Clinical evaluation of constant rate infusion of alfaxalone–medetomidine combined with sevoflurane anesthesia in Thoroughbred racehorses undergoing arthroscopic surgery

Abstract

BackgroundAlfaxalone has a number of pharmacological properties which are desirable for constant rate infusion (CRI). Previously, the co-administration of alfaxalone and medetomidine is shown to be suitable for short-term anesthesia in horses. However, the use of alfaxalone–medetomidine CRI with inhalational anesthesia under surgical procedures have not been investigated in clinical cases. The aim of the present study was to evaluate the clinical efficacy of alfaxalone–medetomidine CRI in sevoflurane-anesthetized Thoroughbred racehorses undergoing arthroscopic surgery. Sevoflurane requirement, cardiovascular function, and induction/recovery quality were compared between horses maintained with sevoflurane in combination with medetomidine CRI (3 µg/kg/h) (Group M; n = 25) and those maintained with sevoflurane in combination with alfaxalone–medetomidine CRI (0.5 mg/kg/h and 3 µg/kg/h, respectively) (Group AM; n = 25).ResultsThe mean end-tidal sevoflurane concentrations were significantly lower in Group AM (1.8 ± 0.2%) than in Group M (2.4 ± 0.1%). The mean dobutamine infusion rate required for maintaining mean arterial blood pressure within the target values (60–80 mmHg) was significantly lower in Group AM (0.53 ± 0.20 µg/kg/min) than in Group M (0.85 ± 0.32 µg/kg/min). Induction and recovery scores were not significantly different between two groups. However, excitatory response during recovery were observed in five horses in Group AM. The mean plasma alfaxalone concentrations were stable throughout the maintenance period (0.77 ± 0.12 to 0.85 ± 0.13 µg/mL), and decreased significantly immediately after standing (0.32 ± 0.07 µg/mL).ConclusionsAlfaxalone–medetomidine CRI reduced sevoflurane requirement by approximately 26% with good maintenance of cardiopulmonary function in Thoroughbred racehorses undergoing arthroscopic surgery. Sevoflurane in combination with alfaxalone–medetomidine CRI may be a clinically effective anesthetic technique for Thoroughbred racehorses. However, 20% of horses administered alfaxalone showed remarkable excitatory response during recovery. Greater attention to excitatory response may be advisable if alfaxalone is used for induction or maintenance of anesthesia. A larger study is needed to explore the clinical relevance of these findings.

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

“…The addition of butorphanol, 111,112 alfaxalone, 148 propofol, 96 guaifenesin‐ketamine 121,122 or ketamine‐romifidine 120 to PIVA protocols did not improve QR in several studies.…”

“…Alfaxalone administered as an infusion to maintain GA resulted in prolonged recoveries and CNS excitation (from mild muscle tremors and twitching to profound paddling and muscle rigidity) 73,74,148 . A reduction in dosage of alfaxalone infusion to 1.5‐2 mg/kg/h and co‐administration of medetomidine reduced excitement and hyperaesthesia in recovery 75,76 .…”

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

“…(32) Cardiopulmonary effects and recovery quality of remifentanil-isoflurane anesthesia in horses [247] (33) Clinical comparison of two regimens of lidocaine infusion in horses undergoing laparotomy for colic [248] (34) Effects of medetomidine constant rate infusion on sevoflurane requirement, cardiopulmonary function, and recovery quality in Thoroughbred racehorses undergoing arthroscopic surgery [249] (35) The cardiovascular status of isoflurane-anaesthetized horses with and without dexmedetomidine constant rate infusion evaluated at equivalent depths of anaesthesia [250] (36) Cardiopulmonary effects and anaesthesia recovery quality in horses anaesthetized with isoflurane and low-dose S-ketamine or medetomidine infusions [251] (37) Comparison of the effects of an intravenous lidocaine infusion combined with 1% isoflurane versus 2% isoflurane alone on selected cardiovascular variables and recovery characteristics during equine general anaesthesia [252] (38) Clinical usefulness of intravenous constant rate infusion of fentanyl and medetomidine under sevoflurane anesthesia in Thoroughbred racehorses undergoing internal fixation surgery [253] (39) Effect of detomidine or romifidine constant rate infusion on plasma lactate concentration and inhalant requirements during isoflurane anaesthesia in horses [254] (40) Clinical comparison of dexmedetomidine and medetomidine for isoflurane balanced anaesthesia in horses [255] (41) Clinical evaluation of constant rate infusion of alfaxalone-medetomidine combined with sevoflurane anesthesia in Thoroughbred racehorses undergoing arthroscopic surgery [256] (42) Clinical effects of constant rate infusions of medetomidine-propofol combined with sevoflurane anesthesia in Thoroughbred racehorses undergoing arthroscopic surgery [257] (43) Plasma concentrations at two dexmedetomidine constant rate infusions in isoflurane anaesthetized horses: A clinical study [258] 2 (44) Hemodynamic function during neurectomy in halothane-anesthetized horses with or without constant dose detomidine infusion [259] (45) Combination of continuous intravenous infusion using a mixture of guaifenesin-ketamine-medetomidine and sevoflurane anesthesia in horses [260] (46) Evaluation of a mixture of thiopental-guafinesine-medetomidine and sevoflurane anesthesia in horses [261] (47) Influence of ketamine or xylazine supplementation on isoflurane anaesthetized horses-a controlled clinical trial [262] (48) Comparative study on sevoflurane anesthesia alone and combined with partial intravenous anesthesia using dexmedetomidine in healthy horses [263] 3 (49) Problems associated with perioperative morphine in horses: A retrospective case analysis [264] (50) Recovery quality after romi...…”