The goal of asthma exacerbation treatment is to relieve symptoms and return patients to their best lung function. Treatment includes
Inhaled bronchodilators (beta-2 agonists and anticholinergics)
Usually systemic corticosteroids
(See also Asthma and Drug Treatment of Asthma.)
> 80% of baseline), the acute exacerbation may be managed in the outpatient setting. Patients who do not respond, have severe symptoms, or have a PEF persistently < 80% should follow a treatment management program outlined by the physician or should go to the emergency department (for specific dosing information, see table Drug Treatment of Asthma Exacerbations).
Emergency department care
Inhaled bronchodilators
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).
Systemic corticosteroids1, 2).
Magnesium sulfate relaxes smooth muscle, but efficacy in management of asthma exacerbation in the emergency department is debated.
Antibiotics are indicated only when history, examination, or chest x-ray suggests underlying bacterial infection; most infections underlying asthma exacerbations are probably viral in origin.
Supplemental oxygen is 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%.
histamine by mast cells; these drugs may increase mortality and the need for mechanical ventilation.
Hospitalization
Hospitalization generally is required if patients have not returned to their baseline within 4 hours of aggressive emergency department treatment. Criteria for hospitalization vary, but definite indications are
Failure to improve
Worsening fatigue
Relapse after repeated beta-2 agonist therapy
Significant decrease in PaO2 (to < 50 mm Hg)
Significant increase in PaCO2 (to > 40 mm Hg)
A significant increase in PaCO2 indicates progression to respiratory failure.
Noninvasive positive pressure ventilation (NIPPV) may be needed in patients whose condition continues to deteriorate despite aggressive treatment, to alleviate the work of breathing. Endotracheal intubation and invasive mechanical ventilation may be needed for respiratory failure. NIPPV can be used to prevent intubation if used early in the course of a severe exacerbation and should be considered in patients with acute respiratory distress with a level of PaCO2 that is inappropriately high in relation to the degree of tachypnea. It should be reserved for exacerbations that, despite immediate therapy with bronchodilators and systemic corticosteroids, result in respiratory distress, using criteria such as tachypnea (respiratory rate > 25 per minute), use of accessory respiratory muscles, PaCO2 > 40 but < 60 mm Hg, and hypoxemia. Mechanical ventilation should be used rather than NIPPV if patients have any of the following:
PaCO2 > 60 mm Hg
Decreased level of consciousness
Excessive respiratory secretions
Facial abnormalities (ie, surgical, traumatic) that could impede noninvasive ventilation
Mechanical ventilation should be strongly considered if there is no convincing improvement after 1 hour of NIPPV.
Intubation
Generally, volume-cycled ventilation in assist-control mode is used because it provides constant alveolar ventilation when airway resistance is high and changing. The ventilator should be set to a relatively low frequency with a relatively high inspiratory flow rate (> 80 L/minute) to prolong exhalation time, minimizing auto positive end-expiratory pressure (auto-PEEP). Initial tidal volumes can be set to 6 to 8 mL/kg of ideal body weight, and extrinsic PEEP should be used to facilitate patient-initiated triggering and minimize ventilator dyssynchrony from auto-PEEP. High peak airway pressures will generally be present because they result from high airway resistance and inspiratory flow rates. In these patients, peak airway pressure does not reflect the degree of lung distention caused by alveolar pressure. However, if plateau pressures exceed 30 to 35 cm water, then tidal volume should be reduced to limit the risk of pneumothoraxRespiratory Failure and Mechanical Ventilation.)
Other therapy
Other therapies are reportedly effective for asthma exacerbation, but none have been thoroughly studied. A mixture of helium and oxygen (heliox) is used to decrease the work of breathing and improve ventilation through a decrease in turbulent flow attributable to helium, a gas less dense than oxygen. Despite the theoretical benefits of heliox, studies have reported conflicting results concerning its efficacy; lack of ready availability and inability to concurrently provide high concentrations of oxygen (due to the fact that 70 to 80% of the inhaled gas is helium) may also limit its use. However, heliox could be beneficial for the management of patients with vocal cord dysfunction.
