Preinduction oral clonidine: Effects on ketamine cardiostimulation at induction of anesthesia

Abstract

Background and Purpose: Most of the available intravenous (IV) induction agents produce hypotension except ketamine. However, its use is limited due to cardiovascular stimulation. We therefore investigated the effects of oral clonidine premedication on ketamine-induced cardiostimulation.Methodology: This was a prospective, double-blind, randomized controlled study of 156 patients scheduled for general anesthesia. The patients were randomized into three Groups A, B, and C of 52 patients each and all the patients received 10mg diazepam the night before the surgery and 90 minutes before induction of anaesthesia. In addition, patients in Groups A and B received 0.1 mg and 0.3 mg oral clonidine, respectively, at the time of premedication while no clonidine was administered to patients in Group C. Anesthesia was induced with IV ketamine 2 mg/kg and 100% oxygen 8 L/min via the Bain's circuit. The pulse rate (PR), systolic blood pressure, diastolic blood pressure, and mean arterial pressure were measured noninvasively and recorded every minute for 10 min before induction of anesthesia.Results: The peak values of PR in the 0.1 mg and 0.3 mg clonidine groups were significantly lower than the corresponding value in the control (C) group (86 ± 5 bpm and 83 ± 7 bpm vs. 118 ± 14 bpm, P < 0.05). However, the peak mean blood pressure in the Group B was significantly reduced when compared with the corresponding values in the Groups A and C (97 ± 9 mmHg vs. 117 ± 7 mmHg and 115 ± 14 mmHg, respectively P < 0.05).Conclusion: Preanesthetic oral clonidine reduced cardiostimulation following ketamine-induction in spontaneously breathing patients.