Urine output: how and why is it monitored in acute medical environments?

Abstract

Background: Urinary tract infection is a leading cause of healthcare associated infection in hospitals with around half of these being attributable to indwelling urinary catheters. Overuse of urinary catheters in healthcare settings is a known problem yet the extent to which it is possible to avoid catheter use is unclear. Urine output monitoring is one of the main indications for short-term catheter use, with acute kidney injury (AKI) and sepsis as key drivers to detect oliguria (low urine output). However, published guidance lacks clarity on when a catheter is needed for urine output monitoring, fueling uncertainty and potential for overuse in clinical practice. Aim: The aim of this research is to explore how and why urine output is monitored in acute medical environments. Methods: A sequential, explanatory mixed methods study was designed. Two approaches to data collection were used: a point prevalence survey of 17 medical wards, using the whole source population as the sample and analysed using descriptive statistics, followed by a focused ethnography in an acute medical unit and a medicine for older people ward using a purposive sample and reflexive thematic analysis. Findings: The prevalence survey identified 107/389 (27.5%) patients had an indwelling urinary catheter. Almost half (n=49/107; 46%) were placed solely for the purpose of urine output monitoring. Most (n=87/107; 81%) catheters had a urine meter attached to enable 1-2 hourly measurements, but only 12% (n=7/60) were utilised for this purpose outside of critical care. The focused ethnography revealed how clinicians were influenced both by clinical and non-clinical rationales when justifying the need for a urinary catheter to monitor urine output. Distrust in the use of non-invasive collection methods was a significant contributing factor to catheter use. Conclusion: Urinary catheters are thought to champion the accuracy of urine output monitoring, but it is debatable whether the drive for accuracy is jeopardising rather than improving patient safety. The redundancy of most urine meters outside of critical care in one hospital reveals considerable potential for reduction in urinary catheters and thereby in catheter-associated infections. However, uncertainty about the reliability and practical application of non-invasive approaches for urine output monitoring is likely to hinder such reduction and requires further investigation.

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Identifiers

ORCID for Camilla, Elizabeth Holmes: orcid.org/0000-0002-6530-2259

ORCID for Jacqui Prieto: orcid.org/0000-0002-5524-6775

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