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Acute asthma exacerbation

Last updated: March 30, 2021

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An asthma exacerbation is the acute worsening of asthma symptoms caused by reversible lower airway obstruction. The diagnosis is usually clinical and should involve early evaluation of the severity of asthma exacerbation. Complementary diagnostic studies include peak expiratory flow rates (PEFR), arterial blood gas, and, in some cases, chest x-ray. Immediate treatment is essential as asthma exacerbations can be life-threatening and may progress to respiratory arrest. The pillars of treatment are oxygen therapy, bronchodilators (short-acting β2-agonists or SABA; short-acting muscarinic antagonists or SAMA), and corticosteroids, which are administered based on the severity of the exacerbation. After the acute exacerbation is under control, close follow-up and long-term treatment should be continued to reduce the risk of recurrence (see “Asthma” for details regarding long-term management).

The information in this article applies to patients older than 5 years of age.

The definitions listed here are for patients older than 5 years of age.

  • Asthma exacerbation: a typically reversible episode of lower airway obstruction (bronchospasm) characterized by a worsening of asthma symptoms within a short period of time (acute or subacute) and accompanied by a change in baseline lung function. [1]
  • Bronchospasm: a constriction in the bronchial muscles that results in airway obstruction within seconds to minutes. It is the characteristic symptom of asthma exacerbations, but it may also be triggered by certain medications or mechanical ventilation.
  • Status asthmaticus: : a term used to describe severe asthma exacerbations that progress rapidly and do not respond to standard acute asthma therapy [2]

Asthma exacerbations occur when a patient with underlying asthma is exposed to a trigger. See “Etiology” in “Asthma” for a detailed list of triggers.

Risk factors for fatal or nearly-fatal asthma exacerbations [3][4]

  • Asthma history
    • History of previous near-fatal asthma episode (e.g., requiring intubation, respiratory acidosis, ICU admission)
    • Hospital admission for asthma exacerbation
    • Multiple visits to the emergency department for asthma exacerbations in the past year
    • Need for ≥ 3 medications for asthma control
    • Heavy reliance on or increased frequency of need for SABA
  • Comorbidities
    • Obesity
    • Cardiovascular or respiratory disease
    • Psychiatric disease
  • Behavioral or psychosocial features

Signs and symptoms vary depending on the severity of asthma exacerbation. For some patients, an acute exacerbation may be the first manifestation of asthma. [1][2]

Features characteristic of imminent respiratory arrest include silent chest, altered mental status, bradycardia, paradoxical breathing, respiratory muscle exhaustion, and signs of respiratory failure on ABG (e.g., normalization of pH and PaCO2 in a fatiguing patient). [1]

Crackles on auscultation are rare in asthma exacerbations and may indicate a viral or bacterial trigger (e.g., pneumonia). [1]

Approach [1][4]

Use appropriate PPE as viral infections are a common trigger for asthma exacerbations.

Oxygen therapy, bronchodilators, and if needed, corticosteroids form the basis of initial therapy of an acute asthma exacerbation

Intubation in acute severe asthma is risky and challenging. It should be performed by an experienced practitioner whenever possible.

Severe asthma exacerbations can be life-threatening! Do not delay immediate treatment measures for diagnostic testing.

COVID-19 considerations [1]

  • Moderate to severe asthma is considered a risk factor for a severe course and higher mortality with COVID-19 infection. [5]
  • Avoid withdrawing inhaled corticosteroids in patients who regularly take them. [6]
  • Minimize viral transmission.
    • MDI with spacers are preferred; avoid nebulizers, if feasible, in patients with suspected/confirmed COVID-19. [1]
    • If NIPPV is attempted, a helmet interface should be used whenever possible.
  • See “COVID-19” for further information.
  • There are several severity assessment scores for acute exacerbation of asthma that can be used to guide treatment decisions and disposition.
  • The following severity assessment is based on the 2007 National Asthma Education and Prevention Program (NAEPP) guidelines.
Severity assessment of asthma exacerbations [4]
Severity Symptoms Signs
(adults)
Functional assessment
Mild asthma exacerbation
Moderate asthma exacerbation
  • Dyspnea at rest
  • Ability to talk in phrases
  • Agitation
  • Preference to sit up than lie down
  • Tachypnea
  • Loud wheezing throughout exhalation
  • Possible use of accessory muscles
  • Tachycardia (< 120/min)
  • PEFR: 40–69% predicted
  • SpO2 90–95%
Severe asthma exacerbation

Life-threatening asthma exacerbation (imminent respiratory arrest)

  • Inability to speak due to dyspnea
  • Drowsiness, confusion, sweating

Early recognition of hypercapnic respiratory failure and/or hypoxemic respiratory failure is vital.

Approach [1][4]

Urgently consult critical care team and respiratory therapist.

Apneic or comatose patients

All other patients

Although efforts should be maximized to prevent the need for mechanical ventilation, intubation should not be delayed once an indication to intubate in asthma is identified. Anticipate and plan for intubation prior to the onset of complete respiratory failure, due to the risks and difficulties of the procedure. [4]

Intubation and mechanical ventilation in asthma

NIPPV can be used as a bridge to intubation, as it may be more effective for preoxygenation than NRB. More research is required before NIPPV can be recommended as a method of preventing intubation. Consult a critical care specialist if considering NIPPV.

Intubation [3][4]

Invasive mechanical ventilation

Continue bronchodilator therapy even when patients are mechanically ventilated.

Initial treatment [1][4]

Treatment escalation [1][4]

Initial treatment [1][4]

Treatment escalation [1][4]

Initial treatment [1][4]

Treatment escalation [1][4]

Monitoring [4]

  • Assess response to initial treatment
  • Stratify response to therapy: Evaluate post-treatment parameters to guide decisions on further treatment and disposition.
Response to initial therapy [4]
Poor response to acute asthma therapy
Incomplete response to acute asthma therapy
Good response to acute asthma therapy
  • All of the following sustained for ≥ 60 minutes:

Disposition [1][4]

Disposition is determined by the severity of asthma exacerbation at presentation as well as response to initial therapy.

The diagnosis of an acute asthma exacerbation is mainly clinical. Diagnostic studies are required to assess the severity of asthma exacerbation as well as to evaluate for potential underlying causes and/or differential diagnoses of dyspnea.

Pulmonary function tests [1]

  • Indication: before initiating treatment for acute asthma exacerbation (only if rapidly available and tolerated by the patient)
  • Objective
    • To assess severity at presentation
    • To monitor response to initial treatment
  • Modalities
    • Spirometry: more reliable measurement, but may not be feasible during exacerbations
    • Peak flow meter; : easier to obtain in emergency situations; only measures PEFR
  • Supportive findings
  • Special consideration: may not be feasible in life-threatening asthma and in young children

Do not delay treatment to complete assessment of lung function.

Arterial blood gas [1]

Patients with acute asthma exacerbations initially have hypocapnia (PaCO2) and respiratory alkalosis (↑ pH) due to tachypnea. Rising PaCO2 and normalizing pH in a patient with respiratory muscle fatigue are signs of impending respiratory failure!

Chest x-ray [1]

Not routinely required

Additional diagnostic studies [4]

In patients with acute asthma, consider the possibility of complicating concomitant factors such as pneumonia, atelectasis, or pneumothorax.

The following conditions manifest as sudden dyspnea with/without altered breath sounds. [8]

The differential diagnoses listed here are not exhaustive.

Treatment goals

Overview of initial treatment of acute asthma

Follow a stepwise approach to initial pharmacotherapy and adjust treatment according to clinical response with serial evaluations and monitoring. See relevant sections above for details on drugs and dosages. [1][4]

Short-acting beta-2 agonist (SABA) [1][4]

  • Indication: recommended for all patients with asthma exacerbations
  • Administration
    • Nebulizer
      • Preferred in severe crisis and in patients who are unable or refuse to use an inhaler [4]
      • There is no evidence to favor continuous over intermittent nebulization. [1]
    • Pressurized metered-dose inhaler plus spacer (valved holding chamber)
      • Preferred in mild/moderate crisis
      • No aerosol dissemination [1]
      • Effective delivery system (reaches doses equivalent to nebulizer) [4]
  • Agents: Selective SABAs are preferred, e.g., albuterol. [1][4]
  • Response
    • Onset of action: < 5 minutes
    • Significant clinical improvement: typically expected after 3 initial doses (i.e., in 1 hour).
    • No improvement : Escalate treatment.

Frequent administration of an inhaled SABA is the treatment of choice to reverse airway obstruction caused by bronchospasm.

Systemic corticosteroids [1][4]

  • Indication [1]
    • All asthma exacerbations in patients > 6 years of age (with the possible exception of very mild episodes).
    • Recommended within the first hour of presentation
  • Agents and administration
  • Response: effects expected in ∼ 4 hours

Short-acting muscarinic antagonists (SAMA) [4]

  • Indications
    • Emergency management of severe exacerbations
    • Consider for emergency management in moderate exacerbations.
  • Administration
  • Agent: Ipratropium bromide

IV magnesium sulfate [1]

  • Indication: life-threatening/severe exacerbations with no improvement after 1 hour of adequate treatment
  • Cautions: Monitor for signs of hypermagnesemia.

ASTHMA: Albuterol, STeroids, Humidified O2, Magnesium (severe exacerbations), and Anticholinergics (ipratropium bromide) are the meds for asthma exacerbations.

Additional pharmacotherapy [1][4]

The following therapies should be avoided, as their benefits do not justify the harm and unnecessary stress they can cause: theophylline, aminophylline, mucolytics, anxiolytics, and chest physiotherapy. [4]

Reduction of relapse risk [1]

  • Inhalers
  • Systemic corticosteroids
    • Indicated if systemic corticosteroids were administered for acute management
    • Continue regimen initiated in the emergency room.
    • Recommended duration: 3–10 days [4]
  • Patient education
    • Review and/or teach inhaler technique; emphasize the importance of spacers with MDIs.
    • Identify and avoid asthma triggers, if possible.
    • Review symptom recognition and reasons to seek care (e.g., increased need for rescue therapy).
    • Teach the use of a peak flow meter and the recording and interpretation of PEFRs.
    • Provide an individualized written action plan for patients and/or caregivers.
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  13. Niimi A. Cough and asthma. Curr Respir Med Rev. 2011; 7 (1): p.47-54. doi: 10.2174/157339811794109327 . | Open in Read by QxMD
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