A 34-year-old woman with known myasthenia gravis presents in respiratory distress. She is unable to move without assistance. Her vital signs are: temperature 36°C (96.8°F), heart rate 50/min, blood pressure 100/60 mm Hg, respiratory rate 35/min and shallow. She is drooling and has upper airway rhonchi and bilateral wheezing. Her respiratory rate appears to be decreasing. You immediately:
Administer 2–4 mg of intravenous edrophonium.
+Perform endotracheal intubation.
+Administer 1 mg of atropine; if there is an improvement in her wheezing, administer pralidoxime.
+Start an intravenous atropine drip.
+Arrange emergent hyperbaric therapy.
You should be able to differentiate a myasthenic crisis from a cholinergic crisis. Both can present with progressive muscle weakness and respiratory depression, dysphagia, and other physical signs. Bradycardia, wheezing, and salivation suggest cholinergic crisis. A common error is to mistake a cholinergic as a myasthenic crisis and administer additional acetylcholinesterase inhibitor. The immediate treatment for either type is ABCs and intubation at the first clinical signs of respiratory failure. In a cholinergic crisis, atropine can be used for the muscarinic symptoms, but it is not a substitute for airway management and ventilatory assistance.