It is almost 20 years since the largest observational, multicentre study evaluating the risks of mortality associated with general anaesthesia in horses. We proposed an internet-based method to collect data (cleaned and analysed with R) in a multicentre, cohort, observational, analytical, longitudinal and prospective study to evaluate peri-operative equine mortality. The objective was to report the usefulness of the method, illustrated with the preliminary data, including outcomes for horses seven days after undergoing general anaesthesia and certain procedures using standing sedation. Within six months, data from 6701 procedures under general anaesthesia and 1955 standing sedations from 69 centres were collected. The results showed (i) the utility of the method; also, that (ii) the overall mortality rate for general anaesthesia within the seven-day outcome period was 1.0%. In horses undergoing procedures other than exploratory laparotomy for colic (“noncolics”), the rate was lower, 0.6%, and in “colics” it was higher, at 3.4%. For standing sedations, the overall mortality rate was 0.2%. Finally, (iii) we present some descriptive data that demonstrate new developments since the previous CEPEF2. In conclusion, horses clearly still die unexpectedly when undergoing procedures under general anaesthesia or standing sedation. Our method is suitable for case collection for future studies.

To evaluate intravenous (IV) detomidine with methadone in horses to identify a combination which provides sedation and antinociception without adverse effects. Randomized, placebo-controlled, blinded, crossover. A group of eight adult healthy horses aged (mean ± standard deviation) 7 ± 2 years and 372 ± 27 kg. A total of six treatments were administered IV: saline (SAL); detomidine (5 μg kg-1; DET); methadone (0.2 mg kg-1; MET) alone or combined with detomidine [2.5 (MLD), 5 (MMD) or 10 (MHD) μg kg-1]. Thermal, mechanical and electrical nociceptive thresholds were measured, and sedation, head height above ground (HHAG), cardiopulmonary variables and intestinal motility were evaluated at 5, 15, 30, 45, 60, 75, 90, 120 and 180 minutes. Normal data were analyzed by mixed-model analysis of variance and non-normal by Kruskal-Wallis (p < 0.05). Nociceptive thresholds in horses administered methadone with the higher doses of detomidine (MMD, MHD) were increased above baseline to a greater degree and for longer duration (MMD: 15-30 minutes, MHD: 30-60 minutes) than in horses administered low dose with methadone or detomidine alone (MLD, DET: 5-15 minutes). No increases in nociceptive thresholds were recorded in SAL or MET. Compared with baseline, HHAG was lower for 30 minutes in MMD and DET, and for 45 minutes in MHD. No significant sedation was observed in SAL, MET or MLD. Intestinal motility was reduced for 75 minutes in MHD and for 30 minutes in all other treatments. Methadone (0.2 mg kg-1) potentiated the antinociception produced by detomidine (5 μg kg-1), with minimal sedative effects. Detomidine (5 μg kg-1) with methadone (0.2 mg kg-1) produced antinociception without the adverse effects of higher doses of detomidine.

Recovery remains the most dangerous phase of general anaesthesia in horses. The objective of this publication was to perform a structured literature review including levels of evidence (LoE) of each study with the keywords “recovery anaesthesia horse”, entered at once, in the search browsers PubMed and Web of Science. The two authors independently evaluated each candidate article. A final list with 444 articles was obtained on 5 April 2021, classified as: 41 “narrative reviews/expert opinions”, 16 “retrospective outcome studies”, 5 “surveys”, 59 “premedication/sedation and induction drugs”, 27 “maintenance with inhalant agents”, 55 “maintenance with total intravenous anaesthesia (TIVA)”, 3 “TIVA versus inhalants”, 56 “maintenance with partial intravenous anaesthesia (PIVA)”, 27 “other drugs used during maintenance”, 18 “drugs before/during recovery”, 18 “recovery systems”, 21 “respiratory system in recovery”, 41 “other factors”, 51 “case series/reports” and 6 “systems to score recoveries”. Of them, 167 were LoE 1, 36 LoE 2, 33 LoE 3, 110 LoE 4, 90 LoE 5 and 8 could not be classified based on the available This review can be used as an up-to-date compilation of the literature about recovery after general anaesthesia in adult horses that tried to minimise the bias inherent to narrative reviews.

To report on the Confidential Enquiry into Perioperative Equine Fatalities 4 (CEPEF4). Confidential, observational, prospective, multicentre, cohort study. 47,396 horses/ponies undergoing general anaesthesia (GA). Characteristics of each GA (249 variables) were collected. Outcomes after seven days were ALIVE (or discharged), EUTHANASIA or DEAD. Logistic regression analysed patient demographics and the anaesthetic drugs (p < 0.05). Data were collected from 47,396 GAs in 93 centres in 28 countries. Death rates were 1.2% overall, 0.6% for cases classified as NON-COLIC and 4.2% for COLIC. For NON-COLICs (227 deaths from 39,798 NON-COLICs), the main three causes of death were fractures (35.7%), abdominal complications (18.1%) and central nervous system problems (13.2%). Logistic regression analyses revealed an increase in the odds of death for pregnant mares, geriatrics, thin horses, those with a higher American Society of Anesthesiologists grade, urgent procedures and those lasting < 1 hour or > 2 hours. Ketamine infusions and plasma lactate measurement during maintenance were associated with elevated risk. By contrast, monitoring invasive arterial pressure, end-tidal CO₂, blood gases and body temperature were each associated with reduced odds of death. Premedication with agonist-antagonist/partial-agonist opioids with non-steroidal anti-inflammatory drugs and administration of α₂-adrenoceptor agonists during recovery, alone or with acepromazine, were associated with reduced odds of death. CEPEF4 reports a reduction in the death rate compared with CEPEF2 in 2002: overall 1.2% versus 1.9%, colic death rate 4.2% versus 7.8% and non-colic death rate 0.6% versus 0.9%. Healthy horses still die, the majority because of fractures during recovery. We identified factors that may influence clinical decision-making and enhance patient safety. The CEPEF4 database will continue to provide clinically applicable information, with potential for further insights and improvements in equine anaesthesia.