A retrospective observational cohort study on the postoperative respiratory complications and their risk factors in brachycephalic dogs undergoing BOAS surgery: 199 cases (2019-2021)

Abstract OBJECTIVES: To observe the occurrence of post-anaesthetic respiratory complications and to determine their prevalence and risk factors in dogs undergoing brachycephalic obstructive airway syndrome (BOAS) surgery. MATERIALS AND METHODS: Data from 199 clinical records were retrospectively analysed. Univariable logistic regression followed by multivariable logistic regression was used to identify associations between the dependent variables (set as the postoperative respiratory complications observed in the study dogs) and various independent covariates. The quality of model-fit was assessed using the Likelihood Ratio Test (LRT). P ≤ 0.05 was considered statistically significant. RESULTS: Four postoperative respiratory complications were observed: hypoxaemia (n = 10/199; 5%), dyspnoea requiring tracheal re-intubation (n = 13/199, 7%), dyspnoea requiring tracheostomy (n = 10/199, 5%) and aspiration pneumonia (n = 12/199, 6%). Univariable logistic regression showed an association between postoperative aspiration pneumonia and increasing body condition score (BCS) and American Society of Anaesthesiology (ASA) classification; however, when these covariates were evaluated in the multivariable model significance was not maintained (LRT p = 0.029). Risk factors for tracheostomy were preoperative and postoperative aspiration pneumonia (OR: 9.52, 95% CI: 1.56 – 57.93, p = 0.014) and increasing BOAS grade (OR: 4.65, 95% CI: 0.79 – 27.50, p = 0.045; LRT p < 0.001). CLINICAL SIGNIFICANCE: High BOAS grade and aspiration pneumonia – either developing peri-operatively or as pre-existing condition - may represent risk factors for postoperative tracheostomy. Preoperative diagnosis of aspiration pneumonia may further increase the risk of postoperative complications