ICU Acquired Weakness

Original Editor - Tolulope Adeniji.

Top Contributors - Tolulope Adeniji, Umamah Ejaz, Lucinda hampton, Kim Jackson, Vidya Acharya, Saud Alghamdi, Natalie Patterson and Misha Ahir

Introduction

Intensive Care Unit

Intensive care unit-acquired weakness (ICUAW), is a skeletal muscle disorder that commonly occurs following sepsis, mobility restriction, hyperglycemia, and glucocorticoids or neuromuscular blocking agents use . The three subsets of ICUAW are Critical Illness Neuromyopathy (CINM), Critical Illness Polyneuropathy (CIP) and Critical Illness Myopathy (CIM)). This muscle weakness evolves as a secondary disorder while patients are in the ICU with life-threatening conditions.

ICUAW's causes

• Generalized muscle weakness, effecting respiratory muscles more often than the limb muscles.
• Delayed mobilization
• Prolongated hospitalization.

Knowledge of ICUAW among clinicians, such as physiotherapists, enhances effective delivery of healthcare to ICU patients. This page examines the literature on ICUAW including its management and physiotherapy role in ICUAW. See also Physiotherapists Role in ICU

Risk Factors

Predictors of ICU-acquired weakness.

Intrinsic predictor variables	Intensive care predictor variables
Age Medical comorbidities Frailty Level of independence at admission Number of medical comorbidities, including mental health issues and musculoskeletal pathology	Hyperglycaemia Sepsis and inflammation Corticosteroids Prolonged use of neuromuscular blockers Duration of ventilation Duration of bed rest Duration of ICU stay

Clinical Presentation

Common clinical presentation of ICUAW is

• Presents about 1 week into the critical illness
• Sensation is (generally) preserved, but peripheral sensation can eventually be lost
• A generalized, usually symmetrical, limb weakness, with proximal muscles more affected than the distal muscles.
• Cranial nerve function and autonomic nervous system function usually preserved
• Reduction of tendon reflexes,
• Facial grimacing to painful stimulation without withdrawal of limbs is another clinical presentation.
• May have autonomic dysfunction

Diagnostic Procedures

Diagnosis of ICUAW may involve:

• Medical Research Council (MRC) sum score for muscle strength evaluation. The MRC sum score ranges between 0 and 60, and a score of <48 is suggesting ICUAW.
• Electrophysiological like EMG, Nerve Conduction (NC) test to evaluates neuromuscular integrity
• Handheld dynamometry and handgrip strength for evaluating some neuromuscular function
• Maximal inspiratory pressure to assess inspiratory muscle strength,

Outcome Measures

1. Oxford Scale.
2. ICU Mobility Scale.
3. Respiratory Muscles assessment (Incentive spirometer)
4. Functional Independence Measure (FIM)

An exploratory study investigating functional outcomes at hospital discharge and health-related quality of life after six months in critically ill patients with severe, moderate, or no ICUAW suggested that the participants without ICUAW had superior functional performance at hospital discharge and shorter length of hospital stays when compared to participants with ICUAW. The primary functional outcomes for this analysis were the Functional Independence Measure (FIM) and the 6-Minute Walk Test (6MWT) at hospital discharge. Additional secondary outcomes of interest were FIM at ICU discharge, Timed ‘Up & Go’ at hospital discharge, hospital length of stay and discharge destination, tracheostomy incidence, ICU readmissions, hospital, and 6-month mortality as well as participants’ health-related quality of life determined with the Short Form 36 (SF-36) six months after hospital discharge.

Outcome Measures

Name of measure	Description	Purpose	Population	Scoring/ Interpretation
Oxford Scale	A numerical rating scale developed by the Medical Research Council (MRC) to quantify muscle strength, scored from 0 (no contraction) to 5 (normal strength).	Measures muscle strength in different muscle groups.	Patients with neuromuscular disorders, general population.	0: No contraction 1: Contraction but no movement 2: Movement without gravity 3: Movement against gravity 4: Movement against gravity and resistance 5: Normal strength.
ICU Mobility Scale	A 10-point scale used to assess the highest level of mobility a patient achieves during their stay in the ICU.	To evaluate and track the mobility levels of patients in the ICU, particularly those on ventilators.	ICU patients, including those on mechanical ventilation.	Scored from 0 (no mobility, lying in bed) to 10 (walking independently without assistance). Mobility levels are classified by activities ranging from passive movement (0) to independent walking (10), based on patient capability and physical assistance needed.
Respiratory Muscles assessment (Incentive spirometer)	A device used to encourage slow, deep breaths and sustained maximal inspiration (SMI) through visual feedback, aimed at improving lung function and preventing complications such as atelectasis.	To promote lung expansion, enhance inspiratory muscle function, and prevent pulmonary complications post-surgery or during extended bed rest.	Patients at risk of pulmonary complications, such as those undergoing thoracic or abdominal surgery, prolonged bed rest, or restrictive lung diseases.	Patients are coached to take slow, deep breaths and hold their breath for 4-5 seconds while receiving visual feedback. Progress is gauged by achieving and sustaining target inspiratory volumes set by the healthcare provider.
Functional Independence Measure (FIM)	An 18-item, seven-level ordinal scale used to assess a patient's functional independence and level of disability.	To evaluate and track a patient’s functional abilities and their need for assistance during rehabilitation.	Individuals with functional mobility impairments, including those with neurologic, musculoskeletal, or other disorders.	The FIM score ranges from 18 to 126, with higher scores indicating greater independence. It is divided into motor and cognition subscales, with motor scores ranging from 13-91 and cognition scores ranging from 5-35.
6-Minute Walk Test (6MWT)	A sub-maximal exercise test measuring the distance an individual can walk in 6 minutes, assessing aerobic capacity and endurance.	To evaluate changes in functional capacity and endurance by measuring the distance walked over 6 minutes.	Used in individuals of all ages (children to older adults), including those with cardiopulmonary, neuromuscular, musculoskeletal, and metabolic disorders.	Greater distances indicate higher endurance and aerobic capacity. A minimum change of 45 meters is needed to reflect a significant improvement in patients' mobility, particularly in amputee rehabilitation.
Timed ‘Up & Go	A simple test where a patient stands up from a chair, walks 3 meters, turns around, walks back, and sits down, with time measured.	To determine fall risk and measure progress in balance, sit-to-stand, and walking abilities.	Older adults, including those with Parkinson's Disease, Multiple Sclerosis, Alzheimer's, hip fractures, total knee/hip arthroplasties, stroke, and Huntington's disease.	≥12 seconds indicates high fall risk.
Short Form 36 (SF-36)	A self-reported questionnaire consisting of 36 questions covering eight health domains.	To measure quality of life (QOL) and overall health status.	Designed for individuals in clinical settings, research, and population health evaluations; applicable to specific disease populations.	Scores are calculated for eight health domains, leading to a total QOL score. Two component scores (physical and mental health) can be summarized but should be interpreted with caution.

Implications for Clinical Practice for Physiotherapists

Early Mobilisation:

Early mobilisation is better looked at as a spectrum. From passive joint mobilisations to actively being out of bed and walking. To minimise ICUAW the body of evidence suggests early interventions (within 72hrs of ICU admission). Furthermore, There seems to be a link between the duration of physiotherapy interventions for ICU patients and the severity of ICUAW; higher doses seem to reduce the risk of mortality and lead to shorter ICU and hospital LOS. This reinforces previous research whereby each addiditonal 10 minutes of Physiotherapy and or Ocuupational therapy in the ICU was associated with a 1.2 day lower hospital LOS.

Respiratory Muscle Training:

Respiratory muscle weakness is a common feature of ICUAW patients. One explanation for this is that the critically ill patient depends on the mechanical ventilator for a longer period of time, which makes the respiratory muscles weak. Inspiratory muscle training when the patient is on a mechanical ventilator and when weaned improves the strength of the respiratory muscle. Inspiratory muscle training can be achieved by : Spontaneous breathing by means of a nonlinear resistor that increases respiratory workload; Insensitive trigger threshold can be used during assisted mechanical ventilation support; A threshold device (a device that provides a known constant inspiration resistance through the use of a flow-independent one-way valve) can also be used.

Post ICU Rehabilitation:

Post-ICU rehabilitation for patients with ICUAW must very personalised. Furthermore, mixing a physiotherapy exercise regimen with individualised educational material seems to improve patient satisfaction. When designing a rehab plan, consider the following:

• Strength training program.
• Aerobic session such as walking, arm and leg cycling exercises.
• Functional activities therapy regime.
• Educational materials and self-help manuals & programmes.