Pre-operative feeding effects on post-anaesthetic colic and faecal output in horses.

Background: Post-anaesthetic colic (PAC) is a complication in horses undergoing general anaesthesia (GA). Various preoperative feeding strategies are used in equine practice, yet their impact on PAC remains unclear.

Objectives: To identify perioperative risk factors associated with PAC and evaluate the influence of preoperative fasting on PAC prevalence and faecal output.

Study design: Retrospective cohort study.

Methods: Medical records of horses undergoing non-abdominal surgery under GA were reviewed. Horses were categorised into fasted and non-fasted groups based on their pre-anaesthetic feeding regimen. Multivariable logistic regression was used to identify variables associated with PAC. Differences in faecal output and water intake between groups were analysed using a two-tailed hypothesis test.

Results: A total of 620 cases were included. Fasting (odds ratio [OR] 2.7, 95% CI 1.4-5.5, p = 0.005), increased surgery duration (per minute) (OR 1.01, 95% CI 1.002-1.02, p = 0.017) and increasing age (OR 1.08, 95% CI 1.02-1.15, p = 0.012) were significantly associated with PAC. Non-fasted horses passed significantly more manure post-operatively. Median (IQR) manure production per hour was 0.44 (0.31-0.61) piles in non-fasted versus 0.38 (0.25-0.50) piles in fasted horses during the first 24 h post-anaesthesia (p < 0.001) and 0.53 (0.42-0.67) versus 0.50 (0.36-0.63) in the second 24 h post-anaesthesia (p = 0.04). Water intake 12 h pre-anaesthesia was also higher in non-fasted horses (1.02 [0.73-1.75] L/h) compared to fasted horses (0.88 [0.53-1.75] L/h; p < 0.001).

Main limitations: Poor overall accuracy of the predictive model obtained. The retrospective design of the study may introduce bias due to possible inconsistencies in medical records.

Conclusion: Pre-operative fasting was associated with increased risk of PAC and reduced faecal output in horses. These findings support reconsidering fasting practices in equine anaesthesia.