300 Section - Functional-Structural Dissociation in ICU-Acquired Weakness Recovery: A Prospective Cohort Study

ICU-acquired weakness (ICU-AW) affects over 50% of intensive care patients, leading to prolonged disability and reduced quality of life. While functional recovery patterns have been studied, the relationship between functional and structural recovery remains poorly understood. This study aimed to comprehensively evaluate both functional and structural changes in ICU-AW patients using multi-modal assessment tools.

Design:

This prospective observational study enrolled 13 adult patients admitted to the medical ICU. Multi-modal assessments were conducted at three time points: ICU admission within 72 hours (T1), ICU discharge (T2), and 2 weeks post-ICU discharge (T3). Functional measures included MRC sum score, hand grip strength, FSS-ICU, and JH-Mobility Scale. Structural measures comprised quantitative muscle ultrasonography and bioimpedance analysis.

Results:

Mean skeletal muscle mass was 23.9±4.2 kg. Participant retention was high (84.6%), and ultrasonography data were successfully acquired in all participants (100%). From T1 to T3, all functional measures showed significant improvements, whereas structural measures declined. Functional improvements included: MRC sum score 44.6±9.6 to 52.3±6.6 (+17.3%, p< 0.01), FSS-ICU 14.3±7.5 to 29.6±9.1 (+107%, p< 0.001), and JH-Mobility Scale 4.3±2.0 to 7.2±0.8 (+67%, p< 0.001). Hand grip strength improved from 12.9±6.2 to 16.0±6.1 kg (+24%, p=0.098). Despite these functional gains, all ultrasonographic muscle thickness measures significantly decreased between T1 and T3: biceps brachii 15.16±4.42 to 11.76±2.61 cm (-22.4%, p< 0.05), rectus femoris 12.52±3.82 to 9.75±3.79 cm (-22.1%, p< 0.05), tibialis anterior 22.81±3.59 to 20.17±3.50 cm (-11.6%, p< 0.001), and FCR 11.50±2.42 to 10.10±2.45 cm (-12.2%, p< 0.05).

Conclusion:

Despite significant functional improvements, patients experienced marked muscle mass loss, suggesting that early recovery is driven by neural adaptations rather than muscle hypertrophy. Rehabilitation strategies should be designed to address both functional and structural impairments, and extended rehabilitation may be necessary to reverse persistent structural deficits and support long-term recovery.