Evaluation of the site specificity of acute disuse muscle atrophy developed during a relatively short period in critically ill patients according to the activities of daily living level: A prospective observational study.

Introduction: In critically ill patients, excessive bed rest and immobilisation have been shown to cause disuse muscle atrophy, which contributes to prolonged hospitalisation and decreased activity of daily living (ADL) levels. However, the degree and site specificity of acute disuse muscle atrophy in critically ill patients during a relatively short intensive care unit (ICU) stay have not been fully elucidated.

Methods: Critically ill patients, who required bed rest on ICU admission, were eligible for this study. The degree of skeletal muscle atrophy was evaluated on the day of, and 72 and 144h after ICU admission by measuring the limb circumference in ADL-dependent or -independent patients separately at five different sites: the midpoint of the upper limb between the acromion and the olecranon, the maximum diameter of the triceps surae in the lower leg, and three different sites in the thigh at 5, 10, and 15cm above the superior pole of the patella. Value of the limb circumference was presented as a percentage relative to the baseline (median).

Results: In ADL-dependent patients, limb circumferences at all five sites were decreased significantly at 144h compared with the baseline (98.9-100% in the upper limbs, 97.1-97.2% in the lower legs, and 96.5-99.1% in the thighs), but not at 72h. In contrast, the limb circumferences at almost all sites decreased significantly at both 72 and 144h (100% in the upper limbs, 94.5-94.7% in the lower legs, and 89.7-94.7% in the thighs), compared with the baseline in ADL-independent patients. Muscle atrophy was greater at the four different lower-limb sites compared to the upper limb during 144h in the ICU in the ADL-independent, but not in the ADL-dependent patients.

Conclusions: Compared to ADL-dependent patients, ADL-independent patients are prone to develop muscle weakness, especially in the lower limbs.