Equine veterinary journal2026; doi: 10.1002/evj.70183

Fatalities within seven days after equine standing sedation: A prospective, multicentre study.

Gozalo-Marcilla, M
·
Redondo, JI
·
Taylor, PM
·
Domenech, L
·
Doménech, J
·
Johnston, GM
·
Bettschart-Wolfensberger, R

Abstract: Information regarding mortality associated with standing procedures in horses is sparse. Objective: To report data from >12,000 standing sedations. Methods: Confidential, observational, prospective, multicentre, cohort study. Methods: We collected records of horses/ponies undergoing standing sedation for surgery or advanced diagnostic imaging using at least one top-up or controlled rate infusion (CRI). Procedures were either NON-COLIC or COLIC. Outcome at seven days was recorded as (i) ALIVE, (ii) EUTHANASIA or (iii) DEAD. Data were collected with a portable document format (PDF) questionnaire, which evolved into a webpage, and processed with the statistical software R. Results: Data were collected from 12,307 standing sedations in 61 centres in 23 countries. Death rates were 0.15% overall (19/12,307), 0.13% for NON-COLICs (16/12,237) and 4.29% for COLICs (3/70). The causes of death in the 16 NON-COLICs were abdominal complications in 10 (62.50%), fracture/repeat fracture in three (18.75%), two were 'found dead' (12.50%) and one (6.25%) for 'other reasons'. In most cases premedication consisted of combinations of alpha-2 agonists/opioids with or without acepromazine. Sedation was maintained using top-ups (9668/12,307), CRIs (3795/12,307) or CRI + top-up (1156/12,307). Detomidine was the alpha-2 agonist most frequently used for top-ups (8258/12,307) and butorphanol the most common opioid (2754/12,307). Detomidine was the most frequently used alpha-2 agonist for CRI (3231/12,307); 364 and 305/12,307 received butorphanol and morphine as CRIs, respectively. Only 24.2% received fluid therapy. Loco-regional anaesthesia was performed in 37.6% of the cases. Monitoring was minimal, with temperature (5.8%), electrocardiogram (3.8%), non-invasive arterial pressure (2.1%), end-tidal carbon dioxide (1.1%) and pulse-oximetry (0.9%). Conclusions: Sample size, selection bias, questionnaire initially designed for general anaesthesia, potential human errors for data entry and potential missing cases. Conclusions: Standing sedation in horses is not risk free. Horses die unexpectedly within seven days of sedation. Efforts should be made to reduce these mortality rates further.

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Publication Date: 2026-06-25 PubMed ID: 42345327DOI: 10.1002/evj.70183Google Scholar: Lookup

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Objective Overview

This study analyzed mortality within seven days following standing sedation in horses by collecting and examining data from over 12,000 sedation events across multiple centers worldwide.
It aimed to quantify death rates, identify causes of death, describe sedation protocols, and assess monitoring practices during standing sedation.

Study Design and Methods

The research was a prospective, observational, multicenter cohort study involving 61 centers across 23 countries.
Data were collected on horses and ponies undergoing standing sedation for surgical or advanced diagnostic procedures classified as either NON-COLIC or COLIC cases.
All cases involved at least one sedation top-up or a controlled rate infusion (CRI) of sedative drugs.
A confidential questionnaire initially distributed as a PDF (later evolving into a webpage) was used to gather procedural and outcome data.
Outcomes were recorded at seven days post-sedation as ALIVE, EUTHANASIA, or DEAD.
Data were analyzed using the statistical software R.

Key Findings: Mortality Rates and Causes

A total of 12,307 standing sedation events were analyzed.
The overall mortality rate within seven days was 0.15% (19 deaths).
Breaking down by procedure type:
- NON-COLIC procedures had a mortality rate of 0.13% (16 deaths out of 12,237 cases).
- COLIC cases had a notably higher mortality rate at 4.29% (3 deaths out of 70 cases).
For NON-COLIC deaths, major causes were:
- Abdominal complications: 62.5% (10/16 deaths).
- Fractures or repeat fractures: 18.75% (3/16).
- “Found dead” without known cause: 12.5% (2/16).
- Other unspecified reasons: 6.25% (1/16).

Details on Sedation Protocols

Premedication commonly combined alpha-2 agonists and opioids, sometimes with acepromazine.
Maintenance sedation was achieved through:
- Top-up doses alone in 9,668 cases.
- CRIs alone in 3,795 cases.
- Combination of CRI and top-up in 1,156 cases.
The most frequently used sedatives were:
- Alpha-2 agonist: Detomidine (used in 8,258 top-up cases and 3,231 CRI cases).
- Opioids: Butorphanol (2,754 top-up cases, 364 CRI cases) and morphine (305 CRI cases).
Fluid therapy was administered in approximately 24.2% of sedation events.
Loco-regional anesthesia was performed in 37.6% of cases alongside sedation.

Monitoring Practices

Minimal physiological monitoring was reported during sedation:
- Temperature was monitored in only 5.8% of cases.
- Electrocardiogram (ECG) used in 3.8%.
- Non-invasive arterial blood pressure measured in 2.1%.
- End-tidal carbon dioxide monitored in 1.1%.
- Pulse oximetry used in 0.9% of sedations.

Study Limitations

Potential selection bias influenced by voluntary participation of centers and case inclusion.
The initial questionnaire design was tailored for general anesthesia cases, which may have affected data relevance for standing sedation.
Human error risks associated with manual data entry and reporting.
Possible missing cases that were not captured by the data collection method.

Conclusions and Implications

Standing sedation in horses carries a non-negligible risk of mortality, including unexpected deaths within a week after the procedure.
Though relatively low overall, death rates are significantly higher in colic cases, highlighting the critical nature of these patients.
Abdominal complications and fractures are primary causes of death, underscoring the need for careful patient selection and monitoring.
The low rates of physiological monitoring during sedation raise concerns and suggest a potential area to improve patient safety.
Further efforts should focus on:
- Reducing mortality through better monitoring and sedation protocols.
- Improving data collection methods to obtain more comprehensive safety profiles.
- Increasing awareness of sedation risks, even in standing procedures considered less invasive than general anesthesia.

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APA

Gozalo-Marcilla M, Redondo JI, Taylor PM, Domenech L, Doménech J, Johnston GM, Bettschart-Wolfensberger R. (2026). Fatalities within seven days after equine standing sedation: A prospective, multicentre study. Equine Vet J. https://doi.org/10.1002/evj.70183

Publication

Equine veterinary journal

ISSN: 2042-3306

NlmUniqueID: 0173320

Country: United States

Language: English

Researcher Affiliations

Gozalo-Marcilla, Miguel

The Royal (Dick) School of Veterinary Studies and The Roslin Institute, The University of Edinburgh, Edinburgh, UK.

Redondo, José I

Departamento de Medicina y Cirugía Animal, Facultad de Veterinaria, Universidad Cardenal Herrera-CEU, CEU Universities, Valencia, Spain.

Taylor, Polly M

Taylor Monroe, Little Downham, UK.

Domenech, Luis

Departamento de Matemáticas, Física y Ciencias Tecnológicas, Escuela Superior de Enseñanzas Técnicas, Universidad Cardenal Herrera-CEU, CEU Universities, Valencia, Spain.

Doménech, Javier