Asthma is the most common chronic disease of childhood and the most frequent reason for hospitalization of children. The primary pathologic event is airway inflammation causing recurrent episodes of wheezing, dyspnea, and cough associated with airflow obstruction that is variably reversible. The most common triggers are viral infections, allergens, exercise, and environmental irritants including cigarette smoke and cold air.
Wheezing, a high-pitched sound that occurs when there is an elevation of airway resistance, is the hallmark of an acute asthma exacerbation. Associated findings may include cough, shortness of breath, and chest tightness or pain. To optimize medical management, clinical features are used to classify severity as mild, moderate, or severe. In addition to degree of wheezing, the other important clinical features used to define illness severity include respiratory rate, work of breathing as indicated by retractions and/or nasal flaring, aeration quality, and inspiratory/expiratory ratio. Serial assessments are key to emergency department (ED) management because changes in clinical status and response to treatment are usually more relevant to outcome and need for admission than the level of severity at presentation.
Hypoxemia, while frequent, is usually mild (SpO2 > 92%) and due to V/Q mismatch, which may worsen during initial treatment with bronchodilators for a period of 1 to 2 hours. If available, end-tidal CO2 (ETCO2) by capnometry should be monitored during severe exacerbations. Hypocapnia is expected early in the course of an asthma exacerbation, thus a normal or minimally elevated ETCO2 may be a sign of impending ventilatory failure.
Diagnosis and Differential
The differential diagnosis of wheezing in infants and children is extensive—asthma and bronchiolitis being the most common causes. Consideration of patient age, presenting signs and symptoms, response to therapy, and time of year helps differentiate the two diseases. For children >2 years old who do not have a prior history of asthma, a provisional diagnosis of asthma is made when there are signs and symptoms of wheezing, shortness of breath, cough, dyspnea, diminished air entry, or retractions and demonstration of reversibility with an inhaled β2-agonist (e.g., albuterol). On the other hand, children <2 years old without a prior history or family history of wheezing and presenting during a respiratory viral epidemic with a preceding upper respiratory infection should be treated as having bronchiolitis.
Chest radiography should be considered if the patient fails to improve as expected, fever is present, there is concern for possible pneumothorax (pain or significant hypoxia) or foreign body (unilateral wheezing), or for patients with focal lung findings.
Emergency Department Care and Disposition
An inhaled β2-agonist, most often albuterol, is the mainstay of acute asthma therapy and its frequency of administration should be titrated to the child’s degree of illness.
Administer oxygen for saturations below 92%.
Deliver albuterol by metered-dose inhaler with spacer 4 to 8 puffs every 20 minutes up to three doses or nebulization 2.5 to 5 mg every 20 minutes up to three doses. These routes are equally effective ...