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

BACKGROUND: Information regarding mortality associated with standing procedures in horses is sparse. OBJECTIVES: To report data from >12,000 standing sedations. STUDY DESIGN: 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%). MAIN LIMITATIONS: 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.