A systematic review of the prevalence of post-operative complications after general anaesthesia in adult horses (2000-2023)

Background: Equine post-operative morbidity represents a significant concern for both veterinary surgeons and horse owners. Objectives: To estimate the prevalence of post-operative complications in horses after elective/non-abdominal surgery or colic surgery. Study design: Systematic review. Methods: A database search identified eligible studies which reported the prevalence of equine post-operative complications published as a full paper in English in a peer-reviewed journal between 2000 and 2023. Studies were evaluated using the JBI Critical Appraisal Checklist for Prevalence Studies and GRADE (Grading of Recommendations, Assessment, Development and Evaluations) framework. Data for the most commonly reported complications were analysed using Chi-squared analysis of weighted means to answer 13 PICO (Population, Intervention, Comparator and Outcomes) questions. Results: Sixty-seven studies met inclusion criteria. Data for eight post-operative morbidities (colic, surgical site complications, myopathy/neuropathy, laminitis, diarrhoea/colitis, fever/pyrexia, jugular thrombophlebitis/thrombosis, respiratory complications) were sufficient to allow statistical analyses. The weighted mean of the overall proportion of post-operative complications after elective/non-abdominal surgery is 17.48% (95% confidence interval [95% CI]: 13.20–22.92), significantly increasing to 55.62% (95% CI: 45.79–65.03) after colic surgery (odds ratio [OR] 6.63; 95% CI: 5.83–7.56; p < 0.001). The most commonly reported morbidity was post-operative colic, with a weighted mean prevalence of 7.45% (95% CI: 4.83–11.76) after elective/non-abdominal surgery, significantly rising to 26.46% (95% CI: 19.11–35.97) after colic surgery (OR 4.11; 95% CI: 3.60–4.71; p < 0.001). The weighted mean prevalence of surgical site complications, laminitis, diarrhoea/colitis, fever/pyrexia, jugular thrombophlebitis/thrombosis and respiratory complications were significantly higher after colic surgery compared with elective/non-abdominal surgery. Myopathy/neuropathy was the only morbidity where prevalence was not different between groups (OR 1.86; 95% CI: 0.86–4.16; p = 0.16). Main limitations: The majority of studies were retrospective. Morbidity definitions, data collection periods, follow-up time and methods varied between studies. Conclusions: Based on current evidence, the prevalence of post-operative colic, surgical site complications, laminitis, diarrhoea/colitis, fever/pyrexia, jugular thrombophlebitis/thrombosis and respiratory complications is significantly higher after colic surgery compared with elective/non-abdominal surgery under general anaesthesia.