In a multicenter observational cohort of patients-admitted to intensive care units (ICU), we assessed whether creatinine elevation prior to dialysis initiation in acute kidney injury (AKI-D) further discriminates risk-adjusted mortality. AKI-D was categorized into four groups (Grp) based on creatinine elevation after ICU admission but before dialysis initiation: Grp I ？>？0.3？mg/dL to <2-fold increase, Grp II ≥2 times but <3 times increase, Grp III ≥3-fold increase in creatinine, and Grp IV none or <0.3？mg/dl increase. Standardized mortality rates (SMR) were calculated by using a validated risk-adjusted mortality model and expressed with 95% confidence intervals (CI). 2,744 patients developed AKI-D during ICU stay; 36.7%, 20.9%, 31.2%, and 11.2% belonged to groups I, II, III, and IV, respectively. SMR showed a graded increase in Grp I, II, and III (1.40 (95% CI, 1.29–1.42), 1.84 (1.66–2.04), and 2.25 (2.07–2.45)) and was 0.98 (0.78–1.20) in Grp IV. In ICU patients with AKI-D, degree of creatinine elevation prior to dialysis initiation is independently associated with hospital mortality. It is the lowest in those experiencing minor or no elevations in creatinine and may represent reversible fluid-electrolyte disturbances. 1. Introduction Acute kidney injury (AKI) requiring dialysis is a serious complication in critically ill patients, bringing increased morbidity, mortality, and costs of care [1–4]. AKI requiring dialysis is usually considered the most severe form of kidney injury, and these patients have been conventionally regarded as a relatively “homogenous” group of patients, either when describing epidemiological information or while conducting clinical trials [5, 6]. However, studies examining interventions in dialysis patients (e.g., dialysis modality or frequency have not demonstrated unequivocal survival benefits [7–9]. It is well recognized that small changes in creatinine (mild-to-moderate AKI) independently predict mortality [10, 11]; we also recently reported that patients with AKI requiring dialysis represent a wider spectrum of severity of kidney injury, contrary to the prevalent notion [12]. Thus, it can be hypothesized that the degree of elevation of creatinine prior to initiating dialysis may discriminate risk-adjusted mortality, similar to the observations in nondialysis requiring AKI. The Acute Kidney Injury Network (AKIN) has issued standard definitions of AKI; currently, in these criteria, AKI requiring dialysis is classified as stage III (or severe) AKI [13]. The consensus panel also proposed that the examination of natural history
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