Clinical Context

Asthma prevalence has generally increased in most countries; however, long-term asthma exacerbation (LTAE) incidence has decreased because of improved management strategies, treatments, and healthcare access.

Management of life-threatening asthma exacerbations requiring hospitalization involves assessing airway function and response to therapy. Treatment strategies include bronchodilation with inhaled beta 2 agonists, muscarinic antagonists, and magnesium sulphate as well as reduction of inflammation with systemic corticosteroids. Non-invasive mechanical ventilation may also be needed to correct hypoxemia and hypercapnia.

Study Synopsis and Perspective

In assessing and managing patients presenting with acute, life-threatening asthma, if the exacerbation does not resolve relatively quickly, clinicians need to start looking for other causes of the patient's respiratory distress, a review of the literature suggests.

"I think one of the most important points of this review is that asthma is a self-limiting disease, and it's important to understand that with appropriate treatment and immediate response to it, exacerbations will get better with time," Orlando Garner, MD, Baylor College of Medicine, Houston, Texas, told Medscape Medical News.

"So I think one of the key points is, if these exacerbations do not resolve within 24 to 48 hours, clinicians need to start thinking, 'This could be something else,' and not get stuck in the diagnosis that this is an asthmatic patient who is having an exacerbation. If the distress doesn't resolve within 48 hours, it's time to look for other clues," he stressed.

The study was published online February 23 in Chest.

Appropriate triage is key in the management of acute asthma, Garner and colleagues pointed out. A simplified severity score for the evaluation of asthma in the emergency department (ED) can help in this regard. Depending on the presence or absence of a number of key signs and symptoms, patients can be readily categorized as having mild, moderate, or severe asthma.

"Static assessments and dynamic assessments of acute asthma exacerbation in the ED can also help triage patients," the authors added.

Static assessment involves evaluating the severity at presentation, which, in turn, determines the aggressiveness of initial treatment. Objective static assessments include the measurement of peak expiratory flow (PEF) or forced expiratory volume in the first second (FEV1). A severe exacerbation is usually defined as a PEF or an FEV1 of less than 50% to 60% of predicted normal values, the authors noted.

Dynamic assessment is more helpful than static assessment because it gauges response to treatment.

"A lack of improvement in expiratory flow rates after initial bronchodilator therapy with continuous or worsening symptoms suggests need for hospitalization," Garner and colleagues observed.

The main treatment goals for patients with acute asthma are reversal of bronchospasm and correction of hypoxemia.

These are achieved at least initially with conventional agents, such as repeated doses of inhaled short-acting β agonists (SABAs), inhaled short-acting anticholinergics, systemic corticosteroids, and occasionally intravenous (IV) magnesium sulfate (MgSO4). If there is concomitant hypoxemia, oxygen therapy should be initiated as well. Patients who have evidence of hypercapnic respiratory failure or diaphragmatic fatigue need to be admitted to the intensive care unit (ICU), the authors indicated.

For these patients, clinicians need to remember that there are therapies other than inhalers, such as epinephrine and systemic terbutaline. During a life-threatening asthma episode, airflow in the medium and small airways often becomes turbulent, increasing the work of breathing, the researchers pointed out.

Heliox, a combination of helium and oxygen, reduces turbulent flow, they noted, although FiO2 requirements need to be less than 30% for it to work.

"Heliox can be used in patients with severe bronchospasm who do not respond to the conventional therapies," the authors noted, "[but] therapy should be abandoned if there is no clinical improvement after 15 minutes of use."

Although none of the biologics have yet been approved for the treatment of acute exacerbations, Garner predicts they will become the "future of medicine" for patients with severe asthma as well.

Rapid sequence intubation is generally recommended for patients who require mechanical ventilation, but as an alternative, "we are advocating a slower approach, where we get patients to slow down their breathing and relax them with something like ketamine infusions and wait before we given them a paralytic to see if the work of breathing improves," Garner said.

Bag-mask ventilation should be avoided because it can worsen dynamic hyperinflation or cause barotrauma, the authors also stressed.

Salvage therapies such as the use of bronchoscopy with N-acetylcysteine instilled directly into the airway is another option in cases in which mucus plugging is considered to be the main driver of airflow limitation.

Asked to comment on the review, Brit Long, MD, an emergency medicine physician at the Brooke Army Medical Center in San Antonio, Texas, felt the review was extremely useful and well done.

"We see these patients very frequently, and being able to assess them right away and get an accurate picture of what's going on is very important," he told Medscape Medical News.

The one thing that is often more difficult, at least in the ED, is obtaining a PEF or the FEV1-- "both very helpful if the patient can do them," Long noted, "but if the patient is critically ill, it's more likely you will not be able to get those assessments, and if patients are speaking in one-word sentences and are working really hard to breathe, that's a severe exacerbation, and they need immediate intervention," he added.

Long also liked all the essential treatments the authors recommended that patients be given immediately, although he noted that heliox is not going to be available in most EDs.

On the other hand, he agreed with the authors' recommendation to take a slower approach to mechanical ventilation, if it is needed at all.

"I try my best to absolutely avoid intubating these patients -- you are not fixing the issue with mechanical ventilation, you are just creating further problems," Long stressed.

"And while I see the entire spectrum of asthma patients from very mild to severe patients, these authors did a good job in explaining what the goals of treatment are and what to do with the severe ones," he said.

Orlando and Long have disclosed no relevant financial relationships.

Chest. Published online February 23, 2022.^[1]

Clinical Implications

• Treatment strategies focus on effective bronchodilation, correction of hypoxemia, and inflammation reduction with systemic IV corticosteroids.
• If conservative therapies fail to achieve clinical improvement within 30 to 60 minutes, endotracheal intubation and mechanical ventilation should not be delayed.
• Implications for the Healthcare Team: Patients with progressive respiratory distress should be admitted to the ICU for close monitoring and NIV if tolerated.

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