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Stem
A candidate is asked to manage a classic presentation of Croup in an exam setting. Use precise definitions, scores, doses, and decision thresholds.
Core knowledge (model answer backbone)
Croup (acute laryngotracheobronchitis) is the most common cause of acute upper airway obstruction in young children, peaking at 6 months to 3 years, caused mainly by parainfluenza virus type 1 and 2. Presentation: barking seal-like cough, harsh inspiratory stridor, hoarse voice, low-grade fever, worse at night. Most are mild and self-limiting over 3 to 7 days. Severe croup: stridor at rest, marked retractions, cyanosis, altered mental state. Treatment: oral dexamethasone 0.15 to 0.6 mg/kg single dose for all children; nebulised adrenaline 1:1000, 0.5 mL/kg max 5 mL, for moderate to severe with stridor at rest; observe at least 2 to 4 hours after adrenaline for rebound.
Red flags
- Stridor at rest, marked retractions, cyanosis, altered mental state - severe croup (Westley over 5), admit and treat aggressively
- Drooling, dysphagia, muffled voice, high fever, sitting forward tripod, no cough - epiglottitis - immediate anaesthetic and ENT, do not examine throat, secure airway in theatre
- Toxic child, high fever, purulent secretions, rapid deterioration - bacterial tracheitis (Staph aureus), ICU, broad antibiotics, prepare for airway
- Recurrent croup (more than 2 to 3 episodes) or atypical age (under 6 months, over 6 years) - think anatomical (subglottic stenosis, laryngeal web, haemangioma, foreign body), refer to ENT
High-yield structure examiners expect
Cover: Overview & Definition, Classification, Epidemiology & Risk Factors, Pathophysiology, Clinical Presentation, Differential Diagnosis.
Key doses / thresholds (from topic teaching)
- kg max 5 mL**, for moderate to severe (stridor at r
- Dexamethasone 0.6 mg/kg PO/IM; observe 2 to 4 hours; conside
- kg max 5 mL PLUS dexamethasone 0
- IM adrenaline 0.01 mg/kg (1:1000, 0
- maximum 5 mL)**, given via a nebuliser with oxygen,
- Dexamethasone 0.6 mg/kg PO/IM/IV** (maximum 16 mg) as a sing
Questions
a) Define the condition and give the most important classification or severity framework used in exams. (3 marks)
- Clear one-line definition matching standard teaching.
- Named classification / stages / types with discriminating features.
- One sentence on why classification changes management.
b) Outline pathophysiology in a mechanism chain that explains the main clinical features. (3 marks)
- Initiating insult → intermediate pathway → end-organ effect.
- Link at least two symptoms/signs to mechanism.
- Mention one complication pathway (e.g. shock, perforation, herniation, arrhythmia).
c) List discriminating clinical features and bedside assessment. (3 marks)
- Classic presentation plus one atypical group (elderly, pregnancy, child, immunocompromised).
- Named signs/manoeuvres if relevant.
- What must never be missed on exam/bedside (pregnancy test, airway, glucose, etc.).
d) Investigations with thresholds and one named score if applicable. (3 marks)
- First-line tests and what positive findings mean.
- Gold-standard or definitive investigation when needed.
- Score components reproduced exactly if a named score is standard for this topic.
e) Immediate resuscitation and definitive management with doses where standard. (3 marks)
- ABC / time-critical steps first.
- First-line drug(s) with agent + dose + route (or procedure steps).
- Escalation triggers (theatre, ICU, thrombolysis window, antidote, etc.).
- Disposition and safety-netting.
Marking tips
Full marks require specificity (numbers, names, doses) not generic "give antibiotics/fluids." Regional practice (ICMR / NICE / AHA) may be cited as alternative where relevant.