Pediatric Respiratory and Allergy
Respiratory and Allergy questions test pattern recognition (wheeze versus stridor versus crackles), severity grading, and the specific drugs that change outcome. Examiners frequently contrast conditions that look alike in infants, so focus on the discriminating features and on what you should not do.
Asthma
- In children of 6 years and over, confirm with spirometry showing a bronchodilator response (FEV1 rise of 12% or more). Under 5 years the diagnosis is clinical and reassessed over time.
- Inhaled corticosteroids are the cornerstone of controller therapy; a spacer with a mask is preferred to a nebuliser for delivery.
- Acute attack: titrate oxygen to a saturation of 94-98%, give repeated salbutamol, add ipratropium in severe attacks, give prednisolone 1-2 mg/kg (maximum 40 mg) for 3-5 days, and consider intravenous magnesium sulfate 40-50 mg/kg in severe or life-threatening attacks.
Bronchiolitis
- Under 2 years, peak at 3-6 months, usually respiratory syncytial virus. Coryza, then tachypnoea, wheeze and fine crackles.
- Management is supportive: oxygen if saturation falls below 90-92%, and fluids. Do not give routine bronchodilators, corticosteroids, antibiotics or chest physiotherapy.
Croup
Barking cough, hoarse voice and inspiratory stridor. Give a single dose of dexamethasone 0.15-0.6 mg/kg. For stridor at rest, add nebulised adrenaline (0.5 mL/kg of 1:1000, maximum 5 mL) and observe for at least three to four hours because of rebound.
Pneumonia
World Health Organization tachypnoea thresholds: 60 or more breaths per minute under 2 months, 50 or more at 2-11 months, 40 or more at 1-5 years. Amoxicillin is first-line for community-acquired pneumonia; add a macrolide when atypical infection is suspected over 5 years.
Allergy and anaphylaxis
Give intramuscular adrenaline 0.01 mg/kg of 1:1000 (maximum 0.5 mg) into the anterolateral thigh, repeated every 5-15 minutes. Antihistamines and steroids are adjuncts and never first-line. Cow's milk protein allergy has IgE-mediated and non-IgE forms; extensively hydrolysed formula is the usual substitute.
Worked example
A 14-month-old has three days of coryza, low-grade fever, audible wheeze, subcostal recession and saturation of 91% in air. The picture is bronchiolitis, not asthma. Give oxygen and fluids; a trial of salbutamol is not indicated, steroids are not indicated, and antibiotics are not indicated without consolidation. Reassess for apnoea and poor feeding.
Traps
Steroids for bronchiolitis, antibiotics for wheeze, subcutaneous rather than intramuscular adrenaline, and discharging a child with croup who still has stridor at rest.