Assessment of skeletal muscle mass in critically ill patients: considerations for the utility of computed tomography imaging and ultrasonography

Purpose of review: Low muscularity and skeletal muscle atrophy are commonly exhibited in critically ill patients and have major implications on patient outcomes. Typically, in the ICU, body composition is assessed through anthropometrics or bioelectrical impedance analysis, but these modalities cannot specifically quantify skeletal muscle; thus, we evaluate the merits and challenges of using computed tomography (CT) and ultrasonography to specifically measure skeletal muscle in the ICU. Recent findings: CT-based cut points have been used to identify critically ill patients with low muscle mass, and low muscularity associates with poor clinical outcomes and function. Ultrasonography is emerging as a useful tool to quantify skeletal muscle loss and degradation in architecture, as well as prospectively track changes in these parameters over time. Rates of muscle atrophy and changes in muscle architecture has been quantified by ultrasonography and associated with poor clinical outcomes, but identification of critically ill patients with low muscularity is still in its infancy. Summary: CT imaging and ultrasonography require additional comprehensive validations against accurate measures of whole body muscle mass. As these validations begin to emerge, there will be a need to translate this knowledge into a simple tool that clinicians can apply as part of routine care

Development of a bedside-applicable ultrasound protocol to estimate fat mass index derived from whole body dual-energy x-ray absorptiometry scans

The final publication is available at Elsevier via https://doi.org/10.1016/j.nut.2018.04.012. © 2019. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/Objectives: Precise measures of adiposity are difficult to obtain in clinical settings due to a lack of access to accurate and reliable techniques. The aim of this study was to develop and internally validate a bedside-applicable ultrasound protocol to estimate fat mass index. Methods: We conducted an observational cross-sectional study of 94 university and community dwelling adults who attended a single data-collection session. Adipose tissue thickness was quantified in a supine or prone position using the four-site protocol (images two anterior sites on each thigh) and the nine-site protocol (images nine anterior and posterior sites). Adipose tissue thicknesses from the four-site protocol were compared against the fat mass index that was derived from dual-energy x-ray absorptiometry scans. Subsequently, we optimized the accuracy of the four-site protocol with the addition of bedside-accessible adipose tissue thicknesses from the nine-site protocol and easily obtained covariates. Results: The four-site protocol was strongly associated (R2 = 0.65) with fat mass index but wide limits of agreement (-3.53 kg/m2 and 3.50 kg/m2) were observed using the Bland-Altman analysis. With the addition of the anterior upper arm and abdomen adipose tissue thicknesses as well as the covariates age, sex, and body mass index, the model accuracy improved (R2 = 0.93) and the Bland-Altman analysis displayed narrower limits of agreement (-1.57 kg/m2 and 1.60 kg/m2). Conclusions: This optimized protocol developed can be applied bedside and provide accurate assessments of fat mass index.This work was supported by Canada Graduate Scholarship (Master) - Canadian Institute of Health Research, Province of Ontario Ministry of Research and Innovation Early Researcher Award, Canada Foundation for Innovation, Natural Sciences and Engineering Research Council, and Canadian Institute of Health Research

Site-specific skeletal muscle echo intensity and thickness differences in subcutaneous adipose tissue matched older and younger adults

This is the peer reviewed version of the following article: Paris, M. T., Letofsky, N., &amp; Mourtzakis, M. (2020). Site‐specific skeletal muscle echo intensity and thickness differences in subcutaneous adipose tissue matched older and younger adults. Clinical Physiology and Functional Imaging, 41(2), 156–164, which has been published in final form at https://doi.org/10.1111/cpf.12679. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.Background: Age-related deterioration of muscle mass does not occur uniformly across the body. However, there is limited knowledge on the uniformity of age-related muscle composition changes across the body. Objective: Our primary objective was to evaluate muscle composition differences between younger and older adults across multiple muscle groups. Methods: We re-analysed data from a previously published cohort to evaluate differences in ultrasound muscle composition (echo intensity) between younger (60 years) adults, when matched for adipose tissue mass at the anterior upper arm, anterior upper leg and abdominal muscles. Analysis of echo intensity is confounded by subcutaneous adipose tissue (SAT) thickness overlaying the muscle; we accounted for these effects by matching older and younger adults (1:1), stratified by sex, for absolute SAT thickness at each landmark. Results: From 96 adults (n = females), 58 (n = 34) were SAT matched at the anterior upper arm, 52 (n = 30) at the anterior upper leg and 60 (n = 30) at the abdominal region; thus, there were no age group differences in SAT thickness at each landmark. In comparison with younger adults, older adults presented with greater echo intensity at the anterior upper leg (females:40.3 ± 6.8 vs. 52.4 ± 7.6; males:35.7 ± 8.0 vs. 54.3 ± 9.8, p < .01) and abdominal (females:38.7 ± 27.6 vs. 73.4 ± 31.0; males:18.7 ± 15.2 vs. 60.9 ± 23.4, p < .01) muscles, but not anterior upper arm muscles (females:47.0 ± 6.5 vs. 53.2 ± 13.1; males:43.4 ± 8.9 vs. 48.9 ± 10.1, p = .18). Conclusions: Distinct age-related differences in trunk and lower limb muscle composition were evident compared to upper limb muscles; highlighting the importance of quantifying specific muscle groups when evaluating age-associated muscle characteristics.This work was supported by Canada Graduate Scholarship - Canadian Institute of Health Research, Province of Ontario Ministry of Research and Innovation Early Researcher Award, Canada Foundation for Innovation, Natural Sciences and Engineering Research Council and Canadian Institute of Health Research

Myokines and adipokines in sarcopenia: understanding cross-talk between skeletal muscle and adipose tissue and the role of exercise

The final publication is available at Elsevier via https://doi.org/10.1016/j.coph.2020.06.003. © 2020. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/Detrimental age-associated changes in skeletal muscle and adipose tissue increase the risk of sarcopenia. Age-related changes in myokines, such as myostatin and irisin, as well as adipokines, such as leptin and adiponectin, contribute to cross-talk between muscle and adipose tissue. These age-related changes in myokines and adipokines have important implications for sarcopenia, however, recent literature highlights discrepancies in these relationships. Exercise may alter serum profiles and muscle receptor expression of these factors, but future work is needed to determine whether these changes in myokines and adipokines relate to improvements in muscle mass and function. Here, we describe myokine-mediated and adipokine-mediated interactions between muscle and adipose tissue, and discuss the fundamental importance of these cytokines to understanding the development of sarcopenia

Expression of executive control in situational context: Effects of facilitating versus restraining cues on snack food consumption

Objectives: To examine the effects of executive function (EF) on objectively measured high-calorie snack food consumption in 2 age groups and to explore the moderating influence of environmental cues. Methods: In Study 1, 43 older adults (Mage = 74.81) and in Study 2, 79 younger adults (Mage = 18.71) completed measures of EF and subsequently participated in a bogus taste-test paradigm wherein they were required to rate 3 highly appetitive (but high-calorie) snack foods on taste and texture. Grams of snack food consumed was measured covertly in the presence randomly assigned contextual cues (explicit semantic cues in Study 1; implicit visual cues in Study 2) that were facilitating or restraining in nature. Results: Findings indicated that in both age groups, stronger EF predicted lower consumption of snack foods across conditions, and the effects of EF were most pronounced in the presence of facilitating cues. Conclusions: Older and younger adults with weaker EF tend to consume more high-calorie snack food compared with their stronger EF counterparts. These tendencies appear to be especially amplified in the presence of facilitating cues

Malnutrition defined by GLIM criteria identifies a higher incidence of malnutrition and is associated with pulmonary complications after oesophagogastric cancer surgery, compared to ICD-10-defined malnutrition

Background & Objectives Low muscle mass, measured using computed tomography (CT), is associated with poor surgical outcomes. We aimed to include CT-muscle mass in malnutrition diagnosis using the Global Leadership Initiative on Malnutrition (GLIM) criteria, compare it to the International Classification of Diseases 10th Revision (ICD-10) criteria, and assess the impact on postoperative outcomes after oesophagogastric (OG) cancer surgery. Methods One hundred and eight patients who underwent radical OG cancer surgery and had preoperative abdominal CT imaging were included. GLIM and ICD-10 malnutrition data were assessed against complication and survival outcomes. Low CT-muscle mass was determined using predefined cut-points. Results GLIM-defined malnutrition prevalence was significantly higher than ICD-10-malnutrition (72.2% vs. 40.7%, p < 0.001). Of the 78 patients with GLIM-defined malnutrition, low muscle mass (84.6%) was the predominant phenotypic criterion. GLIM-defined malnutrition was associated with pneumonia (26.9% vs. 6.7%, p = 0.010) and pleural effusions (12.8% vs. 0%, p = 0.029). Postoperative complications did not correlate with ICD-10 malnutrition. Severe GLIM (HR: 2.51, p = 0.014) and ICD-10 (HR: 2.15, p = 0.039) malnutrition were independently associated with poorer 5-year survival. Conclusions GLIM criteria appear to identify more malnourished patients and more closely relate to surgical risk than ICD-10 malnutrition, likely due to incorporating objective muscle mass assessment

Targeted full energy and protein delivery in critically ill patients : A pilot randomized controlled trial (FEED Trial)

Background International guidelines recommend greater protein delivery to critically ill patients than they currently receive. This pilot randomized clinical trial aimed to determine whether a volume-target enteral protocol with supplemental protein delivered greater amounts of protein and energy to critically ill patients compared with standard care. Methods Sixty participants received either the intervention (volume-based protocol, with protein supplementation) or standard nutrition care (hourly-rate-based protocol, without protein supplementation) in the intensive care unit (ICU). Coprimary outcomes were average daily protein and energy delivery. Secondary outcomes included change in quadriceps muscle layer thickness (QMLT, ultrasound) and malnutrition (subjective global assessment) at ICU discharge. Results Mean (SD) protein and energy delivery per day from nutrition therapy for the intervention were 1.2 (0.30) g/kg and 21 (5.2) kcal/kg compared with 0.75 (0.11) g/kg and 18 (2.7) kcal/kg for standard care. The mean difference between groups in protein and energy delivery per day was 0.45 g/kg (95% CI, 0.33–0.56; P < .001) and 2.8 kcal/kg (95% CI, 0.67–4.9, P = .01). Muscle loss (QMLT) at discharge was attenuated by 0.22 cm (95% CI, 0.06–0.38, P = .01) in patients receiving the intervention compared with standard care. The number of malnourished patients was fewer in the intervention [2 (7%) vs 8 (28%); P = .04]. Mortality and duration of admission were similar between groups. Conclusions A high-protein volume-based protocol with protein supplementation delivered greater amounts of protein and energy. This intervention was associated with attenuation of QMLT loss and reduced prevalence of malnutrition at ICU discharge

Influence of subcutaneous adipose tissue and skeletal muscle thickness on rectus femurs echo intensity in younger and older males and females

This is the peer reviewed version of the following article: Paris, M. T., Bell, K. E., Avrutin, E., Rosati, K., &amp; Mourtzakis, M. (2021). Influence of subcutaneous adipose tissue and skeletal muscle thickness on rectus femoris echo intensity in younger and older males and females. Journal of Ultrasound in Medicine, 41(9), 2355–2364. , which has been published in final form at https://doi.org/10.1002/jum.15922. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.Objectives—Ultrasound measurements of muscle echo intensity are commonly used surrogates of muscle composition (eg, intramuscular adipose tissue). However, given that soundwaves are increasingly attenuated with tissue depth, the interpretation of echo intensity may be confounded by adipose and skeletal muscle thickness. Our objectives are to compare the associations between adipose or muscle tissue thickness and rectus femoris echo intensity in younger and older males and females. Methods—Participants included in this analysis were derived from 3 previously published cohorts of younger (<45 years) and older (≥60 years) males and females. Ultrasound images of the rectus femoris were evaluated for muscle thickness, echo intensity, and subcutaneous adipose tissue thickness. Results—Older adults (n: 49 males, 19 females) had a higher body mass index (P = .001) compared with younger adults (n: 37 males, 49 females). Muscle thickness was negatively associated with echo intensity in older males (r =  0.59) and females (r =  0.53), whereas no associations were observed in younger males (r = 0.00) or females (r =  0.11). Subcutaneous adipose tissue thickness displayed no associations with echo intensity in any group. Conclusions—Despite the known influence of subcutaneous adipose tissue thickness on beam attenuation, we observed no association with muscle echo intensity, indicating that adipose tissue correction may be required to better understand muscle echo intensity across differences in adiposity. The negative associations between muscle thickness and echo intensity in older, but not younger adults, suggests these associations may be related to the co-occurrence of skeletal muscle atrophy and intramuscular adipose tissue infiltration with advancing age.This research was funded by the Network for Aging Research at the University of Waterloo. MTP was supported by a CIHR Doctoral research award and KEB was supported by a CIHR Fellowship