Differences in the incidence, characteristics, and outcomes of patients with acute kidney injury in the medical and surgical intensive care units

Background Though acute kidney injury (AKI) is a prevalent complication in critically ill patients, knowledge on the epidemiological differences and clinical characteristics of patients with AKI admitted to medical and surgical intensive care units (ICUs) remains limited. Methods Electronic medical records of patients in ICUs in Pusan National University Hospital and Pusan National University Hospital Yangsan, from January 2011 to December 2020, were retrospectively analyzed. Different characteristics of AKI between patients were analyzed. The contribution of AKI to the in-hospital mortality rate was assessed using a Cox proportional hazards model. Results A total of 7,150 patients were included in this study. AKI was more frequent in medical (48.7%) than in surgical patients (19.7%), with the severity of AKI higher in medical patients. In surgical patients, hospital-acquired AKI was more frequent (51.0% vs. 49.0%), whereas community-acquired AKI was more common in medical patients (58.5% vs. 41.5%). 16.9% and 5.9% of medical and surgical patients died in the hospital, respectively. AKI affected patient groups to different degrees. In surgical patients, AKI patients had 4.778 folds higher risk of mortality (95% confidence interval [CI], 3.577–6.382; p < 0.001) than non-AKI patients; whereas in medical AKI patients, it was 1.239 (95% CI, 1.051–1.461; p = 0.01). Conclusion While the prevalence of AKI itself is higher in medical patients, the impact of AKI on mortality was stronger in surgical patients compared to medical patients. This suggests that more attention is needed for perioperative patients to prevent and manage AKI.