Feasibility of Serial Ultrasound Measurements of the Rectus Femoris Muscle Area to Assess Muscle Loss in Patients Awaiting Liver Transplantation in the Intensive Care Unit

Abstract

Background. End-stage liver disease (ESLD) patients requiring intensive care unit (ICU) care before liver transplantation (LT) often experience significant muscle mass loss, which has been associated with mortality. In this exploratory study, we primarily aimed to assess the feasibility of serial ultrasound (US) rectus femoris muscle area (RFMA) measurements for the evaluation of progressive muscle loss in ICU-bound potential LT candidates and describe the rate of muscle loss as assessed by sequential US RFMA measurements. Secondarily, we sought to identify patient characteristics associated with muscle loss and determine how muscle loss is associated with survival. Methods. We prospectively enrolled 50 ESLD adults (≥18 y old) undergoing evaluation for LT candidacy in the ICU. A baseline computed tomography measurement of psoas muscle area (PMA) and serial bedside US measurements of RFMA were obtained. The associations between patient characteristics, PMA, RFMA, ICU stay, and survival were analyzed. Results. Rapid decline in muscle mass by RFMA measurements was ubiquitously present and correlated to baseline PMA and length of ICU stay. RFMA normalized by body surface area decreased by 0.013 cm2/m2 (95% confidence interval, 0.010-0.016; P < 0.001) for each day in the ICU. Decreased RFMA normalized by body surface area was associated with poor overall survival (adjusted hazard ratio, 0.42; 95% confidence interval, 0.18-0.99; P = 0.047). Conclusions. In this exploratory, prospective study, serial US RFMA measurements in ESLD patients in the ICU are feasible, demonstrate progressive time-dependent muscle loss, and are associated with mortality. Further large-scale assessment of this modality compared with static PMA or performance-based dynamic assessments should be performed.

Monitoring muscle mass using ultrasound: a key role in critical care

“…Pita et al [7] studied 50 liver transplant patients, in which they monitored RFMA by using ultrasound and assessed psoas muscle area at baseline by CT. They showed loss of muscle mass in 10 days of ICU stay ranging from 11% (0.17 cm 2 /m 2 versus baseline 1.606 cm 2 /m 2 ) versus 13% when indexed on BSA (0.11 cm 2 /m 2 versus baseline 0.837 cm 2 /m 2 ), and 15% when indexed against height squared (0.09 cm 2 /m 2 versus baseline 0.601 cm 2 /m 2 ).…”

Sarcopenia in high acuity liver transplantation: Does it predict outcomes?

“…LT given the progressive nature of sarcopenia; we attempted to minimize this effect, however, by only using CTs within 30 days pre-LT. Other modalities, such as serial ultrasound measures, may therefore serve as an adjunct to static CT measurements. 33 This study demonstrates that favorable outcomes are achievable in patients at the extremes of frailty, as evidenced by a 72.8% 5-year sur-vival rate in all patients with MELD ≥ 35. In so doing, it also underscores the difficulty of stratifying such a cohort and validates the need for a more nuanced approached to stratifying these patients.…”

“…Finally, it is important to note that the SMIs used represent a static time point that may not be reflective of the patient's true SMI at LT given the progressive nature of sarcopenia; we attempted to minimize this effect, however, by only using CTs within 30 days pre‐LT. Other modalities, such as serial ultrasound measures, may therefore serve as an adjunct to static CT measurements 33 …”

“…32 A recent study by Kuo et al is the only other study analyzing an acutely ill cohort. 14 In a 126 patient [median MELD: 32 (25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)] multicenter study, the authors determined a cut-off SMI ≤ 48 cm 2 /m 2 to be associated with increased mortality in men, but did not identify a cut-off in women. 14 Their findings reflect the higher SMI cut-offs, as well as SMI medians and ranges, reported in previous studies of outpatient LT candidates.…”

Muscular abnormalities in liver cirrhosis

“…In this area, the quadriceps muscle evaluation, especially its thickness and quality, is most often cited in the literature. Pita et al [ 39 ] estimated a daily decline in muscle mass in patients with cirrhosis who were waiting for a liver transplant in the intensive care unit. In a relatively small cohort, CT-estimated muscle mass was used for comparison demonstrating the ability of the US to monitor muscle mass decline with daily measurements of rectus femoris muscle diameter, as well as the association between this result and mortality in the studied patients.…”