TY - JOUR

T1 - The effects of flumazenil on ventilatory and recovery characteristics in horses following midazolam-ketamine induction and isoflurane anaesthesia

AU - Douglas, Hope

AU - Hopster, Klaus

AU - Cerullo, Michelle

AU - Hopster-Iversen, Charlotte

AU - Stefanovski, Darko

AU - Driessen, Bernd

PY - 2021

Y1 - 2021

N2 - Background: Flumazenil antagonises the actions of benzodiazepines. There has been no prior research specifically investigating this anaesthetic reversal agent for horses. Objectives: To determine the effects of flumazenil administration in horses on (a) ventilatory parameters after midazolam-ketamine induction and maintenance with isoflurane in oxygen and on (b) the characteristics of recovery from general anaesthesia. Study design: Blinded, randomised, crossover experiment. Methods: Six horses were randomly assigned to receive high-dose flumazenil (Fhigh, 20 µg/kg), low-dose flumazenil (Flow, 10 µg/kg) and saline (control). Cardioventilatory parameters were monitored. After 90 minutes of isoflurane anaesthesia, a bolus of Fhigh, Flow or saline was administered i.v. The horses were recovered using head and tail rope assistance. The times to first movement, to achievement of sternal recumbency, to the first attempt to stand and the total recovery time were determined. The recovery quality was evaluated using a 115-point recovery scoring system. The cardioventilatory parameters and recovery times were analysed using mixed-effects regression analyses. Intraclass correlation (ICC) analysis was used to evaluate the recovery scores. A Mann-Whitney U test assessed the relationship between recovery score and flumazenil administration. Results: A significant difference with flumazenil administration was found for SpO2, mean arterial pressure, I:E ratio, minute volume of ventilation (MV) and peak inspiratory pressure. There was a significant difference with flumazenil administration for the time to sternal recumbency, the time to the first attempt to rise and the total recovery time. There was no significant difference in total recovery score with flumazenil administration. Main limitations: Plasma levels of midazolam and flumazenil were not obtained. Conclusions: Flumazenil has a dose-dependent effect on MV and recovery time, which may make it useful in cases for which a prolonged anaesthetic recovery is undesirable.

AB - Background: Flumazenil antagonises the actions of benzodiazepines. There has been no prior research specifically investigating this anaesthetic reversal agent for horses. Objectives: To determine the effects of flumazenil administration in horses on (a) ventilatory parameters after midazolam-ketamine induction and maintenance with isoflurane in oxygen and on (b) the characteristics of recovery from general anaesthesia. Study design: Blinded, randomised, crossover experiment. Methods: Six horses were randomly assigned to receive high-dose flumazenil (Fhigh, 20 µg/kg), low-dose flumazenil (Flow, 10 µg/kg) and saline (control). Cardioventilatory parameters were monitored. After 90 minutes of isoflurane anaesthesia, a bolus of Fhigh, Flow or saline was administered i.v. The horses were recovered using head and tail rope assistance. The times to first movement, to achievement of sternal recumbency, to the first attempt to stand and the total recovery time were determined. The recovery quality was evaluated using a 115-point recovery scoring system. The cardioventilatory parameters and recovery times were analysed using mixed-effects regression analyses. Intraclass correlation (ICC) analysis was used to evaluate the recovery scores. A Mann-Whitney U test assessed the relationship between recovery score and flumazenil administration. Results: A significant difference with flumazenil administration was found for SpO2, mean arterial pressure, I:E ratio, minute volume of ventilation (MV) and peak inspiratory pressure. There was a significant difference with flumazenil administration for the time to sternal recumbency, the time to the first attempt to rise and the total recovery time. There was no significant difference in total recovery score with flumazenil administration. Main limitations: Plasma levels of midazolam and flumazenil were not obtained. Conclusions: Flumazenil has a dose-dependent effect on MV and recovery time, which may make it useful in cases for which a prolonged anaesthetic recovery is undesirable.

KW - anaesthesia

KW - benzodiazepine

KW - flumazenil

KW - horse

KW - recovery

U2 - 10.1111/evj.13391

DO - 10.1111/evj.13391

M3 - Journal article

C2 - 33220066

AN - SCOPUS:85097596294

VL - 53

SP - 1257

EP - 1267

JO - Equine Veterinary Journal

JF - Equine Veterinary Journal

SN - 0425-1644

IS - 6

ER -