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Measuring the Impact of Intensive Care Unit Strain on Patient Outcomes with the Activity Index: An Observational Nation-Wide Study
23 Pages Posted: 29 Nov 2022
More...Abstract
Background: Strain on resources may lead to poor patient outcomes following admission to an Intensive Care Unit (ICU). Consistent quantifiable markers of ICU strain have not been described.
Methods: Data from the Critical Health Resources Information System were matched to the Australian and New Zealand Intensive Care Society Adult Patient Database between June 2020 and March 2022. An Activity Index was calculated as census total of ‘patients with 1:1 nursing’ + ‘invasive ventilation’ + ‘renal replacement’ + ‘extracorporeal membrane oxygenation’ + ‘COVID-19’, divided by total staffed ICU beds. Patients were categorised as admitted to very quiet (Activity Index <0·1), quiet (0·1 to <0·6), intermediate (0·6 to <1·1), busy (1·1 to <1·6) or very busy ICUs (≥ 1·6). The primary outcome was in-hospital mortality. Secondary outcomes included in-ICU mortality, post-ICU mortality, after-hours discharge, discharge delay and readmission.
Findings: 277,737 patients admitted to 175 Australian ICUs were analysed. Median Activity Index was 0·87 (IQR 0·40-1·24). 19,177 (6·9%) patients died. In-hospital mortality ranged from 2·4% in very quiet ICUs, to 10·9% in very busy ICUs. After adjusting for patient and hospital confounders, being in a busier ICU was associated with increased risk of in-hospital mortality (OR 1·49, 99%CI 1·41-1·58), in-ICU mortality (OR 1·59, 99%CI 1·49–1·71), post-ICU mortality (OR 1·24, 99%CI 1·15-1·34), after-hours discharge (OR 1·27, 99%CI 1·23-1·32), readmission (OR 1·18, 99%CI 1·12-1·26) and reduced likelihood of discharge delay (OR 0·58, 99%CI 0·56-0·61).
Interpretation: The Activity Index is a marker of strain which identifies ICUs at risk of adverse patient outcomes.
Funding: This was an unfunded study undertaken by the authors.
Declration of Interest: The authors declare no conflicts of interest or competing interests.
Ethical Approval: The study was approved as a low-risk project by the Human Research and Ethics Committee of The Alfred Hospital (HREC 87/22).
Keywords: Intensive care unit, strain, activity, occupancy, outcomes, mortality, readmission, after-hours discharge
Suggested Citation: Suggested Citation