pulmonary disorders
Treatment of Acute Asthma Exacerbations
Emergency department care
Inhaled bronchodilators(beta-2 agonists and anticholinergics) are the mainstay of asthma treatment in the emergency department. In adults and older children,albuterolgiven by a metered-dose inhaler (MDI) and spacer is as effective as that given by nebulizer. Nebulized treatment is preferred for younger children because of difficulties coordinating MDIs and spacers. It should be emphasized that, contrary to popular belief, no data favor continuous beta-2 agonist nebulization over intermittent administration. Evidence suggests that bronchodilator response improves when the nebulizer is powered with a mixture of helium and oxygen (heliox) rather than with oxygen. Given its lower density, helium is thought to assist with delivery of bronchodilators to distal airways. However, technical aspects of using helium for nebulization (availability, calibration of helium concentration, need for custom masks to avoid dilution with room air) have limited its widespread acceptance. Subcutaneousepinephrine1 mg/mL (1:1000) solution orterbutalineis an alternative for children.Terbutalinemay be preferable toepinephrinebecause of its lesser cardiovascular effects and longer duration of action, but it is no longer produced in large quantities and is expensive. Subcutaneous administration of beta-2 agonists in adults raises concerns of adverse cardiostimulatory effects. However, clinically important adverse effects are few, and subcutaneous administration may benefit patients unresponsive to maximal inhaled therapy or patients unable to receive effective nebulized treatment (eg, those who cough excessively, have poor ventilation, or are uncooperative). Nebulizedipratropiumcan be co-administered with nebulizedalbuterolfor patients who do not respond optimally toalbuterolalone; some evidence favors simultaneous high-dose beta-2 agonist andipratropiumas first-line treatment. 50 to 60 mg once a day) are recommended for the management of more severe exacerbations requiring in-patient care while lower doses (40 mg once a day) are reserved for outpatient treatment of milder exacerbations. Although evidence about optimal dose and duration is weak, a treatment duration of 3 to 5 days in children and 5 to 7 days in adults is recommended as adequate by most guidelines and should be tailored to the severity and duration of an exacerbation ( General references ). Theophyllinehas very little role in treatment of an acute asthma exacerbation. Magnesium sulfate relaxes smooth muscle, but efficacy in management of asthma exacerbation in the emergency department is debated. Antibioticsare indicated only when history, examination, or chest x-ray suggests underlying bacterial infection; most infections underlying asthma exacerbations are probably viral in origin. Supplemental oxygenis indicated for hypoxemia and should be given by nasal cannula or face mask at a flow rate or concentration sufficient to maintain oxygen saturation>90%. Reassurance is the best approach when anxiety is the cause of asthma exacerbation. Anxiolytics andmorphineare relatively contraindicated because they are associated with respiratory depression, andmorphinemay cause anaphylactoid reactions due to release ofhistamineby mast cells; these drugs may increase mortality and the need for mechanical ventilation. 