Acute kidney injury in intensive care patients: Incidence, time course, and risk factors

Background Acute kidney injury (AKI) is frequent and influences the prognosis of intensive care unit (ICU) patients. The aim of this study was to estimate the incidence, time-course, risk factors, and mortality of AKI among unselected ICU patients. Methods All adult ICU patients admitted to the ICU at the University Hospital in Central Norway from 2010 to 2015 with a stay of 24 h or more were included in the study. AKI was defined according to the Kidney Disease: Improving Global Outcomes (KDIGO) guidelines. All patients were followed with respect to reversal of AKI. Risk factors for AKI were analyzed using Cox regression. Results Among 2325 ICU patients, 1245 developed AKI during the ICU stay, corresponding to an incidence of 53.5 % (CI, 51.5-55.5). The incidence according to KDIGO AKI stages 1, 2, and 3 was 26.2, 11.7, and 15.7%, respectively. The median duration of AKI was 24 (CI 19-24), 32 (CI 26-39), and 101 (CI 75-164) hours for AKI KDIGO stage 1, 2, and 3, respectively. AKI was transient, persistent, or AKD in 73.4, 16.5, and 10.0% of the patients with a known outcome. AKI reversal was observed in 72.9% of all AKI patients. Independent risk factors for AKI in a multivariate analysis were hypertension, diabetes, heart disease, and higher body weight. Episodes of mean arterial pressure below 73 mmHg were associated with a higher risk of AKI. Conclusions In our material, the incidence of AKI was comparable to what has been reported previously. Risk factors for the development of AKI were a MAP below 73, hypertension, diabetes, heart disease, chronic kidney disease, and higher body weight. Most AKI patients regain their kidney function during the ICU stay, particularly in the KDIGO AKI stages 1 and 2.