General anaesthesia in horses has become significantly safer
over the past two decades,
according to the latest findings from the
Confidential Enquiry into Perioperative Equine Fatalities (CEPEF4). The large
international study shows that advances in anaesthetic techniques, monitoring
and recovery management have reduced the number of horses dying after
anaesthesia, although the risks remain substantially higher than those seen in
both human and small animal medicine.
Approximately every 10 years, the CEPEF project brings
together veterinary hospitals around the world to assess the safety of equine
general anaesthesia and identify factors that influence patient outcomes. The
fourth phase of the study (CEPEF4) analysed 47,396 general anaesthetic
procedures performed at 93 veterinary centres across 28 countries between
November 2020 and June 2023, making it the largest and most comprehensive
assessment of equine anaesthesia undertaken to date.
Researchers followed every horse for seven days after
anaesthesia, recording whether the animal survived, was euthanased or died,
while also analysing 249 different patient, surgical and anaesthetic variables.
The overall mortality rate associated with general
anaesthesia was 1.2%, representing a substantial improvement compared with the
1.9% reported in the previous major enquiry (CEPEF2) in 2002. Horses undergoing
procedures unrelated to colic had an even lower mortality rate of 0.6%,
compared with 0.9% previously. Among horses requiring emergency surgery for
colic, where patients are already critically ill, mortality fell from 7.8% to
4.2%.
Despite this encouraging progress, horses remain one of the
highest-risk domestic species to anaesthetise. In comparison, modern human
anaesthesia carries an anaesthesia-related mortality estimated at around one
death in 100,000 to 200,000 anaesthetics (approximately 0.001% or lower) in
healthy patients. In dogs, reported anaesthetic mortality is typically around
0.05–0.2% in healthy animals, increasing in those that are seriously ill. Even
with recent improvements, healthy horses therefore continue to face a
considerably greater risk.
The study highlights the recovery period as the most
dangerous stage of anaesthesia. Unlike people or dogs, horses are large prey
animals whose instinct is to stand as quickly as possible when they regain
consciousness. This natural behaviour can result in panic, falls and
catastrophic injuries while they are still uncoordinated.
Among otherwise healthy horses undergoing non-colic
procedures, fractures sustained during recovery accounted for more than
one-third (35.7%) of all deaths. Abdominal complications were responsible for
18.1%, while central nervous system disorders accounted for 13.2%.
The researchers also identified several factors associated
with increased risk. Pregnant mares, geriatric horses, animals in poor body
condition, patients with more severe underlying disease, urgent procedures and
anaesthetics lasting either less than one hour or more than two hours all
carried greater odds of death.
Importantly, the study also identified clinical practices
associated with improved survival. Horses whose anaesthesia included invasive
blood pressure monitoring, end-tidal carbon dioxide measurement, arterial blood
gas analysis and continuous body temperature monitoring experienced
significantly lower odds of death. Adequate pain relief, including combinations
of opioid drugs with non-steroidal anti-inflammatory medications before
anaesthesia, together with the administration of alpha-2 agonist sedatives immediately
before recovery, were also associated with improved outcomes.
The findings provide valuable evidence that continued
investment in monitoring equipment, careful anaesthetic management and recovery
protocols is improving safety for equine patients. They also offer practical
guidance to veterinarians when planning anaesthesia for higher-risk horses and
help owners make informed decisions about treatment.
Although healthy horses can still die following routine
anaesthesia, the steady decline in mortality over successive CEPEF studies
demonstrates how advances in veterinary medicine continue to make equine
anaesthesia safer. Researchers believe the extensive CEPEF4 database will
continue to generate new insights that could further reduce risks in the years
ahead, particularly during the critical recovery period where the greatest
opportunities for improvement remain.
For more details, see:
Miguel Gozalo-Marcilla,
José I. Redondo, Regula Bettschart-Wolfensberger, Luis Domenech, Javier
Doménech, G Mark Johnston, Polly M. Taylor.
The Confidential
Enquiry into Perioperative Equine Fatalities: phase 4 (CEPEF4) – a worldwide
observational, prospective, multicentre cohort study in 2025.
Veterinary Anaesthesia
and Analgesia (2025) Vol 52, (5), p
525-538.
https://doi.org/10.1016/j.vaa.2025.06.005