Urine Output and Development of Acute Kidney Injury in Sepsis: A Multicenter Observational Study

Background: Acute kidney injury (AKI) is common in sepsis and a urine output <0.5 mL/kg/h associated with increased mortality is incorporated into AKI diagnosis. We aimed to identify the urine-output threshold associated with increased AKI incidence and hypothesized that a higher urine output than a specified threshold, which differs from the predominantly used 0.5 mL/kg/h threshold, would be associated with an increased AKI incidence. Methods: This was a post-hoc analysis of a nationwide prospective observational study. This study included adult patients newly diagnosed with sepsis and requiring intensive care. Urine output on the day of sepsis diagnosis was categorized as low, moderate, or high (<0.5, 0.5-1.0, and >1.0 mL/kg/h, respectively), and we compared AKI incidence, renal replacement therapy (RRT) requirement, and 28-day survival by category. Estimated probabilities for these outcomes were also compared after adjusting for patient background and hourly fluid administration. Results: Among 172 eligible patients, AKI occurred in 46.3%, 48.3%, and 53.1% of those with high, moderate, and low urine output, respectively. The probability of AKI was lower in patients with high urine output than in those with low output (43.6% vs 56.5%; P =.028), whereas RRT requirement was lower in patients with high and moderate urine output (11.7% and 12.8% vs 49.1%; P <.001). Patients with low urine output demonstrated significantly lower survival (87.7% vs 82.8% and 67.8%; P =.018). Cubic spline curves for AKI, RRT, and survival prediction indicated different urine-output thresholds, including <1.2 to 1.3 mL/kg/h for AKI and <0.6 to 0.8 mL/kg/h for RRT and mortality risk. Conclusions: Urine output >1.0 mL/kg/h on the day of sepsis diagnosis was associated with lower AKI incidence. The urine-output threshold was higher for developing AKI than for RRT requirement or mortality.