The impact of opioid administration on the incidence of postanaesthetic colic in horses
Authors: R. Haralambus, Michaela Juri, Anna Mokry, F. Jenner
Journal: Frontiers in Pain Research
Summary
# Editorial Summary Post-anaesthetic colic remains a significant welfare concern in equine practice, yet evidence regarding opioid-induced gastrointestinal dysfunction has been contradictory, creating uncertainty around optimal pain management protocols. Haralambus and colleagues conducted a retrospective analysis of 782 horses (659 surgical, 123 diagnostic imaging) to determine whether systemic opioid administration—specifically butorphanol, morphine, and methadone—influenced colic incidence within 72 hours of general anaesthesia, stratifying animals by procedure type and opioid duration. Overall post-anaesthetic colic occurred in 15.1% of cases, with important procedural distinctions emerging: diagnostic imaging patients experienced only 6.5% incidence versus 16.7% in surgical cases, whilst emergency procedures showed significantly lower rates (5.8%) than elective surgery (18%). The critical finding relates to opioid pharmacology: neither intraoperative nor short-term postoperative opioid administration increased colic risk, but extended (≥24 hours) morphine use substantially elevated incidence to 34%, whereas long-term butorphanol (5.3%) and methadone (18.4%) demonstrated no such effect. For practitioners, this suggests that post-operative pain management using butorphanol or methadone does not warrant restriction on duration grounds, yet prolonged morphine protocols warrant reconsideration, particularly in elective surgical cases where baseline colic risk is already elevated.
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Practical Takeaways
- •Intraoperative opioids and short-term postoperative opioids are safe to use for pain management without increasing colic risk; choice of opioid matters primarily for extended (>24h) analgesia
- •Avoid long-term morphine administration postoperatively due to 34% PAC incidence; use butorphanol or methadone instead if extended opioid analgesia is needed
- •Diagnostic imaging patients have substantially lower PAC risk (6.5%) than surgical patients (16.7%), and emergency surgeries carry lower colic risk than elective procedures—consider procedure type when planning pain management strategy
Key Findings
- •Overall postanaesthetic colic incidence was 15.1% across 782 horses undergoing general anaesthesia
- •Long-term morphine administration (≥24 h) significantly increased PAC incidence to 34% (p=0.0038), whereas butorphanol and methadone did not
- •Intraoperative and short-term postoperative opioids did not increase PAC rates regardless of drug type
- •Emergency surgeries had significantly lower PAC rates (5.8%) compared to elective procedures (18%)