|Year : 2023 | Volume
| Issue : 3 | Page : 94-100
Differences and similarities in severe bronchiolitis and status asthmaticus
Alicia Williams, Archana Dhar
Department of Pediatrics, Division of Pediatric Critical Care, Children's Medical Center of Dallas, University of Texas Southwestern, Dallas, TX, USA
|Date of Submission||24-Mar-2023|
|Date of Decision||10-Apr-2023|
|Date of Acceptance||21-Apr-2023|
|Date of Web Publication||19-May-2023|
Dr. Alicia Williams
5323 Harry Hines Blvd, Dallas, TX 75390
Source of Support: None, Conflict of Interest: None
Bronchiolitis and status asthmaticus are common diagnoses encountered in the pediatric intensive care unit setting with overlapping clinical manifestations that can create perplexity in treatment following hospital admission. While there are clear first-line therapies for each of these medical conditions, the use of adjunct therapies has been inconsistent and more dependent on provider preference at times. In this review, a brief introduction to the epidemiology, clinical presentation, and diagnosis allows for a review of proposed therapies to highlight the distinctions between these two entities.
Keywords: Asthma, bronchiolitis, pediatrics
|How to cite this article:|
Williams A, Dhar A. Differences and similarities in severe bronchiolitis and status asthmaticus. J Pediatr Crit Care 2023;10:94-100
|How to cite this URL:|
Williams A, Dhar A. Differences and similarities in severe bronchiolitis and status asthmaticus. J Pediatr Crit Care [serial online] 2023 [cited 2023 Jun 2];10:94-100. Available from: http://www.jpcc.org.in/text.asp?2023/10/3/94/377433
| Introduction|| |
This review aims to summarize current evidence for the diagnostic approach and management of acute bronchiolitis and status asthmaticus (SA). Although both present with respiratory distress in children, we hope to highlight the differences in the epidemiology, clinical assessments, and management of these patients.
| Bronchiolitis|| |
Bronchiolitis is an acute, lower respiratory tract viral infection in infants and children younger than 24 months of age, with an impressive global health-care burden.,, 2%–3% of all children are hospitalized with bronchiolitis during their 1st year of life with 5%–30% requiring admission to the pediatric intensive care unit (PICU).,
| Epidemiology|| |
Respiratory syncytial virus (RSV) is the most common virus causing bronchiolitis. Epidemics occur during winter months in the northern hemisphere. Ten percent of the patients with RSV bronchiolitis require hospitalization while 23.8% need the PICU. Infants with non-RSV bronchiolitis, especially Rhinovirus, appear to have a shorter illness characterized by wheezing.
| Clinical Presentation|| |
Bronchiolitis presents as a constellation of signs and symptoms in children younger than 2 years, including an upper respiratory tract prodrome followed by increased respiratory effort and wheezing. The clinical course is variable ranging from transient events, such as apnea, to progressive respiratory distress from lower airway obstruction. It is a dynamic disease and minute-to-minute variations in clinical findings are characteristic as mucus clearance changes. Indications for hospitalization are respiratory rate (RR) >60/min, saturation <92% or less, presence of retractions or when there is poor feeding or concern regarding the home environment or parental reliability.,,
Although many scoring systems are available to grade the disease severity, none has achieved widespread acceptance or the ability to predict whether illness will progress to needing PICU care.
Risk factors for PICU include prematurity, low birth weight, age <6 months, infants with congenital heart defects, chronic lung disease or immunodeficiencies, exposure to cigarette smoke, or those presenting with apneic events.,,,,, Premature infants are especially prone to apnea, especially if their corrected age <2 weeks, their birth weight is <2.3 kg, their RR <30 or >70, and their saturation is <90% on presentation.
| Diagnosis|| |
The American Academy of Pediatrics (AAP) strongly recommends that clinicians diagnose bronchiolitis and assess disease severity based on history and physical examination. There is no value in identifying the specific causative viral etiology. The current evidence does not support routine chest radiography (CXR). The AAP recommends a CXR when the severity of illness warrants an intensive care unit admission. Studies show that infants that undergo a CXR are 10 times more likely to receive antibiotics.
Laboratory tests are not usually indicated for routine work-up of these infants. Guidelines recommend against complete blood counts and cultures unless there is clinical evidence or strong suspicion of sepsis. The clinical examination is considered sufficient to assess the hydration status; thus, the measurement of electrolytes is not supported.
| Management|| |
Bronchiolitis is a self-limiting disease. Most have mild diseases and can be optimally managed with supportive care at home. No available treatment hastens the resolution of symptoms. The Canadian guidelines remind clinicians “primum non nocere” i.e., “first, do no harm” in the treatment of otherwise healthy children with bronchiolitis.
For those requiring admission, supportive care with assisted feeding, minimal handling, gentle nasal suctioning, and oxygen therapy form the mainstay of treatment. Based on review of the international guideline, we propose an in-house treatment algorithm [Figure 1].
Transient desaturation is a normal phenomenon in healthy infants. In this patient population, continuous pulse oximetry is not well studied and potentially problematic for children who do not require oxygen. AAP guidelines recommend usage only for patients requiring supplemental oxygen. The Canadian guidelines recommend usage only in high-risk patients and in the acute phase of the disease. They mention the appropriateness of intermittent checks.
Oxygen therapy is recommended in children with peripheral oxygen saturation <92%., The AAP guidelines do not recommend routine use of oxygen if saturations >90% in the absence of acidosis.
Heated high-flow nasal cannula
Analysis of the literature shows that despite its widespread use, the role of high flow nasal cannula (HFNC) in preventing respiratory failure in bronchiolitis is not evidence based. The absence of any randomized controlled trial (RCT) for the efficacy of HFNC in bronchiolitis precludes specific recommendations on it use at present.,,, The 2022 Italian guidelines mention that HFNC should not be used as the primary modality but can be considered if standard oxygen therapy fails in hypoxemic infants. A precise definition for treatment failure for standard oxygen therapy and refining the subset of patients who may benefit from HFNC therapy is needed.
Continuous positive airway pressure
Continuous positive airway pressure (CPAP) is often used as a modality of noninvasive respiratory support for infants with acute, moderate-to-severe bronchiolitis. CPAP, delivered by nasal prongs or helmet, increases the positive end-expiratory pressure (PEEP), counteracts airway resistance, and prevents atelectasis. However, RCTs supporting its use in this population are lacking. There is no mention of CPAP usage in the AAP guidelines while the NICE guidelines recommend consideration of CPAP in infants with impending respiratory failure or severe disease.,
Nebulized hypertonic saline
In cystic fibrosis, nebulized hypertonic saline (NHS) hydrates the airway surface, reduces airway edema, and improves mucus clearance. However, multiple RCTs have failed to establish any benefit in patients with moderate–to-severe bronchiolitis., There is no current evidence to support the use of NHS in bronchiolitis.
Most RCTs have failed to demonstrate a consistent benefit from alpha-or beta-adrenergic usage so there is consensus in international guidelines about not using beta-agonists in bronchiolitis.,,,,
A recent study found that infants >6 months who initially presented with a wheeze are more prone to receiving beta-agonist therapy. There is a school of thought that there may be a subset of infants >6 months who have viral-induced wheezing or their first episode of asthma and may hence be responsive to a bronchodilator trial.,
Epinephrine or adrenaline
Several RCTs have not found any benefit from using nebulized Epinephrine in bronchiolitis. There was no improvement in the duration of the symptoms or length of stay (LOS). None of the international guidelines recommend the usage of nebulized Epinephrine.,,
Though steroids are beneficial in other respiratory diseases like asthma and croup, there is no benefit from their use in bronchiolitis. Using nebulized and systemic corticosteroids alone or in combination with either Epinephrine or bronchodilators in treating acute bronchiolitis is not recommended. Steroids have not been shown to prevent hospital admission and have no impact on LOS in hospitalized patients.,,,,
Since infants are obligate nasal breathers, nasal suctioning to clear the secretions has been studied as a treatment modality in this cohort. However, it irritates the nasal mucosa and may result in edema. International guidelines support only superficial suctioning., Currently there is no evidence to support deep suctioning. In fact, there is evidence that deep suctioning may be associated with adverse events and may increase LOS.
Patients with bronchiolitis are at risk for atelectasis due to airway edema and sloughing of the respiratory epithelium into airways. Chest physiotherapy (CPT) has often been proposed as a supportive therapy in these patients.
However, several RCTs utilizing different modes including vibration, percussion, slow passive expiration, and forced passive expiratory techniques have failed to establish any reduction in the severity of the disease., No published guidelines recommend CPT for the management of uncomplicated bronchiolitis.,,,, CPT could be considered in those infants with co-morbidities like spinal muscular atrophy who have impaired secretion clearance.
There is consensus among international guidelines that the use of antibiotics is not justified in bronchiolitis.,,,,, Despite the lack of evidence, approximately 50% of the patients with bronchiolitis are prescribed antibiotics in both the inpatient and outpatient settings. Although concern for secondary bacterial infection is the driving force for the antibiotics, multiple studies have shown that bacterial co-infections occur in <30% of the hospitalized cohort with bronchiolitis. The risk does increase up to 42% in children admitted to a PICU in the need of mechanical ventilation (MV). The AAP guidelines justify antibiotic therapy usage in some children with bronchiolitis who require intubation and MV for respiratory failure.
Hydration and nutrition
Maintaining hydration is crucial in infants with bronchiolitis. Nasal congestion, tachypnea, or hypoxemia may contribute to difficulty in feeding. Fever and tachypnea also lead to insensible fluid losses. International guidelines recommend Nasogastric (NG) or intravenous fluids for this patient population who cannot maintain hydration orally. There is no difference in the safety or efficacy of feeding through the NG versus intravenous (IV) route. Guidelines recommend that infants should receive enough fluid to restore fluid loss and avoid dehydration, and the amount should not exceed 100% of daily fluid requirements., These infants are prone to fluid retention due to anti-diuretic hormone secretion so isonatremic fluids are recommended.,
| Status Asthmaticus|| |
Asthma is a chronic medical condition in pediatrics accounting for a significant number of emergency department (ED) visits and hospitalizations.,,, All patients with asthma are at risk for developing SA. SA itself occurs in more than 20% of pediatric asthma hospitalizations and is one of the most common indications for PICU admission.,,,
| Epidemiology|| |
Globally, asthma affects more than 300 million people including 10% of all children.,,, Prevalence is notably highest in developed countries and has been increasing rapidly in developing countries over recent years. Asthma is more severe in males than females.,,
| Clinical Presentation|| |
Asthma is a heterogeneous disease with variable phenotypes and a wide range of clinical manifestations based on age, gender, and environmental factors.,, Atopy is present in >50% of children with asthma. However, children with late-onset asthma tend to be nonatopic and more severe. Outside of allergic triggers, viral infections are typical causes of exacerbations.,
Characteristic pathophysiology revolves around the triad of airway reactivity, mucosal airway inflammation, and mucus production leading to lower airway obstruction. Signs and symptoms can include wheezing, tachypnea, tachycardia, shortness of breath, cough, use of accessory muscles, diaphoresis, cyanosis, inability to phonate, decreased or absent air entry, and even altered mental status.,,,,,,,
| Diagnosis|| |
The diagnosis of SA is clinical, as no gold standard test exists.,, Physical exam is the most helpful in making a diagnosis and determining the degree of severity. The utilization of clinical asthma scores, such as the Pediatric Asthma Severity Score [Table 1], aid in communication of severity between providers and deciding level of care.,, No scoring system has been found to be more superior but it is recommended to use one with a high degree of reliability between users.
Blood gases in patients with SA can predict impending respiratory failure but should not outweigh clinical judgment.,, Results usually show hypoxemia and hypocarbia with sicker patients often having a mixed respiratory and metabolic acidosis. A normal or rising pCO2 can be a danger sign, although, some hypercarbia can be well tolerated without need for escalation in respiratory support.
CXR is not routinely indicated in a child with a known history of asthma presenting with SA, however, it is routinely obtained if they require PICU admission., CXR might be helpful if there are localizing lung findings on the exam or concern for air leak, or cause of wheezing is unclear.,,
| Management|| |
The main therapeutic goal is a reversal of bronchospasm and correction of hypoxemia. Administration of inhaled short-acting beta-agonists (SABAs) and systemic corticosteroids should be started on presentation. PICU admission should be considered for patients with ongoing hypoxemia, hypercarbia, evidence of air leak, or those requiring escalated respiratory support. Through review of current literature and guidelines, we propose a PICU algorithm for the escalation of care [Figure 2].
| First-Line Therapies|| |
Hypoxemia is a common finding as children are at a higher risk of ventilation/perfusion mismatching due to age-related differences in pulmonary mechanics. This mismatching can be made worse with the initiation of SABAs., O2 saturations >92% are recommended and supplemental oxygen should be administered if hypoxemia is present.,
Children presenting with SA are often dehydrated secondary to poor oral intake and increased insensible losses., Therefore, fluid resuscitation and ongoing maintenance are indicated to improve decreased venous return., However, it requires careful monitoring, as fluid overload can lead to pulmonary edema in these patients with elevated intrathoracic pressures.,
Rapid reduction in airflow obstruction is important in caring for patients with SA. Inhaled bronchodilators can be given via metered dose inhalers or nebulized route. SABAs are the primary medication choice typically starting with intermittent delivery in the ED. However, if no improvement in exam or clinical asthma scores, continuous delivery is recommended. Studies have shown that the use of continuous nebulized beta-agonist to be a more efficient and effective therapy.,,,,,
Systemic corticosteroids are considered first-line due to the underlying inflammatory process in an asthma exacerbation. Conversely, inhaled corticosteroids play no role in the management of an acute asthma exacerbation. Studies have shown that children with SA who receive systemic corticosteroids within 75 min of arrival to an ED have a lower rate of hospital admission and shortened length of therapy., There is no preference for oral versus IV route however in PICUs, methylprednisolone is preferred due to its IV formulation and limited mineralocorticoid effect.,,,,
| Second-Line Therapies|| |
Magnesium has been utilized in SA given its bronchodilation effect and inhibition of mast cell degranulation., Children who received magnesium in the ED were less likely to require MV and were more effective than systemic beta-agonists or methylxanthines in the reduction of clinical scores., Continuous magnesium has been reviewed but there is notable variability in dosing regimens. Clinical outcomes with more prolonged administration of magnesium have not been widely assessed., Ultimately, iv magnesium is a low-risk adjunct therapy and should be used following first line treatments.,,,
Ipratropium is considered standard of care for children presenting to the ED with an acute asthma exacerbation. There has been insufficient data to support its continued use after admission as studies have not shown a clear benefit in hospitalized patients. However, some PICUs have continued its use in patients with refractory SA.,,
In SA, bronchial constriction can be so severe that it prevents adequate delivery of inhaled SABAs. Therefore, systemic beta-agonists, like terbutaline or epinephrine, are utilized for bronchodilation.,, However, if beta receptors are already saturated, there may be minimal benefit. A Cochrane review found no significant benefit with the addition of systemic beta-agonists.,, Therefore, the preferred route for beta-agonist delivery continues to be inhalation however the systemic route is utilized in refractory cases of SA.
Noninvasive respiratory support
Over recent years, HFNC and noninvasive positive pressure ventilation (NIV) have been increasingly used in SA. The benefit of NIV is based on its direct bronchodilator effect and alveolar recruitment and reduction of work of breathing by offloading the patient's respiratory muscles.,, Clinical improvement with NIV is usually seen in the first 1–2 h of use. Difficulties with its use include finding an interface that properly fits as well as tolerance of the device. HFNC can be a nice alternative as it is usually better tolerated than NIV and still allows continuous nebulized beta-agonist therapy to be delivered. Data evaluating HFNC's effectiveness in pediatric SA is lacking but, in adults, it has shown reduced work of breathing.
| Rescue Therapies|| |
There are case studies reporting the use of volatile anesthetics which act by direct bronchial smooth muscle relaxation and interruption of hypocapnic bronchoconstriction.,,, This therapy is associated with longer lengths of ventilation, longer LOS, and higher costs. A major challenge with this therapy is the need for pediatric anesthesiology support.,, If utilizing this therapy, efforts should be made to wean adjunct therapies to limit unwanted side effects.
Decision to intubate a patient with SA is clinical. Indications include altered level of consciousness, exhaustion, and respiratory arrest. Strategies that best support ventilated SA patients include permissive hypercapnia with sufficient exhalation time. A ventilator mode with a decelerating flow pattern results in lower peak airway pressures and promotes lung protective measures., Addition of PEEP remains under debate but current recommendations advocate for its use while following plateau airway pressures closely.,,
Extracorporeal membrane oxygenation
Extracorporeal membrane oxygenation (ECMO) should be considered for patients not responding to MV. Although the outcomes are excellent on ECMO, cost and resource intensity limit its usage., Veno-venous route is preferred for support to allow lung rest while the more definitive treatments can take effect.
| Future Directions|| |
Since both bronchiolitis and asthma are heterogeneous entities, creating comprehensive universal recommendations is challenging. Although unique knowledge gaps exist with each, i.e., severity scales for bronchiolitis and escalation/de-escalation pathways for SA, both diseases would benefit from further research into NIV modes for support. While the risk-benefit profile for most of the discussed adjunct therapies is low, it is imperative for our patients that we continue to work at standardizing care.
| Conclusions|| |
While the clinical presentation of bronchiolitis and asthma may appear similar, there is little or no overlap in the pathophysiology and thus the management. Children hospitalized with bronchiolitis in infancy may have an increased risk of subsequent asthma The association between bronchiolitis and asthma is complex, multifactorial, and needs to be studied further.
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Conflicts of interest
There are no conflicts of interest.
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