The rise of the internet has opened new avenues for the next major international study to evaluate the risks of death associated with general anaesthesia in horses, according to researchers.
Miguel Gozalo-Marcilla and his fellow researchers noted that it has been almost 20 years since the largest observational, multi-centre study evaluating death risks linked to general anaesthesia in horses, known as the Confidential Enquiry of Perioperative Fatalities (CEPEF).
The high risk of mortality associated with general anaesthesia in horses remains one of the biggest concerns for equine practitioners and veterinary anaesthetists, the researchers said.
Many studies have reported anaesthesia-related mortality risks, most of which were retrospective, they said.
To date, the second Confidential Enquiry into Perioperative Equine Fatalities (CEPEF2), published in 2002, remains the largest observational, multi-centre study on the subject to date, with 41,824 cases collected from 62 clinics over six years. That study found that the overall death rate up to seven days after anesthesia was 1.9% = 0.9% in non-colic cases and 7.8% in colic cases.
“Although much has changed since then, we are still far from reducing these numbers, and the need for an update on the CEPEF data was proclaimed eight years ago,” the study team said.
“Avoiding general anaesthesia by undertaking some procedures in standing horses may reduce the mortality, but there are no data as yet to support this hypothesis,” they noted.
The authors proposed that an online method could be used to collect data for a fresh major study on the subject. The internet, they said, would make online data collection possible from a large pool of participants with few geographical limitations.
“Online data collection is quick, cheap and increases the accuracy and efficacy of data entry. The data could be analysed interactively with the ability to follow-up with participants.”
The researchers set out in their study to assess the usefulness of an internet-based method for a multi-centre study that used an electronic questionnaire and statistical software to show the data and report outcomes from horses undergoing general anaesthesia and certain procedures using standing sedation.
Within six months, 8656 cases from 69 centres (covering 20 countries and four continents) were collected, comprising 6701 procedures under general anaesthesia and 1955 under standing sedation. Of these, only 39 cases were procedures in the field — 31 total intravenous anaesthetics and eight standing sedations.
Typically, 48 cases a day were reported during the study period.
Sixty-six of the 6701 horses that underwent general anaesthesia died, representing a 1% death rate. Of these, 35 (out of 5784) were classified as non-colic deaths (0.6%); and 31 (out of 917) as colic deaths (3.4%).
Deaths reported in the seven-day window following surgery rose, with horses euthanized because of post-operative complications. This was especially significant for colic-related surgeries. While 31 deaths occurred among the 917 horses related directly to general anaesthesia, 253, or 27.6%, were subsequently euthanised in the following seven days because of problems.
Of the 5784 surgeries that were classified as non-colic, 76 were euthanised.
In all, 329 of the 6701 horses that underwent general anaesthesia were euthanised.
Four of the 1955 horses that underwent standing sedation died (0.2%). All were non-colic surgeries.
The study team said the results showed the usefulness of an internet-based method of data collection. It also showed that some horses died unexpectedly when undergoing not only general anaesthesia, but also standing sedation.
The researchers concluded that the internet-based method they employed proved suitable for this type of study, proving to be a reliable, easy, quick and cheap means of collecting data, with minimal geographical limitations.
They said their final goal is to use the same method to collect about 45,000 cases of general anaesthetics for the next CEPEF survey in order to increase the statistical power and to compare the results with those of nearly 20 years ago.
The impact of the last CEPEF study, cited by 448 other publications, reflects the importance of undertaking an update, they said.
On the basis of the cumulative cases collected per week to date, the proposed case numbers sought should be reached in about two years.
As reported in the last CEPEF study, the overall equine anaesthetic mortality rate is still higher than in other veterinary species such as dogs and cats, they said. However, the preliminary data from a small population suggests that the current rate is lower than 20 years ago.
As stated by researchers A.H.A. Dugdale and P.M. Taylor in a 2016 paper: “We still lose horses after anaesthesia to a range of catastrophes that would not occur if the horse were not anaesthetised.”
“Our preliminary results confirm this statement,” Gozalo-Marcilla and his fellow researchers said.
They noted that many of the procedures previously performed only in anaesthetised horses are now carried out using standing sedation. Indeed, 23% of the cases in this study were standing sedations.
New techniques may reduce the mortality rate, they said. However, the results presented in the current study should be interpreted cautiously, as they are only preliminary, with lower numbers than the last CEPEF.
The case details were collected between November 1, 2020, and April 30 this year.
The study team comprised Gozalo-Marcilla, with The Royal (Dick) School of Veterinary Studies and The Roslin Institute in Edinburgh; Regula Bettschart-Wolfensberger, with the University of Zurich in Switzerland; Mark Johnston, with Vetstream Ltd in Cambridge, England; Polly Taylor, with Taylor Monroe, also in Cambridge; and Jose Redondo, with the CEU Cardinal Herrera University in Spain.
Gozalo-Marcilla, M.; Bettschart-Wolfensberger, R.; Johnston, M.; Taylor, P.M.; Redondo, J.I. Data Collection for the Fourth Multicentre Confidential Enquiry of Perioperative Fatalities (CEPEF4) Study: New Technology and Preliminary Results. Animals 2021, 11, 2549. https://doi.org/10.3390/ani11092549