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Impact of frailty on persistent critical illness: a population-based cohort study
Jai N Darvall1,2, Rinaldo Bellomo3,4,5,6, Michael Bailey5
1Department of Intensive Care Medicine, Royal Melbourne Hospital, Grattan St., Parkville, Melbourne, VIC, 3050, Australia. jai.darvall@mh.org.au.
Insights
Patients with frailty have a higher risk of developing and dying from persistent critical illness (PerCI). Frailty becomes a more significant predictor of mortality the longer a patient stays in the intensive care unit (ICU).
Area of Science:
- Critical care medicine
- Geriatric medicine
- Prognostic modeling
Background:
- Acute illness severity predicts mortality in intensive care unit (ICU) patients, but its predictive value diminishes over time.
- Persistent critical illness (PerCI) is defined by the increasing predictive value of pre-ICU characteristics after approximately 10 days.
- The impact of patient frailty on the development and outcomes of PerCI remains largely unknown.
Purpose of the Study:
- To investigate how patient frailty influences the timing of PerCI onset and the risk of developing PerCI.
- To determine the association between frailty and in-hospital mortality among patients with PerCI.
- To assess the predictive value of frailty for mortality in relation to ICU length of stay.
Main Methods:
- Secondary analysis of a prospective binational cohort study of 269,785 critically ill adults from 168 ICUs in Australia and New Zealand.
- Frailty was measured using the Clinical Frailty Scale (CFS), with frailty defined as CFS ≥ 5.
- Logistic regression and area under the receiver operating characteristics (AUROC) curves were used to assess associations between frailty and mortality prediction.
Main Results:
- Patients with frailty (CFS ≥ 5) had a higher incidence of PerCI (4.3%) compared to those without frailty (CFS ≤ 4) (3%) (P < 0.001).
- In-hospital mortality was significantly higher for patients with PerCI who had frailty (30.5%) versus those without frailty (18%) (P < 0.001).
- While the onset timing of PerCI did not vary with frailty, frailty's importance as a mortality predictor increased with ICU length of stay, improving discrimination by 3.6% on ICU day 17.
Conclusions:
- Patients with frailty are more likely to develop PerCI and experience higher mortality rates compared to non-frail patients.
- Frailty emerges as an increasingly important predictor of mortality as the length of ICU stay extends.
- Incorporating frailty into prognostic models is recommended, especially for long-staying ICU patients, to improve mortality prediction.
Purpose:
Acute illness severity predicts mortality in intensive care unit (ICU) patients, however, its predictive value decreases over time in ICU. Typically after 10 days, pre-ICU (antecedent) characteristics become more predictive of mortality, defining the onset of persistent critical illness (PerCI). How patient frailty affects development and death from PerCI is unknown.
Methods:
We conducted a secondary analysis of data from a prospective binational cohort study including 269,785 critically ill adults from 168 ICUs in Australia and New Zealand, investigating whether frailty measured with the Clinical Frailty Scale (CFS) changes the timing of onset and risk of developing PerCI and of subsequent in-hospital mortality. We assessed associations between frailty (CFS ≥ 5) and mortality prediction using logistic regression and area under the receiver operating characteristics (AUROC) curves.
Results:
2190 of 50,814 (4.3%) patients with frailty (CFS ≥ 5) versus 6624 of 218,971 (3%) patients without frailty (CFS ≤ 4) developed PerCI (P < 0.001). Among patients with PerCI, 669 of 2190 (30.5%) with frailty and 1194 of 6624 without frailty (18%) died in hospital (P < 0.001). The time point defining PerCI onset did not vary with frailty degree; however, with increasing length of ICU stay, inclusion of frailty progressively improved mortality discrimination (0.1% AUROC improvement on ICU day one versus 3.6% on ICU day 17).
Conclusion:
Compared to patients without frailty, those with frailty have a higher chance of developing and dying from PerCI. Moreover the importance of frailty as a predictor of mortality increases with ICU length of stay. Future work should explore incorporation of frailty in prognostic models, particularly for long-staying patients.
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