Asthma

A four-year-old male with a history of eczema presents to the ED with difficulty breathing. Mother reports patient developed cough, congestion, and runny nose yesterday. Mother reports that when she woke the patient up this morning, he appeared like he was having difficulty breathing, so she brought him to the ED to be evaluated. Triage vital signs are respiratory rate 37, pulse ox 90% on RA, heart rate 128, blood pressure 95/50, temperature 100.4 degrees. On exam, patient appears fatigued and in respiratory distress. He is sitting up, awake, but appears tired. He has subcostal, intercostal, and supraclavicular retractions. He can only speak in partial sentences. He has decreased breath sounds throughout all lung fields with faint scattered wheezes noted in all lung fields.

When a child presents to the ED, they are often brought in for wheezing, persistent cough, decrease in level of activity, and/or an increased work of breathing. The primary survey involves the following:

1. Is the child maintaining their airway? This can be assessed by their ability to speak or cry.
2. What is the general appearance of the child? Are they awake or drowsy? Can they speak in full sentences without pauses? Are they using accessory respiratory muscles, breathing fast, exhibiting retractions, nasal flaring, grunting, abdominal breathing, or cyanosis?
3. What is the oxygen saturation? Place the child on pulse oximetry. If SpO2<94% then place on O2 to keep O2 saturations above 94%.
4. Auscultate the child's lungs. Is there adequate air entry? Do you hear diffuse wheezing? Do you hear any focal areas of decreased breath sounds? Do you hear any rales or rhonchi?

Initial Actions

• During the initial survey, if the patient is cyanotic, unresponsive, not maintaining an adequate airway, or showing signs of impending respiratory failure ("tiring out"), place the patient on oxygen while preparing for Rapid Sequence Intubation.
• If there is any change in mental status, remember to check a bedside fingerstick glucose level and treat hypoglycemia if possible.
• If the child does not need immediate intubation, complete primary assessment followed by complete physical exam, with focus on the ear, nose, and throat to evaluate for other causes of symptoms.
• If wheezing is present, begin a nebulized treatment with a short acting beta-agonist such as albuterol combined with a nebulized anticholinergic agent such as ipratropium. This will be discussed further in the treatment section below.

The diagnosis and severity of an asthma exacerbation can be determined from a thorough history and physical exam alone. The severity can be assessed by the clinical presentation, vital signs, and peak expiratory flow rates (PEFR) in children who are old enough to perform this test, usually >8 years old. There is no indication for diagnostic laboratory tests or imaging in children with a known history of asthma with clinical presentation consistent with asthma. A few ancillary tests with some utility in specific circumstances are listed below. However, prompt recognition and treatment of asthma should be initiated before any tests are ordered.

• Blood Gas Analysis: The use of blood gas analysis is most useful in patients who are refractory to maximized medical management or those with associated neurological changes/conditions. The use of pulse oximetry, end tidal capnography, and serial examinations can be used to monitor respiratory status instead of using blood gas analysis. If obtained, initial findings can be hypocarbia due to hyperventilation and hypoxia. However, as the symptoms progress and air-trapping gets worse, blood gas analysis may show respiratory acidosis with hypercarbia. A venous blood gas (VBG) can be used as an alternative to an ABG in patients who are not hypoxic, as pH and PCO₂ have shown correlation in studies and it is less painful to perform. Blood gas analysis should not be the only factor in determining if a patient requires intubation, as this decision should be based on clinical presentation and response to treatment alone. However, repeating a VBG in patients with hypercarbia can assess the degree of improvement after treatment. If a trial of non-invasive positive pressure ventilation is conducted, a blood gas can also help assess response.
• Chest X-Ray (CXR): A CXR should not be routinely ordered in children with an acute asthma exacerbation. It should be considered if it is a patient's first presentation of wheezing to rule out other causes. A CXR should be considered in patients with rhonchi, uneven breath sounds, or areas of focal consolidation on lung exam, patients in respiratory failure, and patients not responding to treatment. If there is suspicion of another process such as pneumonia, pneumothorax, or congenital congestive heart failure, then a CXR should be ordered.
• Peak Expiratory Flow Rate (PEFR): PEFR is included in many care pathways and guidelines related to asthma care. PEFR is used to longitudinally follow patients and assist in early recognition of exacerbations and institution of a patient's asthma action plan. In the acute care setting, PEFR has been shown to be less reliable due to technique and effort related effects, especially in children under ten years of age. As a result, many institutions do not use PEFR in the acute setting and rely upon severity scores and clinical pathways for treatment plans. When used, children are instructed to take a deep breath and blow as hard and as fast into the peak flow meter. Here are the normal values based on height.

Scoring instruments combining physical examination findings and vitals have been developed to assist in ED management and subsequent disposition. Examples of these instruments include the Pediatric Respiratory Assessment Measure (PRAM), Pediatric Asthma Severity Score (PASS), and Pulmonary Index Score (PIS), among others. These instruments are typically included as part of an asthma pathway which includes medical management recommendations based on severity score. Use of such pathways have shown improvement in usage and timing of bronchodilators and steroids, along with reducing ED length of stay and admission rates.

The goals of treatment of an asthma exacerbation in the acute care setting are to reverse hypoxia, bronchospasm, and inflammation, while also aiming to prevent recurrence of another exacerbation. Below is a list of treatment options available.

Primary Agents

The mainstay of treatment in an acute asthma exacerbation is nebuliezed albuterol and ipratropium bromide as well as corticosteroids, which can be given intravenously, intramuscularly, or orally. Oxygen administration should be provided for patients experiencing hypoxia.

Albuterol: Short Acting Beta Agonists

• Albuterol is an inhaled short acting β2-adrenergic agonist. It is a critical component of treatment in an asthma exacerbation. It works by reversing bronchoconstriction.
• It can be given as a treatment via nebulizer or through an MDI with spacer (+/- mask). Studies have shown that there is no difference in effect our outcome between the two methods, although young children may not be able to use an MDI as effectively.
• Albuterol delivered by an MDI with spacer in acute exacerbation is typically administered as four-eight puffs (dose dependent on weight) every 20 minutes.
• Albuterol can be given as stacked nebulized treatments of 0.15 mg/kg (minimum 2.5 mg) every 20 minutes for a maximum of three doses, then 0.15-0.3 mg/kg every one-four hours as needed. In severe exacerbation, continuous nebulized albuterol has been shown to reduce hospitalization rates. The dose is 0.5mg/kg/hr, not to exceed 20 mg/hr.
• Inhaled albuterol has been found to be superior to oral, intravenous, and subcutaneous albuterol.
• The side effects of albuterol are tachycardia, tremors, and hypokalemia. An alternative to albuterol is its racemic epimer levalbuterol, however use of levalbuterol has not shown to lead to less tachycardia or asthma scoring when compared to albuterol.

Ipratropium Bromide: Anticholinergic

• Ipratropium Bromide is an inhaled anticholinergic agent which blocks cholinergic receptors, producing bronchodilation. It works synergistically with albuterol when nebulized together. It is also a mainstay therapy in an acute asthma exacerbation, and its use has been shown to reduce the need for hospitalizations.
• The nebulized dose is 0.25-0.5mg every 20 minutes with a maximum of three doses. The MDI dose is four-eight puffs every 20 minutes x three doses (dose dependent on weight in kg).
• Use of ipratropium bromide beyond three doses in the ED or with hospitalization has been shown to be effective.

Corticosteroids

• Giving corticosteroids (CS) to patients with moderate to severe acute asthma exacerbation is an integral part of treatment, with early administration correlated with reduced admission rates.
• They work be reducing airway inflammation and by upregulating the production of beta receptors.
• Acutely, CS can be given orally, intramuscularly, or intravenously. There is no evidence that one works better than the other. If the patient can tolerate oral therapy, it is preferred.
• Inhaled CS are used primarily in maintenance therapy. Recent studies have shown that addition of inhaled CS in the treatment regimen of acute exacerbations may lead to a reduction in hospital length of stay and admissions, with additional studies needed to evaluate efficacy of inhaled CS in the acute setting.
• Prednisone, methylprednisolone, prednisolone, and dexamethasone are all steroids which are equally efficacious.
• Dexamethasone has become common in asthma pathways as the CS of choice. Dexamethasone is given at a dose of 0.6mg/kg with a maximum dose of 16mg as a single dose in the ED or for a total maximum treatment duration of two days.
• Prednisone, methylprednisolone, and prednisolone are given at a dose of one-two mg/kg with a maximum dose of 50mg/day divided once to twice a day dosing for five days.

Adjunctive Agents

These agents are used in concert with primary agents for patients with severe exacerbation or for those who are not responding to primary agents alone.

Magnesium Sulfate

• Promotes bronchodilation by relaxing bronchial smooth muscles.
• Dosing is 25-75mg/kg up to 2g total IV over 20 minutes.
• Nebulized magnesium has not been shown to be beneficial in children with asthma exacerbations.

Epinephrine (1:1000)

• Promotes bronchodilation.
• Dosing is 0.01 mg/kg up to 0.3-0.5mg total SQ or IM every 20 minutes, up to a maximum of three doses.

Heliox

• A combination of 70% helium and 30% oxygen used to deliver albuterol.
• It is less dense than oxygen and can provide more laminar flow through tight airways to deliver albuterol distally to obstructed bronchioles.
• Not routinely recommended, but can be considered as adjunctive therapy in severe exacerbations.

High Flow Nasal Cannula (HFNC)

• HFNC use has increased over the past decade with use in bronchiolitis and the COVID-19 pandemic.
• Delivers warm, humidified oxygen at flow rates up to 30-50mL/min.
• Typical rates of flow are between one-two L/kg/min.
• Use of HFNC has not shown a decrease in hospital or PICU LOS when used in asthma exacerbations.

Non-Invasive Positive Pressure Ventilation (NIPPV)

• NIPPV has demonstrated efficacy in severe asthma exacerbation in the pediatric population with reduction of heart rate, respiratory rate, and decreased need for intubation.
• Initial settings for IPAP/EPAP should be eight-ten cm H₂O / 5cm H₂O and not exceed 20 cm H₂O / 10 cm H₂O.

Ketamine

• A dissociative anesthetic used for induction in rapid sequence intubation and also can maintain sedation.
• Has bronchodilatory properties and is not routinely indicated but should be considered as an adjunctive agent in children with severe exacerbations requiring intubation.
• Dosing is 0.3mg/kg IV bolus (maximum is 25mg), then 0.5mg/kg/hr for up to two hours.

Intubation and Mechanical Ventilation

• Intubation is indicated in children with persistent hypoxia, unresponsive hypercapnia with change in mental status, and respiratory fatigue due to increased work of breathing.
• The decision to intubate is a clinical one and should not be delayed for any diagnostic testing or therapies when indicated.
• If intubated, mechanical ventilation settings must allow adequate time for expiration due to air trapping from bronchospasm. The inspiratory to expiratory (I:E) ratio should be adjusted to 1:4 to allow more time for expiration for each breath given by the ventilator. This prevents a phenomenon known as autoPEEP or breath stacking where air is trapped in the lungs creating a persistently positive intrathoracic pressure leading to barotrauma, decreased venous return, and hemodynamic collapse.

Disposition

Patients who are treated in the ED may be discharged after treatment if they have improved symptoms, no signs of respiratory distress, and no hypoxia after a period of observation in the ED. Patients who continue to have signs of unresolved asthma symptoms including wheezing, respiratory distress, and hypoxia often require hospitalization with level of care dependent on the patient's level of support, degree of respiratory distress, mental status, and institutional care pathways.

• Asthma is a clinical diagnosis, and routine imaging or testing is not required to make a diagnosis and should not delay therapy.
• Patients without wheezing may have more severe asthma than those with wheezing, as these patients may have near-complete airway obstruction.
• Early and aggressive treatment with steroids and inhaled albuterol and ipratropium is the mainstay of treatment. Delaying treatment can lead to increased morbidity.
• Asthma management pathways have been shown to be effective in shortening timing of bronchodilators and decreasing unnecessary testing, ED length of stay, and hospital admissions.
• A trial of NIPVV should be attempted in severe asthma exacerbations, if possible, before deciding to intubate.
• Intubation is indicated in patients with impending respiratory failure not responsive to treatment. Signs of respiratory failure are persistent hypoxia, respiratory fatigue from increased work of breathing, and altered mental status. Remember to adjust I:E to allow for more time for expiration.

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4. Trottier ED, Chan K, et al. Managing an Acute Asthma Exacerbation in Children. Canadian Paediatric Society. 2021 Nov 5.