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USMLE Step 3 Hub

Pediatric Emergencies & Acute Inpatient Management

Pediatric Stridor & Upper Airway Obstruction

flowchart TD
    Presentation["Child Presenting with Acute Stridor / Respiratory Distress"] --> Toxic{"Toxic Appearing, Drooling, Tripod Posture?"}


    Toxic -- "YES (Suspected Epiglottitis)" --> Airway["EMERGENCY AIRWAY PROTOCOL:\n1. Do NOT agitate child (no tongue blade/IV attempts)\n2. Immediate transport to OR with ENT and Anesthesiology\n3. Intubation under general anesthesia\n4. IV Ceftriaxone + Vancomycin after airway secured"]


    Toxic -- "NO (Barking Seal-Like Cough)" --> Croup["Suspected Croup (Laryngotracheobronchitis)"]


    Croup --> Severity{"Stridor at Rest or Retractions?"}
    Severity -- "No (Mild Croup)" --> Mild["Single Dose Oral Dexamethasone (0.6 mg/kg) + Cool Mist / Discharge Home"]
    Severity -- "Yes (Moderate-Severe Croup)" --> Mod["1. Single Dose Oral/IM/IV Dexamethasone (0.6 mg/kg)\n2. Nebulized Racemic Epinephrine\n3. Observe for 3-4 Hours for Rebound Stridor"]

Acute Upper Airway Comparison

Key Differential Contrast

Croup (Laryngotracheobronchitis) vs Acute Epiglottitis

Clinical Feature Croup (Viral Laryngotracheitis) Acute Epiglottitis Discriminating Clue
Etiologic Organisms Parainfluenza virus (Types 1 and 2 most common) Haemophilus influenzae type b (Hib), Streptococcus pyogenes, Staph aureus Viral prodrome in Croup; acute fulminant bacterial onset in Epiglottitis
Clinical Hallmark Presentation Inspiratory stridor, hoarseness, and classic 'barking seal-like' cough in child 6 mo – 3 yr High fever, toxic appearance, severe dysphagia, drooling, and 'tripod' neck-extended posture Drooling and absence of cough point directly to Epiglottitis
Radiographic Neck Signs 'Steeple Sign' (subglottic tracheal narrowing) on AP soft tissue neck X-ray 'Thumbprint Sign' (swollen, enlarged epiglottis) on lateral soft tissue neck X-ray Steeple sign on AP view = Croup; Thumbprint sign on lateral = Epiglottitis
Initial Emergency Management Oral Dexamethasone + Nebulized Racemic Epinephrine (if stridor at rest) Emergency endotracheal intubation in the Operating Room. NEVER examine pharynx with tongue depressor in unmonitored setting Airway preservation in OR before any diagnostic testing in Epiglottitis

Kawasaki Disease (Mucocutaneous Lymph Node Syndrome)

Vasculitis of medium-sized arteries with a predilection for coronary arteries. Most common cause of acquired heart disease in children in developed nations.

Diagnostic Criteria: High Fever for ≥ 5 Days Plus ≥ 4 of 5 “C-R-A-S-H” Features

  1. C - Conjunctivitis: Bilateral, non-exudative, painless bulbar conjunctival injection with limbic sparing.
  2. R - Rash: Polymorphous erythematous exanthem (maculopapular, scarlatiniform) primarily on trunk and perineum.
  3. A - Adenopathy: Cervical lymphadenopathy > 1.5 cm, usually unilateral and non-tender.
  4. S - Strawberry Tongue / Oral Mucosa: Erythema, cracking/fissuring of lips, diffuse mucosal erythema, prominent lingual papillae.
  5. H - Hands & Feet Changes: Erythema and indurated edema of palms and soles in acute phase; periungual desquamation in convalescent phase (2–3 weeks post-onset).

Step 3 Treatment Protocol (Prevents Coronary Aneurysms)

  1. Intravenous Immune Globulin (IVIG): 2 g/kg as a single infusion over 10–12 hours administered within the first 10 days of fever onset (reduces coronary aneurysm risk from 25% to < 4%).
  2. High-Dose Aspirin: 80–100 mg/kg/day divided q6h for anti-inflammatory effect during the acute febrile phase.
  3. Transition to Low-Dose Aspirin: When patient is afebrile for 48 hours, switch to 3–5 mg/kg/day for antiplatelet effect, continued for 6–8 weeks (or indefinitely if coronary aneurysms develop).
  4. Echocardiogram: Baseline at diagnosis, repeated at 2 weeks and 6–8 weeks to screen for coronary artery dilation.
  5. Vaccine Counseling: Delay live virus vaccines (MMR, Varicella) for 11 months following IVIG administration due to interference from passively transferred antibodies.

Neonatal Fever Protocol (≤ 28 Days Old)

Fever ≥ 38.0°C (100.4°F) in an infant under 28 days of age is an emergency until proven otherwise:

  • Mandatory Full Sepsis Workup:
    1. Complete blood count with manual differential.
    2. Blood cultures (two sets).
    3. Catheterized urinalysis and urine culture.
    4. Lumbar puncture for CSF analysis and culture (cell count, protein, glucose, Gram stain, viral PCR).
  • Immediate Empiric Antimicrobial Coverage:
    • IV Ampicillin (covers Listeria monocytogenes and Streptococcus agalactiae / GBS) + IV Gentamicin OR IV Cefotaxime (covers Gram-negative bacilli like E. coli).
    • Step 3 Contraindication: Do NOT use Ceftriaxone in neonates ≤ 28 days old due to displacement of bilirubin from albumin (causes kernicterus) and precipitation with IV calcium in biliary tree.