Below is a concise but complete paediatric reference for major respiratory infections in children: Croup, Acute Epiglottitis, Acute Bronchiolitis, Pneumonia, Atypical Pneumonia, Pneumococcal Pneumonia, and Staphylococcal Pneumonia.
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Respiratory Infections in Children (Paediatrics)
Respiratory infections are among the most common causes of morbidity and hospitalization in children. They range from upper airway infections causing obstruction to lower respiratory tract infections affecting alveoli and bronchioles.
1. CROUP (Acute Laryngotracheobronchitis)
Definition
Croup is an acute viral infection of the upper airway causing inflammation of the larynx, trachea, and bronchi, resulting in barking cough, hoarseness, and inspiratory stridor.
Pathophysiology
Viral infection causes:
- mucosal edema
- subglottic inflammation
- narrowing of airway
Children have narrow subglottic airway, so even small swelling causes obstruction.
Causes
Most common viruses:
- Parainfluenza virus type 1 (most common)
- Parainfluenza type 2 and 3
- RSV
- Influenza virus
- Adenovirus
- Human metapneumovirus
Age group: 6 months – 3 years
Clinical Features
Classic triad:
- Barking seal-like cough
- Inspiratory stridor
- Hoarseness
Other symptoms:
- Fever (usually low grade)
- respiratory distress
- suprasternal retractions
- worse at night
Severe disease signs:
- stridor at rest
- hypoxia
- agitation
- cyanosis
Investigations
Usually clinical diagnosis.
If done:
- Neck X-ray → Steeple sign (subglottic narrowing)
- Pulse oximetry
- Viral PCR if severe
Differential Diagnosis
- Epiglottitis
- Foreign body aspiration
- Bacterial tracheitis
- Laryngeal edema
- Retropharyngeal abscess
Management
Mild Croup
- Humidified oxygen
- Oral corticosteroids
Drug: Dexamethasone
Indication
Moderate–severe croup
Mechanism
Anti-inflammatory corticosteroid → reduces airway edema.
Dose
- 0.15–0.6 mg/kg orally or IM single dose
(max 10 mg)
Pharmacokinetics
- Long acting glucocorticoid
- Half-life 36–54 hours
Adverse Effects
- irritability
- hyperglycemia
- gastritis (rare)
Contraindications
- systemic fungal infection
Monitoring
- respiratory status
- oxygen saturation
Moderate–Severe Croup
Nebulized adrenaline.
Drug: Epinephrine (Adrenaline)
Mechanism
α-adrenergic vasoconstriction → reduces mucosal edema.
Dose
- 0.5 ml/kg of 1:1000 solution
(max 5 ml) nebulized.
Adverse Effects
- tachycardia
- hypertension
- tremor
Monitoring
Observe for rebound symptoms.
Severe Cases
- oxygen
- ICU care
- possible intubation
2. ACUTE EPIGLOTTITIS
Definition
Acute epiglottitis is a rapidly progressive bacterial infection of the epiglottis causing life-threatening airway obstruction.
Etiology
Previously most common:
- Haemophilus influenzae type b (Hib)
Other causes:
- Streptococcus pneumoniae
- Staphylococcus aureus
- Group A Streptococcus
Age group: 2–7 years
Pathophysiology
Infection → severe epiglottic edema → airway obstruction.
Clinical Features
Classic presentation:
- sudden high fever
- severe sore throat
- drooling
- dysphagia
- muffled “hot potato voice”
Characteristic posture:
Tripod position
- sitting
- leaning forward
- mouth open
Signs:
- inspiratory stridor
- respiratory distress
- toxic appearance
Investigations
Avoid throat examination until airway secured.
Possible tests:
- Lateral neck X-ray → Thumb sign
- Blood culture
- CBC (leukocytosis)
Differential Diagnosis
- Croup
- retropharyngeal abscess
- bacterial tracheitis
- foreign body
Management
Medical emergency
Immediate priorities
- Secure airway
- Oxygen
- IV antibiotics
Antibiotics
Ceftriaxone
Indication
Hib epiglottitis
Mechanism
Third-generation cephalosporin → inhibits bacterial cell wall synthesis.
Dose
- 50–75 mg/kg/day IV
Adverse Effects
- diarrhea
- biliary sludge
- rash
Contraindications
- severe cephalosporin allergy
Monitoring
- clinical response
- cultures
Alternative
Cefotaxime or Ampicillin-sulbactam.
3. ACUTE BRONCHIOLITIS
Definition
Bronchiolitis is a viral infection of the lower respiratory tract causing inflammation of bronchioles, mainly in infants <2 years.
Etiology
Most common:
- Respiratory Syncytial Virus (RSV)
Other viruses:
- Rhinovirus
- Parainfluenza
- Adenovirus
- Human metapneumovirus
Pathophysiology
Virus infects bronchiolar epithelium →
- edema
- mucus secretion
- airway obstruction
- air trapping
Clinical Features
Early:
- rhinorrhea
- cough
- low-grade fever
Later:
- tachypnea
- wheezing
- crackles
- feeding difficulty
Severe signs:
- apnea
- hypoxia
- cyanosis
Investigations
Usually clinical.
If severe:
- Pulse oximetry
- Chest X-ray → hyperinflation
- RSV antigen testing
Differential Diagnosis
- asthma
- pneumonia
- congenital heart disease
Management
Supportive Treatment
- oxygen therapy
- hydration
- nasal suction
Bronchodilators generally not routinely recommended.
Severe Cases
- CPAP
- mechanical ventilation
Prevention
Palivizumab
Indication
High-risk infants (premature, congenital heart disease)
Mechanism
Monoclonal antibody against RSV fusion protein.
Dose
15 mg/kg IM monthly during RSV season.
Adverse Effects
- fever
- injection site reaction
4. PNEUMONIA IN CHILDREN
Definition
Pneumonia is infection of lung parenchyma causing inflammation of alveoli and consolidation.
Etiology
Neonates
- Group B Streptococcus
- E. coli
- Listeria
Infants
- RSV
- Streptococcus pneumoniae
Older children
- Streptococcus pneumoniae
- Mycoplasma pneumoniae
- Chlamydia pneumoniae
Pathophysiology
Microorganisms infect alveoli →
- inflammatory exudate
- impaired gas exchange
- consolidation
Clinical Features
- fever
- cough
- tachypnea
- chest indrawing
- crackles
- decreased breath sounds
WHO sign:
Fast breathing
Investigations
- Chest X-ray → consolidation
- CBC
- Blood culture
- Pulse oximetry
Differential Diagnosis
- bronchiolitis
- asthma
- tuberculosis
- foreign body
Management
Mild Pneumonia
Oral antibiotics.
Amoxicillin
Mechanism
Inhibits bacterial cell wall synthesis.
Dose
40–90 mg/kg/day divided doses.
Adverse Effects
- diarrhea
- rash
- allergy
Severe Pneumonia
Hospitalization
IV antibiotics:
- Ampicillin
- Ceftriaxone
Supportive care:
- oxygen
- fluids
5. ATYPICAL PNEUMONIA
Definition
Atypical pneumonia is pneumonia caused by atypical organisms with mild symptoms and diffuse lung involvement.
Etiology
Common organisms:
- Mycoplasma pneumoniae
- Chlamydia pneumoniae
- Legionella (rare in children)
Age group:
School-age children and adolescents
Pathophysiology
Pathogens cause interstitial inflammation rather than alveolar consolidation.
Clinical Features
- persistent dry cough
- mild fever
- headache
- sore throat
- malaise
Chest findings often mild compared to X-ray changes.
Investigations
- Chest X-ray → diffuse interstitial infiltrates
- PCR or serology
Management
Macrolide Antibiotics
Azithromycin
Mechanism
Inhibits bacterial protein synthesis (50S ribosome).
Dose
10 mg/kg day 1
then 5 mg/kg daily for 4 days.
Adverse Effects
- nausea
- diarrhea
- QT prolongation
Contraindications
- severe liver disease
Monitoring
- ECG if cardiac risk.
6. PNEUMOCOCCAL PNEUMONIA
Definition
Pneumonia caused by Streptococcus pneumoniae, the most common bacterial pneumonia in children.
Pathophysiology
Bacteria invade alveoli →
- intense inflammation
- fibrin deposition
- lobar consolidation.
Clinical Features
- sudden high fever
- productive cough
- chest pain
- tachypnea
- crackles
Complications:
- pleural effusion
- empyema
- bacteremia
Investigations
- Chest X-ray → lobar consolidation
- Blood culture
- sputum culture
Treatment
First-line
Amoxicillin
Severe infection
Ceftriaxone or Cefotaxime
Prevention
Pneumococcal conjugate vaccine (PCV)
7. STAPHYLOCOCCAL PNEUMONIA
Definition
Severe pneumonia caused by Staphylococcus aureus, often following influenza infection.
Pathophysiology
Produces toxins →
- lung necrosis
- abscess formation
- pneumatocele
Clinical Features
- high fever
- severe respiratory distress
- cough with purulent sputum
- rapid progression
Complications:
- lung abscess
- empyema
- pneumothorax
Investigations
- Chest X-ray → pneumatoceles
- Blood culture
- sputum culture
Management
Antibiotics
Vancomycin
Mechanism
Inhibits bacterial cell wall synthesis.
Dose
10–15 mg/kg IV every 6 hours.
Adverse Effects
- nephrotoxicity
- ototoxicity
- red man syndrome
Monitoring
- serum trough levels
- renal function
Alternative
Clindamycin (for MSSA).
Key Differences Between Major Pediatric Respiratory Infections
| Disease | Main Site | Hallmark Symptom |
| ------------------------ | ------------- | ----------------- |
| Croup | Upper airway | Barking cough |
| Epiglottitis | Epiglottis | Drooling |
| Bronchiolitis | Bronchioles | Wheezing |
| Pneumonia | Alveoli | Fever + tachypnea |
| Atypical pneumonia | Interstitium | Dry cough |
| Pneumococcal pneumonia | Lobar lung | High fever |
| Staphylococcal pneumonia | Lung necrosis | Pneumatoceles |
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