Summary of Miastenia Gravis: ¿Cómo Manejar las Crisis? - Dra. Lina Marcela Hoyos
Summary of Key Wellness Strategies, Self-Care Techniques, and Productivity Tips for Managing Myasthenia Gravis (MG) Crisis
Understanding Myasthenia Gravis and Crisis:
- MG is an autoimmune disease causing muscular weakness due to autoantibodies affecting the neuromuscular junction.
- A myasthenic crisis involves progression to ventilatory failure, often requiring emergency respiratory support.
- Crisis can be the first manifestation or progression of known MG.
Epidemiology & Clinical Presentation:
- Average diagnosis age: ~39 years, with two incidence peaks (<30 years and >70 years).
- More common in women, especially younger patients.
- Mortality has decreased from ~20% to below 5% with improved management.
- Common symptoms: muscle fatigue, ptosis, diplopia, dysphagia, respiratory weakness.
- Fatigue worsens with activity and improves with rest and cold.
Triggering Factors for Crisis:
- Infections (most common)
- Certain medications (antibiotics, anticonvulsants, neuromuscular blockers, calcium channel blockers, lidocaine)
- Surgery, pregnancy, extreme temperatures
- Sometimes no identifiable trigger (~40% cases)
Clinical Assessment & Red Flags:
- Monitor respiratory rate carefully as an early sign of deterioration.
- Warning signs include:
- Fever or recent infection/antibiotic use
- Decreased tidal volume
- Nasal voice or nasal regurgitation
- Ineffective cough
- Increased secretions
- Weight loss from dysphagia
- Physical tests to assess fatigue and respiratory function:
- Forced vital capacity (FVC) measurement sitting and supine
- Maximum inspiratory pressure (MIP)
- Counting inspiration (patient counts aloud on one breath; <20 is concerning)
- Holding gaze for 30-60 seconds
- Head lift test in supine position for 30 seconds
- Ice test for ptosis: placing ice on eyelid improves ptosis if MG positive.
Diagnostic Workup:
- Antibody testing (acetylcholine receptor, muscle kinase, low-density protein 4)
- Neurophysiological tests (repetitive nerve stimulation, single fiber electromyography)
- Imaging: Chest CT to evaluate thymus and lung status
- Labs: renal, liver, thyroid function, electrolytes, beta-hCG in women of childbearing age, ECG
Respiratory Support & Ventilation:
- Ventilatory failure is mixed hypoxic and hypercapnic.
- Poor prognostic indicators for intubation include:
- FVC < 20 ml/kg
- MIP < -30 cm H2O
- Max expiratory pressure < 40 cm H2O
- Non-invasive ventilation (NIV), especially BiPAP, can reduce need for intubation in selected patients.
- NIV contraindicated or likely to fail in patients with:
- Altered consciousness or lethargy
- Excessive secretions
- Severe hypercapnia (PaCO2 > 45-50 mmHg)
- Intubation and invasive ventilation required if NIV fails or patient deteriorates.
Pharmacological & Immunotherapy Management:
- Avoid Acetylcholinesterase inhibitors during acute crisis due to unpredictable effects and increased secretions.
- Immunotherapy options:
- Intravenous immunoglobulin (IVIG): rapid onset, improves symptoms within a week, lasts weeks.
- Plasmapheresis: removes pathogenic antibodies, rapid effect lasting ~4 weeks.
- IVIG and Plasmapheresis have comparable efficacy; used based on availability and patient factors.
- Steroids: continue if already on them; start only after immunotherapy to avoid symptom worsening.
- Immunosuppressants have delayed effect; used for long-term management.
- Avoid combining IVIG and Plasmapheresis simultaneously as Plasmapheresis removes immunoglobulin.
Supportive Care:
- Monitor and maintain glycemic control.
- Provide nutritional support.
- Use thromboprophylaxis to prevent clots.
- Monitor for and treat infections, cardiovascular complications, and atelectasis.
- Early recognition and management in high-dependency or intensive care units is critical.
Prognosis and Follow-up:
- Early diagnosis and treatment reduce mortality.
- Regular pulmonary function monitoring helps detect deterioration early.
- Diaphragmatic ultrasound may be useful for early detection of respiratory muscle weakness.
- Aim to minimize duration of mechanical ventilation.
Key Takeaways (Bullet Points)
- Recognize early signs of myasthenic crisis: respiratory distress, fatigue, dysphagia, ineffective cough.
- Monitor respiratory function: respiratory rate, Forced vital capacity, inspiratory pressures, and counting inspiration.
- Avoid precipitating medications and treat infections promptly.
- Use non-invasive ventilation cautiously, with close monitoring for failure signs.
- Intubate early if signs
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