Cardiovascular Journal of Africa: Vol 32 No 6 (NOVEMBER/DECEMBER 2021)

CARDIOVASCULAR JOURNAL OF AFRICA • Volume 32, No 6, November/December 2021 308 AFRICA Factors associated with acute kidney injury and mortality during cardiac surgery Gontse Leballo, Hlamatsi Jacob Moutlana, Michel Kasongo Muteba, Palesa Motshabi Chakane Abstract Background: Cardiac surgery with cardiopulmonary bypass (CPB) is known to contribute towards the incidence of acute kidney injury (AKI) and peri-operative morbidity and mortal- ity. There are several patient, anaesthetic and surgical factors that contribute to its occurrence. It is imperative to know the profile of a patient who is likely to develop this complication to mitigate for modifiable risks. This study aimed at describ- ing a profile of AKI in an adult patient (over the age of 18 years) following cardiac surgery on CPB. Factors associated with the development of cardiac surgery-associated acute kidney injury (CSA-AKI) are described, as well as the rela- tionship between CSA-AKI and in-hospital mortality. Methods: This was a contextual, descriptive and retrospec- tive 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 cardi- ac surgery on CPB were included. Peri-operative factors such as patient demographics, baseline renal function, 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 devel- oped 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), higher serum creatinine level ( p = 0.025), and lower estimated glomerular filtration rate (eGFR) ( p = 0.025) were associated with the development of CSA-AKI, while a history of hyper- tension 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%), respectively ( p = 0.001)]. 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. Keywords: cardiac surgery-related acute kidney injury, cardio- pulmonary bypass, adults, kidney disease improving global outcomes, renal replacement therapy Submitted 29/5/20, accepted 23/12/20 Published online 3/2/21 Cardiovasc J Afr 2021; 32 : 308–313 www.cvja.co.za DOI: 10.5830/CVJA-2020-063 Cardiac surgery-associated acute kidney injury (CSA-AKI) is a peri-operative complication that carries increased mortality rates, 1 as high as 50% in patients who require renal replacement therapy (RRT) following surgery. 1,2 The incidence of AKI is reported in up to 30% of patients who present for cardiac surgery, with risk factors in the peri-operative period. 3 An increase in pre-operative serum creatinine (SCr) level is significantly prognostic of morbidity and mortality following cardiac surgery. 4 There are nearly two million cardiac surgeries performed globally per year. 5 There is a paucity of statistical data with regard to the incidence and mortality rate of CSA-AKI in sub-Saharan Africa. Studies that have reported on AKI in this region have been in non-surgical patients. 6,7 These reported on mortality rates of up to 43.5% from AKI. Insufficient resources such as RRT and renal transplant services in developing countries should encourage clinicians and scientists in developing approaches aimed at early recognition, diagnosis and the timeous management of AKI. Peri-operative risk factors of CSA-AKI have been investigated and reported on extensively. 3,8,9 These are classified as modifiable and non-modifiable risk factors. 9 They include illnesses such as renal insufficiency, diabetes mellitus, peripheral vascular disease, chronic obstructive pulmonary disease, congestive cardiac failure, left main coronary artery disease and a left ventricular ejection fraction of less than 30%. 10 Procedure-related modifiable risk factors include surgical urgency, the length of cardiopulmonary bypass (CPB) time, aortic cross-clamping time, off-pump surgery, non-pulsatile flow, haemolysis, haemodilution, 10 and the rewarming process following hypothermic arrest. 11 Knowledge of the risk factors allows for optimisation in the peri-operative period. Charlotte Maxeke Johannesburg Academic Hospital (CMJAH), a hospital affiliated to the University of the Witwatersrand in Johannesburg, South Africa, performs over 200 adult cardiac surgeries annually. The incidence of CSA-AKI and factors associated with it in this population are not known. Department of Anaesthesiology, School of Clinical Medicine, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa Gontse Leballo, MB BCh, DA (SA), BSc, gleballomothibi@gmail.com Hlamatsi Jacob Moutlana, MB ChB, DA (SA), FCA (SA), MMed Michel Kasongo Muteba, MB ChB, MSc (Biostatistics) Palesa Motshabi Chakane, BSc, MBChB, DA (SA), FCA (SA), PhD