Marked losses of computed tomography–derived skeletal muscle area and density over the first month of a critical illness are not associated with energy and protein delivery

Abstract

Objectives: Changes in muscularity during different phases of critical illness are not well described. This retrospective study aimed to describe changes in computed tomography (CT)–derived skeletal muscle area (SMA) and density (SMD) across different weeks of critical illness and investigate associations between changes in these parameters and energy and protein delivery. Methods: Thirty-two adults admitted to the intensive care unit (ICU) who had ≥2 CT scans at the third lumbar area performed ≥7 d apart were included in the study. CT-derived SMA (cm2) and SMD (Hounsfield units) were determined using specialized software. A range of clinical and nutrition variables were collected for each day between comparator scans. Associations were assessed by Pearson or Spearman correlations. Results: There was a significant decrease in SMA between the two comparator scans where the first CT scan was performed in ICU wk 1 (n = 20; P < .001), wk 2 (n = 11; P < .007), and wk 3 to 4 (n = 7; P = .012). There was no significant change in SMA beyond ICU wk 5 to 7 (P =. 943). A significant decline in SMD was observed across the first 3 wk of ICU admission (P