Evaluating the ABCDEF Bundle in Australian ICUs: Impacts on Delirium, Functional Status, and Long-Term Quality of Life

Highlight

• The ABCDEF bundle did not reduce delirium incidence or duration compared to usual care in adult ICU patients.
• Functional independence at ICU discharge was similar between intervention and control groups.
• At 90 days post-ICU discharge, patients receiving the ABCDEF bundle reported significantly better ability to perform usual activities, indicating a potential long-term quality of life improvement.
• Adherence to the complete ABCDEF bundle was achieved in only half of the patients on each study day, reflecting real-world implementation challenges.

Study Background

Delirium is a common, serious complication in critically ill patients receiving intensive care, associated with increased morbidity, prolonged hospital stays, and long-term cognitive and functional impairment. Preventive strategies to reduce delirium incidence and severity are therefore critical to improving patient outcomes. The ABCDEF bundle is a multicomponent, evidence-based approach incorporating components such as Assessing and managing pain, Both spontaneous awakening and breathing trials, Choice of sedation, Delirium prevention and management, Early mobility, and Family engagement. This bundle aims to improve delirium and functional outcomes in ICU patients by integrating multiple interventions targeting known risk factors.

Although the ABCDEF bundle has been recommended by critical care guidelines and implemented in many centers worldwide, high-quality randomized data from diverse settings, including Australia, remain limited. This study sought to evaluate the bundle’s effect on delirium incidence and duration, functional status at ICU discharge, and quality of life at 90 days after ICU discharge in a pragmatic clinical trial conducted in a metropolitan Australian hospital ICU.

Study Design

This investigation was a single-center, pragmatic, randomized controlled trial conducted in an eight-bed medical/surgical ICU in Australia. Adult patients expected to remain in the ICU for at least 48 hours were randomized 1:1 to receive either the ABCDEF bundle-based care or usual care.

The intervention arm implemented the ABCDEF bundle, integrating protocolized pain assessment and management, spontaneous awakening and breathing trials, sedation choice optimization, delirium monitoring and management, early mobilization, and family engagement strategies. Usual care reflected standard ICU practices without mandated bundle elements.

The primary outcome was the cumulative incidence of delirium measured by the Confusion Assessment Method for ICU (CAM-ICU). Secondary outcomes included delirium duration, functional independence at ICU discharge measured by the Functional Independence Measure (FIM), and health-related quality of life assessed using the EuroQol 5D five-level questionnaire (EQ-5D-5L) at 90 days post-ICU discharge.

Key Findings

Adherence rates to the complete ABCDEF bundle averaged 50% per patient day, underscoring challenges of consistent implementation in clinical practice.

The primary outcome, delirium incidence, was 37.9% in the ABCDEF group and 36.4% in the usual care group, with an odds ratio of 1.1 (95% CI, 0.5-2.2; p=0.86), indicating no significant difference.

Similarly, median delirium duration did not differ significantly between groups (ABCDEF: 2.0 days [IQR 1.3-3.5] vs usual care: 2.5 days [IQR 1.0-4.4]; mean difference -0.4 days, 95% CI -1.6 to 0.8; p=0.53).

Regarding functional status, FIM scores at ICU discharge were comparable (median 55.0 [IQR 37.0-67.3] ABCDEF vs 53.0 [IQR 43.8-62.5] usual care; mean difference 0, 95% CI -7.7 to 7.6; p=0.83), indicating no significant benefit on immediate functional outcomes.

However, at 90 days post-ICU discharge, patients in the ABCDEF bundle group reported significantly higher scores in the “usual activities” domain of the EQ-5D-5L (p<0.001), suggesting improved ability to perform routine daily tasks. No other quality-of-life domains differed significantly.

Expert Commentary

This pragmatic trial reflects challenges in translating protocols like the ABCDEF bundle into routine ICU practice, evidenced by only partial adherence and lack of impact on the primary outcome of delirium incidence. Prior literature supports the bundle’s potential, but real-world effectiveness may vary based on institutional factors, staff training, and patient selection.

Importantly, the lack of delirium reduction does not negate the possible downstream functional benefits seen at 90 days, possibly mediated by cumulative effects of multi-domain interventions improving overall patient recovery trajectories.

Some limitations include the single-center design limiting generalizability, incomplete bundle adherence possibly attenuating measurable benefits, and absence of long-term cognitive assessments beyond quality-of-life self-reports. Future larger multicenter trials with enhanced adherence strategies and extended follow-up are warranted.

Conclusion

In this Australian ICU study, the ABCDEF bundle did not reduce delirium incidence or duration nor improve functional independence at ICU discharge compared with usual care. Nonetheless, the observed improvement in patients’ ability to perform usual activities at 90 days suggests potential long-term quality-of-life benefits that merit further investigation. Efforts to optimize bundle adherence and explore underlying mechanisms may help maximize its patient-centered value in critical care.

Funding and Registration

The study was funded as detailed in the primary publication by Sosnowski et al. (2026). Trial registration details are included in the original report.

References

Sosnowski KJ, Ranse KL, Mitchell ML, Ware RS, White HT, Morrison LA, Schweitzer VC, Chaboyer WP. Effects of the ABCDEF Bundle on Delirium, Function, and Quality of Life in Australian ICU Patients: A Pragmatic Randomized Controlled Trial. Crit Care Med. 2026 May 20;54(7):1610-1621. doi:10.1097/CCM.0000000000006178. PMID: 42159452.

Ely EW, et al. The ABCDEF Bundle: Science and philosophy of how ICU liberation serves patients and families. Crit Care Med. 2017;45(2):321-330.

Balas MC, et al. Effectiveness of the ABCDEF bundle on delirium prevention and patient outcomes: a systematic review. Crit Care Nurse. 2019;39(2):e1-e15.

Needham DM, et al. Implementing the ABCDEF bundle: Clinical and organizational considerations. Crit Care Med. 2019;47(2):204-215.