A Comparison of Injectable Anesthetic Combinations in Horses

Abstract

Six combinations of injectable anesthetic agents were administered to six adult horses in a Latin square design. The drug combinations were xylazine-ketamine, xylazine-butorphanol-ketamine, xylazine-tiletamine-zolazepam, xylazine-butorphanol-tiletamine-zolazepam, detomidine-ketamine, and detomidine-butorphanol-ketamine. Measured variables were heart rate, respiratory rate, systolic blood pressure, arterial pH (pHa), PaCO2, PaO2, recumbency time, and number of attempts necessary to stand. Quality of induction and recovery, muscle relaxation, and response to stimulus were evaluated subjectively. The horses required significantly more attempts to stand after administration of xylazine-tiletamine-zolazepam, xylazine-butorphanol-tiletamine-zolazepam, and detomidine-ketamine than after xylazine-ketamine, xylazine-butorphanol-ketamine, or detomidine-butorphanol-ketamine. Mean recumbency times varied from 23.0 minutes with xylazine-ketamine to 41.3 minutes with xylazine-butorphanol-tiletamine-zolazepam. There were significant differences in mean heart rates at minute 15, mean respiratory rates at minutes 5, 10 and 15, and mean systolic blood pressures at minute 10 of anesthesia. There were no significant differences in pHa, PaCO2 or PaO2.

Assessing the efficacy of medetomidine and tiletamine–zolazepam for remote immobilisation of feral horses (Equus caballus)

“…These effects, however, sometimes result in prolonged recovery and there is no readily available antagonist, or reversal agent (Matthews et al 1991;Muir et al 2000). The solubility of the concentrated ketamine preparations is insufficient to allow dosing darts with a capacity restricted to 3ml.…”

Dissociative Anaesthesia in Foals for Umbilical Herniorrhaphy under Field Conditions

“…In the present study, the clinical anaesthesia parameters resulting from the anaesthesia protocol applied (Table 3) was found to be in compliance with the findings of the studies referred to above. In several studies 1,3,8,[10][11][12][13][14] , it has been reported that, in horses, tiletamine-zolazepam anaesthesia, and in particular anaesthesia prolonged by the administration of sustaining doses, tend to be problematic due to the continuous attempts of the animals to stand up, the standing position of the animals being unsafe owing to ataxia, and consequential falls of the animals. These problems have been indicated to result from the half life elimination time (t ½) of zolazepam from the organism taking a longer time than that of xylazine and tiletamine, thereby, leading to longer muscle relaxation and ataxia during recovery from anaesthesia.…”

“…In previous studies carried out in horses and foals by administering different doses of the anaesthetic combination of xylazine-tiletamine-zolazepam for the induction of general anaesthesia 5,8,[10][11][12][13][14] , anaesthesia induction time was reported to range between 34-75 sec, the duration of anaesthesia between 22.5-35.7 min, and the period of regaining standing position (standing time) between 30-50 min. Furthermore, it has been indicated that, if required, the duration of anaesthesia could be prolonged by administering half or one-third of the initial doses of the anaesthetics used for sustainment, yet, in such cases, complications such as serious hypoxaemia, myositis and delayed recovery from anaesthesia could be encountered as a result of cardiovascular/pulmonary depression 1,3,4,6,11,27 .…”

“…The quality of the induction of anaesthesia, anaesthesia/analgesia and recovery from anaesthesia was scored subjectively by the use of the modification of criteria previously applied by A89 CEYLAN various researchers 11,12,15 . Accordingly, good, fair and poor were scored with 3 points, 2 points and 1 point, respectively (Table 1).…”

“…Owing to certain features it displays, this short-term general anaesthesia is described as dissociative anaesthesia 3,[7][8][9] . Many researchers have used the tiletamine-zolazepam combination in horses 5,[10][11][12][13] and foals 8,14 , in association with various sedatives, tranquilizers and analgesics, and have reported the induction of safe general anaesthesia, resembling that induced by the combined use of xylazine and ketamine, but longer. However, the majority of these studies have been conducted on horses and foals that were not subjected to nociceptive stimulation in clinical environment with no surgical intervention.…”