Asthma is a chronic condition affecting roughly 300 million people around the world; however, the term “acute asthma attack” is no longer an accurate clinical description.1 Rather, “asthma exacerbation” is used to define a provoked imbalance in the asthmatic disorder, often due to an external agent or poor compliance with treatment.1

Severe asthma exacerbation results from particularly severe bronchospasm and may lead to severe obstructive syndrome, which could be life-threatening.1 Defining severe asthma exacerbation in accurate clinical terms is the first step in effectively guiding the emergency management of asthma.

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Recommendations for the areas of diagnosis, pharmacological treatment, and oxygen therapy and ventilation (including advances in noninvasive ventilation and high-flow oxygen therapy) were recently updated to improve care of adult and pediatric patients with severe asthma exacerbation.

In diagnosing patients with asthma exacerbation, clinicians should assess severity criteria in the patient’s medical history as well as in an initial physical examination. It is important for clinicians to identify factors predictive of severe exacerbation and criteria associated with increased risk for mortality or intensive care admission.


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In adults, a history of hospital admission for asthma or the need for mechanical ventilation are associated with increased risk for asthma-related death, especially in patients who report recent corticosteroid use or increased use of beta-2 adrenergic agonists.1 Lack of a controller therapy, advanced age >70 years, neurological disorders (difficulty speaking, altered consciousness, or shock), a respiratory rate >30 breaths per minute, or potential underlying pneumonia are also associated with a poor prognosis.1

In pediatric patients with asthma exacerbation, risk factors predictive of intensive care admission include a sensitization to multiple allergens (especially food allergens), insufficiently controlled asthma, a history of hospitalization for asthma, exposure to passive smoking, and hypoxemia at initial management.1

Chest radiography as a diagnostic method is only recommended in adults to make a differential diagnosis. Specifically, chest radiography should be performed in patients who present with wheezing/dyspnea and have suspected pneumonitis, are in an immunosuppressed state, or have a history of chronic obstructive pulmonary disease, heart disease, or thoracic surgery.1

Blood gas measurements — used to predict respiratory failure — are considered clinically unnecessary in the initial assessment of asthma exacerbation and should only be recommended in adult patients who have failed to respond to first-line oxygen therapy or whose oxygenation is not restored to >90%.1

In patients who are either adults or pediatrics with severe asthma exacerbation, intravenous beta-2 adrenergic agonists are not recommended as first-line treatment, even in patients receiving mechanical ventilation. Rather, beta-2 adrenergic agonists should be administered by continuous nebulization during the first hour. Continuous vs intermittent administration of inhaled beta-2 adrenergic agonists (independent of dose) is associated with a significant decrease in hospitalizations and improvements in ventilatory parameters, and was well tolerated with no increase in side effects.1

Anticholinergic drugs may be combined with inhaled beta-2 adrenergic agonists in both adult and pediatric patients, in which experts propose a dosage of 0.5 mg of ipratropium bromide administered every 8 hours in adults and children aged over 6 years, and a 0.25 mg dose every 8 hours in children aged under 6 years.1 Compared with administration of beta-2 adrenergic agonists alone, combination therapy resulted in a significant decrease in hospitalizations (about 30%) with the greatest effect on patients with nonsevere asthma exacerbation.1

Corticosteroids should be administered early during the first hour of management of patients with severe asthma exacerbation, in which systemic corticosteroid therapy using an intravenous or oral route was more effective than inhalation.1 Among adult patients, a dosage of 1 mg/kg of methylprednisolone equivalent is suggested and should not exceed 80 mg per day.1 Among pediatric patients, a dosage of 2 mg/kg of methylprednisolone equivalent is suggested and should not exceed 80 mg per day.1

Intravenous magnesium sulfate is indicated for routine administration in pediatric patients with severe asthma exacerbation but has not shown to be clinically efficacious for adult patients.1 In pediatric studies, magnesium sulfate (dose ≥20 mg/kg) has shown to improve respiratory parameters, limit the use of mechanical ventilation, and reduce hospitalizations by 68% in children with moderate to severe asthma exacerbation.1,2

Antibiotic therapy should be reserved for cases of suspected bacterial infection, which are often the underlying cause of asthma exacerbation, and should be prescribed based on the usual clinical, radiological, and laboratory signs.1 However, there is limited or no evidence that the routine administration of antibiotics offers any additional benefit to patients with severe asthma exacerbation.1

Fixed-flow oxygen therapy using a titrated oxygen regime is recommended as a treatment strategy for both adult and pediatric patients with severe asthma exacerbation, in which oxygen therapy is titrated to a pulse oxygen saturation of 94% to 98%.1

Currently, there is little evidence on the effect of noninvasive ventilation on outcomes of mortality, intubation, hospitalization, and improvement of ventilation parameters.1 Although this method is not recommended in adults with severe asthma exacerbation and hypoxemia, the use of noninvasive ventilation in pediatric patients may be indicated when conventional oxygen treatments fail.1

High-flow nasal oxygen therapy is typically used in an intensive care or emergency setting to treat high-risk patients with respiratory failure due to infection or post extubation.3 However, this modality has not been shown to benefit length of hospitalization or reduce the need for invasive ventilation in patients — especially children — with severe asthma exacerbation.1

Intubation of adults or pediatric patients with severe asthma exacerbation is required in just 2% of hospitalizations and is only indicated if well-conducted medical treatment fails or if the initial presentation of asthma exacerbation is severe (altered consciousness or bradypnea).1 Intubations should be performed by an experienced physician, in which experts recommend the orotracheal route and use of ketamine as the first-line hypnotic agent during rapid sequence induction.1

Moreover, to prevent lung overdistension in mechanically ventilated patients and maintain plateau pressure <30 cmH20, experts recommend reducing tidal volume to 6 to 8 mL/kg and positive end-expiratory pressure to ≤5 cmH20, while increasing inspiratory flow to 60 to 80 L/min in mechanically ventilated patients.1

During the initial phase of invasive mechanical ventilation, experts recommend deep sedation (Richmond Agitation-Sedation Scale of -4 to -5) along with continuous or transient neuromuscular block in the most severely ill patients.1 Continuous administration of ketamine or halogenated gas — which both have marked bronchodilator properties — in addition to sedation has not been shown to benefit either adult or pediatric patients with severe asthma exacerbation.1

The use of nebulizers in the administration of therapeutic agents is generally preferred in the treatment of spontaneously breathing patients, in which aerosols of salbutamol are often indicated.1 So far, no particular aerosol generator for patients receiving mechanical ventilation has been recommended. Although helium used as a carrier gas can optimize the deposition of bronchodilators, a standard air-oxygen mixture is recommended over a helium-oxygen mixture in nebulizing adult and pediatric patients.1

In spontaneously breathing children with severe asthma exacerbation, a sufficient flow of air or oxygen should be provided to ensure the nebulization of inhaled treatments. In children who are mechanically ventilated, continuous nebulization is recommended.1

The use of extracorporeal life support — venovenous extracorporeal membrane oxygenation or extra corporeal CO2 removal — should be discussed with the appropriate experts as the criteria for use of life support in managing severe asthma exacerbation has not been described in current literature.1 In the setting of asthma exacerbation, candidates may include patients reporting respiratory acidosis or severe hypoxemia despite receiving optimal treatment and well-conducted mechanical ventilation.1

References

1. Le Conte P, Terzi N, Mortamet G, et al. Management of severe asthma exacerbation: guidelines from the Société Française de Médecine d’Urgence, the Société de Réanimation de Langue Française and the French Group for Pediatric Intensive Care and Emergencies [published online October 10, 2019]. Ann Intensive Care. doi: 10.1186/s13613-019-0584-x

2. Stojak BJ, Halajian E, Guthmann RA, Nashelsky J. Intravenous magnesium sulfate for acute asthma exacerbations. Am Fam Physician. 2019;99(2):127-128.

3. Lodeserto FJ, Lettich TM, Rezaie SR. High-flow nasal cannula: mechanisms of action and adult and pediatric indications. Cureus. 208:10(11):e3639.