A profile of cardiac surgery-related acute kidney injury in adult patients at an academic hospital

Leballo, Gontse
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Background: Cardiac surgery with cardiopulmonary bypass (CPB) is known to contribute towards the incidence of acute kidney injury (AKI) and perioperative morbidity and mortality. There are several patient, anaesthetic, and surgical factors that also contribute to its occurrence. It is imperative to know the profile of a patient that is likely to develop this complication and mitigate the modifiable risks. This study aimed at describing the profile of AKI in an adult (over the age of 18 years) patient following cardiac surgery on CPB. Factors associated with cardias surgery-associated acute kidney injury (CSA-AKI) are described, as well as the relationship between CSA-AKI and in-hospital mortality. Methods: This was a contextual, descriptive, and retrospective single-centre study with data of 476 adult patients admitted post-cardiac surgery between January 2016 and December 2017. Data were collected from Charlotte Maxeke Johannesburg Academic Hospital (CMJAH) in South Africa. All adult patients who presented for elective cardiac surgery (coronary artery bypass graft), valvular, aortic, and other cardiac surgery on CPB were included. Peri-operative factors such as patient demographics, baseline renal functions, co-morbid factors, length of CPB and aortic cross-clamp time, degree of hypothermia, use of assist devices, and post-operative serum creatinine (SCr) levels were collected. Incomplete essential peri-operative data and data for patients who presented on renal replacement therapy (RRT) already were excluded. AKI was defined by Kidney Disease Improving Global Outcomes (KDIGO) criteria. Results: One hundred and thirty-five (28%) patients developed CSA-AKI and 20, 5 and 3% were in KDIGO 1, 2 and 3, respectively. Older age (p = 0.024), female gender (p = 0.015), high serum creatinine level (p = 0.025), and a lower estimated glomerular filtration rate (eGFR) (p = 0.025) were associated with the development of CSA-AKI, while a history of hypertension was predictive. Forty-six of the 476 patients died. Mortality rates were significantly higher in those with AKI compared to those without [28 (21%) vs 18 (5%) p = 0.001], respectively. The incidence was significantly worse in those with severe kidney injury, as evidenced by mortality rates of 44 versus 5% between KDIGO 3 and KDIGO 1 (p ˂ 0.001). pre-operative eGFR and CSA-AKI requiring RRT were significantly associated with mortality, while pre-operative eGFR was an independent predictor of mortality (hazard ratio 0.99, 95% confidence interval: 0.97 – 0.99, p = 0.019). Conclusion: A history of hypertension was predictive of the development of CSA-AKI, and pre-operative eGFR was an independent predictor of mortality in this cohort. Both factors are modifiable
A research report submitted to the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, in the partial fulfilment of the requirements for the degree of Master of Medicine in the branch of Anaesthesiology, 2021