A PHARMACODYNAMIC STUDY OF PROPOFOL OR PROPOFOL AND KETAMINE INFUSIONS IN PONIES UNDERGOING SURGERY

The pharmacodynamics of infusions of propofol alone (group 1) were com pared with the pharmacodynamics of infusions of propofol and ketamine together (group 2) in eight ponies undergoing castration. Anaesthesia was induced with detomidine, 20 mu g kg(-1), followed by ketamine, 2.2 mg kg(-1). Subsequently, a bolus dose of propofol, 0.5 mg kg(-1), was administered intravenously to both groups, and an infusion of propofo l was given for an average of 74 minutes to group 1, and an infusion o f propofol and ketamine was given for 60 minutes to group 2. The mean (SD) infusion rates of propofol were 0.330 (0.050) mg kg(-1) min(-1) i n group 1, and 0.124 (0.009) mg kg(-1) in group 2, and the ketamine in fusion rate was maintained constant at 40 mu g kg(-1) min(-1). Arteria l hypotension and marked respiratory depression were evident in some o f the ponies receiving propofol alone, whereas in the ponies anaesthet ised with propofol and ketamine, respiratory and cardiovascular parame ters were well maintained. All the ponies in both groups recovered qui ckly from anaesthesia, with mean times to sternal recumbency and stand ing of 19.8 (8.0) minutes and 27.2 (74) minutes respectively for group 1 and 8.4 (3.2) min and 14.9 (10.1) minutes for group 2.