Which is the priority assessment for a patient experiencing an acute asthma exacerbation?

Inhaled bronchodilators (beta-2 agonists and anticholinergics) are the mainstay of asthma treatment in the emergency department. In adults and older children, albuterol given 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.

Subcutaneous epinephrine 1 mg/mL (1:1000) solution or terbutaline is an alternative for children. Terbutaline may be preferable to epinephrine because 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).

Nebulized ipratropium can be co-administered with nebulized albuterol for patients who do not respond optimally to albuterol alone; some evidence favors simultaneous high-dose beta-2 agonist and ipratropium as first-line treatment.

Systemic corticosteroids (prednisone, prednisolone, methylprednisolone) should be given for all but the mildest acute exacerbation; they are unnecessary for patients whose PEF normalizes after 1 or 2 bronchodilator doses. IV and oral routes of administration are probably equally effective. IV methylprednisolone can be given if an IV line is already in place and can be switched to oral dosing whenever necessary or convenient. In general, higher doses (prednisone 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 (1, 2 General references 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)... read more ).

Theophylline has 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.

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%.

Reassurance is the best approach when anxiety is the cause of asthma exacerbation. Anxiolytics and morphine are relatively contraindicated because they are associated with respiratory depression, and morphine may cause anaphylactoid reactions due to release of histamine by mast cells; these drugs may increase mortality and the need for mechanical ventilation.

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)

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 Tracheal Intubation Most patients requiring an artificial airway can be managed with tracheal intubation, which can be Orotracheal (tube inserted through the mouth) Nasotracheal (tube inserted through the nose)... read more and invasive mechanical ventilation Overview of Mechanical Ventilation Mechanical ventilation can be Noninvasive, involving various types of face masks Invasive, involving endotracheal intubation Selection and use of appropriate techniques require an understanding... read more 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

Intubation and mechanical ventilation allow the provision of sedation to further alleviate the work of breathing, but the routine use of neuromuscular blocking agents should be avoided because of possible interactions with corticosteroids that can cause prolonged neuromuscular weakness. Ketamine may be used for awake intubation if the user has familiarity with its use and adverse effects (eg, laryngospasm, rigidity, and bronchorrhea).

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 pneumothorax Pneumothorax Pneumothorax is air in the pleural space causing partial or complete lung collapse. Pneumothorax can occur spontaneously or result from trauma or medical procedures. Diagnosis is based on clinical... read more

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.

General anesthesia with agents such as sevoflurane and isoflurane in patients with status asthmaticus causes bronchodilation by an unclear mechanism, perhaps by a direct relaxant effect on airway smooth muscle or attenuation of cholinergic tone.