What Is Asthma?

Asthma is characterized by hyperresponsiveness to a variety of stimuli that provoke reversible airway obstruction. Airway obstruction is caused by two main processes: bronchospasm from constriction of smooth muscles around the airway and inflammation with edema of the respiratory mucosa and increased mucus production. Symptomatically, airway obstruction may produce cough, chest tightness or pain, decreased air flow, and wheezing.

What Are the Common Clinical Patterns of Asthma?

Intermittent asthma is the most common pattern of asthma in children. Other patterns are persistent asthma and seasonal allergic asthma (Table 69-1). Although the National Asthma guidelines classify intermittent asthma as “mild,” symptoms during an exacerbation of intermittent asthma in a child may be severe enough to warrant hospitalization. Therefore, intermittent asthma in childhood is best considered to have a range of severity from mild to severe. Young children commonly have a pattern of frequent, recurrent exacerbations of asthma, usually triggered by viral upper respiratory infections (URIs). Approximately 15% of children have 12 or more URIs a year, each of which may trigger an acute asthma exacerbation. This translates to approximately one URI-triggered asthma “attack” every 3 to 4 weeks for many young asthmatics during the fall and winter viral infection season. The frequency of URI-induced exacerbations makes the distinction between intermittent and persistent asthma difficult in infants and toddlers.

Do the National Asthma Guidelines Apply to Children?

The guidelines from the National Asthma Education and Prevention Program (NAEPP) place major emphasis on persistent asthma, the most common form in adults. The guidelines classify asthma as mild intermittent, mild persistent, moderate persistent, and severe persistent. Asthma in infancy and early childhood tends to have an intermittent pattern, although as children reach school age, the prevalence of atopic, IgE-mediated, and persistent asthma increases. Frequent recurrent viral-induced intermittent exacerbations that are commonly seen in early childhood are less well covered by the guidelines. As mentioned earlier, symptoms of intermittent asthma in children range from mild to severe.

What Are Common Triggers for Childhood Asthma?

Table 69-2 shows common triggers for asthma and their usual timing. All patterns of asthma can be exacerbated by viral illnesses. Up to 85% of acute exacerbations that require emergency department (ED) or hospital care are associated with viral illnesses.

Table 69-2 Common Triggers for Asthma

What History and Examination Findings Are Important?

The asthmatic child or adolescent often comes to attention because of cough (see Chapter 25). Table 69-3 shows important history and physical findings in asthma. Asthma diagnosis is primarily made from the patient’s history and response to medications.

Table 69-3 Findings in Asthma

ED, Emergency department; ICU, intensive care unit.

What Tests Are Helpful in Diagnosing Asthma?

Pulmonary function tests can document reversibility of airway obstruction. Pulse oximetry obtained during an asthma exacerbation may show decreased oxygen saturation, and any value below 92% should be viewed with concern as this is the start of the steep portion of the oxygen desaturation curve. A blood gas determination will occasionally detect increased PaCO₂, but this is a late finding that may indicate impending respiratory failure. If a chest radiograph is obtained, it may show hyperinflation but could also have areas of streaky atelectasis and peribronchial thickening, similar in pattern to viral bronchiolitis. Methacholine challenge or exercise testing can provoke bronchoconstriction in a patient who is not currently symptomatic. Radioallergosorbent testing (RAST) or skin testing can be useful to identify potential allergens. A symptom diary helps identify the timing, pattern and triggers of asthma.

How Does a Therapeutic Trial Help with Diagnosis?

A therapeutic trial of bronchodilators usually relieves symptoms of bronchospasm, but there may be little or no relief if bronchospasm is accompanied by airway inflammation. A therapeutic trial of oral corticosteroids (5 to 7 days, maximum 10 days) should completely reverse the inflammation and relieve all asthma symptoms. If a patient’s symptoms fail to clear completely after an adequate course of steroids, then diagnoses other than asthma should be considered.

How Can Peak Flow Meters Be Used to Monitor Asthma?

Peak expiratory flow rate falls during asthma exacerbations. A child older than 5 or 6 years can usually be taught to use a peak flow meter to allow symptom monitoring, which can guide medication use. The peak flow meter is especially useful for those patients who underestimate or do not recognize the severity of their symptoms. The predicted average peak flow for a child is based on height, but peak flow should be determined individually for each child by frequent measurements when the patient is well.

How Would I Treat an Acute Exacerbation of Asthma?

An inhaled bronchodilator should be the first medication prescribed. Oral bronchodilators are much less effective than inhaled forms and have increased side effects. If there is incomplete response to inhaled bronchodilators, or if treatments are needed more often than every 4 hours (or more than four times a day), then a short course of oral corticosteroids should be started. For older patients who are able to check peak flows, persistent flows in the “red zone” should also prompt treatment with oral steroids. Early intervention with oral steroids can decrease hospitalizations by 90% and clinic visits by 50%. Pediatricians often prescribe oral steroids to be kept on hand at home and teach parents how to recognize symptoms that warrant use of steroids. This decreases the time to initiation of therapy and duration of symptoms.

When Should an Asthmatic Be Hospitalized?

Most asthmatics can be treated as outpatients. Table 69-4 shows key reasons for hospitalization.

Table 69-4 Criteria for Hospital Admission in Asthma

How Are Oral Steroids Prescribed for Acute Asthma?

For acute exacerbations of asthma, daily oral prednisone or prednisolone is typically prescribed at a dose of 1 to 2 mg/kg/day divided into two equal doses and continued until the patient’s symptoms are entirely resolved for at least 1 day. This generally takes from 5 to 7 days. Discontinuation of treatment before complete resolution of symptoms may result in a rebound of cough and wheeze. There is usually a 1- to 3-day lag time between starting oral steroids and improvement of symptoms, although response may be slower if the inflammation is severe or more chronic. Oral steroid treatment for asthma generally should not be continued past 10 days.

Should Steroids Be Tapered?

Tapering of steroids is not necessary for courses shorter than 14 days. Tapering increases the length of steroid therapy, subjects the patient to subtherapeutic doses that are not clinically useful, and increases the potential for side effects.

What Are the Side Effects of Steroids?

Short courses of oral steroids generally have minor, but often distressing, temporary side effects that include increased appetite, irritability, joint aches, and stomach ache. If steroids must be used frequently in short courses or for prolonged courses (> 14 days), more prominent side effects may occur, including Cushingoid features and hyperglycemia. Table 69-5 shows common corticosteroid side effects. Oral steroids also have a bitter taste, which complicates adherence to the treatment plans for young children.

Table 69-5 Corticosteroid Side Effects

How Is Persistent Asthma Treated?

Patients with persistent asthma have daily or near-daily symptoms, including difficulty with exercise and night waking with shortness of breath or cough. These patients often use albuterol daily but have inadequate relief of symptoms. Maintenance medications taken daily may reduce or prevent the symptoms of persistent asthma. Intermittent asthmatics do not benefit from maintenance asthma medications because these medications neither prevent symptoms of viral-induced intermittent asthma nor decrease the frequency of asthma exacerbations.

How Do I Choose a Medication for Persistent Asthma?

Table 69-6 lists different classes of maintenance medications for persistent asthma and shows some advantages and disadvantages of each. Inhaled steroids are generally the first line treatment for persistent asthma. The newer inhaled steroids—budesonide (Pulmicort), fluticasone (Flovent), or beclomethasone HFA (Qvar)—are more effective at lower doses than older preparations. Although long-acting beta-agonists are not as effective as inhaled steroids for monotherapy, medications such as salmeterol (Serevent) act synergistically with inhaled steroids and allow a decrease in steroid dose. They are available in combination with inhaled steroids, such as fluticasone/salmeterol (Advair). Recently, a small but significant increase in asthma-related deaths or life-threatening experiences was found in African-Americans older than 12 years using salmeterol in addition to their usual asthma care (Nelson et al., 2006). Montelukast (Singulair) is the preferred leukotriene modifier because it is a once-a-day medication with almost no side effects. Other leukotriene modifiers are either more difficult to administer or have more side effects: zileuton (Zyflo) must be given four times a day and can have hepatotoxicity, and zafirlukast (Accolate) must be given twice a day and has some drug-drug interactions. Mast cell stabilizers, cromolyn (Intal) and nedocromil (Tilade), have almost no effective role in the treatment of childhood asthma. Although theophylline (Theo-Dur, Slo-bid) is effective, it is not often prescribed because of the potential side effects and narrow therapeutic window.

Table 69-6 Maintenance Medications for Asthma

BID, Twice per day; QID, four times per day.

What Dose of Inhaled Steroid Should I Prescribe?

The preferred approach to inhaled steroid dosing is to start at a mid- to-high-level dose (400 or 800 mg/day) to establish good control of the asthma. The dose should then be decreased every few months until the minimum dose is reached that maintains good control (usually 100 to 200 mg/day). Growth delay can occur with inhaled steroids when total daily dose is above 500 mg/day; doses less than 500 mg/day are generally believed to be safe in children older than 5 years. For younger children and infants, safety is not well studied, and lower doses should be used if possible.

When Should I Make a Referral to a Pulmonologist?

The decision to make a referral to a pulmonary specialist depends on the severity of the asthma, the experience and comfort of the physician, and the comfort level of the family. In general, patients are referred to a specialist when asthma is not well controlled on one maintenance medication, when they have severe or frequent exacerbations, or when the history is complicated or confusing.

What Is Bronchiolitis?

Bronchiolitis is an acute viral infection that occurs most commonly in the winter months, usually affects children younger than 2 years, and is most problematic in young infants. Prematurity, congenital heart disease, and chronic lung disease greatly increase the risk of adverse outcomes. Bronchiolitis causes inflammation and edema of the bronchioles and is characterized by wheezing and respiratory distress. Respiratory syncytial virus (RSV) accounts for about one-third of cases. Other less common causes include parainfluenza virus, adenovirus, rhinovirus, enterovirus, influenza A and B, and Mycoplasma pneumoniae.

What History and Examination Findings Are Important?

History and examination findings for bronchiolitis are shown in Table 69-7.

Table 69-7 Findings in Bronchiolitis

What Tests Are Helpful in Diagnosing Bronchiolitis?

RSV can be identified rapidly by a direct fluorescent antibody test or by antigen detection with enzyme immunoassay [EIA]. Other respiratory viruses are detected by direct or indirect fluorescent antibodies. Viral cultures can be obtained but take 2 to 4 days to grow. All patients with suspected bronchiolitis should have pulse oximetry to guide use of supplemental oxygen. An infant whose respiratory rate is more than 60 breaths/min is likely to be hypoxic. A chest radiograph should be obtained in severe cases.

When Should I Hospitalize an Infant with Bronchiolitis?

An infant with bronchiolitis should be hospitalized for severe respiratory distress, hypoxia, dehydration, poor feeding, or complicating social reasons. Most hospitalizations last 2 to 5 days, but the length of the hospital stay depends on the severity of respiratory distress, the requirement for supplemental oxygen, and the ability of the patient to take adequate oral fluids. Patients who have mild respiratory distress, who are able to take adequate fluids, and whose oxygen saturation by pulse oximetry is above 94% can be managed on an outpatient basis with close follow-up. Symptoms usually resolve by 2 weeks but can last for 4 weeks in about 10% of patients.

Do Steroids or Bronchodilators Help in Bronchiolitis?

The use of oral corticosteroids in bronchiolitis is controversial. Most studies have failed to show benefit from steroid administration in terms of length of hospital stay or improvement of symptoms. Guidelines (2006) recommend that oral steroids should not be used routinely for bronchiolitis. Either nebulized albuterol or epinephrine can reduce wheezing in some patients. Oral albuterol should not be used.

What Other Medications Are Used for Bronchiolitis?

RSV immune globulin (RSV-IGIV) or paluvizamide (Synagis) can be given during the RSV outbreak season to prevent serious complications of infection in premature infants and those with congenital heart disease or chronic lung disease. A combination of RSV-IGIV and ribavirin has been used to treat patients with compromised immune systems. Antibiotics should be used only if secondary bacterial pneumonia complicates bronchiolitis.

What Is the Prognosis of Bronchiolitis?

Patients with RSV or other viral bronchiolitis that is severe enough to warrant hospitalization have up to a 50% chance of having episodes of recurrent wheezing with subsequent URIs. The parents or caretakers should be counseled to monitor closely future viral illnesses for increased or prolonged respiratory difficulties. It is not necessary to perform repeat chest radiographs if the clinical picture is consistent with bronchiolitis as long as the patient has complete clinical recovery.

What Is Pneumonia?

Pneumonia is an infection of the lung parenchyma that causes fever, cough, and respiratory distress. Most pneumonias are viral. Patients with bacterial pneumonia almost always appear toxic and have significant respiratory distress. Exceptions to this are pneumonias caused by M. pneumoniae (“walking pneumonia”) and Bordetella pertussis (“whooping cough”).

What Causes Bacterial Pneumonia at Different Ages?

The bacterial and bacteria-like pathogens that cause pneumonia vary at different ages, as shown in Table 69-8. Neonatally acquired Chlamydia trachomatis is often associated with a history of conjunctivitis. If pulmonary abscesses are present, Staphylococcus aureus is the most likely organism. Anaerobic organisms need to be considered in aspiration pneumonias. Recurrent pneumonias are often associated with underlying chronic diseases such as cystic fibrosis, ciliary dyskinesia syndrome, or immunodeficiencies. These diseases can lead to less common bacterial infections, such as Pseudomonas aeruginosa in cystic fibrosis and Pneumocystis carinii in immunocompromised patients.

Table 69-8 Common Causes of Bacterial Pneumonia at Different Ages

What Complications Occur with Pneumonia?

Bacterial pneumonias can cause respiratory failure, abscess, empyema, pleural effusion, pneumatocele, pneumothorax, and pyopneumothorax. Viral pneumonias occasionally can be severe and cause respiratory failure but generally have far fewer complications than bacterial disease. One exception is adenoviral pneumonia, which can cause bronchiolitis obliterans.

What History and Examination Findings Are Important?

Important history and examination considerations are listed in Table 69-9. Some physical findings may be less prominent in infants. For example, decreased breath sounds or dullness to percussion may not be apparent. Tachypnea is almost always present.

Table 69-9 Findings in Pneumonia

What Tests Help to Diagnose and Manage Pneumonia?

All patients with pneumonia should have pulse oximetry. Patients with suspected bacterial infection should have a chest radiograph, to look for lobar and lobular infiltrates. Complete blood count (CBC) may show an increased white blood cell (WBC) count (> 10,000/mm³) but has poor sensitivity and specificity for differentiating between viral and bacterial pneumonias. Rapid diagnostic testing can be used to identify viral pathogens from samples obtained with nasopharyngeal washings. Sputum or blood culture can be useful to identify bacterial pathogens. Bacterial cultures are optimally obtained before antibiotics are started.

What Are the Goals of Therapy?

Therapy must first manage respiratory distress and maintain adequate ventilation and oxygenation. Subsequent goals include management of complications, treatment of any underlying illness (e.g., cystic fibrosis), and maintenance of hydration and nutrition. Antibiotic therapy should be used when appropriate.

When Should Antibiotics Be Used?

The decision to treat pneumonia with antibiotics depends on the ability to distinguish bacterial from viral pneumonia, which can be difficult. A patient with bacterial pneumonia who receives an antibiotic to which the organism is susceptible generally improves significantly within 1 day of beginning therapy. When the cause of pneumonia is not certain at the time of diagnosis, treatment is usually started with broad-spectrum antibiotics and coverage is later narrowed, either based on culture results or on clinical improvement if no culture results are available. Mild-to-moderate pneumonia is usually treated on an outpatient basis, often with macrolide antibiotics (erythromycin, azithromycin) because these drugs cover Mycoplasma and Chlamydia species. This benefit must be weighed against the increasing resistance of Streptococcus pneumoniae to macrolides. Semisynthetic beta-lactamase–resistant antibiotics, such as amoxicillin-clavulanate (Augmentin), are also widely used, although they have no effect against Mycoplasma species.

What Is Croup?

Croup is a viral syndrome that causes swelling of the laryngeal and subglottic areas and is also known as laryngotracheobronchitis. It is characterized by a barking cough, hoarseness, inspiratory stridor, and respiratory distress. It most commonly affects infants and toddlers.

What Are the Common Causes of Croup?

The common causes of croup are shown in Table 69-10. Other rare causes include adenovirus, enterovirus, and rhinovirus.

Table 69-10 Common Causes of Croup

RSV, Respiratory syncytial virus.

What History and Examination Findings Are Important?

Important elements in the history of stridor are listed in Table 38-2 The most important physical signs to consider are the amount of respiratory distress and the degree of inspiratory stridor. Signs of “toxicity” must also be looked for. Epiglottitis is rare because of immunization against Haemophilus influenzae type b (Hib); however, this disease should still be carefully considered in toxic patients with severe croup. Patients with epiglottitis are usually 2 to 7 years of age (older than typical patients with croup), have a more acute and toxic presentation, and often present with the 4 D’s: dysphagia, dysphonia, drooling, and distress. Bacterial tracheitis occurs more commonly today than epiglottitis and can also be life-threatening if not recognized. Patients have more toxic symptoms than patients with viral croup and have stridor that is less responsive to treatment. A subset of younger patients with bacterial tracheitis may appear less severely ill initially but may still need aggressive management of the tracheal membranes (Salamone et al., 2004). Foreign-body aspiration and retropharyngeal abscess should also be considered in the differential diagnosis of croup.

What Tests Help Diagnose and Manage Croup?

Patients with viral croup usually have a CBC that shows a “viral” pattern, although leukocytosis of greater than 15,000/mm³ occurs in 20% of patients. Hypoxia by pulse oximetry or elevated pCO₂ on blood gas are late findings and indicate advanced disease. Neck radiographs classically show a narrowed subglottic area (steeple sign), but this sign is not reliably present. Never send a child with suspected epiglottitis or bacterial tracheitis for a neck radiograph! Such patients will need careful airway management and usually require intubation. Direct laryngoscopy in the operating room can verify the diagnosis of epiglottitis, but this is now rarely needed except in cases of bacterial tracheitis.

What Medications Reduce Croup Symptoms?

Nebulized racemic epinephrine and oral or intramuscular dexamethasone are the two medications used most often to treat croup (Table 69-11). A patient who requires nebulized racemic epinephrine in the ED should also receive dexamethasone. High-dose nebulized budesonide has shown some benefit in croup but is less effective and more expensive than intramuscular or oral dexamethasone. There is evidence that dexamethasone can effectively control croup at even the low dose of 0.15 mg/kg (Geelhoed et al., 1996). Intramuscular dexamethasone should be administered to patients with severe respiratory distress and those unable to tolerate oral dosing.

When Can a Patient with Croup Safely Return Home?

A child with croup may be discharged to home from the ED if pulse oximetry is greater than 95% and if stridor at rest and intercostal retractions have been absent for 2 to 3 hours after treatment with nebulized epinephrine and dexamethasone. The family must have access to a functioning telephone and also have transportation in case return to the ED is needed.

What Is Laryngomalacia?

Laryngomalacia is a congenital disorder that causes upper airway obstruction because of collapse of the supraglottic laryngeal structures. Stridor (Chapter 38) is produced when “floppy” structures such as the aryepiglottic folds or the epiglottis are drawn into and obstruct the airway during inspiration. Laryngomalacia is associated with other airway abnormalities in some patients, but most of these are not significant. Gastroesophageal reflux is hypothesized to aggravate laryngomalacia by causing inflammation and edema of the supralaryngeal structures, leading to increased edema and obstruction.

What History and Examination Findings Are Important?

Common history and physical findings in laryngomalacia are shown in Table 69-12. Laryngomalacia will classically have its onset at 2 weeks to 2 months of age, have an increase in symptoms until around age 6 to 10 months, and then resolve spontaneously by 2 years of age.

Table 69-12 Findings in Laryngomalacia

URI, Upper respiratory infection.

When Should the Patient Be Evaluated by Bronchoscopy?

A presumptive diagnosis of laryngomalacia can be made from the history and by observation of the child, but the definitive diagnosis is made during bronchoscopy by direct visualization of the invaginating supralaryngeal structures during inspiration. Any infant with significant persistent stridor and respiratory distress should be evaluated by bronchoscopy. Bronchoscopy can also identify other causes for stridor including vocal cord anomalies, laryngeal webs, hemangiomas, lymphangiomas, vascular abnormalities, and mucus retention or brachial cleft cysts.

What Are the Treatment Options for Laryngomalacia?

Because laryngomalacia typically resolves spontaneously, observation or conservative treatment is generally the best approach and will allow the infant to “outgrow” the laryngomalacia. Changing feeding positions or feeding the infant slowly can sometimes be helpful. Severe laryngomalacia can cause life-threatening airway obstruction or cor pulmonale. Generally, surgical correction with laryngoplasty is reserved for infants who demonstrate poor growth or have recurrent episodes of severe respiratory distress. Laryngoplasty is highly successful in most patients, and tracheostomy is rarely needed.

Does a Trial of Antireflux Medications Help?

A trial of antireflux medications is relatively benign and should be tried for patients who are candidates for surgery. A therapeutic trial can also be tried for patients with less severe symptoms, especially if there is significant parental concern over the infant’s symptoms. The medication trial should last at least 1 month to document any improvement. Medications include proton pump inhibitors (omeprazole, lansoprazole) or H₂-receptor antagonists (ranitidine, cimetidine) with or without the addition of a motility agent (metoclopramide).

What Are the Common Causes of Hypoxia?

The most common cause of hypoxia is ventilation-perfusion (V/Q) mismatch. Cardiac diseases cause hypoxia only when there is shunting of unoxygenated blood from the right to left side of the heart. Table 69-13 shows the four main causes of hypoxia. A fifth and less common cause would be decreased PaO₂, which is seen mainly at high altitude.

Table 69-13 Hypoxia

ASD, Atrial septal defect; V/Q, ventilation-perfusion ratio; VSD, ventricular septal defect.

What Tests Help Determine the Cause of Hypoxia?

Hypoxia from cardiac lesions can be distinguished from hypoxia caused by respiratory problems because it does not improve with supplemental oxygen, as exemplified by the infant with complete transposition of the great arteries. If hypoventilation is severe enough to cause hypoxia, a blood gas test will have an elevated PaCO₂ even when the PaO₂ is increased with supplemental oxygen. Pulmonary function testing can detect a decreased adjusted diffusion capacity of the lung for carbon monoxide (DLCO) that indicates diffusion impairment. A V/Q scan can reveal areas of V/Q mismatch; however, a plain chest radiograph can usually locate these same areas of infiltrate or atelectasis.

How Is Hypoxia Treated?

In general, oxygen is administered while the underlying disorder is identified. See Chapter 59 for a discussion of the emergency management of a child with respiratory distress and hypoxia.

When Can Oxygen Be Harmful to a Hypoxic Patient?

Giving oxygen to a hypoxic patient can be harmful in several situations. Oxygen acts as a pulmonary vasodilator and can cause pulmonary edema in a patient with a left-to-right cardiac shunt. Oxygen dilates the pulmonary arteries and can decrease pulmonary vascular resistance, which results in more shunting, increased pulmonary blood volume, and eventual congestive heart failure. Chronic treatment with higher than 40% oxygen can cause oxygen toxicity to growing organs. Premature infants and neonates are particularly vulnerable to oxygen toxicity because their organs are undergoing substantial growth. In particular, they develop retinopathy of prematurity and bronchopulmonary dysplasia as a result of oxygen toxicity.

KEY POINTS

Discuss the causes of wheezing and recognize the history that suggests asthma

This boy most likely has viral-induced asthma. Symptoms are triggered by viral infections. Between infections, he is asymptomatic.

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