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

Purpose: To evaluate whether oral clonidine premedication affects the induc tion dose of propofol and awakening time from epidural and propofol anesthe sia. 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 inducti on of anesthesia. After epidural anesthesia was achieved with lidocaine, ge neral anesthesia was induced with continuous iv infusion of propofol at a r ate of 50 mg.min(-1) until loss of eyelash reflex and responses to verbal c ommands, which were judged by a blinded observer. After a laryngeal mask ai rway was inserted, anesthesia was maintained with N2O 67%, O-2 33% and prop ofol adjusted to maintain hemodynamic stability. After completion of surger y, 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), w hile 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 induc tion dose of propofol, but delayed emergence from propofol anesthesia.