The impact of nursing workforce skill-mix on patient outcomes in intensive care units in Victoria, Australia

Objective: This article aims to examine the impact of nursing workforce skill-mix (percentage of critical care registered nurses [CCRN]) in the intensive care unit (ICU) during a patient's stay. Design: Registry linked cohort study of the Australian and New Zealand Intensive Care Society Adult Patient Database and the Critical Health Resources Information System using real-time nursing workforce data. Settings: Fifteen public and 5 private hospital ICUs in Victoria, Australia. Participants: There were 16,618 adult patients admitted between 1 December 2021 and 30 September 2022. Main outcome measures: Primary outcome: in-hospital mortality. Secondary outcomes: in-ICU mortality, development of delirium, pressure injury, duration of stay in-ICU and hospital, after-hours discharge from ICU and readmission to ICU. Results: In total, 6563 (39.5%) patients were cared for in ICUs with >75% CCRN, 7695 (46.3%) in ICUs with 50–75% CCRN, and 2360 (14.2%) in ICUs with <50% CCRN. In-hospital mortality was 534 (8.1%) vs. 859 (11.2%) vs. 252 (10.7%) respectively. After adjusting for confounders, patients cared for in ICUs with 50–75% CCRN (adjusted OR 1.21 [95% CI 1.02–1.45]) were more likely to die compared to patients in ICUs with >75% CCRN. A similar but non-significant trend was seen in ICUs with <50% CCRN (adjusted OR 1.21 [95% CI 0.94–1.55]), when compared to patients in ICUs with >75% CCRN. In-ICU mortality, delirium, pressure injuries, after-hours discharge and ICU length of stay were lower in ICUs with CCRN>75%. Conclusion: The nursing skill-mix in ICU impacts outcomes and should be routinely monitored. Health system regulators, hospital administrators and ICU leaders should ensure nursing workforce planning and education align with these findings to maximise patient outcomes.