, Volume 27, Issue 1, pp 65-71

Urine output on ICU entry is associated with hospital mortality in unselected critically ill patients

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Background and objective

Urine output (UO) is routinely measured in the intensive care unit (ICU) but its prognostic value remains debated. The study aimed to investigate the association between day 1 UO and hospital mortality.


Clinical data were abstracted from the Multiparameter Intelligent Monitoring in Intensive Care II (version 2.6) database. UO was recorded for the first 24 h after ICU entry, and was classified into three categories: UO >0.5, 0.3–0.5 and ≤0.3 ml/kg per hour. The primary endpoint was the hospital mortality. Four models were built to adjust for the hazards ratio of mortality.


A total of 21,207 unselected ICU patients including 2,401 non-survivors and 18,806 survivors were included (mortality rate 11.3 %). Mortality rate increased progressively across UO categories: >0.5 (7.67 %), 0.3–0.5 (11.27 %) and ≤0.3 ml/kg/h (18.29 %), and this relationship remained statistically significant after rigorous control of confounding factors with the Cox proportional hazards regression model. With UO >0.5 as the referent group, the hazards ratios for UO 0.3–0.5 and UO ≤0.3 were 1.41 (95 % CI 1.29–1.54) and 1.52 (95 % CI 1.38–1.67), respectively.


UO obtained on ICU entry is an independent predictor of mortality irrespective of diuretic use. It would be interesting to examine whether strategies to increase UO would improve clinical outcome.