Introduction

Bronchiolitis is an acute inflammatory condition of the bronchioles that is a result of virusinduced injury.

Etiology

Respiratory syncytial virus (RSV) is the most common viral agent isolated in about 75% (30–70% in Indian studies).

Other viruses: Rhinovirus, parainfluenza, adenovirus, human metapneumovirus, and bocavirus are the other viruses commonly causing the condition. Mycoplasma is more frequently implicated in older children with bronchiolitis.

Diagnosis

·       Persistent cough, following a prodrome of coryza lasting 1–3 days, with tachypnea with or without chest recessions and wheeze and/or crackles occurring in a child <2 years of age (usually below 1 year of age, with a peak between 3 and 6 months).

·       Associated fever, usually below 39°C, in around 30% cases and poor feeding, vomiting usually after 3–5 days of illness.

·       Apnea may be the only presenting feature, particularly below 6 weeks of age.

·       The chest may appear hyperexpanded and may be hyper-resonant to percussion. Wheezes and fine crackles may be heard throughout the lungs.

Indications for Hospitalization

·       Persistent tachypnea >60 breaths/minute or respiratory distress in form of grunting, recessions

·       Inadequate oral intake, inability to feed, dehydration, and inadequate fluid intake (50–75% of usual volume)

·       Oxygen saturation (SpO2) <92% in room air

·       Child appears seriously unwell to the healthcare provider

·       Skill and confidence of the caregiver to look after the child at home and distance from the hospital

Signs of Severe Bronchiolitis

·       Apnea, observed/reported

·       Marked respiratory distress (severe grunting/chest indrawing/tachypnea

>70/minute)

·       Central cyanosis, or SpO2 below 90% (age > 6 weeks) or below 92% (age < 6 weeks, or any age with underlying health conditions)

Risk Factors for Severe Bronchiolitis

Predictors of severe bronchiolitis are presented in Table 1

Differential Diagnosis

·       Pneumonia: Fever >39°C with persistent focal crackles

·       Episodic viral wheeze: Persistent wheeze without crackles, or recurrent episodes with or without a family history of atopy

Investigations

·       Is a clinical diagnosis based on age, seasonal occurrence, typical clinical presentation, and physical examination?

·       Blood investigations and radiology is routinely not indicated.

·       A pulse oximetry reading helps to identify hypoxia and need for admission.

·       Investigations in admitted patients to rule out alternate diagnosis such as bacterial pneumonia, congenital heart disease with failure, or sepsis might occasionally be indicated.

·       Admitted babies may need an arterial blood gas (ABG) analysis, complete blood count, C-reactive protein (CRP), serum electrolytes, and chest radiography for managing the more serious patients.

·       Measurement of lactate dehydrogenase (LDH) concentration in the nasal-wash fluid has been proposed as an objective indicator of bronchiolitis severity (Table 2).

·       Identification of viral agents does not affect management in the majority of patients. However, in the hospital setting, to avoid antibiotic abuse and prevent nosocomial transmission may be done by:

·       Antigen detection, immunofluorescence, polymerase chain reaction (PCR), and culture of respiratory secretions obtained by nasal wash or nasal aspirate.

·       New techniques such as real-time PCR, nested PCR, and multiplex PCR have improved the virologic diagnosis of bronchiolitis immensely.

Management

·       Treatment is focused on symptomatic relief and maintaining hydration and oxygenation.

·       Fever should be controlled with paracetamol.

·       Nose block should be cleared with saline nasal drops and gentle suctioning.

·       Child should be made to lie in a propped up or head end elevated positioning.

·       Orogastric tube feeding may be indicated in admitted patients. Intravenous

(IV) fluids in children with impending respiratory failure or who do not tolerate orogastric/nasogastric (OG/NG) fluids.

·       Suctioning of the upper airway in children with apnea, respiratory secretions, and feeding difficulties due to upper airway secretions

·       Supplemental oxygen in children with SpO2 below 90% (>6 weeks) or below 92% (<6 weeks or with underlying health issues)

·       Continuous positive airway pressure (CPAP) in babies with impending respiratory failure (limited low-quality evidence)

·       High-flow nasal cannula (HFNC) oxygen may have a role as a rescue therapy to reduce proportion of those requiring intensive care

·       Drugs with questionable value might reduce need for admission or length of hospital stay, but broad consensus is lacking.

§  Nebulized hypertonic saline: In children hospitalized for >3 days

§  Nebulized adrenaline: 0.1–0.3 mL/kg/dose of 1:1,000 as a potential rescue medication; however inconsistent and short-lived improvement

§  Beta-agonists: Optional single trial; may be continued if there is clinical response (a trial of bronchodilator therapy may be initiated, but should be discontinued if there is no objective improvement)

·       No role of:

·       Chest physiotherapy

·       Antibiotics

·       Antivirals

·       Montelukast

·       Ipratropium bromide

·       Systemic or inhaled steroids

·       Steam inhalation

·       RSV    polyclonal    immunoglobulin/palivizumab            (no                 roll            in                    acute management but useful in prophylaxis)

·       Inhaled furosemide/inhaled interferon alfa-2a/inhaled recombinant human deoxyribonuclease (DNase)

·       Interventions which are possibly effective for most severe cases:

§  CPAP

§  Surfactant

§  Heliox

§  Aerosolized ribavirin

Criteria for Discharge

§  Clinically stable

§  Taking adequate oral feeds, at least 75% of usual

§  Maintaining SpO2 above 90% (>6 weeks) and 92% (<6 weeks or with health issues) in room air

§  Ability of the caregiver to look after at home and distance from the hospital, and have understood the “red flag” signs Red flag signs for the caregiver at home:

§  Increased work of breathing (e.g., grunting, nasal flaring, and chest retractions)

§  Fluid intake <50–75% of normal or no urine for 12 hours

§  Apnea or cyanosis

§  Exhaustion (i.e., not responding normally to social cues and responds only with prolonged stimulation)

Prevention

§  Breastfeeding: Three-fold greater risk in non-breastfed infant

§  Hand hygiene

§  Avoid passive smoking

§  Immune prophylaxis:

•• Palivizumab: Monoclonal antibody, monthly injections during seasonal epidemics

Indications: Infants <12 months with prematurity <29 weeks; CLD of prematurity; hemodynamically significant heart disease

Palivizumab is administered intramuscularly at a dose of 15 mg/kg monthly       (every 30 days) during the RSV season. A maximum of five doses is generally sufficient prophylaxis during one season.

•• Nirsevimab: On trial; single dose for 5 months

•• Motavizumab, a second-generation mAb, and Numax-YTE, a third- generation           mAb—under trial

Complications

·       Acute respiratory distress syndrome (ARDS)

·       Myocarditis

·       Congestive heart failure

·       Arrhythmias

·       Bronchiolitis obliterans

·       Secondary bacterial infection

·       Predisposition to childhood asthma

Summary

Flowchart 1: Summary of viral bronchiolitis.

(ABG: arterial blood gas; ICU: intensive care unit; IV: intravenous; SpO2: oxygen saturation)

Further Reading

·       Gupta S, Shamsundar R, Shet A, Chawan R, Srinivasa H. Prevalence of respiratory syncytial virus infection among hospitalized children presenting with acute lower respiratory tract infections. Indian J Pediatr. 2011;78:1495- 7.

·       National Institute for Health and Care Excellence. (2015). Bronchiolitis in children: diagnosis and management. [online] Available from www.nice.org.uk/guidance/ng9. [Last accessed March, 2022].

·       Ralston SL, Lieberthal AS, Meissner HC, Alverson BK, Baley JE, Gadomski AM, et al. Clinical practice guideline: the diagnosis, management and prevention of bronchiolitis. Pediatrics. 2014;134(5): e1474-502.