A 68-year-old man with myasthenia gravis is evaluated for progressive weakness while hospitalized. The patient was admitted 2 days prior due to fever, productive cough, and pleuritic chest pain. Chest x-ray demonstrated a right lower lobe consolidation for which the patient has been receiving intravenous ceftriaxone and azithromycin. He also has been receiving his outpatient dose of pyridostigmine. In the past several hours, he has experienced progressive generalized weakness and an inability to cough out sputum. His temperature is 37.6 C (99.8 F), blood pressure is 130/70 mm Hg, pulse is 110/min, and respiratory rate is 25/min. Oxygen saturation is 89% on 4 L/min oxygen by nasal cannula. The patient appears to be in distress, and his breathing pattern is rapid and shallow with occasional gurgling sounds. Lung auscultation reveals coarse crackles throughout. There is mild weakness of the extremities, but deep tendon reflexes are normal. His vital capacity is now 1.0 L compared to 1.5 L at the time of admission, and arterial blood gas shows pH 7.27, pCO₂ 55 mm Hg, and pO₂ 60 mm Hg. The patient is intubated and moved to the intensive care unit. Which of the following is the best next step in management of this patient?

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11ec25c8_d560_2ee9_bc81_750a89afe6e0_MD0003_00 This patient with myasthenia gravis (MG) is most likely suffering from myasthenic crisis, characterized by severe respiratory muscle weakness leading to respiratory failure. Individuals often have increasing generalized and bulbar muscle weakness (eg, difficulty coughing up sputum) prior to the onset of crisis. The condition may be precipitated by infection (eg, pneumonia), surgery, or various medications (eg, azithromycin). Patients with deteriorating respiratory status (eg, declining oxygen saturation and vital capacity) should first be intubated for airway protection. Following intubation, acetylcholinesterase inhibitors (eg, pyridostigmine) used in the daily management of MG are temporarily held to reduce excess airway secretions and the risk of aspiration (Choice B). Once stabilized, patients in myasthenic crisis require treatment with intravenous immunoglobulins or plasmapheresis (preferred) in addition to corticosteroids. Other immunomodulatory therapy (eg, mycophenolate mofetil or azathioprine) can be considered, especially if corticosteroid therapy is ineffective, but usually requires several weeks to reach clinical efficacy. (Choice A) Close observation and monitoring of respiratory muscle strength (eg, vital capacity, maximal inspiratory force) are important in the management of myasthenic crisis. However, observation alone is insufficient as this patient requires treatment to reverse his respiratory failure. (Choice C) Oral antimotility agents containing atropine may be used to treat the muscarinic side effects (eg, diarrhea) of anticholinesterase therapy in patients with MG. However, intravenous atropine has no role in myasthenic crisis management. (Choice E) Thymectomy is generally recommended in MG patients with thymoma as it can lead to long-term clinical improvement. However, it is not the best next option in this critically ill patient. Educational objective: The management of myasthenic crisis with respiratory failure consists of endotracheal intubation followed by treatment with plasmapheresis (or intravenous immunoglobulins) and corticosteroids. References: The myasthenic patient in crisis: an update of the management in neurointensive care unit. (http://www.ncbi.nlm.nih.gov/pubmed/24141444)

A 68-Year-Old Man with Myasthenia Gravis Is Evaluated for Progressive