Antimicrobial prophylaxis is not indicated for horses undergoing general anaesthesia for elective orthopaedic MRI.
Authors: Hoblick Sloane, Denagamage Thomas N, Morton Alison J, McCarrel Taralyn M
Journal: Equine veterinary journal
Summary
# Editorial Summary: Prophylactic Antimicrobials Unnecessary for Elective Orthopaedic MRI Post-anaesthetic fever is a recognised complication of general anaesthesia in horses, yet its true incidence during elective orthopaedic MRI remained poorly characterised. Sloane and colleagues conducted a retrospective analysis of 791 elective orthopaedic MRI procedures performed between 2006 and 2020 on systemically healthy horses, examining associations between fever development and various patient factors, anaesthetic parameters, and prophylactic treatments using multivariable logistic regression. Contrary to their initial hypothesis, horses receiving prophylactic antimicrobials were significantly *more* likely to develop post-anaesthetic fever (odds ratio 3.8; p≤0.001), with fever occurring in only 5.6% of cases overall; younger horses (1–4 years) also showed increased susceptibility compared with adults (≥5 years, OR 2.8; p=0.01). Most fevers resolved spontaneously before hospital discharge without identified infection, suggesting post-anaesthetic fever in this context represents a transient, self-limiting inflammatory response rather than true infection requiring treatment. These findings directly challenge current practice and suggest that prophylactic antimicrobial administration for uncomplicated elective MRI procedures may be counterproductive, potentially exposing horses to unnecessary medication and associated risks without conferring protective benefit.
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Practical Takeaways
- •Do not routinely give prophylactic antimicrobials to healthy horses undergoing elective orthopaedic MRI, as this practice is associated with increased post-anaesthetic fever rather than prevention
- •Expect post-anaesthetic fever in approximately 5-6% of elective MRI cases, but recognise it is usually self-limiting and resolves before discharge without treatment
- •Be alert for post-anaesthetic fever in younger horses (1-4 years old), which show higher incidence than adult horses
Key Findings
- •Post-anaesthetic fever occurred in 44 of 791 cases (5.6%) undergoing elective orthopaedic MRI
- •Horses receiving prophylactic antimicrobials were 3.8 times more likely to develop post-anaesthetic fever than those without antimicrobials (OR 3.8, 95% CI 1.98-7.46; p≤0.001)
- •Young horses aged 1-4 years were 2.8 times more likely to develop fever than adult horses ≥5 years (OR 2.8, 95% CI 1.26-6.17; p=0.01)
- •The majority of early post-anaesthetic fevers resolved before hospital discharge with no identified infectious cause