Near-Fatal Asthma

By Mark D. Siegel, MD, FCCP

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Management

Bronchodilators

Short-acting inhaled b-agonists, such as albuterol, metaproterenol, or isoetharine, are essential. Treatment must be given frequently and in high doses because airway narrowing adversely affects the dose-response curve and duration of action.⁵ Medication can be delivered either with a metered-dose inhaler (MDI) and spacer or via nebulization. In nonintubated patients, reasonable doses include 2.5 mg of albuterol by nebulization every 15 to 20 min or 4 to 6 puffs (360 to 540 mg) every 10 to 20 min using an MDI/spacer.⁵

In mechanically ventilated patients, it is critical to ensure drug delivery, recognizing that inadequate systems may deposit too much medication on ventilator tubing and deliver little to the patient.^5,38 Doses should be titrated until a physiologic benefit, such as decreased peak airway pressure, is demonstrated or until side effects such as tachycardia occur.^5,38 Both MDIs and nebulizers can be effective.^38,39 If an MDI is chosen, a spacer ashould be used and medication instilled through the ventilator circuit's inspiratory limb.⁵ If a nebulizer is used, it should be placed close to the airway opening, humidifiers stopped, and peak inspiratory flow rates decreased to approximately 40 L/min to minimize turbulence, watching carefully for worse air trapping.⁵ Few data support parenteral delivery, except perhaps in young patients in whom inhaled therapy has failed.

Both theophylline and ipratropium have been used as adjunct bronchodilators. Theophylline is associated with many side effects, particularly tachyarrhythmias, nausea, and reflux. Concurrent medications, such as cimetidine, ciprofloxacin, and macrolides, can raise theophylline levels and induce toxicity.⁵ Although its use is controversial, theophylline may help some patients who are not responding to high-dose albuterol and steroids.⁴⁰ In patients without therapeutic blood levels, a 5-mg/kg load can be given over a 30-min period, followed by a maintenance dose of 0.4 mg/kg/h.⁴⁰

Although published results are inconsistent, ipratropium, combined with high-dose albuterol, may improve bronchodilation.⁴¹ Treatment is generally well tolerated. A dose of 0.5 mg delivered by nebulization or 4 to 10 puffs (72 to 180 mg) by an MDI/spacer can be given every 1 to 4 h.^5,40

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