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

Information regarding mortality associated with standing procedures in horses is sparse.

To report data from >12,000 standing sedations.

Confidential, observational, prospective, multicentre, cohort study.

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.

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%).

Sample size, selection bias, questionnaire initially designed for general anaesthesia, potential human errors for data entry and potential missing cases.

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.