achieved with lidocaine, general anesthesia was induced with continuous iv infusion of propofol at a rate of 50 mg.min(-1) until loss of eyelash reflex and responses to verbal commands, which were judged by a blinded observer. After a laryngeal mask airway was inserted, anesthesia was maintained with N2O 67%, O-2 33% and propofol adjusted to maintain hemodynamic stability. After completion of surgery, a blinded observer recorded the time from discontinuance of propofol and N2O until the patient was awake and responsive (awakening time), and then, the laryngeal mask airway was removed. Results: The induction dose of propofol in the clonidine group (1.4 +/- 0.3 mg) was less than that in the control group ( 1.9 +/- 0.4 mg, P < 0.05), while the awakening time of the clonidine group (470 +/- 145 sec) was longer than that of the control group (329 +/- 123 sec, P < 0.05). Conclusion: Premedication with 5 mu g.kg(-1) clonidine Po reduced the induction dose of propofol, but delayed emergence from propofol anesthesia.