Comparison of Recovery Quality Following Medetomidine versus Xylazine Balanced Isoflurane Anaesthesia in Horses: A Retrospective Analysis

Abstract

Medetomidine partial intravenous anaesthesia (PIVA) has not been compared to xylazine PIVA regarding quality of recovery. This clinical retrospective study compared recoveries following isoflurane anaesthesia balanced with medetomidine or xylazine. The following standard protocol was used: sedation with 7 µg·kg−1 medetomidine or 1.1 mg·kg−1 xylazine, anaesthesia induction with ketamine/diazepam, maintenance with isoflurane and 3.5 µg·kg−1·h−1 medetomidine or 0.7 mg·kg−1·h−1 xylazine, and sedation after anaesthesia with 2 µg·kg−1 medetomidine or 0.3 mg·kg−1 xylazine. Recovery was timed and, using video recordings, numerically scored by two blinded observers. Influence of demographics, procedure, peri-anaesthetic drugs, and intraoperative complications (hypotension, hypoxemia, and tachycardia) on recovery were analysed using regression analysis (p < 0.05). A total of 470 recoveries (medetomidine 279, xylazine 191) were finally included. Following medetomidine, recoveries were significantly longer (median (interquartile range): 57 (43–71) min) than xylazine (43 (32–59) min) (p < 0.001). However, the number of attempts to stand was similar (medetomidine and xylazine: 2 (1–3)). Poorer scores were seen with increased pre-anaesthetic dose of xylazine, intraoperative tetrastarch, or salbutamol. However, use of medetomidine or xylazine did not influence recovery score, concluding that, following medetomidine–isoflurane PIVA, recovery is longer, but of similar quality compared to xylazine.

Retrospective Study on Risk Factors and Short-Term Outcome of Horses Referred for Colic from 2016 to 2022

“…The outcome was dichotomized as discharged/non-discharged. For those horses that underwent laparotomy, the following data were retrieved from surgery and the anesthetic records: anesthetic protocol, duration of anesthesia and surgery (minutes), time to standing (minutes) and recovery score [ 29 ], type of lesion (ischemic/non-ischemic), and occurrence of complications (if any/the type of complication).…”

Influence of hypoxaemia, hypotension and hypercapnia (among other factors) on quality of recovery from general anaesthesia in horses

“…However, to the authors' knowledge this has never been confirmed in a larger study population and in non-emergency cases. Conversely, use of salbutamol, a short acting β 2 -adrenoceptor agonist, used to treat hypoxaemia in anaesthetized horses, has been related to poorer recovery scores, and identified as a risk factor for catastrophic fractures or luxation's during recovery (Kälin et al 2021;Bennell et al 2022). Although salbutamol is used routinely for the treatment of hypoxaemia, neither of the two studies identified hypoxaemia itself as a risk factor.…”

Comparison of Xylazine and Lidocaine Infusion versus Medetomidine Continuous Rate Infusion during General Anesthesia with Isoflurane in Horses Undergoing Emergency Laparotomy

“…We must highlight that all horses in Group X received a bolus of xylazine once in the recovery room. Previous studies also emphasize the need for this measure [53,54] to improve recovery scores from general anesthesia during elective surgery. In all cases, recoveries were unassisted since no consensus was found in the literature concerning this aspect [55][56][57].…”