CEPEF4: update and plan.

Mortality related to anaesthesia is higher in horses than in other domestic species. Overall mortality rates in dogs, cats and rabbits were 0.17%, 0.24% and 1.34%, respectively, in the multicentre, prospective, cohort study reported by Brodbelt et al. (2008). Several studies have been published establishing mortality rate and factors associated with the risk of death in horses; however, many studies were single-centre and/or retrospective (Senior 2013).

It is almost 20 years since Johnston et al. (2002) published the Confidential Enquiry into Perioperative Equine Fatalities 2 (CEPEF2) study. This is still the largest multicentre investigation with a collection of 41,824 cases from 62 clinics worldwide spanning 6 years. The CEPEF2 study reported an overall equine mortality rate of 1.9%. This was reduced to 0.9% when only elective procedures in healthy horses were included, and increased to 11.7% in horses with colic. This study included 7 days follow-up after anaesthesia. Subsequently in 2004, CEPEF3 was published as a randomised controlled trial investigating the relative outcomes after halothane or isoflurane anaesthesia (Johnston et al. 2004).

In retrospect, it is clear that much has changed since 2004. For instance, halothane was then the most commonly used inhalant agent whereas it is now neither manufactured nor used in many countries. Other advancements have been made, including new drugs and anaesthetic protocols, more sophisticated monitoring, improved anaesthesia machines, ventilators and ancillary equipment, such as infusion pumps, all considered likely to improve safety. The ultimate aim is to provide anaesthesia and recovery with minimal complications, thereby reducing mortality and morbidity related to anaesthesia.

With these new developments we should expect that the death rate of one healthy horse out of 100 anaesthetized is reduced. However, Dugdale & Taylor (2016) in their narrative review claimed that even with all these improvements, “we are still a long way from greatly reducing the mortality associated with equine anaesthesia”. Indeed, their statement “we still lose horses after anaesthesia to a range of catastrophes that would not occur if the horses were not anaesthetized” has been taken up in recent years with a move towards avoiding general anaesthesia when possible, using more refined techniques for long term sedation and analgesia and inclusion of the in vogue ultrasound-guided locoregional techniques.

In an editorial in this journal, Gent & Bettschart-Wolfensberger (2013) declared the need for an update to identify any change in mortality rates from that reported previously in CEPEF2. That is already 7 years ago, providing incentive for initiating CEPEF4. The main aim is to collect an up-to-date dataset as comprehensive as CEPEF2 to document mortality related to equine anaesthesia, but also to identify current trends in equine anaesthesia and analgesia. Highlighting any associations with successful or unsuccessful outcomes should show which, if any, of the new developments are beneficial and point the way to further improvement.

A CEPEF4 team has been created; more information can be found at https://cepef4.wordpress.com/cepef-4-team/. Unfortunately, a presentation describing the proposed CEPEF4 scheduled during the 2020 spring meeting of the Association of Veterinary Anaesthetists in Dublin was lost to the COVID-19 pandemic. This presentation proposed a digital questionnaire based on previously presented methodology for small animals, adapted to the particularities of horses requiring anaesthesia. The questionnaire is user-friendly for use on phone, tablet or laptop and is designed for collecting anaesthetic and horse related data to describe the current worldwide equine anaesthetic practice and to detect factors associated with mortality. The questionnaire builds on the experience of CEPEF2. In particular, the end point of ‘alive or dead’ at 7 days may be reduced to 3 days to facilitate reliable data collection. However, this change is still under consideration because it would impair comparison with CEPEF2.

Launching this study during the COVID-19 pandemic would have biased the case logs in the first months of the study by exerting unnecessary pressure on potential collaborators already dealing with the uncertainties of veterinary care at that time. Instead, we have used our professional network to involve researchers and clinicians with a special interest in this subject to evaluate and comment on the proposed investigation. We are extremely grateful for the invaluable feedback that has undoubtedly improved the quality of the questionnaire.

We hope that this letter will encourage all veterinarians treating horses to participate in CEPEF4 so that the current equine anaesthetic-related mortality rate can be documented. The results may identify areas that can be improved and we hope that CEPEF4 will become a shared resource to stimulate and enable further research for all involved in equine anaesthesia. November 2020 is the scheduled start of CEPEF4. If you are interested in helping, please do not hesitate to contact us via https://cepef4.wordpress.com.