Novel biological risk factors for 7-day postoperative kidney injury in elective major non-cardiac surgery: a retrospective observational study.
Background: Few UK studies have explored the epidemiology of postoperative acute kidney injury after diverse types of elective major non-cardiac surgery. Fewer still have compared postoperative acute kidney injury risk factors with conditions such as peri-operative myocardial injury that might have similar pathophysiology. This study aimed to characterise postoperative acute kidney injury and its clinical consequences in elective major non-cardiac surgery, and to assess risk factors for postoperative acute kidney injury including those related to peri-operative myocardial injury.
Methods: All elective major non-cardiac surgical episodes, occurring between 2015 and 2020, were identified retrospectively. Patients without measured peri-operative renal parameters were not studied. Our primary outcome was 7-day postoperative acute kidney injury rate, defined using Kidney Disease Improving Global Outcomes criteria. Multivariable logistic regression modelling was used to assess risk factors for postoperative acute kidney injury.
Results: Postoperative acute kidney injury occurred in 1334/13,790 (9.7%) episodes, with 663 (49.7%) occurring on day 1. Postoperative acute kidney injury was associated with increased peri-operative complications (OR 1.8, 95%CI 1.6-2.1, p < 0.001), unanticipated critical care admissions (OR 2.4, 95%CI 1.6-3.5, p < 0.001) and in-hospital mortality (OR 8.0, 95%CI 5.1-12.5, p < 0.001). Independent risk factors for postoperative acute kidney injury include: raised creatinine; hypertension; anaemia; platelet: lymphocyte ratio; heart rate; male sex: renin-angiotensin-aldosterone system blockade; and intra-abdominal surgery.
Conclusions: Postoperative acute kidney injury is common and is associated with adverse outcomes. Prevalence peaks initially within the first 48 h, with a secondary rise seen from day 5 onwards, suggesting a different aetiology. It is determined by a combination of patient and surgical risk factors, with the former relating to physiological, rather than chronological, renal age. In common with peri-operative myocardial injury, postoperative acute kidney injury is independently associated with factors affecting autonomic tone and myeloid skewing.