Human limb skeletal muscle wasting and architectural remodeling during five to ten days intubation and ventilation in critical care – an observational study using ultrasound

Abstract

BackgroundCritically ill patients frequently suffer muscle weakness whilst in critical care. Ultrasound can reliably track loss of muscle size, but also quantifies the arrangement of the muscle fascicles, known as the muscle architecture. We sought to measure both pennation angle and fascicle length, as well as tracking changes in muscle thickness in a population of critically ill patients.MethodsOn days 1, 5 and 10 after admission to critical care, muscle thickness was measured in ventilated critically ill patients using bedside ultrasound. Elbow flexor compartment, medial head of gastrocnemius and vastus lateralis muscle were investigated. In the lower limb, we determined the pennation angle to derive the fascicle length.ResultsWe recruited and scanned 22 patients on day 1 after admission to critical care, 16 were re-scanned on day 5 and 9 on day 10. We found no changes to the size of the elbow flexor compartment over 10 days of admission. In the gastrocnemius, there were no significant changes to muscle thickness or pennation angle over 5 or 10 days. In the vastus lateralis, we found significant losses in both muscle thickness and pennation angle on day 5, but found that fascicle length is unchanged. Loss of muscle on day 5 was related to decreases in pennation angle. In both lower limb muscles, a positive relationship was observed between the pennation angle on day 1, and the percentage of angle lost by days 5 and 10.DiscussionMuscle loss in critically ill patients preferentially affects the lower limb, possibly due to the lower limb becoming prone to disuse atrophy. Muscle architecture of the thigh changes in the first 5 days of admission, in particular, we have demonstrated a correlation between muscle thickness and pennation angle. It is hypothesised that weakness in the lower limb occurs through loss of force generation via a reduced pennation angle.ConclusionUsing ultrasound, we have been able to demonstrate that muscle thickness and architecture of vastus lateralis undergo rapid changes during the early phase of admission to a critical care environment.

Development of a bedside viable ultrasound protocol to quantify appendicular lean tissue mass

“…9 Third, the reliability results should be interpreted with caution, due to both a small sample size and having two fixed raters performing all analysis. Lastly, muscle atrophy may not occur uniformly throughout the body,44, 45, 46 and therefore, changes in musculature would only be detected if the atrophy occurs in the anterior upper arm or quadriceps muscles using this protocol.…”

“…Second, no participants were categorized as underweight (BMI < 18.5 kg/m 2 ), potentially limiting the applicability of these results to those individuals with the lowest appendicular lean tissue mass; however, often <10% of patients fall below 18.5 kg/m 2.9 Third, the reliability results should be interpreted with caution, due to both a small sample size and having two fixed raters performing all analysis. Lastly, muscle atrophy may not occur uniformly throughout the body, [44][45][46] and therefore, changes in musculature would only be detected if the atrophy occurs in the anterior upper arm or quadriceps muscles using this protocol.…”

Bedside Ultrasound Measurement of Rectus Femoris: A Tutorial for the Nutrition Support Clinician

“…Lower limbs muscles are prone to early atrophy, showed by a greater decrease of thickness within the first five days of admission to the intensive care unit compared with upper limbs, making these muscles a good target for muscle mass assessment [17]. …”

Low Muscularity as Assessed by Abdominal Computed Tomography on Intensive Care Unit Admission Is Associated With Mortality in a Critically Ill Asian Population

“…Critically ill patients may lose about 18%–30% of their skeletal muscle mass within 10 days of admission to the intensive care unit (ICU) . Low muscularity (LM) and muscle wasting have been associated with various adverse outcomes such as prolonged duration of mechanical ventilation, infectious complications, and increased hospitalization and mortality risk in critically ill patients .…”

“…Critically ill patients may lose about 18%-30% of their skeletal muscle mass within 10 days of admission to the intensive care unit (ICU). [1][2][3] Low muscularity (LM) and muscle wasting have been associated with various adverse outcomes such as prolonged duration of mechanical ventilation, infectious complications, and increased hospitaliza-tion and mortality risk in critically ill patients. [4][5][6][7][8] However, a set of universally accepted cutoff values to identify patients with LM in the critically ill population is lacking (especially in the Asian population), and this hinders accurate risk assessment and effective intervention.…”