Association between serum levels of interleukin-6 on ICU admission and subsequent outcomes in critically ill patients with acute kidney injury

BACKGROUND: Exacerbated inflammatory response is considered one of the key elements of acute kidney injury (AKI). Interleukin-6 (IL-6) is an inflammatory cytokine that plays important roles in the inflammatory response and may be useful for predicting the clinical outcomes in patients with AKI. However, supporting evidence adapted to the current KDIGO criteria is lacking. METHODS: AKI patients admitted to the ICU between Jan 2011 and Dec 2015 were retrospectively screened. Patients were assigned to three groups by admission IL-6 tertiles. Associations between IL-6 on ICU admission and in-hospital 90-day mortality, short-term/long-term renal function were analyzed. RESULTS: Patients (n = 646) were divided into low (1.5–150.2 pg/mL), middle (152.0–1168 pg/mL), and high (1189-2,346,310 pg/mL) IL-6 on ICU admission groups. Patients in the high IL-6 group had higher in-hospital 90-day mortality (low vs. middle vs. high, P = 0.0050), lower urine output (low vs. middle vs. high, P < 0.0001), and an increased probability of persistent of anuria for ≥12 h (low vs. middle vs. high, P < 0.0001) within 72 h after ICU admission. In contrast, the high IL-6 group had a lower incidence of persistent AKI at 90 days after the ICU admission in survivors (low vs. middle vs. high, P = 0.013). CONCLUSIONS: Serum levels of IL-6 on ICU admission may predict short-term renal function and mortality in AKI patients and were associated with renal recovery in survivors.