Asthma is the most common chronic childhood disease and a frequent reason for pediatric emergency medical treatment. This article will review emergency medical services' (EMS) prehospital assessment and management of acute pediatric asthma exacerbations.
Asthma is a chronic disease characterized by airway narrowing (bronchoconstriction), mucous plugging, and inflammation. Symptoms may be chronic, but during exacerbations or flares, those symptoms worsen, and patients experience acute shortness of breath and difficulty with expiration or forced expiration.
Of the estimated 1 to 2 million pediatric EMS encounters in the United States annually, an estimated 10% to 15% are due to asthma and respiratory distress. Albuterol is the most commonly administered medication to children by EMS. EMS providers should be well-versed in the care of a child suffering from an asthma exacerbation.
EMS must quickly assess the patient and obtain their pertinent history due to time constraints as the ultimate goal of every EMS encounter is transport to an emergency department (ED). EMS providers can use the pediatric assessment triangle (PAT) to assess appearance, work of breathing, and circulation as a quick and validated method to determine the level of care required. The PAT can distinguish a stable patient from respiratory distress, and from respiratory failure. Providers should observe the patient’s work of breathing (including positioning, retractions, nasal flaring, audible wheezing), as well as auscultate for abnormal lung sounds. The lack of abnormal lung sounds may be an ominous sign of poor air movement in a patient at risk for respiratory failure. Pertinent items from the patient’s history include prior diagnosis of asthma, onset, and triggers for the exacerbation, current asthma medications, and prior ED visits or hospitalizations for asthma (including intensive care unit admissions and/or intubations). In children younger than 2 years of age, providers should be aware that bronchiolitis may mimic asthma. In toddlers, providers should also be aware that wheezing can be a sign of foreign body ingestion.
Prehospital evaluation is limited to the quickly obtained history and physical, and vital signs. EMS providers can measure oxygenation with pulse oximetry. Oxygen saturation less than 90% to 94% signals hypoxia. Some EMS systems may employ capnography to measure end-tidal carbon dioxide to measure ventilation.
Once an EMS provider has assessed the patient and concluded the most likely diagnosis is an asthma exacerbation, treatment follows according to the provider's level of certification. Emergency medical technician (EMT)-Basics may administer supplemental oxygen and assist the patient in using their beta-2-agonist inhaler (e.g., albuterol).  EMT-Basics should be aware that a patient's inhaled corticosteroids (e.g., fluticasone) are not proven beneficial in the treatment of an acute exacerbation. The scope of practice of an EMT-Intermediate in administering medications will vary based on their local jurisdiction. 
EMT-Paramedics are authorized to administer medications included in local agency protocols for asthma patients. First-line treatment of an asthma patient with any degree of respiratory distress and/or wheezing should be inhaled beta-2-agonists such as albuterol. Beta-2-agonists counteract bronchospasm by relaxing the bronchial smooth muscle and increasing mucociliary clearance. Albuterol may be administered using a metered-dose inhaler (4 puffs per dose) or as a nebulized solution (2.5 milligrams (mg) per dose for patients less than 10 kilograms (kg), and 5 mg per dose for patients greater than 10 kg). Common side effects include tachycardia and tremors, and more rarely children may experience arrhythmias such as supraventricular tachycardia. For children, the addition of ipratropium bromide (0.5 mg per dose) to albuterol has been shown to decrease hospital admissions in the ED setting. The combination of ipratropium bromide and albuterol may be repeated as needed for persistent respiratory distress.
For children suffering from an asthma exacerbation, ED guidelines recommend early administration (within 1 hour of ED arrival) of systemic corticosteroids in addition to inhaled beta-2-agonists. Systemic corticosteroids work synergistically by up-regulating beta receptors in addition to their anti-inflammatory effects. Systemic corticosteroids speed patient recovery, and early administration decreases ED length-of-stay, hospitalizations, and relapse rates. For pediatric ED patients of all severities, systemic corticosteroid effects are time-dependent, with one study reporting that every 30-minute delay in their administration corresponded to a 60-minute increase in ED treatment time.
Evidence for EMS administration of systemic corticosteroids is not as robust as in the ED setting. EMS agencies in both New York City (1996) and Virginia (2003) retrospectively examined a protocol change authorizing intravenous (IV) methylprednisolone for severe adult asthma patients. The New York City study found no difference in ED LOS or admission rates. By contrast, the Virginia study found a threefold decrease in admission rates. Houston’s EMS agency retrospectively analyzed a protocol change authorizing oral dexamethasone for pediatric asthma patients of all severities. For those patients whose outcomes were known, admission rates decreased from 30% to 21%, and average ED LOS decreased by nearly 1.5 hours. However, systemic corticosteroid administration by EMS was low before and after the protocol change (11% and 18%, respectively), and patients post-protocol change had fewer abnormal respiratory rates than patients pre-protocol change.
With respect to selecting a systemic corticosteroid, oral and IV formulations are commercially available. A review of publicly-available EMS protocols reveals the most common systemic corticosteroid utilized is IV methylprednisolone. However, the bioavailability and physiologic effects are the same between oral and IV systemic corticosteroids. Prednisolone is commercially available as both an oral solution, tablet, and oral dissolving tablet. Dexamethasone is available as an IV liquid which can be administered orally, as well as in tablets that can be crushed. ED studies demonstrating dexamethasone as a single or double dose as non-inferior to prednisolone have caused a change in some emergency providers’ selection of systemic corticosteroid from prednisolone to dexamethasone. However, the original study reporting those results used a longer-acting dexamethasone formulation that has since been taken off the market. Additionally, new EMS reports of dexamethasone resulting in multiple episodes of anaphylaxis and intense perineal burning sensations raise concern for its use in pediatric asthma. Therefore, controversy remains as to whether dexamethasone is an appropriate substitute for prednisolone or methylprednisolone.
Adjunctive Therapies for Critically Ill Patients
For critically ill children, several adjunctive therapies are available. EMS stocks epinephrine for a variety of other conditions and subcutaneous epinephrine rapidly relaxes bronchial smooth muscles. Subcutaneous epinephrine is dosed at 0.01 mg/kg of 1:1000 concentration, with a maximum single dose of 0.3 to 0.5 mg. Alternatively, an epinephrine autoinjector (either 0.15 mg or 0.3 mg) can be used to deploy the drug via intramuscular administration rapidly. Intravenous magnesium for pediatric asthma has some evidence for decreased hospital admissions and is dosed at 50 mg/kg (maximum 2000 mg per dose). Common side effects include hypotension, which is rarely clinically significant and usually responds well to fluid administration. Terbutaline is another bronchodilator which can be administered subcutaneously (0.005 to 0.01 mg/kg, maximum dose 0.4 mg) or intravenously (initial bolus 0.01 mg/kg). Terbutaline can have cardiac side effects such as elevated cardiac enzymes and arrhythmias although this is usually seen after several hours of continuous infusion. Finally, positive pressure or mechanical ventilation may be necessary in rare cases. Noninvasive ventilation with bilevel positive airway pressure (BiPAP) can help stave off intubation and preserves the conscious patient’s respiratory drive. Intubation and mechanical ventilation are the last resort for patients with refractory respiratory failure and/or respiratory arrest. It is difficult to match an asthma patient’s hyperventilation, and lower tidal volumes should be used to avoid barotrauma in the setting of hyperinflation. Finally, intravenous ketamine at sub-dissociative doses is gaining favor as an adjunctive bronchodilator, especially for agitated patients in respiratory distress. However, scant evidence exists for its use in the ED and EMS setting.
As stated above, most of the evidence for EMS treatment of pediatric asthma is extrapolated from studies in the ED setting. Future directions for EMS treatment must come from research originating in the heterogeneous and mobile EMS environment. Medical directors and providers would be well-served by keeping abreast of developments in the literature to ensure protocols contain the most up-to-date evidence. Continuing provider education on the assessment and management of the most common chronic disease of childhood is essential for the proper care of pediatric asthma patients.