Comparison of Ultrasound‐Derived Muscle Thickness With Computed Tomography Muscle Cross‐Sectional Area on Admission to the Intensive Care Unit: A Pilot Cross‐Sectional Study

Abstract

Introduction The development of bedside methods to assess muscularity is an essential critical care nutrition research priority. We aimed to compare ultrasound‐derived muscle thickness at 5 landmarks with computed tomography (CT) muscle area at intensive care unit (ICU) admission. Secondary aims were to (1) combine muscle thicknesses and baseline covariates to evaluate correlation with CT muscle area and (2) assess the ability of the best‐performing ultrasound model to identify patients with low CT muscle area. Methods Adult patients who underwent CT scanning at the third lumbar area <72 hours after ICU admission were prospectively recruited. Muscle thickness was measured at mid‐upper arm, forearm, abdomen, and thighs. Low CT muscle area was determined using published cutoffs. Pearson correlation compared ultrasound‐derived muscle thickness and CT muscle area. Linear regression was used to develop ultrasound prediction models. Bland‐Altman analyses compared ultrasound‐predicted and CT‐measured muscle area. Results Fifty ICU patients were enrolled, aged 52 ± 20 years. Ultrasound‐derived muscle thickness at each landmark correlated with CT muscle area (P < .001). The sum of muscle thickness at mid‐upper arm and bilateral thighs, including age, sex, and the Charlson Comorbidity Index, improved the correlation with CT muscle area (r = 0.85; P < .001). Mean difference between ultrasound‐predicted and CT‐measured muscle area was −2 cm2 (95% limits of agreement, −40 cm2 to +36 cm2). The best‐performing ultrasound model demonstrated good ability to identify 14 patients with low CT muscle area (area under curve = 0.79). Conclusion Ultrasound shows potential for assessing muscularity at ICU admission (Clinicaltrials.gov NCT03019913).

How does muscularity assessed by bedside methods compare to computed tomography muscle area at intensive care unit admission? A pilot prospective cross‐sectional study

“…BMI, body mass index; BIS, bioimpedance spectroscopy; CT, computed tomography; L3, third lumbar; NOK, next of kin. *Reasons for exclusion were based on primary study ( 19 ) . **Number of patients out of the 50 patients enrolled in the primary study ( 19 ) who had a valid measurement.…”

“…*Reasons for exclusion were based on primary study ( 19 ) . **Number of patients out of the 50 patients enrolled in the primary study ( 19 ) who had a valid measurement.…”

“…This prospective cross‐sectional observational study was conducted in a single centre ICU between January 2017 and March 2019 after approval from the Research and Ethics Committees at The Alfred hospital and La Trobe University. The data presented were collected as part of a larger study ( 19 ) . The study was registered a priori on clinicaltrials.gov (NCT03019913).…”

“…The data presented were collected as part of a larger study. (19) The study was registered a priori on clinicaltrials.gov (NCT03019913). Written and informed consent were obtained from eligible patients and/or their legal medical decision-maker.…”

“…Of 1580 patients were screened, and of the 373 patients who had a CT scan including the L3 area, 323 patients were excluded, leaving 50 participants included in the primary study. (19) Of these, all participants had a subjective physical assessment, 41 (82%) had arm anthropometry and 26 (52%) had BIS data recorded. The CONSORT diagram is shown in Figure 1.…”