A 25-year-old woman with a history of asthma comes to the emergency department due to severe shortness of breath. The patient experienced rapidly worsening dyspnea, wheezing, and chest tightness after she was exposed to some cleaning chemicals at work. On arrival, the patient is in severe respiratory distress with diffuse wheezing and poor air movement. Blood cell counts, serum electrolyte levels, and chest x-ray are normal. Noninvasive ventilation is started, and continuous nebulized albuterol and intravenous methylprednisolone are administered. Several hours later, the patient's respiratory symptoms have significantly improved, but she has muscle weakness; she has difficulty getting out of bed and lifting her arms over her head. Mild hand tremors are noted, and deep tendon reflexes are diffusely decreased. Which of the following is the best next step in the management of this patient?

Question

A 25-year-old woman with a history of asthma comes to the emergency department due to severe shortness of breath.  The patient experienced rapidly worsening dyspnea, wheezing, and chest tightness after she was exposed to some cleaning chemicals at work.  On arrival, the patient is in severe respiratory distress with diffuse wheezing and poor air movement.  Blood cell counts, serum electrolyte levels, and chest x-ray are normal.  Noninvasive ventilation is started, and continuous nebulized albuterol and intravenous methylprednisolone are administered.  Several hours later, the patient's respiratory symptoms have significantly improved, but she has muscle weakness; she has difficulty getting out of bed and lifting her arms over her head.  Mild hand tremors are noted, and deep tendon reflexes are diffusely decreased.  Which of the following is the best next step in the management of this patient?

Quizplus · Accepted Answer

11ec25c8_d1ee_d65e_bc81_e75605071599_MD0003_00 This patient with wheezing and respiratory distress requiring mechanical intubation had an acute asthma exacerbation (likely precipitated by exposure to cleaning chemicals) that was managed appropriately with inhaled albuterol and systemic corticosteroids (ie, methylprednisolone). Beta-2 agonists such as albuterol reduce serum potassium by driving potassium into cells via stimulation of the sodium-potassium pump (ie, Na⁺/K⁺-ATPase). Patients receiving high doses of inhaled albuterol can develop clinically significant hypokalemia, which manifests as decreased deep tendon reflexes and muscle weakness, as in this patient. ECG changes and potentially fatal arrhythmias (eg, ventricular fibrillation) can occur. Additional adverse effects of beta-2 agonist use include tremor (as seen here) and headache. The next step in management is to order a serum electrolyte panel to confirm and assess the severity of the hypokalemia. An ECG should be obtained to evaluate for life-threatening cardiac complications. Potassium replacement therapy is warranted for symptomatic hypokalemia. (Choice A) Carbon monoxide (CO) poisoning (characterized by an elevated carboxyhemoglobin level) presents with headache, nausea, and confusion, not muscle weakness and hyporeflexia following treatment for asthma. In some patients, the skin and lips have a cherry-red appearance, which is not seen here. (Choice B) Glucocorticoids can cause chronic muscle catabolism (ie, glucocorticoid-induced myopathy), resulting in progressive proximal muscle weakness. However, symptom onset is gradual and occurs weeks to months after starting daily corticosteroids. This patient's acute muscle weakness is inconsistent with an adverse effect of glucocorticoid use, and discontinuation of this medication would likely worsen her current respiratory status. (Choice C) Electromyography and nerve conduction studies are time-consuming tests that are useful in the diagnostic evaluation of muscle weakness due to myopathic or neuropathic conditions (eg, Guillain-Barré syndrome). They may be considered if electrolyte levels are normal, but the priority in this patient undergoing high-dose beta-2 agonist therapy is to assess for life-threatening hypokalemia. (Choice D) Methemoglobin is an oxidized form of hemoglobin that has limited oxygen binding ability, resulting in cyanosis (not just muscle weakness) that is refractory to oxygen therapy. It is most commonly associated with ingestion of nitrates or nitrites (eg, in well water), as well as medications such as dapsone and topical anesthetic agents (eg, benzocaine). Methemoglobinemia is not an adverse effect of albuterol or methylprednisolone use. Educational objective: High doses of beta-2 agonists used in asthma treatment (eg, albuterol) can cause hypokalemia, which may present with muscle weakness, hyporeflexia, and life-threatening arrhythmias. References: Effect of high-dose continuous albuterol nebulization on clinical variables in children with status asthmaticus. (http://www.ncbi.nlm.nih.gov/pubmed/25560428)

A 25-Year-Old Woman with a History of Asthma Comes to the Emergency