Risk factors for colic in horses after general anaesthesia for MRI or nonabdominal surgery: absence of evidence of effect from perianaesthetic morphine.
Authors: Andersen M S, Clark L, Dyson S J, Newton J R
Journal: Equine veterinary journal
Summary
# Editorial Summary Post-anaesthetic colic remains a recognised complication of general anaesthesia in horses, yet its underlying causes have remained largely obscure until now. Andersen and colleagues analysed 553 anaesthetic episodes (342 MRI procedures and 211 nonabdominal surgeries) from 500 horses to identify risk factors for colic development within seven days of recovery, and specifically to investigate whether perianaesthetic morphine administration—a common concern amongst practitioners—increased colic risk. Surgical cases showed significantly higher colic incidence (7.1%) compared with MRI cases (1.5%), and multivariable logistic regression revealed that isoflurane maintenance, benzyl penicillin and/or ceftiofur administration were associated with increased colic risk, whilst romifidine premedication, longer anaesthetic duration, and post-operative sedation within 48 hours were protective factors; importantly, perianaesthetic morphine use showed no association with colic development. For equine professionals, these findings suggest that anaesthetic protocol modifications—specifically selecting alternative maintenance agents to isoflurane where possible, reconsidering prophylactic antibiotic choices, and utilising romifidine premedication alongside appropriate post-recovery sedation—may reduce post-anaesthetic colic incidence, whilst practitioners can reassure clients that morphine administration need not be avoided on colic-risk grounds. The authors acknowledge that the 3.6% overall colic prevalence limits statistical power, warranting larger multicentre studies to confirm these preliminary but practically significant findings.
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Practical Takeaways
- •Surgical patients face 4.7× higher risk of post-anaesthetic colic than MRI patients; heightened vigilance and preventive measures warranted for post-operative orthopaedic cases
- •Consider anaesthetic protocol modifications: romifidine premedication and early post-operative sedation may reduce colic risk, while morphine use is not contraindicated by this evidence
- •Antibiotic choice and anaesthetic agent selection merit review in institutional protocols if colic rates are elevated; further multicentre studies needed to confirm findings
Key Findings
- •Post-anaesthetic colic occurred in 3.6% (20/553) of horses, with surgical cases at 7.1% versus MRI cases at 1.5%
- •Isoflurane maintenance anaesthesia and perioperative administration of benzyl penicillin and/or ceftiofur were associated with significantly increased colic risk
- •Premedication with romifidine, longer anaesthesia duration, and post-operative sedation within 2 days were protective against colic development
- •Perianaesthetic morphine administration was not associated with increased colic risk after controlling for other variables