Elevated Plasma Concentrations of IL-6 and Elevated APACHE II Score Predict Acute Kidney Injury in Patients with Severe Sepsis

Acute kidney injury (AKI) is common in critically ill patients with severe sepsis (SS), and the predictors of AKI in this population have not been well characterized. The study group was the placebo group of the Prospective Recombinant Human Activated Protein C Worldwide Evaluation in Severe Sepsis (PROWESS) data set. PROWESS is a prospective, randomized, controlled study of the use of drotrecogin alpha (activated) for the treatment of SS. Placebo patients who had an admission renal sepsis organ failure score of 2 or more were excluded. AKI was defined as an increase in serum creatinine of 25% or 0.3 mg/dl during the first week postbaseline. The incidence of relevant parameters was then compared in patients with and without AKI. Half of the patients were randomly assigned to a model-building data set, and multivariable Cox regression was used to determine risk factors. Factors that remained significant in the remaining "model validation" data set were considered significant. Of the 840 patients in the placebo group, 547 met inclusion criteria. Of the 547 patients, 127 (23.2%) patients met criteria for AKI. The mean age of the 547 patients was 59.8 +/- 17.0, and 43.3% of the cohort were female. The ethnicity breakdown was as follows: White 83.2%, black 5.9%, and other 11%. Univariate analyses indicated that patients with AKI had a higher incidence of a dependence on the basis of activity of daily living scale (38.6 versus 26.7%; P = 0.01), a lower baseline platelet count (193,000 versus 222,000; P = 0.02), a higher baseline respiratory Sepsis Organ Failure Assessment score (2.9 versus 2.7; P = 0.02), higher preinfusion Acute Physiology and Chronic Health Evaluation II (APACHE II) score (24.8 versus 22.0; P = 0.0002), older age (63.7 versus 58.7 yr; P = 0.008), and higher log IL-6 (6.6 versus 5.8; P = 0.0006). In a multivariable Cox regression, the predictors of AKI were log IL-6 (P < 0.0001) and APACHE II (P = 0.0008). Increased log IL-6 and APACHE II score are significant risk factors of AKI in patients with SS. IL-6 data and the absence of correlation with measures of hypotension (e.g., mean arterial pressure, dosage of vasopressors) support the notion that inflammation is a significant component of AKI in SS.