Introduction: Acute kidney injury (AKI) is an abrupt reduction in kidney function and has been associated with a variety of diseases in hospitalised patients. AKI is one of the recognised complications of cardiac surgery, performed with or without cardiopulmonary bypass (CPB), in people. In this population, development of AKI has a complex and multifactorial aetiology, involving processes such as exposure to exogenous and endogenous toxins, metabolic factors, ischemia-reperfusion, inflammation, oxidative injury and neurohormonal activation. Reported incidence of AKI in people after cardiac surgery varies depending on the identification criteria used and may be as high as 50%. Additionally, development of AKI has been associated with increased in-hospital mortality in this population. Currently there is no information available on incidence of AKI in dogs undergoing cardiac surgery under CPB.

Objectives: To determine the incidence of AKI in dogs undergoing surgery under CPB. To determine if any peri-operative factors influenced development of AKI and to assess if AKI affected survival to discharge.

Materials and methods: Data were retrospectively collected from records of client-owned dogs that had undergone an open heart surgery under CPB between 2005 and 2018 in a single veterinary teaching hospital.

Creatinine and urea were recorded pre-operatively and at three time points post-operatively (0–48 h, 48–96 h and 96–144 h post-operatively). AKI grading was based on the IRIS scheme. Other variables collected included age, breed, surgery type, use of pre-operative diuretics, anaesthesia, bypass, cross-clamp and surgery time, intra-operative hypotension duration, lowest intra-operative mean arterial blood pressure and length of hospitalisation.

Results: Sixty-four dogs were included in the study. The incidence of AKI was 28.2% (18/64). Overall mortality was 22.2% (4/18) for AKI dogs and 28.3% (13/46) for non-AKI dogs, p=0.758. Longer anaesthesia and surgery duration were significantly associated with the development of AKI (p=0.01 and p=0.008 respectively).

Conclusions: AKI is a common occurrence in dogs after open heart surgery under CPB. Future studies are needed to assess the effect of other variables further and to assess whether reducing the anaesthesia and surgery time may reduce the incidence of AKI.