Early Urine Output in the Emergency Room as a Prognostic Indicator for Critically Ill Patients Undergoing Continuous Renal Replacement

Abstract

Objectives: The impact of initial emergency room (ER) factors on survival and renal function in critically ill patients undergoing continuous renal replacement therapy (CRRT) remains unclear. This study aimed to evaluate whether these initial factors influence survival and renal recovery in such patients.

Methods: This single-center, retrospective study included 190 critically ill patients admitted to the intensive care unit (ICU) via the ER for CRRT between 1 March 2018, and 31 May 2021. Clinical parameters, including urine output, estimated glomerular filtration rate (eGFR), and serum neutrophil gelatinase-associated lipocalin (NGAL), were assessed. The primary outcomes were 30-day and 90-day mortality, while secondary outcomes included 30-day and 90-day RRT-free durations.

Results: Patients with low urine output (LUO, defined as the average of <0.5 mL/kg/h over 6 h) were significantly associated with higher 30-day and 90-day mortality rates. Multivariable Cox regression analysis revealed that the LUO group had an increased risk of 30-day and 90-day mortality (hazard ratios: 1.935 and 2.141, respectively) compared to the high urine output (HUO, defined as the average of ≥0.5 mL/kg/h over 6 h) group. No significant association was observed between mortality and initial eGFR or plasma NGAL levels. However, the HUO group and patients with initial eGFR ≥ 30 mL/min/1.73 m² had longer RRT-free durations at 30 and 90 days. Plasma NGAL levels did not significantly correlate with RRT-free durations.

Conclusions: Initial 6-h urine output in the ER is a significant predictor of 30-day and 90-day mortality in critically ill patients undergoing CRRT.

Keywords: 30-day mortality; 90-day mortality; acute kidney injury; emergency room; urine output.

Figure 1

Flow diagram for patients. POLST (Physician Order for Life-Sustaining Treatment); * average urine volume of <0.5 mL/kg/h over 6 h; ** average urine volume of ≥0.5 mL/kg/h over 6 h.

Figure 2

Primary outcome. Kaplan–Meier curves for cumulative probability of 30-day (A) and 90-day mortality (B). Low urine output (LUO) group demonstrates higher mortality compared with high urine output (HUO) group (p = 0.004 for 30-day mortality (A), and p = 0.001 for 90-day mortality (B)). * Average urine volume of <0.5 mL/kg/h over 6 h. ** Average urine volume of ≥0.5 mL/kg/h over 6 h. Urine output < 0.5 mL/kg/h: LUO (n = 124), urine output > 0.5 mL/kg/h: HUO (n = 66).