Chapter 34: Asthma

High-Yield Facts

• Asthma is the most common chronic disease of childhood and is associated with significant morbidity and mortality.

• It is now defined as ‘a common chronic disorder of the airways that is complex and characterized by variable and recurring symptoms, airflow obstruction, bronchial hyperresponsiveness, and an underlying inflammation'

• There is emerging evidence that pre-school wheezers should be treated differently to classic atopic wheezing in older children.

• Inhaled albuterol remains the first line therapy for acute asthmatic exacerbations. Delivery of albuterol by metered dose inhaler and spacer device has been shown to be superior to delivery by nebulization.

• The addition of ipratroprium to the first two to three albuterol doses has been associated with a decreased need for hospitalization in pediatric patients with moderate-to-severe asthma exacerbations.

• Early administration of oral corticosteroids in the emergency department has been shown to enhance recovery from an acute asthma exacerbation and decrease rates of hospitalization.

• Oral dexamethasone (one–two doses) has been shown to be as efficacious as a 5-day course of oral prednisone.

• Magnesium sulfate is of benefit in patients with moderate-to-severe exacerbations who do not respond to initial bronchodilator therapy, and should be the first-line parenteral bronchodilator in severe/critical asthma.

• Asthma education, including asthma action plans on ED discharge, provided to children and their parents while in the ED results in fewer future ED visits and hospital admissions.

Introduction

Asthma is the most common chronic disease of childhood.¹ The International Study of Asthma and Allergies in Childhood (ISAAC) has identified differences in the prevalence of asthma internationally, ranging from 1.6% in Indonesia to 36.7% in the United Kingdom.² Prevalence of asthma in the United States is estimated at 8.9%, affecting an estimated 7.1 million children under 18 years of age.³ The overall prevalence is highest in developed countries and is highest in urban versus rural areas. Most children develop asthma under 5 years of age.

Acute exacerbations of asthma are often managed in emergency departments (EDs). The CDC reported that in 2008 approximately 775,000 US children were treated for an acute exacerbation of asthma in the ED⁴ and accounted for approximately 14.4 million lost school days.

Etiology/Pathophysiology

Asthma has been defined as intermittent, reversible obstructive airway disease and is a chronic inflammatory disorder of the airways with acute exacerbations. The most recent National Heart Lung and Blood Institute (NHLBI) expert panel guidelines (2007) define asthma as “a common chronic disorder of the airways that is complex and characterized by variable and recurring symptoms, airflow obstruction, bronchial hyperresponsiveness, and an underlying inflammation.” The interaction of these features determines the clinical manifestations, severity of asthma, and response to treatment.⁵

The major pathophysiology of asthma includes increased airway responsiveness, inflammation, mucous production, and submucosal edema. Airway responsiveness is defined as the ease with which airways narrow in response to various non-allergic stimuli. The level ...