Step 3 CCS: Pneumonia

Community-acquired pneumonia is a bread-and-butter CCS case. You must risk-stratify using CURB-65 or PSI, select appropriate empiric antibiotics based on severity and setting, and recognize deterioration to sepsis or ARDS. Choosing the wrong antibiotic class or failing to reassess at 48-72 hours is a common scoring trap.

Clinical Approach — What Attendings Do First

The First Minute

  • Supplemental O2 to maintain SpO2 ≥92% (titrate via nasal cannula → Venturi mask → high-flow)
  • Chest X-ray PA and lateral — confirm infiltrate and check for pleural effusion
  • Blood cultures x2 from separate sites BEFORE antibiotics
  • Sputum Gram stain and culture if productive cough
  • Continuous pulse oximetry

Key Orders

  • CBC with differential, BMP, lactate, procalcitonin
  • Ceftriaxone 1g IV q24h + azithromycin 500 mg IV q24h (or levofloxacin 750 mg IV q24h)
  • Normal saline 500 mL bolus if hypotensive or lactate elevated
  • Incentive spirometry q1h while awake
  • Pneumococcal and Legionella urinary antigens for severe CAP or ICU patients
  • ABG if SpO2 <90% or clinical deterioration
  • DVT prophylaxis: enoxaparin 40 mg SQ daily

Time-Sensitive Actions

  • Antibiotics within 1 hour of presentation for sepsis, within 4 hours for non-severe CAP
  • If lactate >4 mmol/L or refractory hypotension → 30 mL/kg crystalloid bolus, norepinephrine if still hypotensive
  • Repeat chest X-ray at 48-72 hours if not improving — look for empyema, abscess, or wrong diagnosis
  • Step down from IV to PO antibiotics once afebrile x 48h, improving clinically, tolerating PO

Common CCS Pitfalls

  • Using fluoroquinolone monotherapy for ICU-level pneumonia (needs combination therapy)
  • Forgetting to order blood cultures before starting antibiotics
  • Not reassessing at 48-72 hours — CCS expects you to advance clock and check progress
  • Missing parapneumonic effusion on initial imaging — order thoracentesis if significant
  • Failing to switch IV → PO and discharge when criteria met (wasted simulated time)

Frequently Asked Questions

How do I risk-stratify pneumonia on CCS to decide admission vs outpatient?

Use CURB-65: Confusion, Urea >20 mg/dL, Respiratory rate ≥30, Blood pressure <90/60, age ≥65. Score 0-1: outpatient. Score 2: consider admission. Score ≥3: ICU evaluation. On CCS, if the patient meets ICU criteria (bilateral infiltrates, requiring vasopressors, or mechanical ventilation), transfer to ICU immediately.

What antibiotics should I order for inpatient CAP on a CCS case?

Non-ICU floor: ceftriaxone 1g IV daily + azithromycin 500 mg IV daily, OR levofloxacin 750 mg IV daily as monotherapy. ICU admission: ceftriaxone + azithromycin (not fluoroquinolone monotherapy in ICU). Add vancomycin if MRSA risk factors (prior MRSA, cavitary lesion, post-influenza). Switch to PO once afebrile x 48h, improving, and tolerating PO.

When do I order blood cultures and sputum cultures on a CCS pneumonia case?

Order blood cultures x2 (from different sites) and sputum Gram stain/culture BEFORE starting antibiotics in any patient sick enough to admit. Also order procalcitonin (helps distinguish bacterial vs viral), CBC with differential, BMP, lactate, and chest X-ray PA and lateral. Legionella and pneumococcal urinary antigens for ICU-level patients.

Related Organ System Topics

Pulmonology

Pulmonary medicine on USMLE Step 3 includes obstructive and restrictive lung diseases, acute respiratory failure, pulmonary embolism, and pneumonia management.

Infectious Disease

Infectious disease is one of the broadest and highest-yield areas on USMLE Step 3.

Practice Pneumonia CCS Cases

Simulate real CCS cases with our Step 3 interface. Manage pneumonia patients in real time — place orders, advance the clock, and get AI-powered clinical feedback.

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