Assessment of muscle mass using ultrasound with minimal versus maximal pressure compared with computed tomography in critically ill adult patients.

BACKGROUND: Preserved skeletal muscle mass identified using computed tomography (CT) predicts improved outcomes from critical illness; however, CT imaging have few limitations such that it involves a radiation dose and transferring patients out of the intensive care unit. This study aimed to assess in critically ill patients the relationship between muscle mass estimates obtained using minimally invasive ultrasound techniques with both minimal and maximal pressure compared with CT images at the third lumber vertebra level. METHODS: All patients were treated in a single Australian intensive care unit. Eligible patients had paired assessments, within a 72-h window, of muscle mass by ultrasound (quadriceps muscle layer thickness in centimetres, with maximal and minimal pressure) and CT axial cross-sectional area (cm2). Data are presented as mean (standard deviation), median (interquartile range), and frequencies [n (%)]. RESULTS: Thirty-five patients [mean (standard deviation) age = 55 (16) years, median (interquartile range) body mass index = 27 (25-32) kg/m2, and 26 (74%) men] contributed 41 paired measurements. Quadriceps muscle thickness measured using the maximal pressure technique was a strong independent predictor of lumbar muscle cross-sectional area. Within a multivariate mixed linear regression model and adjusting for sex, age, and body mass index, for every 1 cm increase in quadriceps muscle layer thickness, the lumbar muscle cross-sectional area increased by 35 cm2 (95% confidence interval = 11-59 cm2). Similar univariate associations were observed using minimal pressure; however, as per multivariate analysis, there was no strength in this relationship [8 cm2 (95% confidence interval = -5 to 22 cm2)]. CONCLUSION: Ultrasound assessment of the quadriceps muscle using maximal pressure reasonably predicts the skeletal muscle at the third lumbar vertebra level of critically ill patients. However, there is substantial uncertainty within these regression estimates, and this may reduce the current utility of this technique as a minimally invasive surrogate for CT assessment of skeletal muscle mass.

A prospective observational study of the effect of critical illness on ultrastructural and microscopic morphology of duodenal mucosa.

OBJECTIVE: Disturbed intestinal barrier function due to 'leaky' tight junctions may cause secondary sepsis via paracellular translocation across the gut wall. Our objective was to describe the effects of critical illness on duodenal morphology and ultrastructure. DESIGN, SETTING AND PARTICIPANTS: Prospective observational study of 12 mechanically ventilated critically ill patients in an intensive care unit and 15 control participants in an outpatient endoscopy suite. INTERVENTION: We took six endoscopic biopsy samples of the duodenum from each participant for analysis by electron and light microscopy. MAIN OUTCOME MEASURES: Our primary outcome was tight junction morphology, examined with electron microscopy. Secondary outcomes were microvillus length and density, vascular endothelium morphology and mitochondrial density and morphology, examined with electron microscopy, and morphology examined with light microscopy. RESULTS: We observed no abnormalities of tight junction ultrastructure in either group. There was a tendency towards shorter microvilli in the critically ill group: mean length in critically ill patients, 1.17 µm (interquartile range [IQR], 1.05-1.60 µm) v mean length in control patients, 1.58 µm (IQR, 1.30-1.72 µm); P = 0.07. There was a tendency towards less dense microvilli in the critically ill group: mean density in critically ill patients, 7.29 microvilli/µm (IQR, 6.83-8.05 microvilli/µm) v mean density in control patients, 8.23 microvilli/µm (IQR, 7.34-9.11 microvilli/µm); P = 0.07. Vascular endothelium appeared normal in all critically ill patients and abnormal in one control participant. Abnormal mitochondrial morphology was noted in one critically ill patient and one control participant, and no differences were seen in mitochondrial density. Using light microscopy, we saw more apoptotic cells in the critically ill patients (P = 0.018), but villus height, crypt depth and lymphocyte density were normal. CONCLUSIONS: We did not detect any morphological abnormalities of duodenal tight junctions in critically ill patients. Our results should be interpreted with caution because of the small sample population, but our observations challenge the concept that paracellular translocation facilitates secondary sepsis.