What is the management approach for critical illness myopathy?

Management of Critical Illness Myopathy

The management of critical illness myopathy (CIM) should focus on prevention, early mobilization, and supportive care, as there are currently no specific pharmacological treatments available beyond symptomatic and rehabilitative interventions. 1

Prevention Strategies

Risk Factor Modification

• Limit use of neuromuscular blocking agents (NMBAs) - Administration beyond 1-2 days significantly increases myopathy risk, especially when combined with corticosteroids 2
• Minimize corticosteroid exposure - Total doses exceeding 1g of methylprednisolone (or equivalent) increase risk 2
• Consider daily "drug holidays" from NMBAs - Though not definitively proven to reduce AQMS (acute quadriplegic myopathy syndrome), this may be rational to minimize exposure 2
• Monitor and correct metabolic/electrolyte disorders - Address nutritional deficiencies, hyperglycemia, renal/hepatic dysfunction, and electrolyte abnormalities 2
• Avoid concurrent administration of NMBAs with aminoglycosides or cyclosporine 2

Monitoring

• Serial CPK measurements - Consider screening patients receiving NMBAs, particularly those concurrently treated with corticosteroids 2
• Manual muscle testing - Routinely conduct until ICU discharge in patients with adequate cognitive function 3
• Neurophysiological investigations - For patients with delirium, coma, or prolonged severe weakness 3
• Muscle biopsy - In selected cases to differentiate between types of critical illness weakness 3

Active Management

Early Mobilization

• Begin mobilization after initial cardiorespiratory and neurological stabilization 2
• Progressive mobilization algorithm:
  1. Positioning to increase gravitational stress (head tilt, upright positioning)
  2. Passive range of motion for immobile patients
  3. Active-assisted exercises
  4. Active exercises against gravity
  5. Standing with assistance (using modified walking frames, tilt tables)
  6. Walking with assistance 2

Exercise Prescription

• Resistance training: 3 sets of 8-10 repetitions at 50-70% of 1 repetition maximum (1RM) daily within patient tolerance 2
• For ventilated patients: Consider non-invasive ventilation during mobilization to improve exercise tolerance 2
• For patients unable to perform voluntary contractions: Consider neuromuscular electrical stimulation (NMES) 2

Respiratory Management

• Positioning to optimize oxygenation by improving ventilation and V/Q matching 2
• Airway clearance techniques for patients with retained secretions 2
• Monitor for respiratory muscle weakness which can cause neuromuscular respiratory failure requiring prompt intervention 3

Long-term Management

Rehabilitation

• Structured physical therapy program - Patients receiving structured physical therapy are more likely to be discharged home rather than to rehabilitation facilities 2
• Combined aerobic and strength training - Improves limb muscle strength, increases ventilator-free time, and improves functional outcomes in patients requiring long-term mechanical ventilation 2
• Upper and lower limb training - A 6-week program has shown benefits for patients requiring prolonged ventilation 2

Follow-up Care

• Multidisciplinary follow-up - Include assessment of activities of daily living, mood, and functional mobility 3
• Nutritional assessment - Longitudinal evaluation guided by a dietician 3
• Surveillance for physical, cognitive, and mental impairments - CIM is associated with long-term deficits requiring ongoing care 3

Special Considerations

Diagnostic Challenges

• Differential diagnosis includes prolonged recovery from NMBAs, myasthenia gravis, Lambert-Eaton syndrome, Guillain-Barré syndrome, and other causes of weakness 2
• Clinical features include acute, diffuse, flaccid weakness, inability to wean from mechanical ventilation, with generally preserved sensory function 2
• Muscle biopsy findings typically show extensive type 2 fiber atrophy, myonecrosis, disarray of sarcomere architecture, and selective loss of myosin 2

Emerging Treatments

• Experimental therapies showing promise in animal models include BGP-15, vamorolone, and ruxolitinib, which have anti-inflammatory effects, reduce muscle wasting, and improve muscle function 1
• Future research is needed to validate early diagnostic approaches and evaluate the effectiveness and safety of these experimental drugs in clinical settings 1

Pitfalls and Caveats

• Hemodynamically unstable patients or those on high FiO2 and ventilatory support are not candidates for aggressive mobilization 2
• Risk of moving critically ill patients must be weighed against risks of immobility 2
• Be particularly vigilant for CIM development in alcoholic patients who may have chronic alcoholic myopathy at baseline 4
• No adverse effects of physical activity on inflammatory status of critically ill patients have been demonstrated 2