Acute kidney injury after major non-cardiac surgery: Incidence and risk factors

Background. Acute kidney injury (AKI) is a major post-surgical complication that contributes to morbidity and mortality. AKI is well documented after cardiac surgery. However, less is known regarding the incidence and risk factors following major non-cardiac surgery. Globally the incidence of AKI post major surgery has been evaluated; however, there are no data available for South Africa (SA).Objectives. To ascertain the incidence of AKI after major non-cardiac surgery at a tertiary academic SA hospital. Secondary outcomes were to identify perioperative risk factors that are associated with an elevated risk to develop AKI in the postoperative period. Methods. The study was conducted at Tygerberg Hospital, a single tertiary centre in Cape Town, SA. Perioperative records of adults who underwent major non-cardiac surgery were retrospectively collected. Variables pertaining to potential risk factors for AKI were captured, and serum creatinine levels were recorded up to 7 days postoperatively and compared with baseline measurements to determine whether AKI had developed. Descriptive statistics along with logistic regression analysis were used to interpret results. Results. The overall incidence of AKI was 11.2% (95% confidence interval (CI) 9.8 12.6). Based on surgical discipline, trauma surgery (19%), followed by abdominal (18.5%) and vascular surgery (17%) had the highest incidence. Independent AKI risk factors were identified after multivariate analysis. These were: chronic obstructive pulmonary disease (odds ratio (OR) 2.19; 95% CI 1.09 4.37; p=0.005), trauma surgery (OR 3.00; 95% CI 1.59 5.64; p=0.001), abdominal surgery (OR 2.14; 95% CI 1.33 3.45; p=0.002), vascular surgery (OR 2.42; 95% CI 1.31 4.45; p=0.004), urology procedures (OR 2.45; 95% CI 1.31 4.45; p=0.005), red blood cell transfusion (OR 1.81; 95% CI 1.21 2.70; p=0.004), emergency surgery (OR 1.74; 95% CI 1.15 2.65; p=0.009) and inotrope use (OR 2.77; 95% CI 1.80 4.26; p<0.001). Conclusion. The results of our study are in keeping with international literature regarding the incidence of AKI after major non-cardiac surgery. The risk factor profile, however, is in several regards different from what has been found elsewhere.