Morphometric parameters of muscle and bone in critically ill patients: Post hoc analysis of the VITdAL-ICU trial

BACKGROUND: Sarcopenia, defined as loss of muscle mass, quality and function, is a part of the frailty syndrome. In critical illness, sarcopenia has rarely been evaluated regarding clinical outcomes. Therefore, we evaluated the association of sarcopenia with both hospital length of stay (HLOS) and 6‑month mortality in critically ill patients using abdominal computed tomography (CT) scans. METHODS: In a post hoc analysis from the high dose vitamin D3 vs. placebo in adult vitamin D deficient patients (VITdAL-ICU) trial, we retrospectively reviewed all available abdominal CT scans (18 women, 19 men). We measured and calculated total psoas area (TPA), psoas muscle density (PMD), skeletal muscle index (SMI) and bone mineral density (BMD) and analyzed the relation of these endpoints with HLOS and mortality. Defining sarcopenia we used cut-off values for TPA as 642.1 mm(2)/m(2) in women and 784 mm(2)/m(2) in men and PMD as 31.1 Hounsfield units (HU) in women and 33.3 HU in men, both measured at the level of L3, as well as for SMI (38.5 cm(2)/m(2) in women and 52.4 cm(2)/m(2) in men). Likely osteoporosis was defined by L1 trabecular attenuation of ≤110 HU. Values for TPA, PMD and SMI could not be obtained in 11 patients and BMD in 1 patient. RESULTS: Mean adjusted TPA was lower in women versus men (478 vs. 749 mm(2)/m(2)) as well as PMD (34.6 vs. 41.3 HU), SMI (62.36 vs. 76.81 cm(2)/m(2)) and BMD (141.1 vs. 157.2 HU). No significant influence on hospital length of stay and on 6‑month mortality was found, irrespective of the morphometric parameter used (TPA, PMD, SMI, BMD; p > 0.05). Survivors showed statistically nonsignificantly better values than nonsurvivors: TPA: 652 vs. 530 mm(2)/m(2) (p = 0.27); PMD: 38.4 vs. 37.4 HU (p = 0.85); SMI: 70.32 vs. 69.54 cm(2)/m(2) (p = 0.91); BMD: 156 vs. 145.8 HU (p = 0.81). CONCLUSION: Although the study is limited by the small sample size, our data do not support a strong predictive value for TPA/PMD/SMI or BMD for HLOS or mortality in critically ill patients with vitamin D deficiency.