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The following is a summary of “Averaged versus Persistent Reduction in Urine Output to Define Oliguria in Critically Ill Patients: An Observational Study,” published in the June 2024 issue of Nephrology by Monard et al.
Oliguria means urine output (UO) of less than 0.5 ml/kg/h over six hours. However, there needs to be an agreement on whether to use an average or persistent value.
Researchers conducted a retrospective study clarifying the criteria for defining and measuring oliguria accurately.
They analyzed all adult ICU admissions (2010 to 2020), excluding patients with chronic dialysis and those who declined consent. The UO was tracked hourly, and the presence of oliguria was assessed using sliding 6-hour windows to check for oliguria. The average (mean UO below threshold) and persistent methods (all measurements below threshold) were compared. The oliguria’s occurrence and correlation with 90-day mortality and AKD at discharge were analyzed for both methods.
The results showed 15,253 patients, the average method detected oliguria more (73% [95%CI 72.3-73.7] vs. 54.3% [53.5-55.1]) with higher sensitivity for predicting 90-day mortality (85% [83.6-86.4] vs. 70.3% [68.5 – 72]) and AKD at discharge (85.6% [84.2-87] vs. 71.8% [70-73.6]). However, specificity was lower for both outcomes (29.8% [28.9-30.6] vs. 49.4% [48.5-50.3] and 29.8% [29-30.7] vs. 49.8% [48.9-50.7]). Adjusting for various factors (like age, illness severity, comorbidities, weight, gender, and AKI on admission), both methods showed a similar 5% mortality increase attributed to oliguria. Similar results were found when focusing on patients without AKI at admission, with recorded body weight, continuous catheter use, and no renal replacement therapy or diuretics.
Investigators concluded that standardizing the definition of oliguria was crucial due to the significant impact on diagnosis and prognosis.
Source: journals.lww.com/cjasn/abstract/9900/averaged_versus_persistent_reduction_in_urine.396.aspx
