A 24-year-old woman with a history of asthma comes to the emergency department at 32 weeks gestation with a 5-day history of increased dyspnea, wheezing, and cough. Her asthma was previously well-managed with a combination fluticasone-salmeterol inhaler twice daily, but the patient stopped using it when she discovered she was pregnant. She reports no nasal congestion, sore throat, or sinus pain. The patient has no other medical conditions, and her pregnancy has progressed normally. Her only other medication is a prenatal multivitamin. She does not use tobacco, alcohol, or illicit drugs. Her father has a history of asthma. On examination, the patient appears to be in mild respiratory distress. She is afebrile. Blood pressure is 110/68 mm Hg, pulse is 104/min, and respirations are 21/min. Pulse oximetry is 94% on room air. Lung examination reveals inspiratory and expiratory wheezes with a prolonged exhalation phase. Heart sounds are normal. Mild bilateral pitting pedal edema is present; there is no calf tenderness in either leg. Fetal heart rate monitoring is reassuring. Nebulized albuterol and inhaled ipratropium are administered and provide some relief. On repeat assessment shortly afterward, the patient continues to feel short of breath, and wheezing is still present on examination. Arterial blood gas analysis shows a pH of 7.45, PaCO₂ of 26 mm Hg, and PaO₂ of 100 mm Hg on 2 L of oxygen by nasal cannula. What is the best next step in management of this patient?

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Explanation: 11ec2b69_c1bb_4a2d_8f63_b3bdb00215c1_MD0005_00 This patient has an acute asthma exacerbation during pregnancy. Poorly controlled asthma is strongly linked to maternal and fetal mortality, premature birth, and low birth weight. The treatment of acute asthma exacerbations in pregnant women and nonpregnant patients is similar. Bronchodilator therapy: An inhaled or nebulized albuterol is given initially, usually along with inhaled ipratropium. Intravenous magnesium sulfate or terbutaline may be needed for refractory bronchoconstriction. Systemic corticosteroids: There is a low threshold to administer systemic corticosteroids, especially in patients who have an incomplete response to bronchodilators, high-risk asthma features (eg, previous intubation), or a breakthrough acute exacerbation despite taking controller medications. Supplemental oxygen should be given to maintain SaO₂≥95% (vs ≥90% in nonpregnant patients) to prevent antenatal fetal hypoxia. There is inconsistent evidence for a weak association between systemic corticosteroids and negative outcomes such as prematurity and cleft palate. When systemic corticosteroids are needed, patients should be reassured that the benefits of pharmacotherapy far outweigh any risk to the mother or fetus. (Choice B) On occasion, patients with very mild acute exacerbations (eg, immediate full resolution with acute bronchodilators) do not require systemic corticosteroids and are discharged with an inhaled ICS-beta agonist inhaler to maintain asthma control. This patient's dyspnea and wheezing indicate an ongoing active asthma exacerbation, which typically cannot be suppressed by the local anti-inflammatory effects of ICS. (Choice C) Evaluation for pulmonary embolism is appropriate in patients with a high index of suspicion (eg, no alternate diagnosis). This patient's history of asthma, presentation with wheezing and prolonged expiration, and absence of signs of deep vein thrombosis make asthma exacerbation far more likely. Furthermore, compression venous ultrasound or ventilation-perfusion scanning are the recommended imaging modalities during pregnancy. (Choice D) Echocardiography and loop diuretic (eg, furosemide) therapy is appropriate in acute heart failure exacerbation. Mild pitting edema can occur in pregnancy; this patient's history of asthma and lack of significant peripheral edema make asthma exacerbation more likely. (Choice E) Pregnancy increases respiratory drive, leading to chronic respiratory alkalosis (PaCO₂ of 27-32 mm Hg); hyperventilation during asthma exacerbation causes superimposed acute respiratory alkalosis. Relative acidosis (normalization of the PaCO₂) during asthma exacerbation suggests impending respiratory failure and is an indication for mechanical ventilation. This patient's arterial blood gas suggests acute-on-chronic respiratory alkalosis, consistent with an appropriate respiratory response. Educational objective: Treatment of acute asthma exacerbations in pregnant women and nonpregnant patients is similar. The minor risks of short-term systemic corticosteroids are greatly outweighed by their beneficial impact in reducing maternal-fetal mortality and morbidity. References: Acute asthma during pregnancy. (http://www.ncbi.nlm.nih.gov/pubmed/16443146) Asthma and pregnancy. (http://www.ncbi.nlm.nih.gov/pubmed/21858482)

A 24-Year-Old Woman with a History of Asthma Comes to the Emergency