The cardiovascular response to ketamine: the effects of clonidine and lignocaine

The effectiveness of clonidine or lignocaine in reducing the cardiostimulatory effects of ketamine was studied. A double-blind, randomized design was used in three groups of 20 patients each, of ASA grade 1 or 2 presenting for minor elective surgery. The clonidine group received 0.3 mg clonidine orally with the premedication while the lignocaine group received 1.5 mg.kg-1 lignocaine prior to induction. The third group formed the controls. All patients were induced with 2 mg.kg-1 ketamine intravenously. The systolic blood pressure in the clonidine group was significantly lower than that of both the control and lignocaine groups throughout the study (P < 0.05). It was concluded that clonidine was effective in reducing the hypertensive response to ketamine, whereas lignocaine had no effect.