What are the management and treatment options for critical illness myopathy (CIM)?

Management and Treatment of Critical Illness Myopathy

Core Treatment Strategy

The primary management of critical illness myopathy centers on early mobilization initiated within 72 hours of ICU admission after cardiorespiratory and neurological stabilization, combined with neuromuscular electrical stimulation for patients unable to move voluntarily, while strictly avoiding prolonged neuromuscular blocking agents and corticosteroid use. 1

Prevention: The Most Critical Intervention

Avoid Known Risk Factors

• Limit neuromuscular blocking agents (NMBAs) to the shortest duration possible (ideally 1-2 days maximum), as administration beyond this substantially increases myopathy risk, particularly when combined with corticosteroids 1, 2
• Avoid concurrent NMBA and corticosteroid administration, as total corticosteroid doses exceeding 1 g methylprednisolone equivalent significantly increase risk 1
• Consider daily "drug holidays" by stopping NMBAs for several hours and restarting only when necessary 1
• Monitor neuromuscular blockade with train-of-four monitoring, adjusting to achieve one or two twitches 2

Early Mobilization Protocol

Begin mobilization within 72 hours of ICU admission after initial cardiorespiratory and neurological stabilization 1. This intervention reduces ICU-acquired weakness incidence by 51%, shortens ICU length of stay by 1.82 days, and reduces hospital length of stay by 3.90 days 1.

Critical timing consideration: Electrophysiological changes in the neuromuscular system occur as early as 48 hours after admission, and muscle loss is rapid—making early intervention essential 1. Mobility programs beginning after ICU discharge have limited impact on mitigating weakness 1.

Active Treatment Strategies

For Unconscious or Sedated Patients

Neuromuscular Electrical Stimulation (NMES):

• Prevents muscle atrophy and reduces critical illness polyneuromyopathy development 1
• Initial parameters: Start with 4 Hz (non-tetanic) frequency to prevent delayed onset muscle soreness 1
• Progress to: 20-25 Hz tetanic contractions 1
• Duty cycle: Begin with 2 seconds on/2 seconds off 1
• Duration: Gradually increase from 10 minutes to 60 minutes as tolerated 1
• Target: Large muscle groups (quadriceps, hamstrings) with maximal tolerable current intensity 1

Passive Interventions:

• Continuous passive motion (CPM) for 3 hours, three times daily, reduces fiber atrophy and protein loss 1
• Passive cycling using bedside ergometers allows prolonged mobilization without requiring patient cooperation 1
• Position upright (≥40° upper body elevation) when hemodynamically stable to increase lung volumes, stimulate autonomic activity, and reduce cardiac stress 1
• Apply positioning, splinting, passive mobilization, and muscle stretching to preserve joint mobility and skeletal muscle length 1

For Alert, Cooperative Patients

Mobilization Hierarchy (progress sequentially): 1

1. Transferring in bed
2. Sitting at edge of bed
3. Bed-to-chair transfers
4. Standing
5. Walking

Active Exercise Programs:

• Resistance training: 3 sets of 8-10 repetitions at 50-70% of 1 repetition maximum, performed daily within patient tolerance 1
• Active cycling: Use bedside ergometers with intensity adjusted to physiological responses 1
• Structured programs: Upper and lower limb training for minimum 6 weeks improves muscle strength, increases ventilator-free time, and enhances functional outcomes 1
• Use walking aids (modified walking frames, tilt tables) which are safe and feasible for mobilization 1

Nutritional Support

• Provide adequate protein delivery: 1.3 g/kg/day combined with physical activity, as critical illness is associated with marked proteolysis and muscle loss 1
• Optimize nutrition while avoiding overfeeding, as excessive energy delivery can be deleterious 1
• Monitor micronutrient deficiencies, particularly in patients on continuous renal replacement therapy 1
• Test for micronutrient status after 6-7 days in ICU, with particular attention to copper, selenium, zinc, and iron levels 1
• Consider values 20% below laboratory reference as concerning and initiate repletion 1
• Correct electrolyte abnormalities, particularly hypophosphatemia and hypermagnesemia 2

Safety Considerations and Contraindications

Patients NOT candidates for aggressive mobilization: 3, 1

• Hemodynamic instability or active resuscitation
• High FiO₂ requirements
• High levels of ventilatory support
• Uncontrolled arrhythmias
• Active myocardial ischemia
• Increased intracranial pressure

Important principle: The risk of mobilizing critically ill patients should be weighed against the risks of immobility and recumbency, as no adverse effects of physical activity on inflammatory status have been demonstrated 1.

Monitoring and Assessment

• Use the six-point Medical Research Council (MRC) score to assess muscle strength, with an MRC sum score less than 48 defining ICU-acquired weakness 1
• Handgrip strength dynamometry provides simple early detection before changes in body composition 1
• Monitor muscle mass using ultrasound or CT scan 1
• Monitor for contraindications during each mobilization session 1

Supportive Care

• Address concurrent renal or hepatic dysfunction 2
• Provide adequate nutritional support as outlined above 2
• Continue physical therapy and mobilization throughout ICU stay 1

Common Pitfalls to Avoid

• Do not delay mobilization thinking patients are "too sick"—this enhances deconditioning and complicates clinical course 3
• Do not combine corticosteroids with prolonged NMBAs unless absolutely unavoidable 1
• Do not wait until ICU discharge to begin rehabilitation—the critical window is early in the ICU course 1
• Assessment tools requiring patient cooperation have limitations in uncooperative or sedated patients 1

Experimental Therapies

While clinical trials are lacking, animal models show promise for BGP-15, vamorolone, and ruxolitinib, which have anti-inflammatory effects, reduce muscle wasting, and improve muscle function and survival 4. However, these require future clinical studies for effectiveness and safety validation 4.