Early postoperative change in serum creatinine predicts acute kidney injury after cardiothoracic surgery: a retrospective cohort study

Background: Acute kidney injury (AKI) is one of the most severe complications after cardiothoracic surgery (CTS). However, diagnosis of AKI by elevation of serum creatinine (SCr) misses a critical time period for prevention and treatment of AKI. We have observed that patients who develop AKI show a smaller SCr decrease after CTS than those without AKI. Hence, we hypothesized that the magnitude of the SCr change (ΔSCr) measured early after CTS can predict subsequent AKI. Methods: We conducted a retrospective analysis from January 2014 to December 2016 to examine the association of ΔSCr with AKI. ΔSCr was calculated as follows: (early postoperative SCr on intensive care unit [ICU] admission) − (preoperative SCr). Established risk factors and demographics were included in the multivariate-adjusted logistic regression model. AKI was defined by SCr criteria of the Kidney Disease: Improving Global Outcomes group. Results: Among 252 patients who underwent CTS, 69 developed AKI. The median ΔSCr was − 0.14 mg/dL (range − 0.96–0.45). Patients were divided into three groups based on ΔSCr: Group 1, ≤ − 0.2 mg/dL (n = 84); Group 2, > − 0.2 to < − 0.1 mg/dL (n = 76); and Group 3, ≥ − 0.1 mg/dL (n = 92). In the multivariate analysis, Group 3 had a significantly higher incidence of AKI than Group 1 (odds ratio, 7.34; 95% confidence interval 2.55–23.3). ΔSCr was an independent risk factor for AKI (odds ratio for every 0.1-mg/dL increase in ΔSCr, 1.55; 95% confidence interval 1.23–1.97). Conclusions: A minor change in the SCr level early after CTS can predict subsequent AKI just after ICU admission.