Overview
Definition:
Bronchiolitis is a common, acute viral lower respiratory tract infection in infants and young children, characterized by inflammation and necrosis of the respiratory epithelium in the bronchioles
When occurring in infants with congenital heart disease (CHD), it poses a significantly higher risk of severe illness, respiratory failure, and cardiac decompensation due to altered cardiopulmonary physiology.
Epidemiology:
Bronchiolitis is most common in infants aged 2-12 months, with a peak incidence in the first year of life
Respiratory Syncytial Virus (RSV) is the most frequent pathogen, responsible for 60-80% of cases
Infants with CHD have a 2-5 fold increased risk of hospitalization for bronchiolitis compared to healthy infants, and a higher incidence of ICU admission and mortality.
Clinical Significance:
Bronchiolitis in infants with CHD is a critical condition requiring careful assessment and often early intervention
The presence of CHD can lead to rapid deterioration due to factors like increased pulmonary blood flow, altered pulmonary vascular resistance, and reduced cardiac reserve, making timely admission and appropriate management paramount to prevent severe morbidity and mortality
This topic is crucial for DNB and NEET SS Pediatrics examinations.
Clinical Presentation
Symptoms:
Initial prodromal symptoms of upper respiratory tract infection for 1-3 days
Development of cough, which may become paroxysmal and productive
Increasing respiratory rate (tachypnea) and difficulty breathing (dyspnea)
Wheezing and crackles on auscultation
Feeding difficulties leading to poor oral intake
Irritability or lethargy
Fever, often low-grade
In infants with CHD, cyanosis may be more pronounced or develop earlier
Signs of cardiac decompensation like poor peripheral perfusion or edema may be present.
Signs:
Tachypnea with respiratory rates exceeding age-appropriate norms
Intercostal, subcostal, or suprasternal retractions indicating increased work of breathing
Nasal flaring
Grunting
Audible wheezing or crackles on lung auscultation
Prolonged expiratory phase
Hypoxia, evidenced by SpO2 <90-92% on room air
Tachycardia
Signs of dehydration if oral intake is poor
In infants with CHD, pre-existing murmurs may change, and signs of heart failure (e.g., hepatomegaly, peripheral edema) may be exacerbated.
Diagnostic Criteria:
Diagnosis is primarily clinical, based on history and physical examination, particularly in infants <2 years old presenting with a viral prodrome followed by lower respiratory symptoms
Specific laboratory or imaging criteria are not typically required for diagnosis but are essential for assessing severity and guiding management
For infants with known CHD, the suspicion for bronchiolitis is high with typical symptoms, and the focus shifts to assessing cardiorespiratory compromise.
Diagnostic Approach
History Taking:
Detailed history of presenting illness, including onset and progression of cough, dyspnea, and fever
Presence of sick contacts, particularly with viral illnesses
Birth history, including gestational age and any known CHD
Previous respiratory or cardiac events
Immunization status
Feeding pattern and fluid intake
Parental concerns regarding breathing or color changes
Red flags include prematurity, presence of significant CHD (especially those with pulmonary hypertension or shunting), prior NICU admission, recurrent respiratory infections, and neurological impairment.
Physical Examination:
Complete assessment of vital signs: heart rate, respiratory rate, temperature, and oxygen saturation
Careful respiratory examination including assessment for work of breathing (retractions, nasal flaring, grunting), breath sounds (wheezing, crackles, diminished sounds), and air entry
Cardiac examination to assess heart sounds, murmurs, rate, rhythm, and signs of heart failure (e.g., hepatomegaly, edema)
Assessment of hydration status and neurological status (activity level, alertness).
Investigations:
Oxygen saturation monitoring is crucial
aim to maintain SpO2 >90-92%
Chest X-ray is generally not indicated for uncomplicated bronchiolitis but may be considered in infants with CHD, significant hypoxia, suspected pneumonia, or if the diagnosis is unclear to evaluate for hyperinflation, atelectasis, or consolidation
Nasopharyngeal swab for viral studies (e.g., RSV antigen detection or PCR) can be helpful in specific settings, especially for epidemiological surveillance or in immunocompromised hosts, but does not usually alter immediate management
Complete Blood Count (CBC) and blood gas analysis may be indicated for severely ill infants or those with suspected sepsis or significant metabolic derangement
Echocardiography may be indicated to assess the status of the underlying CHD and its impact on cardiorespiratory function.
Differential Diagnosis:
Pneumonia (bacterial or viral)
Asthma exacerbation (less likely in infants <1 year)
Gastroesophageal reflux disease (GERD) with aspiration
Congenital anomalies of the airway
Aspiration of foreign body
Allergic bronchitis
Congestive heart failure exacerbation (especially in the context of CHD)
Differentiating bronchiolitis from a simple viral URI or exacerbation of underlying CHD is key.
Management
Initial Management:
Prioritize airway and breathing
Supplemental oxygen to maintain SpO2 >90-92%
Humidified air can be considered but is not universally proven effective
Suctioning of nasal secretions to maintain patent airway, especially before feeding and sleep
Hydration is critical
provide small, frequent oral feeds if tolerated, or consider nasogastric (NG) or intravenous (IV) fluids if oral intake is significantly compromised
Non-invasive positive pressure ventilation (NIPPV) such as CPAP or BiPAP may be considered for infants with moderate to severe respiratory distress and hypoxemia who are not improving with standard supportive care
Mechanical ventilation is reserved for infants with impending respiratory arrest or severe hypoxemia refractory to NIPPV.
Medical Management:
Bronchodilators (e.g., albuterol) are generally not recommended for routine management of bronchiolitis as they are not proven to be effective and can even worsen outcomes in some infants
Nebulized hypertonic saline (3% or 7%) has shown some benefit in reducing hospitalization rates and improving symptoms in outpatients and inpatients but is not a first-line therapy for all
Systemic corticosteroids are not recommended in the routine management of uncomplicated bronchiolitis
Antibiotics are not indicated unless there is a clear clinical suspicion of a co-existing bacterial pneumonia
Antiviral therapy for RSV is not routinely used in immunocompetent infants but may be considered in specific high-risk populations (e.g., immunocompromised, severe underlying cardiac or pulmonary disease) as per expert consensus.
Surgical Management:
Surgical management is not directly indicated for bronchiolitis itself
However, in infants with CHD, their underlying cardiac condition may require surgical or interventional correction, which needs to be carefully timed and considered in conjunction with their respiratory status
For example, closure of a large PDA might be indicated if it is contributing to pulmonary congestion during a severe bronchiolitis episode.
Supportive Care:
Close monitoring of cardiorespiratory status, including continuous pulse oximetry, respiratory rate, and work of breathing
Maintaining adequate hydration through oral feeds, NG tube, or IV fluids
Regular nasal suctioning
Positioning the infant in a semi-upright position to facilitate breathing
Providing a calm and quiet environment to minimize stress
Frequent re-assessment of the infant's condition and response to treatment
Education of parents regarding warning signs and home care
For infants with CHD, monitoring for signs of cardiac decompensation is crucial.
Complications
Early Complications:
Respiratory failure requiring mechanical ventilation
Apnea (particularly in infants <2 months or premature infants)
Secondary bacterial pneumonia
Otitis media
Dehydration
Cardiac decompensation due to increased pulmonary vascular resistance and hypoxemia.
Late Complications:
Recurrent wheezing or asthma-like symptoms in later childhood
Increased susceptibility to subsequent respiratory infections
Long-term pulmonary sequelae in those with severe or prolonged illness
Potential worsening of underlying CHD if prolonged hypoxia or increased pulmonary vascular resistance occurs.
Prevention Strategies:
Palivizumab prophylaxis for high-risk infants (e.g., those with certain CHDs, prematurity) during RSV season
Strict adherence to hand hygiene and infection control measures to prevent viral transmission
Avoiding exposure to tobacco smoke
Prompt management of underlying CHD to optimize cardiopulmonary reserve
Educating parents on early recognition of symptoms and when to seek medical attention.
Prognosis
Factors Affecting Prognosis:
The presence and severity of underlying CHD are the most significant factors affecting prognosis
Infants with severe CHD, particularly those with significant left-to-right shunting or pulmonary hypertension, have a poorer prognosis
Prematurity, younger age at onset, and severe hypoxia also portend a worse outcome
The specific viral pathogen and the infant's immune status also play a role.
Outcomes:
Most infants with bronchiolitis, even with CHD, will recover with supportive care
However, infants with severe CHD or those who develop complications such as respiratory failure or cardiac decompensation have a higher risk of prolonged hospitalization, ICU admission, and mortality
Long-term outcomes may include a predisposition to recurrent wheezing
Careful management aims to minimize the duration and severity of illness, thereby improving both short-term and long-term outcomes.
Follow Up:
Infants who have had bronchiolitis, especially those with underlying CHD, should have follow-up assessments as recommended by their pediatrician and cardiologist
This may include monitoring for recurrent respiratory symptoms, assessing growth and development, and ensuring optimal management of their cardiac condition
Particular attention should be paid to the long-term effects on pulmonary function and the risk of developing reactive airway disease.
Key Points
Exam Focus:
Admission threshold in infants with CHD is lower than in healthy infants
Prioritize oxygenation (SpO2 >90-92%) and work of breathing
RSV is the most common cause
Bronchodilators and steroids are not routinely indicated
Nasogastric feeding and hydration are critical
Mechanical ventilation is for impending respiratory failure
Recognize signs of cardiac decompensation alongside respiratory distress.
Clinical Pearls:
Always consider the underlying CHD when assessing a child with bronchiolitis
A seemingly mild case of bronchiolitis can precipitate significant cardiac decompensation
Early and aggressive supportive care, including respiratory support and hydration, is key
Never hesitate to involve cardiology if cardiac issues are suspected or worsening
Be vigilant for apnea, especially in younger or premature infants.
Common Mistakes:
Over-reliance on bronchodilators or steroids without clear indication
Underestimating the severity of respiratory distress in infants with CHD
Delaying admission when respiratory status is deteriorating
Inadequate hydration management
Not adequately assessing or monitoring for cardiac decompensation
Discharging infants with significant hypoxemia or marked work of breathing.