Guaifenesin-ketamine-detomidine anesthesia for castration of ponies

Abstract

Summary A combination of guaifenesin (G), ketamine (K), xylazine (X) (G:5%, K:2 mg/ml, X:0.5 mg/ml) has been used to maintain anesthesia in horses for overtwenty years. The safety and reliability of this drug combination, referred to as “Triple Drip” (TD), is well established., In the present study, TD was modified by replacing xylazine with detomidine. This modified drug mixture was composed of gauifenesin (50 mg/ml in 5% dextrose in water), ketamine (2 mg/ml) and detomidine (5 μg/ml) and is referred to as GKD. Twelve healthy, intact, male ponies were anesthetized for surgical castration. Fifteen minutes after premedication with detomidine (10 μg/kg IM), anesthesia was induced with 1.0 ml/kg of GKD injected rapidly IV from 60 ml syringes. Anesthesia was maintained with GKD, infused a constant rate of 2.2 ml/kg/hr. Time required for completion of the castrations ranged from 35–45 minutes. During maintenance anesthesia, heart and respiratory rates were stable ranging from 40 to 48 beats/min and 17 to 26 breaths/min. Muscle relaxation and analgesia as assessed by manipulation of the pony's front limbs and response to surgical castration were excellent. Twently minutes after termination of GKD infusion, three ponies, selected at random, were given tolazoline (4 mg/kg IV) to reverse the residual sedative action of detomidine. These ponies assumed sternal position within 5–8 minutes after tolazoline injection and were able to stand but walked with some ataxia 15 minutes later. In the nine ponies not given tolazoline, recovery was smooth but required 35–45 minutes. These nine ponies were able to stand unassisted on their first attempt and walked with minimal ataxia shortly thereafter. We conclude that GKD can be used effectively to induce and maintain anesthesia in ponies subjected to surgical castration. We also believe that this anesthetic drug regimen could be used satisfactorily for other minor surgeries in ponies requiring a similar degree of analgesia and duration of anesthesia.