Acute Severe Asthma (Status Asthmaticus)

Asthma is the most common condition requiring hospitalization in children, and it accounts for a large proportion of PICU admissions. Acute severe asthma (status asthmaticus) refers to patients who are unresponsive to traditional asthma therapies on presentation, including repeated doses of beta-agonists. This distinct patient population has severe asthma exacerbations and is at risk for acute respiratory failure from severe bronchospasm. Few studies exist to guide the evidence-based management of status asthmaticus in the pediatric population. Therefore, practice patterns vary based on local preference and experience. In this section, we review the management of acute severe asthma, including therapies for refractory bronchospasm.

Assessment

The assessment of the patient in status asthmaticus is directed at identifying signs and symptoms of imminent respiratory arrest. Attention must be paid to the patient’s work of breathing, lung exam, and hemodynamic parameters.

Signs of increased work of breathing include:

tachypnea
accessory muscle use
grunting
head bobbing in very young children

Classic findings of asthma on lung examination include:

wheezing
poor aeration
prolonged expiratory phase

However, severe bronchospasm often can present with a “quiet chest,” in which bronchoconstriction is so severe that wheezes are not heard. Attention to volume status is essential because many patients will be volume depleted due to insensible losses. Careful attention to fluid status is paramount to avoid complications of the vasodilatory effects of beta-adrenergic therapies while balancing the risk of pulmonary edema.

Several asthma-severity scores have been designed to guide the stepwise approach to the treatment of the patient with severe asthma and the weaning of medications. One example is the WARME Respiratory Score:

WARME Respiratory Score*

Variable	0 points	1 point	2 points
Wheeze	None	End expiratory	Entire expiratory/any inspiratory
Air exchange	Normal	One area decreased	More than one area decreased
Respiratory rate	Normal	Tachypneic for age	--
Muscle use	None	Subcostal/intercostal	Any neck or abdominal retractions
Expiration	Not long	Expiratory >3x inspiratory	--

Management

The goals of the ICU management of the patient in status asthmaticus are threefold:

to reverse airway obstruction quickly with the aggressive use of beta-agonists and corticosteroids
to correct or prevent hypoxemia with supplemental oxygen therapy
to avoid or treat complications of airway obstruction and respiratory support, including air leak syndromes and respiratory arrest

Pharmacotherapy

Bronchodilators: Beta-2-adrenergic agonists are the mainstay of alleviating life-threatening bronchoconstriction.

Inhaled albuterol is the most commonly used medication and can be delivered continuously through a variety of options, including high-flow nasal cannula systems or face mask. Maximum doses vary by institution but typically range from 5 mg/hour to ≥40 mg/hour.
Ipratropium bromide is an inhaled anticholinergic therapy that is frequently added to a patient’s medication regimen when requiring ICU admission. Studies have shown little-to-no benefit in hospitalized adult patients, and no studies have been conducted in PICU patients.
Magnesium sulfate is another potent bronchodilator if not administered before ICU admission. Evidence of benefit from repetitive dosing is lacking.

Glucocorticoids: Glucocorticoids are the medications of choice for treatment of acute severe asthma to decrease inflammation. They are typically administered intravenously due to an inability in infants and children with respiratory distress to tolerate oral intake. Methylprednisolone is usually given in doses up to 4 mg/kg/day (maximum dose, 60-125 mg/day based on age and weight).

Medications for Refractory Severe Acute Asthma: Patients who do not have a rapid response to the therapies described above are at risk for respiratory arrest and the need for invasive mechanical ventilation.

Treatment in such patients includes the addition of IV beta-agonists such as terbutaline, aminophylline or theophylline, and ketamine infusions.
Inhaled anesthetics have also been used in patients with super-refractory bronchoconstriction at institutions where they are available.

Ventilation Therapies: Patients who continue to worsen despite maximal medical management may benefit from the use of noninvasive positive-pressure ventilation (NPPV). NPPV may decrease the work of breathing created by airflow obstruction and air trapping.

If, despite maximal medical management, respiratory arrest is imminent, intubation and mechanical ventilation can be employed. Intubation is reserved for the most refractory patients given the risk of severe, life-threatening bronchospasm that can occur with direct laryngoscopy.
Mechanical ventilation in the asthmatic patient is quite challenging. Dynamic hyperinflation can occur with severe airflow obstruction, leading to initiation of the next ventilated breath prior to full exhalation and contributing to alveolar overdistention that can result in hypoxemia, hypotension, or alveolar rupture. Thus, experienced intensivists and respiratory therapists must be available to carefully minimize the risks of barotrauma and air leak syndromes.
Extracorporeal membrane oxygenation (ECMO) has also been used at some centers for extreme cases in which optimal ventilation cannot be achieved.

For more information on the diagnosis and treatment of chronic asthma, see Asthma in the Pediatric Pulmonology rotation guide.

For more information on the treatment of acute severe asthma in the emergency care setting, please see Asthma in the Pediatric Emergency Medicine rotation guide.

Research

Landmark clinical trials and other important studies

Research

Inhaled Anticholinergics and Short-Acting Beta(2)-Agonists Versus Short-Acting Beta(2)-Agonists Alone for Children with Acute Asthma in Hospital

Vezina K et al. Cochrane Database Syst Rev 2014.

This Cochrane Review of seven randomized trials found no evidence of benefit for length of hospital stay and other markers of response to therapy when nebulized anticholinergics were added to baseline therapy but noted no conclusions about critically ill children.

Corticosteroid Therapy in Critically Ill Pediatric Asthmatic Patients

Giuliano JS et al. Pediatr Crit Care Med 2013.

This cross-sectional survey found that many pediatric intensivists prescribe doses of intravenous methylprednisolone 2 to 4 times higher than that recommended by national guidelines.

Safety, Efficacy, and Tolerability of Early Initiation of Noninvasive Positive Pressure Ventilation in Pediatric Patients Admitted with Status Asthmaticus: A Pilot Study

Basnet S et al. Pediatr Crit Care Med 2012.

This small, prospective, randomized, controlled trial found that early initiation of NPPV was well tolerated and improved clinical asthma scores.

Theophylline Versus Terbutaline in Treating Critically Ill Children with Status Asthmaticus: A Prospective, Randomized, Controlled Trial

Wheeler DS et al. Pediatr Crit Care Med 2005.

This randomized, controlled trial found that the addition of theophylline to baseline asthma therapy was as effective as terbutaline and more cost-effective in the treatment of critically ill people with asthma.