Persistent critical illness (PerCI) is associated with poorer in-hospital outcomes in patients admitted to an intensive care unit (ICU), and in patients receiving cardiac surgery, yet its association with longer-term survival remains unclear.

We investigated the association between PerCI and long-term survival in patients receiving cardiac surgery.

In this retrospective, multicentre observational cohort study using the Australia and New Zealand Intensive Care Society Adult Patient Database, we included all adults (≥16 years) admitted to 83 ICUs across Australia and New Zealand after cardiac surgery (coronary artery bypass graft, valvular replacement, or both) from January 1 ^st 2018 to December 31 ^st 2022 for Australia and 31 ^st December 2020 for New Zealand. The primary outcome was survival time up to 4 years after ICU admission. We analysed the association between PerCI (defined as ICU length of stay ≥6 days) and survival time up to 4 years from ICU admission using a Cox proportional hazards model.

We included 73,462 patients (90.8% elective, 9.2% emergent), of whom 5,087 (6.9%) developed PerCI. PerCI was associated with shorter survival times (hazard ratio [HR]: 3.14, 95%-CI: 2.77–3.55). As ICU stays became progressively longer, survival times progressively decreased (HR by additional day in ICU: 1.02, 95%-CI: 1.01–1.03). PerCI was associated with larger reductions in survival times in patients aged <65 years (HR: 5.61, 95%-CI: 4.72–6.67) compared to patients ≥65 years (HR: 2.83, 95%-CI: 2.48–3.23, p-interaction <0.0001). However, there were no significant differences amongst the various types of surgeries, and between elective and emergent surgeries.

PerCI was associated with poorer outcomes, and this persisted during longer-term follow-up. Further study is required to identify potential modifiable risk factors for PerCI.