Anaesthetic management and peri-anaesthetic morbidity and mortality in a population of 176 dogs undergoing mitral valve repair under cardiopulmonary bypass.

Objectives: This study aims to describe the anaesthetic management of dogs undergoing mitral valve repair under cardiopulmonary bypass (CPB) and to evaluate the peri-anaesthetic morbidity and mortality of this procedure. Study design: This manuscript presents a retrospective, observational, descriptive cohort analysis performed at a tertiary university hospital. Methods: Medical records of dogs that had undergone mitral valve repair under CPB between August 2017 and June 2024 were examined. Demographic data, perioperative data and complications were recorded. All statistical analyses were conducted in R. The primary endpoint was all-cause mortality before discharge (dead vs. alive at discharge). Descriptive statistic and univariable and multivariable logistic regression models using Firth's penalised maximum likelihood were fitted. Results: A total of 176 dogs underwent CPB for surgical correction of myxomatous mitral valve disease. Perioperative complications were frequent. Certain complications, particularly refractory arrhythmias and low cardiac output events, were often fatal despite aggressive intervention. The overall mortality before discharge was 20.5% (4.0% intraoperatively and 16.5% postoperatively before discharge). Lower body weight, longer CPB time and severe tricuspid regurgitation were factors associated with higher mortality. Conclusions and clinical relevance: Surgical repair of the mitral valve in dogs can be associated with serious intraoperative and postoperative complications. Careful case selection is warranted, particularly in dogs with severe tricuspid regurgitation, low body weight, or other markers of advanced disease. Where feasible, CPB duration should be minimised, and vigilant perioperative monitoring with rapid-response protocols for anticipated complications should be implemented.