Clinical trajectories of the course of a chronic critical illness: a correlation analysis of the temporal dynamics within the inflammation, catabolism, and immunosuppression triad

Introduction. Improved survival in the acute phase of critical illness has led to a growing population of patients with chronic critical illness (CCI). The triad of inflammation, catabolism, and immunosuppression (ICS) is considered a key mechanism underlying CCI; however, its temporal dynamics and the interrelationships among its clinical characteristics remain unexplored.

The objective was to evaluate the internal relationships between the temporal parameters of chronic critical illness and the dynamics of the inflammation, catabolism, and immunosuppression triad. Materials and methods. The RICD database data was analyzed (n = 820). Inclusion criteria were age > 18 years, first ICU admission, and at least one documented ICS episode (defined as CRP > 20 mg/L, albumin < 30 g/L, and lymphocyte count < 0.8×10⁹/L). Demographic and laboratory parameters, ICU length of stay prior to CCI onset, CCI duration, number and cumulative duration of ICS episodes, and the proportion of time spent in ICS during CCI were analyzed using Spearman’s correlation analysis.

Results. The median ICU stay prior to CCI onset was 6 days (maximum 277 days) and correlated positively with lymphocyte (r = 0.57) and albumin levels (r = 0.40), and negatively with SOFA score (r = –0.17) and CRP levels (r = –0.29). The median CCI duration was 21 days (maximum 446 days), with a median proportion of time spent in ICS of 28.6% [IQR 11.1–57.1%]. A strong negative correlation was found between CCI duration and the proportion of ICS time (r = –0.67), while no association was observed between the proportion of ICS time and the number of ICS episodes (r = 0.07). The cohort exhibited high complication rates: nosocomial pneumonia in 72.6%, sepsis in 28.7%, and multiple organ failure in 80.5% of patients.

Conclusions. Chronic critical illness is a discrete process characterized by episodic occurrence of the ICS triad, resulting in two distinct clinical trajectories: a short, intensive course with a high proportion of ICS time, or a prolonged course with infrequent episodes of decompensation. The duration of prolonged critical illness reflects the patient’s physiological reserve and may represent a window of opportunity for preventing progression to CCI.

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