Respiratory failure due to common final pathway of muscle weakness (secondary to disorder of muscle, neuromuscular junction, nerves, nerve roots or anterior horn cells).
Differential includes (acute) myasthenia crisis, motor neuron disease, myopathy, infectious motor neuropathies (polio, WNV), tetanus, botulism and (subacute) critical illness neuropathy or myopathy [1,2].
(Excluding GBS) Not known to be increased in patients with COVID-19.
In one series of five patients with MG exacerbation concurrent with COVID-19, two required intubation for hypoxemic respiratory failure, while one required supplemental oxygen. One treated with tocilizumab was successfully extubated. Two treated for MG with intravenous immunoglobulin had no thromboembolic complications .
In general, if a patient has unexplained respiratory distress with neuromuscular pattern (paradoxical breathing, use of accessory muscles, worse when supine, poor neck flexion strength, unexplained failure to wean off ventilation), neurology consult should be obtained for detailed history and examination to evaluate for possible underlying neuromuscular disorder
PFTs should be ordered upon initial encounter to triage and evaluate need for intubation.
Further workup may include acetylcholine antibodies, creatine kinase, cerebrospinal fluid studies and nerve conduction studies at the discretion of the neurologist.
In very select patients who may be bridged through definitive therapy, for example a patient with myasthenia gravis with mild neuromuscular respiratory distress and no secretions on definitive treatment with IVIg, temporizing with bilevel positive airway pressure (BIPAP) may be considered but patients would need frequent reassessments during this trial ; this may prevent an unnecessary intubation and use of intensive care resources, although all other patients with downward trajectory may require intubation as the only option; note that there may be institutional guidelines re: BIPAP given risk of aerolizing virus so it may not be an option at some institutions.
Serial PFTs should be performed with frequency per neurology consultants; if PFTs become unavailable, nursing examinations may be a substitute.
Serial nursing examinations should be performed to evaluate for respiratory failure, and clinicians should be notified for any of the following: single breath count test < 20 or downtrend, observed/palpated use of accessory muscles (including scalenes, sternocleidomastoid), observed paradoxical breathing, worsening neck flexion weakness/limb weakness
Nursing examinations may be staggered with PFTs (i.e. deferred if patient had reassuring PFT parameters within prior 2 hours) as purpose is to evaluate for impending respiratory failure.
If a patient is intubated, high-frequency q1h or q2h nursing neurological examinations are not necessary as findings are unlikely to change management
For myasthenia exacerbations, prior patients treated with IVIG did not suffer thromboembolic complications .