GUAIFENESIN-KETAMINE-XYLAZINE ANESTHESIA FOR CASTRATION IN PONIES - ACOMPARATIVE-STUDY WITH 2 DIFFERENT DOSES OF KETAMINE

Thirty-five mature male ponies (B.Wt. 115.5-288.6 kg) were used to eva luate the anesthetic effect of continuous intravenous infusion of guai fenesin-ketamine-xylazine (GKX) mixture for castration. This GKX mixtu re contained 50 mg/ml guaifenesin (prepared in 5% dextrose in water), 0.5 mg/ml xylazine and either 1 mg/ml ketamine (GKX-1) or 2 mg/nl keta mine (GKX-2). Group 1 ponies were given GKX-1 and group 2 ponies were given GKX-2. All ponies received intramuscular xylazine (1.1 mg/kg) 15 to 20 minutes before anesthesia was induced by rapid infusion of 1.1 ml/kg of GKX-1 in Group 1 and GKX-2 in group 2. Anesthesia was maintai ned by continuous infusion using a calibrated infusion pump. Total mea n GKX dose required for induction and maintenance of anesthesia for 50 minutes with GKX-1 and 45 minutes with GKX-2 was 4.5+/-0.3 ml/kg/hr a nd 4.3+/-0.2 ml/kg/hr, respectively. Respiration rate decreased in bot h groups but remained within normal limits for ponies. Heart rate was unchanged immediately following induction in either group, but heart r ate was decreased at 40 to 50 minutes for GKX-1 and 30 to 50 minutes f or GKX-2, reflecting the bradycardic action of xylazine somewhat more than the stimulating effect of ketamine. Recovery to standing required a mean time of 21+/-4 minutes with GKX-1 and 23+/-3 minutes with GKX- 2 once the infusion was discontinued. Stability of anesthesia and degr ee of analgesia and muscle relaxation was judged best for GKX-2.