INTRODUCTION — Asthma is the most frequent cause of hospitalization among children in the United States and is the source of nearly 500,000 admissions to pediatric intensive care units (PICUs) [1]. Admission to intensive care has increased in proportion to general hospital admission for asthma [2]. Mortality rates in children are lower than adults, but males and African Americans have a higher risk for death compared with girls and white Americans.
Intensive care unit (ICU) management of children with acute severe asthma exacerbation (ie, status asthmaticus) is discussed here, with the exception that endotracheal intubation and mechanical ventilation are discussed separately. Non-ICU inpatient management is also discussed in detail separately. Mechanical ventilation for adults with severe asthma is also reviewed separately. (See "Acute severe asthma exacerbations in children younger than 12 years: Endotracheal intubation and mechanical ventilation" and "Acute asthma exacerbations in children younger than 12 years: Inpatient management" and "Invasive mechanical ventilation in adults with acute exacerbations of asthma".)
Pharmacologic management of acute asthma exacerbations and management of chronic childhood asthma also are discussed separately. (See "Acute asthma exacerbations in children younger than 12 years: Emergency department management" and "Asthma in children younger than 12 years: Initial evaluation and diagnosis" and "Asthma in children younger than 12 years: Management of persistent asthma with controller therapies" and "Asthma in children younger than 12 years: Quick-relief (rescue) treatment for acute symptoms".)
OVERVIEW — The pathologic hallmarks of asthma are airway inflammation, excessive mucus production, mucus plugging, and airway bronchospasm, all of which may lead to severe airflow obstruction. Airflow obstruction produces varying degrees of respiratory insufficiency and can progress to respiratory failure. Both the severity of the exacerbation and presence of risk factors associated with the need for ICU management are taken into account when admitting a child with an acute asthma exacerbation.
Severity assessment — Severe acute asthma is somewhat loosely defined based upon presenting signs and symptoms and response to therapy (table 1). There are several scoring systems to help assess asthma severity in children. Examples include the Pulmonary Index Score (table 2) [3] and the Pulmonary Score, which is similar to the Pulmonary Index Score except that it scores only respiratory rate, wheezing, and accessory muscle use [4]. Another is the Pediatric Intensive Care Unit Pediatric Asthma Score, which factors in respiratory rate relative to age, oxygen requirement, presence of retractions, breathlessness during speech, and presence of wheezing [5]. The assessment of severity of acute asthma exacerbations is discussed in detail separately. (See "Acute asthma exacerbations in children younger than 12 years: Overview of home/office management and severity assessment", section on 'Assessment of exacerbation severity'.)
Risk factors — Boys, children living in poverty, African Americans, and some Hispanics (especially Puerto Ricans) have high rates of asthma and severe asthma. Patients who are at risk for requiring ICU management for asthma include those who have a history of [6-13]:
●ICU admissions, mechanical ventilation, or rapidly progressive and sudden respiratory deterioration
●Seizures or syncope during an asthma exacerbation
●Exacerbations precipitated by food
●Use of more than two beta-agonist metered-dose inhaler (MDI) canisters per month
●Insufficient controller therapy or poor adherence to controller therapy
●Denial of or failure to appreciate the severity of illness
●Associated depression or other psychiatric disorder
Although these factors are frequently present in patients who require ICU management, they fail to prospectively identify a significant number of cases [6] and should not be interpreted as absolute indications for admission to an ICU. As many as one-third of children who die from asthma would not have been classified as at risk for fatal asthma based upon these risk factors. Risk factors for fatal asthma are discussed in greater detail separately. (See "Identifying patients at risk for fatal asthma", section on 'Identifying high-risk patients'.)
General principles — Children with acute severe asthma who fail to improve with initial treatment in the emergency department should be admitted to the pediatric ICU (PICU). ICU level management of these children entails the administration of glucocorticoids, aggressive bronchodilator therapy, and close monitoring [5]. Mechanical ventilation is reserved for patients with continued progression toward respiratory failure despite maximal medical therapy. (See 'Pharmacotherapy' below and "Acute severe asthma exacerbations in children younger than 12 years: Endotracheal intubation and mechanical ventilation".)
The need for mechanical ventilation should be considered early in the course of illness. Mechanical ventilation in a child with an asthma exacerbation is always challenging, usually due to airway obstruction and difficulty with exhalation. The best way to avoid intubation is to rapidly escalate the preintubation therapies discussed below in patients with a worsening trajectory indicated by increased work of breathing or carbon dioxide (CO2) retention. The decision to intubate a patient should be made with great care since tracheal stimulation often worsens the asthma exacerbation and, in some cases, makes the situation worse.
In many patients who are progressing toward respiratory muscle fatigue, noninvasive positive pressure ventilation (NPPV) can avoid the need for intubation by easing the work of breathing while awaiting the maximal therapeutic effects of pharmacotherapy. NPPV in conjunction with pharmacologic therapy is effective in improving gas exchange in children and adults with asthma. NPPV can be used in school-aged children with relative ease, but light sedation may be required to facilitate tolerance in younger children [5]. (See 'Noninvasive positive pressure ventilation' below.)
Adjunctive therapies may be necessary for children who do not improve despite aggressive pharmacologic therapy and mechanical ventilation. (See 'Adjunctive therapies' below and "Acute severe asthma exacerbations in children younger than 12 years: Endotracheal intubation and mechanical ventilation", section on 'Adjunctive therapies'.)
There are no widely used, evidence-based treatment algorithms or pathways for the management of acute severe asthma in children, and there is considerable variability in care. The use of an algorithm for escalation and weaning of therapy was applied to 385 children older than two years of age with status asthmaticus admitted on continuous albuterol to the medical ICU of one center [14]. The use of this protocol was associated with a decrease in the duration of continuous albuterol therapy and reduced length of hospital stay. Although the findings require replication in other centers, standardized-care protocols could improve outcomes in the future.
PREINTUBATION THERAPIES — The primary preintubation therapies are supplemental oxygen, glucocorticoids, bronchodilators, inhaled anticholinergics, and systemic magnesium sulfate [15]. Noninvasive positive pressure ventilation (NPPV) may help to avoid endotracheal intubation in select patients who continue to have severe or unabated increased work of breathing while awaiting the maximum therapeutic benefit of pharmacotherapy. It is important to determine whether the inhaled bronchodilators can be delivered via the noninvasive ventilation device since this is often not the case and intravenous bronchodilators can be started.
Pharmacotherapy — The goal of pharmacologic therapy for acute severe asthma exacerbations is to ensure adequate oxygenation and ventilation and ease the work of breathing. Pharmacologic therapy of children who are admitted to the ICU with acute severe asthma exacerbation entails the administration of glucocorticoids and aggressive bronchodilator therapy (algorithm 1). We recommend the administration of intravenous glucocorticoids and inhaled albuterol. We also suggest inhaled ipratropium and intravenous magnesium sulfate if the patient was not already treated with these medications.
For those who fail to respond to these interventions, we suggest the administration of parenteral beta2-agonists. The efficacy of these interventions has been documented in meta-analyses and/or randomized, controlled trials, which are described separately. (See "Acute asthma exacerbations in children younger than 12 years: Emergency department management", section on 'Severe exacerbation' and "Acute asthma exacerbations in children younger than 12 years: Emergency department management", section on 'Elements of treatment'.)
Glucocorticoids — Glucocorticoids are usually administered intravenously in children who are admitted to the ICU with acute asthma exacerbation.
●Methylprednisolone (loading dose 2 mg/kg, then 0.5 to 1 mg/kg/dose every six hours, with a maximum dose of 60 mg/day) [16]. (See "Acute asthma exacerbations in children younger than 12 years: Emergency department management", section on 'Management of inflammation'.)
Bronchodilators — The primary bronchodilator therapy is inhaled albuterol. Inhaled ipratropium bromide and intravenous magnesium sulfate are adjunctive therapies that are often also used because they have been shown to decrease the risk of hospitalization for children treated in the emergency department. They have not been shown to offer further benefit in hospitalized patients, but they have not been studied in the pediatric ICU (PICU) population [5]. Additional intravenous bronchodilators may be used in patients who do not respond to initial bronchodilatory therapy.
●Hourly or continuously delivered albuterol via nebulizer (see "Acute asthma exacerbations in children younger than 12 years: Emergency department management", section on 'Inhaled short-acting beta-2 agonists'):
•For hourly administration, albuterol (0.15 mg/kg every hour, minimum 2.5 mg; maximum 5 mg), or
•For continuous administration, albuterol (10 mg/hour for children who weigh 5 to 10 kg, 15 mg/hour for children who weigh 10 to 20 kg, and 20 mg/hour for children who weigh >20 kg). Alternatively, continuous albuterol can be dosed 0.15 to 0.5 mg/kg/hour, up to a maximum dose of 30 mg/hour [5].
●Magnesium sulfate (25 to 75 mg/kg intravenously; maximum 2 grams) is administered over 20 to 30 minutes upon arrival to the ICU if it has not been administered earlier. Patients should be monitored for hypotension, especially if they have received terbutaline and are vasodilated, although this complication is rare [17]. If hypotension does occur, the magnesium sulfate infusion should be paused, a fluid bolus administered, and then the infusion resumed at a lower rate [18]. (See "Acute asthma exacerbations in children younger than 12 years: Emergency department management", section on 'Magnesium sulfate'.)
●Evidence of benefit for ipratropium bromide has not been demonstrated in hospitalized patients, and, therefore, it is not recommended for hospitalized patients by the National Heart Lung and Blood Institute (NHLBI) asthma guidelines [19]. However, it has not yet been specifically studied in the PICU population, and one review found no trials reporting any serious adverse events associated with its use [20]. Thus, some experts will use ipratropium bromide as an adjunctive therapy in hospitalized children with impending respiratory failure due to asthma who fail to respond to the usual therapies. A dosing regimen extrapolated from management of children with chronic lung disease can be used in a child with severe status asthmaticus and impending respiratory failure (250 microgram per dose every 6 hours for 24 hours for children who weigh <20 kg or ≤6 years of age; 500 microgram per dose every 6 hours for 24 hours for children who weigh >20 kg or ≥6 years of age) [5,21]. (See "Acute asthma exacerbations in children younger than 12 years: Emergency department management", section on 'Ipratropium bromide'.)
For patients who fail to respond to the bronchodilator therapy reviewed above, we suggest the transition to intravenous bronchodilators [22,23]. Terbutaline is most commonly used. Theophylline and aminophylline (the water-soluble, ethylenediamine salt of theophylline), methylxanthines with phosphodiesterase inhibitor activity, were historically a standard component of acute asthma management but over the past 30 years have essentially been eliminated from standard treatment algorithms for acute asthma. Evidence in support of their use in the inpatient population is limited at best. Thus, these agents are infrequently used in PICUs for status asthmaticus. However, we reserve aminophylline as an option for the child with severe status asthmaticus and impending respiratory failure who has not responded to terbutaline. Extreme caution should be employed in the patient with risk factors for myocardial ischemia since tachycardia increases myocardial oxygen demand. In addition, children who present with status asthmaticus are predisposed to dehydration/intravascular depletion. Thus, fluid loading may be necessary to blunt some of the tachycardia associated with use of intravenous bronchodilators. (See 'Fluid support' below and "Acute asthma exacerbations in children younger than 12 years: Emergency department management", section on 'Parenteral beta-agonists'.)
●Terbutaline (10 microgram/kg intravenous loading dose administered over 10 minutes, followed by an infusion of 0.1 to 10 microgram/kg/minute). The dosing range found in most references for intravenous terbutaline is remarkably wide. Although dosing as low as 0.1 microgram/kg/minute are suggested, experienced intensivists usually begin with a dose of 0.5 micrograms/kg/minute. The infusion can be increased in 0.1 to 1 microgram/kg/minute increments every 30 minutes, depending upon the patient's degree of respiratory distress, heart rate, perfusion, and quality of aeration, to a maximum dose of 5 to 10 micrograms/kg/minute (the author rarely exceeds a dose of 3 to 5 micrograms/kg/minute) until aeration and work of breathing improve. Continuous albuterol should be discontinued once terbutaline is initiated.
Terbutaline causes tachycardia and, in turn, increases myocardial oxygen consumption. In general, the younger the age, the better tachycardia is tolerated. At the author's center, patients with severe status asthmaticus requiring terbutaline infusion receive fluid boluses in an effort to blunt some of the tachycardia. Serial troponin levels and electrocardiograms are sometimes obtained, particularly in adolescent and preadolescent patients on both terbutaline and aminophylline infusions, to monitor for evidence of myocardial ischemia. Terbutaline infusions may be associated with hypotension, hyperglycemia, hypokalemia, and arrhythmias [23].
●Aminophylline (6 mg/kg intravenous loading dose, followed by infusion of 0.5 to 1 mg/kg/hour that is titrated based upon levels). The recommended starting dose of the infusion (after the loading dose) varies by age for patients:
•6 weeks to 6 months – 0.5 mg/kg/hour
•6 to 12 months – 0.6 to 0.7 mg/kg/hour
•1 to 9 years – 1 mg/kg/hour
•9 to 16 years – 0.8 mg/kg/hour
Aminophylline has a mean volume of distribution of 0.5 L/kg. Thus, a loading dose of 6 mg/kg should generate a serum level of approximately 12 microgram/mL. Therapeutic levels range between 10 and 20 microgram/mL. We suggest target levels of 12 to 15 microgram/mL, particularly upon initiation of therapy. Steady-state levels are checked 6 to 12 hours following the bolus/initiation of the infusion. If the patient's respiratory status does not improve and the six-hour theophylline level is below 15 microgram/mL, then the infusion is increased proportionately to a target level of 15 microgram/mL. Serum levels of aminophylline should be measured once daily (after desired level or response to therapy achieved) and as needed when toxicity is suspected (severe tachycardia, anxiety, persistent emesis, dysrhythmias, and seizures).
A review published in 2005 explored the efficacy of aminophylline in children with acute severe asthma [24]. Improvement in lung function within six hours was demonstrated, but there was no apparent reduction in the number of nebulized treatments given or length of hospital stay. There was insufficient evidence to assess its impact on oxygenation, PICU admissions, and mechanical ventilation. One randomized trial compared terbutaline, theophylline, and combination therapy with both drugs in a cohort of PICU patients [23]. Theophylline was as effective as terbutaline in treating critically ill children with asthma and was more cost effective. Despite the lack of consistent evidence of benefit and the fact that aminophylline is not recommended by National Asthma Education and Prevention Program (NAEPP) guidelines, 59 percent of respondents to a survey administered to pediatric critical care medicine fellowship program directors (academic intensivists), reported using aminophylline for children with severe status asthmaticus refractory to other therapies [25]. (See "Theophylline use in asthma".)
●Intravenous albuterol is not available in the United States. However, in countries where it is available, efficacy in patients with acute severe asthma has been demonstrated in randomized and observational studies [26,27]. The dose is 0.5 to 5 microgram/kg/minute [27]. Subcutaneous or intramuscular epinephrine or terbutaline are additional options if intravenous terbutaline is not available [19]. Dosing for subcutaneous or intramuscular epinephrine is 0.01 mg/kg (0.01 mL/kg of 1:1000 solution [1 mg/mL]) every 20 minutes for up to three doses, maximum dose 0.5 mg. Dosing of subcutaneous or intramuscular terbutaline is 0.01 mg/kg (0.01 mL/kg of a 1 mg/mL solution) every 20 minutes for up to three doses and then every two to six hours as needed, maximum dose 0.25 mg.
Noninvasive positive pressure ventilation — NPPV eases the work of breathing in patients who are progressing toward respiratory muscle fatigue. Thus, NPPV may help to avoid endotracheal intubation in select patients who continue to have severe or unabated symptoms after intravenous bronchodilators or while awaiting the maximum therapeutic benefit of pharmacotherapy. NPPV has been used to treat children with respiratory failure from a number of causes, including neuromuscular disorders, cystic fibrosis, bronchiolitis, and status asthmaticus [28-40]. The benefits for children with status asthmaticus are thus far favorable, with retrospective and prospective studies documenting clinical improvement in the pediatric emergency department and ICU settings [5]. (See "Noninvasive ventilation for acute and impending respiratory failure in children".)
NPPV involves the delivery of positive airway pressure, either as continuous pressure (continuous positive airway pressure [CPAP]) or as mechanically assisted breaths (bilevel positive airway pressure [BiPAP]), without placement of an artificial airway. In most cases, ventilation is delivered via full facial mask. Patients who receive NPPV must be awake and cooperative, have a patent airway, and have spontaneous respirations. Toddlers and small children may require mild sedation to tolerate the mask. (See "Noninvasive ventilation for acute and impending respiratory failure in children".)
Mechanisms of action of NPPV — NPPV may be useful as a temporizing measure while awaiting the maximal therapeutic benefit of pharmacotherapy and may help patents avoid the need for intubation. During an asthma attack, bronchospasm and increased mucus production result in airflow obstruction in the distal airways that cause increased airway resistance and development of long expiratory time constants in lung units. This leads to the development of air trapping and dynamic hyperinflation, also known as auto-PEEP. The development of auto-PEEP necessitates an increase in the work of breathing since a greater negative force must be generated for inspiration to begin in the context of air trapping. NPPV may improve this phenomenon by stenting open collapsing or narrowed airways, thereby allowing for more complete exhalation. This in turn reduces the inspiratory work of breathing. Additionally, the application of inspiratory positive airway pressure (IPAP) further unloads the muscles of respiration [41]. (See "Noninvasive ventilation for acute and impending respiratory failure in children", section on 'Physiology'.)
Efficacy of NPPV — Evidence supporting the benefit of NPPV in children with acute severe asthma is accruing, although further trials are still needed [42].
The safety, efficacy, and tolerability of BiPAP in children admitted to the PICU with status asthmaticus was evaluated in a randomized trial of standard therapy versus standard therapy plus NPPV for 24 hours [43]. The outcome measures included change in clinical asthma score, respiratory rate, oxygen saturation, and oxygen requirement. Adjunctive therapies could be employed, at the discretion of the attending clinician, only if patients experienced an increase in their clinical asthma score beyond two hours after enrollment. Rapid and significant improvements in clinical asthma score were reported at each time point studied, although no significant differences between the two groups were seen for the other outcome measures. NPPV was well tolerated, and no major complications were reported.
In a prospective study, 20 children (median age 4.8 years) admitted to the PICU with acute lower airway obstruction were randomly assigned to two hours of NPPV followed by two hours of standard therapy or to two hours of standard therapy followed by two hours of NPPV [36]. Compared with standard therapy, NPPV decreased respiratory rate, accessory muscle use, and dyspnea. No serious morbidity was noted, but five patients were unable to tolerate NPPV for the duration of the study.
In several observational studies and case series, treatment with NPPV was associated with improved clinical and ventilatory parameters in children with asthma [34,35,37,40,44,45]. A reduction in PICU admissions was reported when BiPAP was used in the pediatric emergency department setting [37]. However, four of five patients in one of the smallest case series were morbidly obese (body mass index ≥30). Thus, the improvement in their respiratory status with NPPV may have been related to underlying obesity hypoventilation syndrome, although none of them reported a previous history [34]. (See "Noninvasive positive airway pressure therapy for the obesity hypoventilation syndrome".)
Possible indications for NPPV — The use of NPPV in children with status asthmaticus varies from center to center. We suggest a trial of NPPV in the following situations, provided that the child is alert, cooperative, and without increased airway secretions:
●The child remains hypoxemic despite high flow oxygen and/or has documented hypercarbia.
●The child is progressing toward respiratory muscle fatigue, but the maximum therapeutic effects of glucocorticoids and bronchodilators have not been reached.
Limitations of NPPV — The use of NPPV is limited because it:
●Requires patient cooperation
●Impairs ability to clear secretions from the respiratory tract
●Does not provide definitive control of the airway
●May cause gastric distension with increased risk of aspiration
●May cause heightened sense of air hunger upon initiation
●Patients may feel claustrophobic
An experienced nurse or respiratory therapist who can coach the patient through the initiation of NPPV is invaluable. Mild sedatives are sometimes used to facilitate the patient's tolerance of NPPV [35], but great care must be taken to avoid diminishing airway protective reflexes and respiratory drive.
NPPV settings — NPPV can begin as CPAP with a pressure of 5 cm H2O in patients with moderately increased work of breathing (table 1) or relatively mild-moderate degrees of hypoxemia (those who can maintain oxygen saturation greater than 92 percent with the provision of simple face mask oxygen at fraction of inspired oxygen [FiO2] of 0.25 to 0.7) or hypercarbia (partial pressure of carbon dioxide in arterial blood [PaCO2] of 45 to 50 mmHg).
BiPAP provides a greater level of support and decreases the work of breathing more efficiently in patients with significantly increased work of breathing and moderate or severe hypoxemia (patients requiring FiO2 >70 percent by simple face mask or nonrebreather mask) and/or hypercarbia (PaCO2 >50 mmHg). The initial BiPAP settings should be relatively low and should be titrated to patient comfort, oxygenation, and ventilation. The inspiratory pressure may start at 8 to 10 cm H2O and the expiratory pressure at 5 cm H2O. These settings may be titrated up to an inspiratory pressure of 10 to 12 cm H2O, and the expiratory pressure may be carefully titrated up to 7 to 8 cm H2O.
High-flow nasal cannula — High-flow nasal cannula (HFNC) is becoming widely available in patients with respiratory embarrassment from a variety of sources including status asthmaticus. There is sparse literature evaluating the use of HFNC specifically in children with status asthmaticus. In a single-center retrospective study evaluating the use of HFNC in children with status asthmaticus, investigators demonstrated the safety and feasibility of HFNC in this setting, with rare instances of treatment failure (progression to NPPV or intubation) and pneumothorax [46,47].
Heliox — Heliox is supplied in fixed gas mixtures 20 percent oxygen and 80 percent helium so that hypoxic gas mixtures are not inadvertently administered to patients. Additional oxygen can be blended and the oxygen concentration measured proximal to the patient. The physiochemical principles of heliox increase laminar flow, as well as lower viscosity, compared with nitrogen and oxygen. However, concentrations of oxygen >40 percent limit the beneficial effects of helium.
There are limited and conflicting data regarding the efficacy of heliox in the treatment of children with acute severe asthma [48]. Clinical improvement based upon a pulmonary index score was reported in a small, prospective study of heliox-driven nebulizer treatments [49]. A subsequent review concluded that heliox may have a role in the initial management of asthma in patients with more severe obstruction based upon available data from a series of small studies [50]. Use of heliox is reviewed in greater detail separately. (See "Physiology and clinical use of heliox", section on 'Use in children'.)
INTUBATION AND MECHANICAL VENTILATION — Mechanical ventilation is reserved for patients with continued progression toward respiratory failure despite maximal medical therapy. Endotracheal intubation should be approached cautiously in patients with status asthmaticus because manipulation of the airway can cause increased airflow obstruction due to exaggerated bronchial responsiveness. Intubation and mechanical ventilation are discussed in detail separately. (See "Acute severe asthma exacerbations in children younger than 12 years: Endotracheal intubation and mechanical ventilation".)
Indications for endotracheal intubation and mechanical ventilation include (see "Acute severe asthma exacerbations in children younger than 12 years: Endotracheal intubation and mechanical ventilation", section on 'Indications'):
●Hypoxia
●Altered mental status, including agitation and obtundation
●Persistent, severe hypercarbia
SUPPORTIVE CARE — Children admitted to the ICU with severe asthma require close cardiopulmonary monitoring, particularly those on mechanical ventilation. Supportive measures for children with asthma who require mechanical ventilation include analgesia, sedation, and muscle relaxation [6]. These measures help to prevent tachypnea, breath stacking, and ventilator dyssynchrony, particularly in the setting of hypercapnia. Most patients are also given intravenous fluids to treat dehydration and prevent hypotension. Sedation and paralysis are reviewed in detail separately. (See "Acute severe asthma exacerbations in children younger than 12 years: Endotracheal intubation and mechanical ventilation", section on 'Sedation and paralysis'.)
Monitoring — Children who are admitted to the ICU for management of acute severe asthma are usually monitored with a cardiorespiratory monitor that displays a continuous electrocardiogram tracing, noninvasive blood pressure, oxygen saturation, and respiratory rate [6].
Additional monitoring includes frequent auscultation. Auscultation provides important information regarding aeration, optimal duration of exhalation (wheezing should terminate before the onset of the next inhalation), and the presence of pneumothorax or mucus plugging (indicated by asymmetric breath sounds) [6].
Fluid support — The fluid status of children with acute severe asthma exacerbation who are admitted to the ICU must be carefully monitored. Many patients are hypovolemic on presentation (related to poor intake and increased insensible fluid loss from the respiratory tract) [6]. The risk of hypotension is increased in patients who are mechanically ventilated and who receive sedatives and paralytics. Intravenous fluids should be administered to replace losses and optimize intravascular volume. However, overhydration should be avoided since it may result in pulmonary edema. (See "Acute severe asthma exacerbations in children younger than 12 years: Endotracheal intubation and mechanical ventilation", section on 'Hypotension'.)
ADJUNCTIVE THERAPIES — In extreme cases, airflow obstruction is so severe that sufficient ventilation cannot be achieved despite intensive bronchodilator therapy, intravenous glucocorticoids, ventilatory support, sedation, and paralysis. In such cases, adjunctive therapies, such as inhalational anesthetics or extracorporeal membrane oxygenation (ECMO), may be successful as rescue measures. However, the routine use of these therapies cannot be recommended on the basis of existing clinical studies. They remain heroic rescue maneuvers for the extremely refractory patient. These therapies are discussed in greater detail separately. (See "Acute severe asthma exacerbations in children younger than 12 years: Endotracheal intubation and mechanical ventilation", section on 'Adjunctive therapies'.)
COMPLICATIONS — Complications can result from the asthma exacerbation itself or the treatments. Patients with an acute severe asthma exacerbation are at risk for progressive air trapping and alveolar hyperinflation, which may lead to alveolar rupture and hemodynamic compromise. Endotracheal intubation with mechanical ventilation in the child with asthma can be associated with significant morbidity including hypotension, barotrauma (including pneumothorax), and myopathy. These and other complications are reviewed in detail separately. (See "Acute severe asthma exacerbations in children younger than 12 years: Endotracheal intubation and mechanical ventilation", section on 'Complications'.)
STEPPING DOWN THERAPIES — Interventions should gradually be weaned as the patient improves.
Discontinuing noninvasive positive pressure ventilation — Bilevel positive airway pressure (BiPAP) can be weaned to continuous positive airway pressure (CPAP) when the patient's work of breathing and respiratory rate are minimally elevated (table 1) and the oxygen requirement is <50 percent. CPAP can be withdrawn when the work of breathing and respiratory rate have normalized and the oxygen requirement is ≤40 percent.
Weaning medications — In the absence of evidenced-based guidelines for many of the adjunctive therapies contained in this topic review, we must acknowledge that clinical judgment and local practice patterns often dictate how patients are weaned from intravenous bronchodilator therapy. More important than the precise order in which medications are discontinued is the careful monitoring of the patient as therapy is withdrawn. Patients treated with intravenous terbutaline should have the medication weaned to 0.5 to 1 mcg/kg/minute once clinical improvement is demonstrated and from there may be transitioned to continuous nebulized albuterol with one hour of overlapping therapy. Thereafter, they may be weaned to hourly nebulizer treatments as tolerated. Although not evidenced based, at the author's institution, if aminophylline is employed, it is generally continued until patients are consistently tolerating intermittent inhaled albuterol at a frequency of every one to two hours.
CRITERIA FOR TRANSFER OUT OF THE ICU — Criteria for transitioning patients from the pediatric ICU (PICU) to the general pediatric ward undoubtedly vary among institutions and are largely a matter of clinical judgment. However, several general criteria are useful to consider when making this decision, including:
●Successful weaning from invasive or noninvasive positive pressure ventilation (NPPV)
●Successful weaning/cessation of intravenous bronchodilators
●Requirement of aerosolized bronchodilators at a frequency that can be safely delivered on the general pediatric ward
●Oxygen requirement within the range of what can be safely and locally appropriate to deliver on the general pediatric ward
●Cardiopulmonary monitoring needs within the range of what can be safely delivered on the general pediatric ward
●Minimal increased work of breathing
PROGNOSIS — While overall mortality is low (0.5 percent in one survey [51]), patients with status asthmaticus who require mechanical ventilation have increased in-hospital mortality compared with patients who do not require mechanical ventilation. Outcomes in ventilated patients are reviewed in detail separately. (See "Acute severe asthma exacerbations in children younger than 12 years: Endotracheal intubation and mechanical ventilation", section on 'Outcomes'.)
Patients who have required an ICU admission for an asthma exacerbation are at risk for having another life-threatening or fatal asthma exacerbation. Thus, they should be closely followed by an asthma specialist in the outpatient setting.
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Asthma in children".)
SUMMARY AND RECOMMENDATIONS
●An acute severe asthma exacerbation is somewhat loosely defined based upon presenting signs and symptoms and response to therapy (eg, a Pulmonary Index Score of ≥12 (table 2) or peak flow rate <40 percent of the predicted value for age, sex, and height or personal best (table 1)). Children with an acute severe asthma exacerbation who fail to improve with initial treatment in the emergency department should be admitted to the pediatric intensive care unit (PICU). (See 'Overview' above and "Acute asthma exacerbations in children younger than 12 years: Emergency department management".)
●Intensive care unit (ICU) management of children with acute severe asthma entails aggressive pharmacotherapy. We recommend the administration of intravenous glucocorticoids and inhaled albuterol (Grade 1A), and we suggest the administration of inhaled ipratropium (Grade 2C) and intravenous magnesium sulfate (Grade 2A). For patients who fail to respond to these measures, we suggest the administration of parenteral beta2-agonists (Grade 2B). (See 'Pharmacotherapy' above and "Acute asthma exacerbations in children younger than 12 years: Emergency department management", section on 'Elements of treatment'.)
●In select patients, noninvasive positive pressure ventilation (NPPV) may avoid the need for intubation. We suggest a trial of NPPV in the following situations, provided that the child is alert, cooperative, and without increased airway secretions (Grade 2C) (see 'Noninvasive positive pressure ventilation' above):
•The child remains hypoxemic despite high-flow oxygen and/or has documented hypercarbia.
•The child is progressing toward respiratory muscle fatigue, but the maximum therapeutic effects of glucocorticoids and bronchodilators have not been reached.
●Children admitted to the ICU with severe asthma require close cardiopulmonary monitoring. Most patients are also given intravenous fluids to treat dehydration and prevent hypotension. (See 'Supportive care' above.)
●Interventions should gradually be weaned as the patient improves. More important than the precise order in which medications are discontinued is the careful monitoring of the patient as therapy is withdrawn. (See 'Stepping down therapies' above.)
●Overall mortality in children with acute severe asthma exacerbations is approximately 0.5 percent. (See 'Prognosis' above.)
