PEDIATRIC EMERGENCY MEDICINE: CURRENT CONCEPTS AND CONTROVERSIES
0733–8627/02 $15.00 .00
CONTEMPORARY APPROACH TO THE EMERGENCY DEPARTMENT MANAGEMENT OF PEDIATRIC ASTHMA Jill M. Baren, MD, and Joseph J. Zorc, MD
PROBLEM STATEMENT Asthma is the most common chronic disease seen in children in the United States.23 Approximately 3 million people under the age of 18 years are affected, and of those, 200,000 require hospitalization each year.23 Hospitalization rates for children have increased markedly in only a 10-year period, from 112 in 100,000 in 1970 to 279 in 100,000 in 1980.23 Hospitalizations for acute asthma have increased disproportionately in all children, but especially in those under 4 years of age.23 Surveillance of mortality data has revealed that asthma deaths doubled from 1977 to 1985.23 These disturbing statistics are present despite advancement in knowledge of the pathophysiology of asthma and in the number of therapeutic modalities available for treatment. The reasons for this are not entirely clear and are the subject of much ongoing research.7, 29, 37 Emergency department (ED) visits by children with acute asthma are a common occurrence. In the authors’ urban, tertiary care children’s
From the Departments of Emergency Medicine (JMB) and Pediatrics (JMB, JJZ), University of Pennsylvania School of Medicine, Hospital of the University of Pennsylvania; and Department of Emergency Medicine, Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania
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hospital, ED visits for asthma represent about 5% to 10% of the total annual ED census. ED care for asthma patients expends considerable resources, including personnel time for monitoring and administering medications as well as for education for outpatient management. Relapse rates for children with asthma seen and released from the ED can be as high as 30%.3 Emergency physicians should be skilled in the assessment, treatment, and proper disposition of these patients. The following article provides guidance for a contemporary approach for handling asthma exacerbations in children.
ACUTE ASTHMA EXACERBATIONS Definition Asthma is a chronic inflammatory disease characterized by exacerbations and remissions. Episodically, and particularly during exacerbations, there is airflow obstruction that is partially reversible with medications.39 Asthma patients are heterogeneous, with a variety of disease manifestations and responses to therapy. Most children experiencing an exacerbation complain of acute or subacute shortness of breath, cough, wheezing, or chest tightness. Airflow obstruction can be documented, and this is more reliable than subjective symptoms. Unfortunately, in children, this information is often not obtained or is unreliable.39
Triggers Exposure to smoking, air pollutants, other allergens, and respiratory viruses are important precipitating factors for acute asthma in children.4 A study of yearly admissions for asthma over an 11-year period showed a repeated yearly pattern, with peaks and trough corresponding to the timing of school holidays. Holidays disrupt the spread of viral infection throughout the childhood community and synchronize subsequent attacks.63 Some of the most common infections implicated in asthma exacerbations are respiratory syncytial virus (RSV), rhinovirus, parainfluenza and influenza viruses, and adenovirus.24 RSV appears to be the most important agent isolated from infants and preschool children with wheezing. Mycoplasma pneumoniae is also an important nonviral respiratory pathogen isolated in wheezing children of school age.27 A careful history designed to elicit identifiable triggers for asthma is crucial, because there are many environmental control measures that can be instituted to prevent further exacerbations. This is particularly true when exposure to cigarette smoke occurs in the home.
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Goals of Exacerbation Management Since 1991, valuable consensus guidelines have been available for the diagnosis and management of all aspects of the disease of asthma. The National Asthma Education and Prevention Program (NAEPP) from the National Heart Lung and Blood Institute, published the second expert panel report in 1997 with input from multidisciplinary members.39 The overall goal of asthma care in the ED is to integrate with home, outpatient, and inpatient care whenever possible.39 What is done in the ED impacts care at other levels. Documentation aids, such as asthma flow sheets, which become part of the medical record, can greatly assist communication between providers and enhance medical care for the patient. The authors’ ED uses one such example of a flow sheet in the ED (Fig. 1). Physicians, nurses, and respiratory therapists all document in the same place. Detailed historical information, medication orders, response to therapy, and discharge instruction and medications can be documented. The chart remains at the bedside of the patient during the ED stay. The flow sheet is also faxed to primary care providers at the completion of the visit and is scanned electronically into the medical record. The approach in the ED can be divided into five parts, each of which is discussed in detail: (1) initial assessment, (2) management of symptoms, (3) identification of risk factors and assessment of response to therapy, (4) disposition from the ED, and (5) post-ED care. ASSESSMENT OF EXACERBATION History The initial assessment of the pediatric asthma patient should be as objective as possible.3 Both children and caretakers should be questioned. Relevant historical points can be divided into questions about the current exacerbation (i.e., type of symptoms, onset, duration, and severity), characterization of past exacerbations (i.e., need for ICU care or intubation, near-fatal asthma episodes), baseline severity of disease (i.e., ED visits, hospitalizations, medication usage, particularly steroids), and socioeconomic factors that can influence disease (i.e., access to regular source of medical care, ability to pay for medications). Although historical information often helps to determine a disposition from the ED, any asthma patient, even those with very mild disease or lack of symptoms for many years, can present with a sudden, severe, life-threatening exacerbation.39 Physical Examination Typical physical examination findings during asthma exacerbation in children are tachypnea, tachycardia, accessory muscle use, wheezing
Figure 1. Emergency department asthma flow sheet. (Courtesy of The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania.)
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or other abnormal breath sounds, and decreased aeration.5 The younger the child, the easier it is to appreciate accessory muscle use because of the increased compliance of the chest wall. At the same time, it is also more difficult to characterize breath sounds because of a smaller chest diameter.5 Wheezes can sound coarse rather than high-pitched and musical and can be mistaken for upper airway congestion. Tachypnea is the most sensitive indicator of lower airway obstruction in children.3 Lack of wheezing at any age, concurrent with other signs of respiratory distress, may indicate poor air entry and a severe exacerbation. The overall assessment of respiratory distress should reflect both ventilation and oxygenation. Tachypnea and accessory muscle (e.g., intercostal, subcostal, supraclavicular) use provide an indication of ventilatory function; oxygenation can be assessed by looking for nasal flaring, color change, and subtle changes in mental status (e.g., irritability, confusion) in addition to direct measure by pulse oximetry.9 Markedly altered mental status, such as somnolence or unresponsiveness, reflects hypercapnia as well as hypoxia and signals respiratory failure or imminent need for intubation.5 NAEPP Guidelines also contain suggestions for assessing the severity of an acute asthma exacerbation and are generally helpful to clinicians (Fig. 2). Clinical Scores Clinical scores, derived predominantly as research tools, combine physical examination findings with objective, reproducible measures of asthma severity, in an attempt to predict the outcome of an asthma exacerbation.17, 65 None has made its way into routine practice because these scores do not have sufficient validity to use for disposition decisions.65 The score familiar to most clinicians is the pulmonary index, which can be calculated using physical examination findings only. The score was developed by Becker et al and was found to correlate with percentage of forced expiratory volume (FEV1) forced vital capacity (FVC). Scores range from 0 to 12, with each item assigned a value between 0 to 3.9 Pulmonary Function Tests (PFTs) PFTs are the best measure of the degree of airflow obstruction in an asthmatic patient and should be measured whenever possible.39 The NAEPP recommends the routine use of objective measures of pulmonary function in children, but many physicians find it difficult to comply with this standard, especially in the ED. Children have a wide variation in verbal and developmental skills, which can create difficulty in teaching or remembering the technique for PFTs. Some PFTs require a strenuous breathing maneuver that cannot be performed during an acute period of dyspnea in the ED.19 Submaximal efforts create falsely low readings,
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often with wide variability between readings.19 Despite these obstacles, every effort should be made to perform objective lung function testing on children who seem amenable to performing the test. Children aged 5 to 6 years can perform PFTs reliably when instructed and monitored.38 Some of the most valuable PFTs for assessment asthma severity, response to treatment, and making disposition decisions are FEV in 1 second (FEV1) and peak expiratory flow (PEF). FEV1 is the most reproducible airway function parameter. FEV1 and PEF both reflect changes in the degree of airway obstruction, with FEV1 being the superior test to estimate small airway obstruction.19 They are the most common forms of ambulatory monitoring because they are inexpensive and portable. PEF has one major drawback; it is effort dependent, but nevertheless it is the most common form of PFTs monitoring in the ED and strongly advocated by many ED asthma experts. Proper PEF technique consists of the following. Have the patient stand and measure all attempts in the same position. Ask the patient to take as deep a breath as possible and blow as quickly and hard as he or she can into the mouthpiece. The best of three attempts can be recorded. Flow rates are measured in liters per minute. Patients or caregivers should be asked if a ‘‘personal best’’ PEF is known. This can be used to determine the percentage predicted, along with the current value. Alternatively, charts are available with normal PEF values based on height, gender, and ethnicity (Table 1).39 Guidelines for interpreting PEF are as follows:39 PEF predicted (%) ⱕ 30 ⬍ 50 50–80 ⬎ 80
Exacerbation severity Possibly life-threatening Severe Moderate Mild
Table 1. PREDICTED PEAK EXPIRATORY FLOW RATES (L/MIN) IN CHILDREN BASED ON SEX AND HEIGHT Height (cm)
Female
Male
110 115 120 125 130 135 140 145 150 155 160 165 170 175 180
145 157 170 184 199 216 234 253 274 296 321 347 376 407 441
145 160 175 191 208 226 247 269 293 319 348 379 414 451 491
Figure 2. National Asthma Education and Prevention Program (NAEPP) guidelines for assessment of exacerbation severity in children.
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Pulse Oximetry Pulse oximetry, a noninvasive technique for measuring oxygen saturation (SaO2), is readily available in most EDs and has gained widespread acceptance for use.16, 67 It is highly sensitive for picking up hypoxia, however, as a predictor of outcome of an exacerbation, it has fair to poor sensitivity and specificity.8, 21 SaO2 does have important properties that advocate for its routine use in the monitoring of asthma patients. SaO2 provides continuous information and can detect changes instantly in arterial oxygen saturation. It also has a normal range of values that apply to all ages.22 Pulse oximetry reflects atelectasis and intrapulmonary shunting, two primary pathophysiologic processes in acute asthma, as opposed to airflow obstruction. There are some minor disadvantages in that it might not be accurate when the oxygen-carrying capacity of blood is markedly decreased, and the pulse signal might not be detectable in low-perfusion states like shock. It also provides no information about ventilation and should not falsely reassure the clinician when there are signs of increased work of breathing.5 TREATMENT Mid-to-moderate Exacerbations Oxygen Most children who present with mild-to-moderate asthma exacerbations will not require supplemental oxygen. According to NAEPP Guidelines (see Figure 3 for NAEPP management algorithm) those who present with initial SaO2 of ⬍ 90% should be given oxygen by whichever route is best tolerated. In these authors’ ED, supplemental oxygen is provided for children with SaO2 ⬍ 95%. SaO2 should be monitored continuously in such patients until a clear response has been established. All pregnant patients and some patients with a comorbid conditions such as congenital heart disease can also need supplemental oxygen.39 Inhaled Beta-agonists Inhaled beta-agonist agents are the standard first-line therapy for the management of acute asthma. They are the most effective way to relieve airflow obstruction, with a rapid onset of action of 5 minutes.39 The most frequently used beta-agonist in the United States is the beta2selective drug, albuterol. Albuterol exerts its bronchodilating effects by relaxing airway smooth muscle to relieve bronchospasm. Albuterol has the additional properties of enhancement of water output from bronchial mucous glands and improvement of mucociliary clearance.40 Betaagonists might even possess anti-inflammatory effects as well.64 There are several important clinical questions regarding the use of
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albuterol: route of administration, dose, and which agent to use. The one that often generates the most controversy is the route of administration. Albuterol is delivered either by small volume jet nebulizer (SVN) or by metered-dose inhaler (MDI). Both require proper technique to be effective. Numerous studies have demonstrated equivalent clinical effects between SVN and MDI as long as the MDI is used with a spacer device, and a few studies have actually shown superior effects with the MDI/ spacer.13, 31, 34–35, 55 Schuh et al compared SVN with MDI in patients aged 5 to 17 years who required albuterol for a mild asthma exacerbation in a randomized, double-blind, placebo-controlled trial. There were no significant differences in FEV1, or in hospitalization or relapse rates between the groups.55 Leversha et al demonstrated similar results on a younger population aged 1 to 4 years with moderate to severe exacerbations. Although there were no differences overall in clinical scores between groups, the MDI group had a greater reduction in wheezing after the first treatment, and only 33% were admitted compared with 60% in the SVN group (P0.04). In addition, the total cost of the SVN was about 50% higher.34 In both studies, most caretakers preferred the MDI/ spacer for future use.34, 55 Despite evidence to the contrary, SVN continues to enjoy greater popularity in most EDs.31 If the SVN is chosen for general use, patients should be able to inhale through a mouthpiece and perform hand-breath coordination. Often the SVN is chosen for younger children who seem to handle the SVN better, but when given by face mask this can limit optimal particle deposition and drug effect.31 Correct MDI/spacer technique requires slow inhalation with breath holding for maximal effectiveness. Whichever method is chosen, the patient should be observed until proper technique is ensured.39 Recommended dose of albuterol is 0.15 mg/kg/dose (0.03 mL/kg/ dose, maximum 1 mL).56–57 Most pediatric patients receive about 0.5 mL/ dose if given by SVN. MDI dose recommendations range between two to eight puffs every 5 minutes. Approximately 2% to 10% of albuterol given by SVN reaches the lungs. An MDI delivers 90 g/puff, but the delivery is more efficient and hence the recommended number of puffs is lower. Higher doses of albuterol have been proposed for children based on the knowledge that much of the medication given goes into the surrounding air. There does not seem to a higher incidence of untoward effects with higher doses. Some investigators have found no clinical or PFT differences in lower versus higher albuterol doses in comparison studies of adults.20 Albuterol is actually a racemic mixture of the R and S isomers of the compound, which have brochodilatory and brochoconstrictive properties, respectively. This is reflected clinically in the development of tolerance after excessive or sustained exposure to albuterol. Recently, the pure R isomer has been marketed as levalbuterol. Clinical research with levalbuterol in the ED is limited. A large study of 328 adults and a small
Figure 3. NAEPP algorithm for emergency department or hospital management of asthma exacerbation in children.
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study of 28 children both demonstrated that levalbuterol produced better bronchodilation on first administration and on repeated exposure when compared with racemic albuterol. Additional trials are ongoing, and this product could come into widespread use in the near future.41 Systemic Corticosteroids Systemic steroids are indicated for most patients in the ED who present with an asthma exacerbation. The NAEPP algorithm for exacerbation management suggests their use when a patient does not respond completely to one inhaled beta-agonist treatment, even if the patient has a mild exacerbation. Corticosteroids speed the resolution of airflow obstruction, potentiate the effects of beta-agonist therapy, and have the potential to decrease hospitalization for sicker patients.39 The most well-known study of the beneficial effects of corticosteroids in the ED is a randomized controlled trial of 75 children older than 1 year of age with moderate to severe asthma given 2 mg/kg of prednisone versus placebo. This trial demonstrated decreased hospitalization rates in the prednisone group amongst the sickest patients (32% vs 72%) and among those who would have been hospitalized at 2 hours after initiation of therapy (45% vs 83%).51 Rowe et al, in a meta-analysis of 30 randomized controlled trials, showed that early steroid use reduced hospital admission in both adults and children. The 95% confidence interval (CI) for reduction in hospitalization for children was odds ratio 0.06 to 0.42.50 This meta-analysis also demonstrated that the effects of IV- and POadministered steroids were equivalent.50 The PO route is clearly preferred in children because it is less painful and less costly. Barnett et al also showed equivalence between methylprednisolone PO and IV (2 mg/kg) in a randomized trial of moderate to severe asthma in children aged 18 months to 18 years. Both groups were similar at baseline, and admission rates were 48% and 50%, respectively.6 In the authors’ ED, the preferred treatment is prednisone PO at 2 mg/kg initially for children with mild to moderate asthma. IV or IM steroids are reserved for those who cannot tolerate the PO preparation after at least two attempts or those who are too ill to receive oral medications. Patients with emesis 30 minutes or less after receiving steroids orally should have their dose repeated. Although currently approved in the United States for maintenance of chronic asthma, inhaled budesonide has not yet been well studied during exacerbations. Nebulized corticosteroids such as budesonide ultimately could prove useful in the ED setting. Anticholinergic Agents The use of anticholinergics such as ipratropium bromide to supplement beta2-agonist therapy has expanded over the past decade. Although recent trials have focused attention on the efficacy of these agents for acute asthma, atropine-containing plants have been known since
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antiquity for their ability to reduce bronchospasm and mucus production. Use of anticholinergics was limited by toxicity until the mid-20th century, when chemists altered the structure of atropine to produce new molecules that do not cross membranes from the lung into the systemic circulation. As a result, nebulized ipratropium bromide effectively blocks acetylcholine-mediated bronchoconstriction, with essentially no effect on heart rate even at high doses.2 The efficacy of ipratropium in the treatment of severe asthma exacerbations in children has been well established. All of the trials assessed the additive benefit of ipratropium to high-dose beta2-agonists because ipratropium by itself is a weak bronchodilator. Schuh and colleagues measured pulmonary function in children with severe exacerbations and found a clear benefit of 250 g of ipratropium compared with placebo; an additional improvement was observed in those who received two more doses during the first hour of therapy.54 The clinical significance of these findings was demonstrated in a meta-analysis44 and a single, large trial, which found a significant reduction in hospitalizations for severe exacerbations;46 one hospitalization appears to be prevented for every 7 to 11 children treated. The benefit of ipratropium in moderate exacerbations is less clear, because some authors have found reductions in duration and amount of beta2-agonist treatment70 whereas others have not;45 these outcomes could depend on the duration of observation allowed for other agents, such as corticosteroids, to act. Ipratropium itself takes approximately 60 to 90 minutes to reach a peak effect and so should be administered as early as possible in the course of therapy. Studies in adults have found mixed results with ipratropium, although overall it appears to have benefit.62 Current NAEPP Guidelines recommend ipratropium for severely ill children and for those who do not respond adequately to high-dose beta2-agonists. Regimens of three doses of 250 g or 2 doses of 500 g during the first hour have been used, although the latter might be more practical because the medication is supplied in 500 g vials. None of the pediatric studies has assessed MDI administration. Ipratropium should be administered in combination with a high-dose dose beta2-agonist such as albuterol. The frequency of further treatment after the first hour has not been established, although some protocols call for readministration every 2 to 4 hours.
Severe Exacerbations Many patients respond to beta-agonists, anticholinergics, and steroids in the initial stages of ED therapy. For the small percentage of patients who do not, there are additional therapeutic agents that can be added (see Fig. 3). Many of these are controversial in terms of their established benefit but certainly can be tried as needed for the severe asthmatic child.
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Continuous Inhaled Beta-agonist There is still debate whether continuous albuterol offers greater improvement in airflow compared with intermittant therapy. At least one study showed improved asthma scores and less need for respiratory therapy time for continuous albuterol, but there were no differences in PEF, admission rates, or adverse effects.56, 57 Severe asthma patients in the authors’ ED are placed on continuous therapy when only minimal response to therapy has been achieved after three intermittent albuterol treatments in the first hour of therapy. The recommended dosage is 0.5 mg/kg/h with a maximum of 15 mg. Patients on continuous albuterol should have continuous cardiopulmonary monitoring to anticipate any untoward effects. Magnesium Like anticholinergics, the efficacy of magnesium for acute asthma has been rediscovered recently and become a subject of intense research interest.51 Although studies dating from the 1930s described intravenous magnesium as a bronchodilator, no well-designed clinical trials were carried out until the 1980s. The precise mechanism of action remains unknown, but magnesium probably counteracts calcium ions to prevent bronchial smooth muscle contraction. Adverse effects of magnesium include nausea, vomiting, weakness, and facial flushing, although usually it is well tolerated. As with anticholinergics agents, good evidence for efficacy exists in children, whereas the results in adults have been varied. Ciarallo and colleagues have published two well-designed pediatric studies assessing two different doses of magnesium: 25 mg/kg and 40 mg/kg.14, 15 Both studies were limited to patients with PEF rate less than 60% of predicted despite three albuterol treatments and systemic corticosteroids. In both studies, pulmonary function improved significantly in the magnesium group compared with controls; greater improvement was observed at the higher dose. Only patients in the magnesium group were able to be discharged home from the ED, suggesting that the findings have clinical relevance. No significant adverse effects were observed. Analysis of the studies of magnesium in adult asthmatic patients is complicated by small sample size and differences in the research protocols; some included patients with much milder disease than those in the Ciarallo studies. Two groups of authors recently performed systematic reviews of the literature; although these meta-analyses differed in some of their findings, both concluded that the current evidence supports the use of magnesium in adults with severe asthma exacerbations.1, 48 Overall, the results on magnesium appear promising, although further data are needed. The appropriate use for this agent at this time appears to be in moderate to severely ill patients who have failed to respond to albuterol. Advantages over other agents such as systemic beta2-agonists include low cost, wide availability, and relative ease of
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administration intravenously over 20 minutes. Doses have ranged from 30 to 75 mg/kg with a maximum of 2 g; magnesium levels need not be measured for single bolus administration, although they should be followed if repeated doses (goal, 4–7 mg/dL) are considered. Parenteral Beta-agonist The use of systemic beta2-agonists for severe asthma has been controversial, although new studies and growing experience in ICUs could better define a specific role for these agents. The NAEPP guidelines caution about the possibility of cardiotoxicity, which was observed with nonselective beta-agonists such as isoproterenol. Studies of intravenous terbutaline in ICUs, as well as case series of albuterol ingestions from the toxicology literature, however, suggest that these selective beta2agonists may be much better tolerated.12, 66 Few well-designed studies have examined the efficacy of systemic beta2-agonists. One recent study was carried out in Australia, where intravenous albuterol is available.10 The investigators of this study viewed systemic administration as a way to dilate obstructed small airways and enhance the efficacy of inhaled beta2-agonists in severe exacerbations. Using a randomized, double-blind design, they found that patients who received a single bolus of albuterol IV in addition to continuous nebulized therapy improved more rapidly than did those who received continuous albuterol alone.10 No adverse effects were reported, although cardiac enzymes were not measured. The sustained improvement well after the intravenous bolus supports the idea that systemic administration can enhance the efficacy of inhaled therapy. Systemic beta2-agonists should be considered in patients with severe asthma exacerbations who have failed to respond to maximal inhaled therapy. Options for SC administration include terbutaline or epinephrine. For IV administration, terbutaline is the primary agent available in the United States. Dosing recommendations call for an initial bolus of 2 to 10 g/kg followed by a continuous infusion starting at 0.4 g/kg/ min to a maximum of 5 g/kg/min. Continuous nebulized therapy should not be interrupted, and close monitoring of cardiac function and potassium is required. Other Therapies Aminophylline was a mainstay of asthma therapy until the past decade when well-designed trials found no benefit compared with inhaled beta2-agonists alone for standard hospital management.18 These findings, in addition to the well-documented adverse effects of aminophylline, led to a recommendation against its use in the most recent version of the NAEPP Guidelines. Whether aminophylline has a role in the most severe patients remains an open question. One recent study of aminophylline in an ICU demonstrated efficacy, although toxicity led to discontinuation in approximately one third of patients.68 Whether systemic beta2-agonists are more effective and better tolerated compared with aminophylline likely will be the topic of future investigation.
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Helium-oxygen (heliox) therapy is an intervention that has been well studied for upper airway obstruction such as croup. By mixing low-density helium with oxygen, turbulent flow and airway resistance are reduced, thereby improving air movement through obstructed areas. Some limited evidence shows that heliox therapy can play a role in asthma.32 Unfortunately, mixtures of at least 60% helium are required to be effective, and hypoxemia limits the usefulness of this therapy for diseases of the lower airways. Other new agents that have become available for chronic management of asthma eventually could play a role in acute management. For example, the leukotriene receptor antagonists are a new class of drugs that block the production of natural mediators involved in bronchoconstriction. These agents are being used increasingly as preventive therapy because they can be given orally once or twice a day. Preliminary evidence suggests that there could be a role for these agents in the acute setting, although further investigation is needed.60 Intubation and Mechanical Ventilation Aggressive management is warranted for severe asthma owing to the high morbidity associated with respiratory failure. Intubation should be viewed as a last resort because it increases airway hyperresponsiveness and can result in complications, such as pneumothorax or cardiac arrest. Early recognition of poor response to therapy should prompt admission to an ICU, where close monitoring and expertise in airway management are available. Signs of respiratory failure include declining level of consciousness, fatigue, and rising CO2 on blood gas. If intubation is required, the patient should initially be preoxygenated with 100% oxygen. Some authors have advocated ketamine (2 mg/ kg) as a preferred sedative agent because it is also a bronchodilator; atropine (0.01 mg/kg) should be administered with the ketamine to reduce airway secretions. Next, a paralytic agent should be administered, using a rapid-sequence protocol. After intubation, careful attention should be given to the ventilatory rate to allow adequate time for expiration (typically 8–12 breaths/min). Buildup of pressure in the thorax can lead to airway leak as well as cardiac arrest owing to impaired venous return. Beta-2-agonist therapy should continue with consideration of systemic therapy. Recent strategies for ventilation of asthmatic patients have included the use of pressure support and permissive hypercapnia, in which elevated CO2 levels are tolerated to reduce barotrauma.42 ANCILLARY TESTING Chest Radiography A chest radiograph is seldom helpful in the assessment of acute asthma, and rarely is the sole determinant of the outcome of an exacerba-
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tion. Nonetheless, chest x-rays, are often performed. A large study in adults indicated that the most common findings on a chest x-ray of an asthmatic patient were normal images, followed by hyperinflation and peribronchial cuffing. Infiltrates were far less common, along with pneumothoraces and pneumomediastinum.69 An additional adult study found that only 3% to 9% of patients required alteration in management based on the chest x-ray findings, with the higher rate of altered management being found in hospitalized patients with severe asthma.43 Although there are no analogous large studies in children, based on these authors’ experience, it is reasonable to conclude that results would be similar. Chest x-rays therefore should not be obtained routinely during asthma exacerbation. They should be reserved for those patients in whom a complication is suspected or for those who do not improve as expected with therapy. Laboratory Testing Information from complete blood counts (CBC) and chemistry profiles in pediatric asthma patients has limited clinical utility, and therefore these studies are not routinely recommended. Arterial blood gas (ABG) is painful, invasive, and also not routinely necessary in acute pediatric asthma. ABG can be performed in children who show signs of impeding respiratory failure.36 The most common pattern seen on ABG is mild hypoxemia, hypocapnia, and respiratory alkalosis, all of which can be predicted clinically by examination, PFTS, and pulse oximetry. Normal or elevated PaCO2 indicates progression to respiratory failure; children are sometimes prone to develop respiratory failure at a lower PaCO2.36 The decision to intubate an asthma patient is never based on an ABG result alone, so they often provide only superfluous information. DISPOSITION FROM THE ED Reassessment As previously mentioned, asthma flow sheets are enormously helpful in the management of asthma in the ED because they allow for a quick review of the patient’s baseline asthma characteristics as well their response to therapy. With the exception of extremely mild exacerbations, most ED asthma patients require at least 2 hours of assessment and therapy. After the initial three bronchodilator treatments, which take about 1 hour, patients whose symptoms have completely or almost completely resolved should be observed for 30 to 60 minutes for symptom recurrence. (Refer to Figure 2 for algorithm of ED management.) Reassessment after therapy is not the only information that contributes to a disposition decision. In certain patients, other risk factors play a role that can make the clinician more inclined to choose hospitalization,
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such as factors that have been associated with sudden fatal asthma episodes. If the patient has any of the following characteristics, hospitalization should be considered more strongly to ensure that a good response to therapy persists: prior history of a sudden, severe exacerbation; prior intubation or ICU admission; ⱖ two hospitalizations in the past year; ⱖ three ED visits in the past year; ⱖ two MDIs used in a month; current steroid use or recent wean from steroids; medical or psychiatric comorbidity; poor perceiver of symptoms (adolescents), substance abuse; or low socioeconomic status or urban residence.3 Criteria for Outpatient Treatment There are no absolute criteria governing the decision to discharge a pediatric asthma patient. NAEPP guidelines are helpful, but final judgment should be based on clinical impression, identification of risk factors and baseline severity of disease, likelihood of urgent follow-up care, and institutional or geographical practices. NAEPP suggested that guidelines for discharge to outpatient care include the following: PEF has returned to ⬎ 70% predicted, exacerbation symptoms are minimal or absent, the patient has been observed for at least 30 and preferably 60 minutes after the last bronchodilator treatment, sufficient medications can be prescribed and maintained, and outpatient care can be established within a several-day time frame.39 Guidelines for hospitalization also are not absolute. The following list represents the most compromised group of asthma patients and those most likely to benefit from inpatient care:3 respiratory failure altered level of consciousness hypotension poor social situation past hospitalization for respiratory failure history of near-fatal asthma significant complications of asthma ED treatment within the last 24 hours inability to tolerate oral medications significant medical or psychiatric comorbidity POST EMERGENCY DEPARTMENT CARE Short-term Medications Beta-agonist Therapy Inhaled beta-agonists should be prescribed on a regular basis for a few days then converted to p.r.n. dosing. The patient or caregiver must understand this distinction. Always prescribe a spacer with MDIs. It is
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useful for patients who will be discharged to receive their last ED bronchodilator treatment through an MDI with a spacer. If ancillary personnel are available, they can teach the patient the proper technique and review outpatient regimens. Corticosteroids Oral steroids should be prescribed as burst therapy for 3 to 10 days. The exact dose and duration of the outpatient course are not well defined in the literature. A general recommendation is to use prednisone PO at 1 to 2 mg/kg/day in one or two divided doses.39 Education It is vital to teach and reinforce the principles of vigilant asthma self-management at every opportunity.39 ED personnel face time constraints and cannot always provide detailed education for patients. If the opportunity does exist, the healthcare team should cover the following: 1. Basic facts about asthma disease 2. The role of quick-relief rescue medications versus long-term stabilizer medications 3. Mechanical skills such as the use of the MDI and PEF meter 4. Identification and avoidance of exacerbation triggers, including suggestions for environmental control 5. When to follow up with a primary care physician or asthma specialist
SUMMARY Asthma continues to be an enormous health problem and economic burden in US society. EDs probably will continue to provide a substantial amount of care for those affected by the disease. Pediatric asthma patients frequently are encountered in EDs. Emergency physicians must remain current in their approach to providing expert care while the management of acute asthma exacerbations continues to evolve, older therapies are challenged and new therapies are developed, tested, and implemented.
References 1. Alter HJ, Koepsell TD, Hilty WH: Intravenous magnesium as an adjuvant in acute bronchospasm: A meta-analysis. Ann Emerg Med 36:191–197, 2000 2. Anderson WM: Hemodynamic and nonbronchial effects of ipratropium bromide. Am J Med 81:45–52, 1986 3. Baren J: The acute asthmatic in the pediatric emergency department: To admit or
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