Frailty and outcomes from pneumonia in critical illness: a population-based cohort study

Abstract

Background: A threshold Clinical Frailty Scale (CFS) of 5 (indicating mild frailty) has been proposed to guide ICU admission for UK patients with coronavirus disease 2019 (COVID-19) pneumonia. However, the impact of frailty on mortality with (non-COVID-19) pneumonia in critical illness is unknown. We examined the triage utility of the CFS in patients with pneumonia requiring ICU.

Methods: We conducted a retrospective cohort study of adult patients admitted with pneumonia to 170 ICUs in Australia and New Zealand from January 1, 2018 to September 31, 2019. We classified patients as: non-frail (CFS 1-4) frail (CFS 5-8), mild/moderately frail (CFS 5-6),and severe/very severely frail (CFS 7-8). We evaluated mortality (primary outcome) adjusting for site, age, sex, mechanical ventilation, pneumonia type and illness severity. We also compared the proportion of ICU bed-days occupied between frailty categories.

Results: 1852/5607 (33%) patients were classified as frail, including1291/3056 (42%) of patients aged >65 yr, who would potentially be excluded from ICU admission under UK-based COVID-19 triage guidelines. Only severe/very severe frailty scores were associated with mortality (adjusted odds ratio [aOR] for CFS=7: 3.2; 95% confidence interval [CI]: 1.3-7.8; CFS=8 [aOR: 7.2; 95% CI: 2.6-20.0]). These patients accounted for 7% of ICU bed days. Vulnerability (CFS=4) and mild frailty (CFS=5) were associated with a similar mortality risk (CFS=4 [OR: 1.6; 95% CI: 0.7-3.8]; CFS=5 [OR: 1.6; 95% CI: 0.7-3.9]).

Conclusions: Patients with severe and very severe frailty account for relatively few ICU bed days as a result of pneumonia, whilst adjusted mortality analysis indicated little difference in risk between patients in vulnerable, mild, and moderate frailty categories. These data do not support CFS ≥5 to guide ICU admission for pneumonia.

Keywords: COVID-19; frailty; intensive care unit; mortality; observational study; pneumonia; respiratory failure.

Fig 1

Distribution of Clinical Frailty Scale (CFS) scores, stratified by age.

Fig 2

Hospital mortality according to Clinical Frailty Scale (CFS) score. ∗Error bars for mortality are standard error of the mean, for odds ratio are 95% confidence interval. (Data in Table 2 [whole cohort], Supplementary Table 7 [patients ≥65 yr], and Supplementary Table 9 [patients mechanically ventilated]). (a) Whole cohort, (b) age >65 yr, and (c) mechanically ventilated.

Fig 3

Total ICU bed days occupied stratified by Clinical Frailty Scale (CFS). ∗Error bars are standard error of the mean.