Myasthenia: Effects on neonate
Advanced, Organ-Based and Clinical Sciences
Myasthenia Gravis is an autoimmune disorder in which antibodies destroy and/or inactivate acetylcholine receptors, preventing the binding of acetylcholine at the neuromuscular junction leading to progressive weakness with repeated muscle use.
Neonatal myasthenia gravis develops from placental transfer of antibodies present in a mother with a history of or currently active myasthenia gravis. Patients present with feeding difficulties and respiratory dysfunction.. While assessing a neonatal patient for myasthenic symptoms, it is important consider other possibilities. Congenital myasthenia gravis is a collection of genetic defects of the neuromuscular junction that is not autoimmune in nature. It presents with activity induced weakness, motor problems, ophthalmologic signs, and respiratory insufficiency. Specialist centers capable of intensive diagnostics are necessary to distinguish transient myasthenia from congenital forms.
Treatment consists of acetylcholinesterase inhibitors and supportive care. Intensive care may be necessary. Neonatal myasthenia is transient in nature requiring only temporary treatment with a low risk of recurrence.
Briefly, regarding anesthetic management in myasthenia gravis patients: patients will exhibit increased resistance to succinylcholine due to the decreased density of acetylcholine receptors. There is an unpredictable degree of increased sensitivity to nondepolarizing agents (titrate slowly to peripheral nerve stimulation). Avoid opioids in setting of potential exacerbation of respiratory depression. May require post-op ventilation.
There is a higher risk of post-op ventilation in patients with a disease duration > 6 years, concomitant COPD, pyridostigmine dose >750 mg daily, and VC <2.9L.