MUSCLE THICKNESS, MEASURED WITH ULTRASOUND, MAY BE AN INDICATOR OF LEAN TISSUE WASTING IN MULTIPLE ORGAN FAILURE IN THE PRESENCE OF EDEMA

Multiple organ failure (MOF) is accompanied by muscle wasting, but cha nges in body composition are frequently obscured by fluid retention (e dema), mainly in superficial and visceral tissue. There is a need to a ssess body composition and changes in body composition in these circum stances independently of edema. A relation was sought between fat-free (lean tissue) mass [calculated from body weight and skinfold thicknes ses and measured by using dual-energy X-ray absorptiometry (DXA)] and muscle thickness (measured using ultrasound at a variety of sites acce ssible in an unconscious supine subject) to determine which sites corr elated best with lean body mass. The three best sites were midbiceps, midforearm anteriorly, and midthigh anteriorly: R(2) for the simple su m of the three sites correlated with fat-free mass from skinfold thick nesses was 71.1%, and with lean tissue mass from DXA was 76.1%. Serial measurements of both muscle thickness and midupper-arm circumference in nine patients with MOF showed a complete dissociation; in all nine there was a significant negative correlation of muscle thickness with time (P < 0.05) but changes in arm circumference were random. Only one patient showed a significant negative correlation with time, seven sh owed no change, and one other showed a significant increase. The muscl e thicknesses that correlate best with lean body mass are measured ove r the biceps, anterior forearm, and anterior thigh. Monitoring muscle thicknesses at these three sites identifies wasting in edematous patie nts as it is happening.