A 64-year-old woman comes to the emergency department due to worsening productive cough and difficulty breathing for the last 3 days. Over the past day, she has also had some difficulty chewing and a sensation of choking on solid foods. Medical history includes hypothyroidism and myasthenia gravis. The patient takes levothyroxine and pyridostigmine. She does not use tobacco, alcohol, or illicit drugs. Temperature is 38.3 C (100.9 F), blood pressure is 130/82 mm Hg, pulse is 110/min, and respirations are 22/min. On physical examination, the patient is diaphoretic and ill-appearing. Lung examination reveals shallow respirations and right basal crackles. Cardiac auscultation is normal with the exception of tachycardia. The abdomen is soft and nontender. There is mild, symmetric muscle weakness of the proximal limbs. Laboratory testing shows the following: Chest x-ray shows evidence of poor inspiratory effort with a right lower lobe consolidation. Which of the following is the best next step in management of this patient?

Question

A 64-year-old woman comes to the emergency department due to worsening productive cough and difficulty breathing for the last 3 days.  Over the past day, she has also had some difficulty chewing and a sensation of choking on solid foods.  Medical history includes hypothyroidism and myasthenia gravis.  The patient takes levothyroxine and pyridostigmine.  She does not use tobacco, alcohol, or illicit drugs.  Temperature is 38.3 C (100.9 F), blood pressure is 130/82 mm Hg, pulse is 110/min, and respirations are 22/min.  On physical examination, the patient is diaphoretic and ill-appearing.  Lung examination reveals shallow respirations and right basal crackles.  Cardiac auscultation is normal with the exception of tachycardia.  The abdomen is soft and nontender.  There is mild, symmetric muscle weakness of the proximal limbs.  Laboratory testing shows the following:  Chest x-ray shows evidence of poor inspiratory effort with a right lower lobe consolidation.  Which of the following is the best next step in management of this patient?

Quizplus · Accepted Answer

11ec25c8_d1ea_4278_bc81_5b998f725d5f_MD0003_00 This patient has evidence of a myasthenic crisis, a life-threatening exacerbation of myasthenia gravis resulting in respiratory failure. Myasthenia gravis is characterized by autoimmune disruption of the neuromuscular junction, most commonly due to autoantibodies to the acetylcholine receptor. A crisis occurs when increased disease activity causes significant generalized muscle weakness, resulting in diaphragmatic impairment and respiratory failure; bulbar weakness (eg, dysphagia) may also be a prominent feature. Patients with myasthenia gravis are at particular risk for underrecognition of the severity of respiratory impairment due to the inability to effectively recruit weakened accessory muscles. Patients may be near respiratory collapse by the time respiratory distress is apparent. autoimmune disruption The most common precipitating event is concurrent infection (eg, pneumonia, as in this patient). Other precipitants include medications, surgery, and pregnancy or childbirth. Common medication classes known to trigger crises include antibiotics (eg, aminoglycosides, fluoroquinolones), beta blockers, calcium channel blockers, and magnesium. Management commonly involves admission to the intensive care unit for close monitoring of respiratory function (eg, vital capacity [VC]). Elective intubation should be performed in patients with evidence of impending respiratory failure, such as this ill-appearing patient with tachypnea, shallow breaths, muscle weakness, and difficulty to clear secretions (eg, choking sensation). Objective measurements that can also indicate impending respiratory failure include severely reduced VC and respiratory acidosis. To bridge to the slower-acting, steroid-sparing medications (eg, azathioprine), patients should also receive rapid-acting therapy such as plasma exchange or intravenous immunoglobulin and high-dose corticosteroids. (Choice A) Pyridostigmine, an acetylcholinesterase inhibitor, can be tried in patients with mild exacerbations but is not effective in those with severe disease. It is typically withheld in intubated patients to reduce airway secretions associated with increased cholinergic activity. (Choice B) Profound hypothyroidism can cause respiratory muscle weakness, resulting in hypoxia and respiratory acidosis; however, hypothyroidism is associated with hypothermia and bradycardia, not fevers and tachycardia. Although myxedema coma, which is initially treated adjunctively with glucocorticoids, can present with respiratory acidosis, it occurs with bradypnea, not tachypnea. (Choices C and E) This patient has evidence of severe community-acquired pneumonia, so blood cultures and antibiotics should be included in her management after urgent treatment for respiratory failure is provided. However, fluoroquinolones (eg, moxifloxacin) are known to exacerbate myasthenia gravis (by blocking neuromuscular transmission) and should be avoided. Educational objective: Myasthenia gravis is characterized by autoimmune disruption of the neuromuscular junction. A myasthenic crisis occurs when increased disease activity causes significant muscle weakness, resulting in diaphragmatic impairment and respiratory failure; bulbar weakness may also be a prominent feature. Precipitants include infection, medications, surgery, and pregnancy or childbirth. Elective intubation should be performed in patients with evidence of impending respiratory failure. References: Clinical profile and outcome of myasthenic crisis in a tertiary care hospital: a prospective study. (http://www.ncbi.nlm.nih.gov/pubmed/23956564) Myasthenic crisis. (http://www.ncbi.nlm.nih.gov/pubmed/23983833) Delayed diagnosis of atypical presentation of myasthenia gravis. (http://www.ncbi.nlm.nih.gov/pubmed/30756011)

A 64-Year-Old Woman Comes to the Emergency Department Due to Worsening