In horses undergoing volatile anaesthesia, is recovery quality superior with sevoflurane compared to isoflurane?



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PICO question

In horses undergoing volatile anaesthesia, is recovery quality superior with the use of sevoflurane compared to isoflurane during the maintenance phase?


Clinical bottom line

The category of research question


Number and type of study designs reviewed

Seven papers were available for critical appraisal. Of the seven papers, six were prospective, randomised trials and four of these were of crossover design. Of the same seven papers, three were experimental and four were clinical.

Strength of evidence


Outcomes reported

Five out of seven critically appraised articles found that there was no clinically significant improvement in recovery quality following volatile anaesthesia with sevoflurane compared to isoflurane. Two of the seven articles did find improvement in recovery quality following the use of sevoflurane over isoflurane, but both studies were of crossover design, one of these studies used non-blinded evaluators and the second study used both unblinded and blinded evaluators and a recovery quality scoring scale that did not show interobserver reliability.


In healthy horses presented for elective surgical and diagnostic imaging procedures in a clinical setting, there is no significant difference in recovery quality following the use of sevoflurane or isoflurane for the maintenance phase.


How to apply this evidence in practice

The application of evidence into practice should take into account multiple factors, not limited to: individual clinical expertise, patient’s circumstances and owners’ values, country, location or clinic where you work, the individual case in front of you, the availability of therapies and resources.

Knowledge Summaries are a resource to help reinforce or inform decision making. They do not override the responsibility or judgement of the practitioner to do what is best for the animal in their care.


Bettschart-Wolfensberger, R. (2021). Sevoflurane versus isoflurane – which agent leads to better recovery from anaesthesia in horses? Veterinary Record. 189(3), 110–112. DOI:

Bidwell, L. A., Bramlage, L. R. & Rood, W. A. (2007). Equine perioperative fatalities associated with general anaesthesia at a private practice – a retrospective case series. Veterinary Anaesthesia and Analgesia. 34(1), 23–30. DOI:

Brosnan, R. J., Steffey, E. P. & Escobar, A. (2012). Effects of hypercapnic hyperpnea on recovery from isoflurane or sevoflurane anesthesia in horses. Veterinary Anaesthesia and Analgesia. 39(4), 335–344. DOI:

Donaldson, L. L., Dunlop, G. S., Holland, M. S. & Burton, B. A. (2000). The Recovery of Horses from Inhalant Anesthesia: A Comparison of Halothane and Isoflurane. Veterinary Surgery, 29(1), 92–101.DOI:

Dugdale, A. H., Obhrai, J. & Cripps, P. J. (2016). Twenty years later: a single-centre, repeat retrospective analysis of equine perioperative mortality and investigation of recovery quality. Veterinary Anaesthesia and Analgesia. 43(2), 171–178. DOI:

Dugdale, A. H. & Taylor, P. M. (2016). Equine anaesthesia-associated mortality: where are we now? Veterinary Anaesthesia and Analgesia. 43(3), 242–255. DOI:

Gozalo-Marcilla, M., Bettschart-Wolfensberger, R., Johnston, M., Taylor, P. M. & Redondo, J. I. (2021). Data Collection for the Fourth Multicentre Confidential Enquiry into Perioperative Equine Fatalities (CEPEF4) Study: New Technology and Preliminary Results. Animals (Basel), 11(9). DOI:

Gozalo-Marcilla, M. & Ringer, S. K. (2021). Recovery after General Anaesthesia in Adult Horses: A Structured Summary of the Literature. Animals (Basel), 11(6), 1777. DOI:

Grosenbaugh, D. A. & Muir, W. W. (1998). Cardiorespiratory effects of sevoflurane, isoflurane, and halothane anesthesia in horses. American Journal of Veterinary Research. 59(1), 101–106.

Johnston, G. M., Eastment, J. K., Wood, J. & Taylor, P. M. (2002). The confidential enquiry into perioperative equine fatalities (CEPEF): mortality results of Phases 1 and 2. Veterinary Anaesthesia and Analgesia. 29(4), 159–170. DOI:

Johnston, G. M., Taylor, P. M., Holmes, M. A. & Wood, J. L. (1995). Confidential enquiry of perioperative equine fatalities (CEPEF-1): preliminary results. Equine Veterinary Journal. 27(3), 193–200. DOI:

Knych, H. K., Seminoff, K., McKemie, D. S. & Kass, P. H. (2018). Pharmacokinetics, pharmacodynamics, and metabolism of acepromazine following intravenous, oral, and sublingual administration to exercised Thoroughbred horses. Journal of Veterinary Pharmacology and Therapeutics. 41(4), 522–535. DOI:

Laurenza, C., Ansart, L. & Portier, K. (2020). Risk Factors of Anaesthesia-Related Mortality and Morbidity in One Equine Hospital: A Retrospective Study on 1, 161 Cases Undergoing Elective or Emergency Surgeries. Frontiers in Veterinary Science. 6(514). DOI:

Leece, E. A., Corletto, F. & Brearley, J. C. (2008). A comparison of recovery times and characteristics with sevoflurane and isoflurane anaesthesia in horses undergoing magnetic resonance imaging. Veterinary Anaesthesia and Analgesia. 35(5), 383–391. DOI:

Loomes, K. & Louro, L. F. (2021). Recovery of horses from general anaesthesia: A systematic review (2000–2020) of the influence of anaesthetic protocol on recovery quality. Equine Veterinary Journal. 54(2), 219–261. DOI:

Matthews, N. S., Hartsfield, S. M., Mercer, D., Beleau, M. H. & MacKenthun, A. (1998). Recovery From Sevoflurane Anesthesia in Horses: Comparison to Isoflurane and Effect of Postmedication With Xylazine. Veterinary Surgery. 27(5), 480–485. DOI:

Platt, J. P., Simon, B. T., Coleman, M., Martinez, E. A., Lepiz, M. A. & Watts, A. E. (2018). The effects of multiple anaesthetic episodes on equine recovery quality. Equine Veterinary Journal. 50(1), 111–116. DOI:

Read, M. R., Read, E. K., Duke, T. & Wilson, D. G. (2002). Cardiopulmonary effects and induction and recovery characteristics of isoflurane and sevoflurane in foals. Journal of the American Veterinary Medical Association. 221(3), 393–398. DOI:

Santos, M., Fuente, M., Garcia-Iturralde, R., Herran, R., Lopez-Sanroman, J., & Tendillo, F. J. (2003). Effects of alpha-2 adrenoceptor agonists during recovery from isoflurane anaesthesia in horses. Equine Veteterinary Journal. 35(2), 170–175. DOI:

Steffey, E. P. (2002). Recent advances in inhalation anesthesia. Veterinary Clinics of North America: Equine Practice. 18(1), 159–168. DOI:

Steffey, E. P., Mama, K. R., Galey, F. D., Puschner, B. & Woliner, M. J. (2005). Effects of sevoflurane dose and mode of ventilation on cardiopulmonary function and blood biochemical variables in horses. American Journal of Veterinary Research. 66(4), 606–614. DOI:

Valverde, A., Gunkel, C., Doherty, T. J., Giguere, S. & Pollak, A. S. (2005). Effect of a constant rate infusion of lidocaine on the quality of recovery from sevoflurane or isoflurane general anaesthesia in horses. Equine Veterinary Journal. 37(6), 559–564. DOI:

Vettorato, E., Chase-Topping, M. E. & Clutton, R. E. (2010). A comparison of four systems for scoring recovery quality after general anaesthesia in horses. Equine Veterinary Journal. 42(5), 400–406. DOI:

White, K. L., Hird, J. F. R. & Taylor, P. M. (2021). Sevoflurane or isoflurane anaesthesia? A prospective, randomised blinded clinical trial in horses undergoing elective surgery. Veterinary Record. 189(3), e507. DOI:

Young, S. S. & Taylor, P. M. (1993). Factors influencing the outcome of equine anaesthesia: a review of 1,314 cases. Equine Veterinary Journal. 25(2), 147–151. DOI:

Vol. 8 No. 1 (2023): The first issue of 2023

Section: Knowledge Summaries

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