Medical and ventilatory management of status asthmaticus

Abstract

Despite improved understanding of the basic mechanisms underlying asthma, morbidity and mortality remain high, especially in the "inner cities." The treatment of choice in status asthmaticus includes high doses of inhaled beta 2-agonists, systemic corticosteroids, and supplemental oxygen. The roles of theophylline and anticholinergics remain controversial, although in general these agents appear to add little to the bronchodilator effect of inhaled beta-agonists in most patients. Anti-leukotriene medications have not yet been evaluated in acute asthma. Other therapies, such as magnesium sulfate and heliox, have their advocates but are not recommended as part of routine care. If pharmacological therapy does not reverse severe airflow obstruction in the asthmatic attack, mechanical ventilation may be temporarily required. Based on our current understanding of ventilator-induced lung injury, optimal ventilation of asthmatic patients avoids excessive lung inflation by limiting minute ventilation and prolonging expiratory time, despite consequent hypercapnia. Unless respiratory function is extremely unstable, the use of paralytic agents is discouraged because of the increased risk of intensive care myopathy. Patients who have suffered respiratory failure due to asthma are at increased risk for subsequent death due to asthma (14% mortality at 3 years) and should receive very close medical follow-up. In general, severe asthmatic attacks can best be prevented by early intervention in the outpatient setting. In the words of Dr. Thomas Petty, "... the best treatment of status asthmaticus is to treat it three days before it occurs".

Status asthmaticus in the medical intensive care unit: A 30-year experience

“…Severe bronchoconstriction, mucous plugging, and air trapping make these patients challenging to manage, and optimal treatment strategies have not yet been delineated. 4 In particular, ventilator strategies and complication rates are not well defined. However, the NAEPP guidelines suggest that "permissive hypercapnia" or "controlled hypoventilation" should be utilized to reduce the risk of barotrauma.…”

Status asthmaticus treated by high-frequency oscillatory ventilation

“…Dynamic air-trapping ensues, with progressive increases in lung volume resulting in hemodynamic compromise and barotrauma. 3 Ventilation with higher frequencies might exacerbate this process. Nevertheless, there are some case reports of the successful use of highfrequency oscillatory ventilation (HFOV) in patients with obstructive airway disease.…”

Human versus Computer Controlled Selection of Ventilator Settings: An Evaluation of Adaptive Support Ventilation and Mid-Frequency Ventilation

“…Although the trend in patient with status asthmaticus [24] was present prior to the ARDS net seminal article [23] it was likely enhanced by it. As a matter of fact, the tidal volume recommended in review articles through time has decreased (1980's: 10–12 [26, 30] 1990's: 8–10 [26, 31] 2000's: 8–10 [32], 6–8 [28, 33] 5–7 [34, 35] mL/kg) in the absence of any new clinical observations since those of Darioli and Perret [25] and Tuxen et al [26, 36]. …”