Chapter 16 Acute Asthma
Definitions
Asthma is defined by the National Asthma Education and Prevention Program, Expert Panel Report 2 (EPR2), as a chronic inflammatory disorder of the airways.
In this chapter, we focus on inpatient management of acute asthma.
Epidemiology
Asthma affects approximately 15 million persons in the United States, accounts for almost 500,000 hospitalizations per year, and causes approximately 5000 deaths annually. The prevalence of asthma is increasing worldwide. Hospitalization rates for acute asthma are highest among children and African Americans. African Americans between 15 and 24 years of age have the highest mortality rate from asthma.
Acute asthma is the 11th most frequent condition seen in the emergency department, representing up to 12% of total cases. Approximately, 30% of patients with acute asthma are ultimately hospitalized, and 4% to 7% of admitted patients required care in the intensive care unit.
In terms of health care expenditures, the United States spends $6 billion on asthma care; hospital-based care (emergency department visits and admissions) accounts for one half those costs. Better outpatient management will likely result in the greatest savings in health care costs.
Pathogenesis
Asthma is a disorder involving chronic airways inflammation, resulting in airflow obstruction due to:
These inflammatory changes, along with airway hyperresponsiveness, cause airflow obstruction and result in symptoms of dyspnea, wheezing, and cough. Airway hyperresponsiveness can be induced by administration of methacholine or histamine. Atopy is the most important identifiable risk factor for the development of asthma.
Numerous potential triggers of airway inflammation have been identified and include respiratory infections, environmental allergens, tobacco smoke, NSAIDs, exercise, cold air, and gastroesophageal reflux disease.
Clinical Features
History
The history should focus on confirming the diagnosis of asthma, identifying potential symptom triggers, and determining disease severity.
Symptoms of dyspnea, cough, wheezing, and chest tightness are consistent with asthma. Studies have found that patients with asthma present with dyspnea in 29%, cough in 24%, and wheezing in 35% of cases. The symptoms tend to worsen at night. Patients may also have intermittent symptoms that occur with certain seasons or times of day.
Symptom pattern and duration should be established. Patients should be asked about age at initial diagnosis, frequency of symptoms, medication use, corticosteroid requirements, prior hospitalizations and any previous intubations, comorbid conditions, and overall disease course (improving or worsening since diagnosis).
Precipitating factors that could either trigger or worsen an asthma attack should be explored:
Known triggers can be avoided, which may decrease the number of acute asthma episodes.
Determination of the severity of asthma is important. The most specific risk for development of fatal asthma is repeated admissions for asthma flares, particularly if the admissions require mechanical ventilation. Patients who have required mechanical ventilation have a 10% mortality rate at 1 year and a 23% mortality at 6 years. Other markers of severity are:
Physical Examination
Physical examination may reveal expiratory wheezing, hyperexpansion of the thorax, or a prolonged expiratory phase. In addition, signs of atopy, such as eczema, atopic dermatitis, nasal discharge or mucosal edema, or nasal polyps may be seen. Evidence of potential triggers, such as respiratory infections, should be sought.
Accessory muscle use, intercostal retractions, or pulsus paradoxus (fall in systolic blood pressure greater than 10 mmHg with inspiration) are indicators of potential respiratory distress.
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