Relationship Between Initial Urine Output and Mortality in Patients Hospitalized in Cardiovascular Intensive Care Units: More Is Not Better

BACKGROUNDS: Decreased urine output (UO) is associated with adverse outcomes in certain patients, but this effect in patients admitted for cardiovascular diseases is still unproven. Moreover, the relationship between increased UO and prognosis is also unclear. OBJECTIVE: To investigate the relationship between decreased or increased UO and outcomes in patients with the cardiovascular intensive care unit (CICU). METHODS: This study was a retrospective cohort analysis based on the medical information mart for intensive care III (MIMIC-III) database. The patients' data were extracted from the Beth Israel Deaconess Medical Center (Boston, MA) between 2001 and 2012. With the initial 24-h UO range from 0.5 to 1.0 ml/kg/h as the reference, participants were divided into the several groups. The primary outcome was 30-day mortality. The secondary outcomes were 90-day mortality, ICU mortality, hospital mortality, use of mechanical ventilation (MV), and vasopressor agents in the first 24-h of ICU. The association between UO and mortality was assessed by multivariable logistic regression. RESULTS: A total of 13,279 patients admitted to CICU were included. Low UO (< 0.5 ml/kg/h) was strongly associated with 30-day mortality (unadjusted OR = 3.993, 95% CI: 3.447–4.625, p < 0.001), and very high UO (≥ 2.0 ml/kg/h) was also a significantly risk factor for 30-day mortality (Unadjusted OR = 2.069, 95% CI: 1.701–2.516, p < 0.001) compared with the reference. The same effects also were shown in the multivariable logistic regression, adjusted by age, gender, vital signs, common comorbidities, and use of diuretics, with an adjusted OR of 2.023 (95% CI: 1.693–2.417, p < 0.001) for low UO and 1.771 (95% CI: 1.389–2.256, p < 0.001) for very high UO. Moreover, both decreased UO and increased UO were risk factors for 90-day mortality, ICU mortality, hospital mortality, use of MV and vasopressor agents. CONCLUSION: The decreased and increased UO both were significantly associated with short-term mortality, the relationship between UO and mortality was U-shape rather than linear.