A 10-year-old boy is brought to the emergency department due to 2 days of rhinorrhea, congestion, cough, and wheezing that worsened over the 6 hours prior to arrival. Chest x-ray reveals hyperinflation and bronchial wall thickening. He receives nebulized albuterol and ipratropium, intravenous corticosteroids, and intravenous magnesium sulfate. Due to lack of significant improvement in symptoms, the patient is admitted to the intensive care unit and given continuous nebulized albuterol, intravenous terbutaline, and bilevel noninvasive positive airway pressure ventilation. After 2 hours, pulse oximetry shows 89% on 0.6 FiO₂, and the patient becomes agitated. Breath sounds are diminished but equal bilaterally, and no wheezing or stridor is heard. The patient's trachea is midline. Laboratory results are as follows: Which is the best next step in management of this patient?

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11ec25c8_d714_bca1_bc81_b14f94e2b2fb_MD0003_00 This child's presentation is consistent with bronchospastic airway disease (ie, wheezing, hyperinflation) triggered by recent viral upper respiratory infection. Given the severe bronchospasm, management is similar to severe acute asthma. Patients are treated with multiple agents (eg, inhaled ± intravenous beta-agonist, inhaled muscarinic antagonist, intravenous magnesium, systemic corticosteroids) to achieve maximal bronchodilation. When severe inflammatory airway obstruction is present, pharmacologic reversal of bronchospasm requires hours to days for full effect, so patients must be closely monitored for respiratory deterioration in the interim. A time-limited (eg, 2-hr maximum) trial of noninvasive positive pressure ventilation (NIPPV) to assist work of breathing may be considered as a "bridge to recovery." Despite a trial of NIPPV, this patient has alarming signs of deterioration, including agitation (altered mental status) and absence of wheezing (ie, "silent chest" due to tight bronchospasm). In addition, acute asthma normally causes respiratory alkalosis (ie, high pH, low PaCO₂) due to increased respiratory drive. An elevated or even (inappropriately) normal PaCO₂, as in this patient, is concerning for respiratory failure due to respiratory muscle fatigue. Therefore, the next step is performing endotracheal intubation and initiating invasive mechanical ventilation. Intubation should ideally be performed in a proactive and controlled manner (eg, no improvement after a time-limited trial of NIPPV). Delayed ("crash") intubation is associated with greater morbidity and mortality (eg, cardiopulmonary arrest, anoxic brain injury). Continued observation on NIPPV would be appropriate only for a patient with clear improvement (Choice A). (Choices C and E) Nebulized racemic epinephrine is typically used in severe croup to reduce upper airway edema through arteriolar constriction. A tracheostomy can be performed to bypasses upper airway obstruction but typically only after unsuccessful intubation. This patient has no evidence of upper airway obstruction (ie, no stridor); his initial examination (wheezing) is more consistent with lower airway constriction (eg, acute asthma). (Choice D) Needle thoracostomy is used for a tension pneumothorax, which can occur as a complication of positive pressure ventilation in patients with asthma. Tension pneumothoraces present with sudden-onset hypoxemia, tracheal deviation, unilateral absence of breath sounds, and/or subcutaneous crepitus; none of these are present in this patient. Educational objective: Indications for intubation and invasive mechanical ventilation in severe acute asthma include impending respiratory failure (high or inappropriately normal PaCO₂ in relation to the work of breathing), altered mental status, and lack of improvement despite a time-limited trial of noninvasive positive pressure ventilation. References: The use of non-invasive ventilation for life-threatening asthma attacks: changes in the need for intubation. (http://www.ncbi.nlm.nih.gov/pubmed/20409027) A review of the use of adjunctive therapies in severe acute asthma exacerbation in critically ill children. (http://www.ncbi.nlm.nih.gov/pubmed/24993063)

A 10-Year-Old Boy Is Brought to the Emergency Department Due