A retrospective comparison of induction with thiopental/guaifenesin and propofol/ketamine in Thoroughbred racehorses anesthetized with sevoflurane and medetomidine during arthroscopic surgery

Abstract

This study compares clinical characteristics between induction with thiopental/guaifenesin and propofol/ketamine in Thoroughbred racehorses anesthetized with sevoflurane and medetomidine. Clinical records of 214 horses that underwent arthroscopic surgery between 2015 and 2016 were retrospectively retrieved. Horses were premedicated with medetomidine and midazolam to sedate at the adequate level for smooth induction, and then induced with either thiopental (4.0 mg/kg) and guaifenesin (100 mg/kg) in Group TG (n=91) or propofol (1.0 mg/kg) and ketamine (1.0 mg/kg) in Group PK (n=123). Anesthesia was maintained using sevoflurane with constant rate infusion of medetomidine. Quality of induction/recovery, sevoflurane requirement, cardiovascular function and recovery characteristics were evaluated. Anesthetic induction scores (median, range) for Group TG (5, 2–5) and Group PK (5, 2–5) were not significantly different. There were no significant differences in end-tidal sevoflurane concentration (mean ± standard deviation) between Group TG and Group PK (both 2.4 ± 0.2%). Dobutamine infusion rate (µg/kg/min) required for keeping mean arterial blood pressure (MAP) above 70 mmHg in Group PK (0.43, 0.10–1.40) was significantly lower than in Group TG (0.67, 0.08–1.56). Recovery score in Group PK (5, 2–5) was significantly higher than in Group TG (4, 2–5). Both propofol/ketamine and thiopental/guaifenesin provided a smooth induction of anesthesia. Moreover, induction with propofol/ketamine resulted in lower dobutamine requirements for keeping MAP above 70 mmHg during maintenance, and better quality of recovery. Induction with propofol/ketamine would be preferable to thiopental/guaifenesin in Thoroughbred racehorses anesthetized with sevoflurane and medetomidine during arthroscopic surgery.

Recovery of horses from general anaesthesia: A systematic review (2000–2020) of the influence of anaesthetic protocol on recovery quality

“…This was corroborated by another study which found that S‐ketamine provided quieter and more controlled recoveries 32 . Administration of propofol and ketamine for induction of anaesthesia resulted in shorter recovery times and better QR compared to thiopental and guaifenesin 140 . In both groups a good QR was noted, therefore, despite the results showing a statistically significant difference, they might be clinically irrelevant.…”

Ketofol: A ketamine‐propofol admixture for induction of anaesthesia in two foals

“…The individual doses of ketamine and propofol used in this report are similar or lower than the previously reported in the literature, with recommendations for ketamine at 2 mg/kg with diazepam after xylazine premedication, 2 or propofol at 2-6 mg/kg when used alone in foals. 9,20 The ketofol doses chosen for these cases were based on similar ratios reported in horses 10,19,21 and dogs 13 which showed smooth inductions and recoveries. There are limited pharmacokinetic studies for propofol in foals.…”

“…In both cases, recovery from general anaesthesia was rapid and of good quality, despite the administration of a propofol top‐up and xylazine in cases 1 and 2, respectively. Similarly, in adult horses, superior recoveries and fewer attempts to standing were also reported using ketamine‐propofol inductions instead of thiopentone guaifenesin 21 and ketamine‐midazolam, 10 respectively. In children, the median recovery time for ketofol was found to be faster than with intravenous ketamine, but longer than when propofol was used alone 14 .…”

Recovery after General Anaesthesia in Adult Horses: A Structured Summary of the Literature

“…Ketamine is the most frequent agent used to induce general anaesthesia in horses [1,70]. Ketamine is superior to thiopental and the mixture tiletamine/zolazepam regarding duration and quality of recovery [94,98,104,109,110,122]. Thiopental might be still used as an alternative in ocular patients to avoid increases in intraocular pressures [102].…”