Automated versus manual urine output monitoring in the intensive care unit

Joni Minor,John A Kellum,Ali Smith,Frederic Deutsch

doi:10.1038/s41598-021-97026-8

Joni Minor, John A Kellum + Show 2 more

Open Access

https://doi.org/10.1038/s41598-021-97026-8

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Abstract

Acute kidney injury (AKI) is defined by changes in serum creatinine and urine output (UO). Significant limitations exist regarding accurate ascertainment of urine output even within the intensive care unit. We sought to evaluate an automated urine output collections system and compare it to nursing measurements. We prospectively collected urine output using an electronic urine monitoring system and compared it to charted hourly UO in 44 patients after cardiac surgery at a single university hospital ICU. We calculated UO and oliguria rates and compared them to data from the sensor and from nursing charting. A total of 187 hourly UO measurements were obtained and on average, UO was reported 47 min late, with a median of 18 min, and a maximum of almost 6 h. Patients had a mean hourly UO of 76.3 ml over the observation period. Compared to manual measurements by study personnel, nurses significantly overestimated hourly UO by 19.9 ml (95% CI: 10.3; 29.5; p = < 0.001). By contrast, the mean difference between the UO measured with the sensor and by study personnel was 2.29 ml (95% CI: − 6.7; 11.3), p = 0.61. Electronic UO monitoring is significantly more accurate than nurse-performed manual measurements in actual intensive care patients. Furthermore, timely ascertainment of UO is difficult to achieve with manual technique, resulting in important delays in detecting oliguria perhaps leading to missed cases of AKI.

Highlights

In recent years, inter-assay variation for serum creatinine has been markedly reduced using isotope dilution mass spectrometry-traceable standards
Jin and coworkers compared intensive urine output (UO) monitoring, defined as hourly recordings and no gaps > 3 h to non-intensive monitoring in more than 15,000 critically ill patients[5]. They found that intensive monitoring was associated with improved survival among patients experiencing Acute kidney injury (AKI)
Because the focus of the study was on urine output measurement and nursing care, patient information was not collected

Summary

Methods

We conducted a prospective observational study comparing the use of the Clarity RMS (RenalSense, Jerusalem, Israel) electronic urine monitoring system to manual recording of a hospitalized patient’s hourly UO. Study coordinators monitored UO by weighing the urine collection bag via a digital scale and this was used the as gold standard for comparisons. Coordinators abstracted hourly UO recordings obtained by the bedside nurses during a 4–6-h period and they downloaded electronic UO data from the Clarity RMS system over the same period of time. We removed any UO recordings that were based on less than 15 min of data or any hours that could not be calculated due to missing information from the scale (the gold standard). Analysis for the sensor validation and comparison to the scale data and nursing measurements consisted of 187 hourly UO measurements from 44 patients. Participating individuals signed an Informed Consent Form approved by the University of Pittsburgh’s Institutional Review Board (IRB#: PRO1703045)

Results

Discussion

Conclusion