Survival after ICU discharge is shaped more by chronic disease than admission severity

Abstract

Background: Mortality is high both during intensive care unit (ICU) stay and in the year following discharge, yet factors influencing long-term survival remain poorly defined. We hypothesized that pre-existing chronic conditions may be more strongly associated with post-ICU survival than acute illness severity or admission diagnosis.

Methods: This is a post-hoc analysis of the prospective, observational, multicenter FROG-ICU cohort, which included all consecutive patients admitted to 21 French ICUs and followed for one year after discharge. ICU survivors with complete data on admission severity scores (Sequential Organ Failure Assessment [SOFA], Simplified Acute Physiology Score II [SAPS-II]), comorbidities (Charlson Comorbidity Index [CCI]), and cardiovascular/renal biomarkers at discharge (n = 1400) were included. Associations with one-year mortality were assessed using Cox models. Discriminatory performance was evaluated with time-dependent area under the receiver operating characteristic curve (AUC).

Results: Among 1548 ICU survivors, 1400 were analyzed (median age 61 years, 63 % male). Admission diagnoses included acute respiratory failure (19 %), septic shock (24 %), and neurologic conditions (16 %). The CCI was the strongest predictor of mortality at day 7 (AUC 0.70 [95 % Confidence Interval [CI], 0.64-0.77]), at 3 weeks (AUC 0.75 [0.69-0.78]), and remained high over one year, outperforming SAPS-II (0.63 [0.54-0.72]) and SOFA (0.61 [0.53-0.68]). Although cardiovascular (NT-proBNP, bio-ADM) and kidney (pNGAL) biomarkers had comparable short-term discriminatory value, CCI performed better for long-term outcomes across different admission diagnoses.

Conclusion: In this analysis, pre-existing chronic conditions were primary drivers of short- and long-term survival after ICU discharge, exceeding prognostic value of acute illness severity at admission.

Clinical trial registration: French and European Outcome Registry in Intensive Care Units (FROG-ICU) study: ClinicalTrials.govNCT01367093. Registered 3 June 2011.

Keywords: Biomarkers; Charlson comorbidity index; ICU mortality; SAPS II; SOFA.