Master Pediatrics
for USMLE Step 2 CK

What the USMLE Step 2 CK Tests in Pediatrics

Pediatrics on USMLE Step 2 CK tests the ability to manage acute and chronic conditions across infancy, childhood, and adolescence, with emphasis on age-specific differentials, developmental milestones, and preventive care. Candidates must demonstrate clinical decision-making for common presentations like fever without source, respiratory distress, vomiting/diarrhea, and failure to thrive. Key areas include neonatal resuscitation (APGAR, NRP algorithm), congenital heart disease (cyanotic vs acyanotic lesions, PDA closure indications), infectious diseases (meningitis, bronchiolitis, UTIs), and childhood immunizations (CDC schedule, contraindications). Management of asthma exacerbations (PEFR, step-up therapy), seizures (febrile vs epilepsy, status epilepticus protocol), and growth/nutrition (WHO growth charts, BMI percentiles) is frequently tested. Knowledge of screening guidelines (lead, anemia, developmental surveillance) and child abuse recognition (sentinel injuries, skeletal survey) is essential.

High-Yield Concepts

• Fever Without Source in Infants: For infants 0–28 days: full sepsis workup (CBC, blood culture, urine culture, LP), empiric ampicillin + cefotaxime (or gentamicin), admit. 29–60 days: use Rochester criteria (low-risk: term, no antibiotics, well-appearing, WBC 5–15k, band-to-neutrophil ratio <0.2, normal UA) to decide observation vs workup. 3–36 months: if well-appearing, no source, and temperature ≥39°C, check UA and urine culture; if positive, treat as UTI.
• Bronchiolitis Management: Caused by RSV; diagnosis clinical (coryza, cough, wheeze, tachypnea). AAP guidelines: no routine bronchodilators, no steroids, no chest physiotherapy. Indications for hospitalization: SpO2 <90%, dehydration, apnea, moderate-severe distress. Supportive care: nasal suction, oxygen to keep SpO2 ≥90%, IV fluids if unable to feed. Palivizumab prophylaxis only for high-risk infants (premature <29 weeks, CLD, CHD).
• Kawasaki Disease Diagnosis and Treatment: Diagnostic criteria: fever ≥5 days plus 4 of 5 (bilateral conjunctivitis, strawberry tongue/cracked lips, polymorphous rash, cervical lymphadenopathy >1.5 cm, extremity changes). Incomplete Kawasaki: fever plus <4 criteria but lab/echo evidence. Treatment: IVIG 2 g/kg single dose (within 10 days) plus high-dose aspirin 80–100 mg/kg/day divided q6h (then low-dose 3–5 mg/kg/day after afebrile). Echo for coronary artery aneurysms.
• Pediatric Dehydration Assessment: Use WHO or Gorelick scale: mild (3–5% loss) – normal vital signs, slightly dry mucous membranes; moderate (6–9%) – sunken eyes, decreased skin turgor, tachycardia; severe (≥10%) – lethargic, prolonged capillary refill >2 sec, hypotension. Rehydration: mild-moderate – oral rehydration solution (ORS) 50–100 mL/kg over 4 hours; severe – IV bolus 20 mL/kg NS or LR, repeat as needed, then D5 ½ NS with KCl.
• Febrile Seizure Management: Simple febrile seizure: generalized <15 minutes, single in 24h, age 6 months–5 years, no postictal deficit. No workup needed if child returns to baseline; treat underlying infection. Complex: focal, >15 minutes, or recurrent within 24h – need EEG, neuroimaging, and LP if meningeal signs. No long-term anticonvulsants; antipyretics do not prevent recurrence. Status epilepticus: benzodiazepine (lorazepam 0.1 mg/kg IV or diazepam 0.5 mg/kg PR), then fosphenytoin 20 mg/kg PE IV.
• Congenital Heart Disease: Cyanotic vs Acyanotic: Acyanotic: VSD (most common, holosystolic murmur at LLSB), ASD (fixed split S2), PDA (continuous machinery murmur, treat with indomethacin/ibuprofen in preterm). Cyanotic: Tetralogy of Fallot (RVH, overriding aorta, VSD, PS – treat hypercyanotic spell with knee-chest, oxygen, morphine, propranolol), Transposition of Great Arteries (cyanosis unresponsive to O2, need prostaglandin E1 to maintain PDA, then arterial switch).
• Childhood Immunization Schedule (CDC): Birth: HepB. 2 months: HepB, DTaP, IPV, Hib, PCV13, RV. 4 months: same as 2mo. 6 months: HepB, DTaP, IPV, Hib, PCV13, RV, influenza (annual). 12–15 months: MMR, varicella, Hib, PCV13, HepA. 4–6 years: DTaP, IPV, MMR, varicella. Contraindications: anaphylaxis to previous dose or component; live vaccines (MMR, varicella) contraindicated in severe immunodeficiency (e.g., HIV with low CD4).
• Acute Otitis Media Diagnosis and Treatment: Diagnosis: acute onset of ear pain/fever plus bulging tympanic membrane with erythema and reduced mobility (pneumatic otoscopy). First-line: amoxicillin 80–90 mg/kg/day divided BID for 10 days (or 5–7 days if ≥6 years and mild). If amoxicillin failure (no improvement in 48–72h) or recent antibiotic use: amoxicillin-clavulanate 90 mg/kg/day. Severe illness (toxic, high fever, bilateral in <2 years): same as failure. Tympanostomy tubes for recurrent AOM (≥3 episodes in 6 months or ≥4 in 12 months).

Common Traps in Pediatrics Questions

• Assuming all febrile infants <3 months need a full sepsis workup; use Rochester criteria to risk-stratify 29–60 day olds.
• Prescribing antibiotics for bronchiolitis; it's viral and supportive care only unless secondary bacterial infection is confirmed.
• Giving aspirin to a child with viral illness (influenza, varicella) due to Reye syndrome risk; use acetaminophen or ibuprofen instead.
• Forgetting to check a urine culture in a febrile infant with no source; UTI is common and often missed on dipstick alone.
• Starting empiric antibiotics for Kawasaki disease; it's inflammatory, not infectious—IVIG and aspirin are the treatments.
• Misclassifying a simple febrile seizure as complex because the child had a fever; always check duration and focality.

How to Revise Pediatrics for the USMLE Step 2 CK

Focus on age-specific decision-making: neonates (0–28 days) always get a full sepsis workup and admission, while older infants can be risk-stratified. Master the CDC immunization schedule and know contraindications cold. For respiratory cases, differentiate bronchiolitis (RSV, supportive care) from asthma (wheeze, response to bronchodilators). Practice calculating dehydration percentages and fluid bolus volumes quickly. For congenital heart disease, memorize the five cyanotic lesions (5 T's: Tetralogy, TGA, Truncus, Tricuspid atresia, TAPVR) and their murmur characteristics. Questions often present a child with fever and a rash; know the viral exanthems (measles, rubella, roseola, erythema infectiosum) and their associated complications. Review the AAP guidelines for UTI diagnosis (clean catch, bag vs catheter) and treatment duration. Prioritize the NRP algorithm (PALS for older children) and be able to interpret ABGs in respiratory distress. Practice vignettes that require you to choose the next best step from a list of tests or treatments, not just the diagnosis.

Practise it: MedLumen has 50 Pediatrics questions for the USMLE Step 2 CK, each with a full explanation and references.