Body composition determined with computed tomography at ICU admission as a potential long-term outcome assessment tool in critically ill patients: a post-hoc analysis of a prospective, observational study.

Background: Body composition evaluated with computed tomography scan (CT) at intensive care unit (ICU) admission is a predictor of short-term mortality (six months). Little is known regarding long-term outcome. Our objective was to evaluate the potential predictor role of body composition at ICU admission evaluated with CT scan and long-term mortality (two years).

Methods: Post-hoc analysis of a prospective observational study. Body composition evaluated at the level of the third lumbar vertebra (L3) was analyzed with dedicated software that automatically calculated the areas (cm²), determined the tissue composition by a Hounsfield unit (HU) and extracted fat component; all parameters were normalized to patient's height. Cox regression analysis was adopted to evaluate the association between statistically significant muscle parameters at univariate descriptive analysis and 2-years survival.

Results: A total of fifty-one patients were evaluated for the analysis. Those who were alive at follow-up had a higher total muscle area compared to those who did not survive, 84.7 (68-99.4) versus 65.4 (59.2-84) cm² per meter of height (P=0.025). However, no significant difference in fat area was found between survivors and non-survivors' group: the former had a fat area of 16.3 (10.9-23.4) cm²/m and the latter had 25.2 (14.8-31.5) cm²/m (P=0.166). Total muscle area was significantly associated with two-year mortality, showing a hazard ratio of 1.03 (1.01-1.06, P=0.023).

Conclusions: Total muscle but not fat area evaluated at L3 at ICU admission is a prognostic marker of mortality at long-term follow-up in critically ill patients.