What is the initial workup and treatment for pneumonia in the emergency department?

Emergency Department Workup and Treatment for Community-Acquired Pneumonia

Initial Risk Stratification and Disposition Decision

Use the Pneumonia Severity Index (PSI) as an adjunct to clinical judgment to determine whether the patient requires hospitalization or can be safely treated as an outpatient. 1

Step 1: Assess for Immediate Hospitalization Criteria

Before calculating any risk score, hospitalize immediately if any of the following are present: 1

• Severe hemodynamic instability
• Acute hypoxemia (PO2 <60 mm Hg or O2 saturation <90% on room air) 1
• Inability to take oral medications
• Active coexisting conditions requiring hospitalization
• Severe social/psychiatric problems compromising home care 1

Step 2: Calculate PSI Risk Class

For patients without immediate hospitalization criteria, calculate the PSI to stratify mortality risk: 1

• Risk Class I-II: Consider outpatient treatment
• Risk Class III: Consider brief observation or outpatient treatment with close follow-up
• Risk Class IV-V: Hospitalize for traditional inpatient care 1

The PSI has been validated in multiple studies and significantly increases appropriate outpatient management of low-risk patients without compromising outcomes. 1

Step 3: Identify Need for ICU Admission

Use the 2007 IDSA/ATS severe CAP criteria to determine ICU need, as patients mis-triaged to regular wards experience higher mortality: 1

Major criteria (1 required for ICU):

• Requiring invasive mechanical ventilation
• Septic shock requiring vasopressors

Minor criteria (3 or more required for ICU): 1

• Respiratory rate ≥30 breaths/min
• PaO2/FiO2 ratio ≤250
• Multilobar infiltrates
• Confusion/disorientation
• Uremia (BUN ≥20 mg/dL)
• Leukopenia (WBC <4,000 cells/mm³)
• Thrombocytopenia (platelets <100,000/mm³)
• Hypothermia (core temperature <36°C)
• Hypotension requiring aggressive fluid resuscitation

Diagnostic Workup

Outpatient Setting

• Chest radiograph: Required to confirm pneumonia diagnosis 2
• No routine laboratory testing or microbiological studies needed for healthy outpatients without comorbidities 2

Hospitalized Patients (Non-ICU)

• Chest radiograph 2
• Blood cultures (before antibiotics) 1
• Sputum Gram stain and culture (if adequate sample obtained) 1
• Complete blood count, basic metabolic panel 2
• Urine pneumococcal antigen test for patients admitted due to illness severity 1
• Urine Legionella antigen test (serogroup 1) for severe cases or when clinically/epidemiologically suspected 1

ICU Patients

All of the above, plus: 1

• Arterial blood gas
• Serum lactate 2
• Consider molecular tests for influenza and respiratory syncytial virus during winter season 1
• Consider PCR for atypical pathogens if results can be obtained rapidly enough to guide therapy 1

Important caveat: Serology for M. pneumoniae, C. pneumoniae, and Legionella is more useful for epidemiological studies than individual patient management and should not be the only diagnostic test if atypical pathogens are suspected. 1

Empiric Antibiotic Treatment

Antibiotic treatment must be initiated immediately after diagnosis, ideally while still in the emergency department, as delays are associated with increased mortality. 1, 3

Healthy Outpatients (No Comorbidities, No Recent Antibiotics)

First-line options: 1, 3

• Amoxicillin 1 g three times daily (preferred) 1, 3
• Doxycycline 100 mg twice daily (alternative; consider 200 mg first dose) 1, 3
• Macrolide (azithromycin 500 mg day 1, then 250 mg daily OR clarithromycin 500 mg twice daily) ONLY if local pneumococcal macrolide resistance is <25% 1

Critical pitfall: Macrolide resistance in S. pneumoniae ranges 30-40% in many areas and often co-exists with beta-lactam resistance, particularly in patients with recent hospitalization or antibiotic exposure. 3

Outpatients with Comorbidities

Comorbidities include: chronic heart, lung, liver, or renal disease; diabetes mellitus; alcoholism; malignancy; asplenia; or recent antibiotic use. 1

Recommended regimens: 1, 3

• Combination therapy: Amoxicillin/clavulanate (875 mg/125 mg twice daily OR 2,000 mg/125 mg twice daily) OR cephalosporin (cefpodoxime 200 mg twice daily OR cefuroxime 500 mg twice daily) PLUS macrolide (azithromycin or clarithromycin) 1
• Monotherapy alternative: Respiratory fluoroquinolone (levofloxacin 750 mg daily OR moxifloxacin 400 mg daily) 3

Fluoroquinolone consideration: Despite FDA warnings about adverse events, fluoroquinolones remain justified for this population due to excellent performance, low resistance rates, coverage of typical and atypical organisms, and convenience of monotherapy. However, reserve for patients with beta-lactam allergies when possible to prevent resistance. 3

Hospitalized Non-ICU Patients

Standard regimen: 1, 3

• Beta-lactam (ceftriaxone 1-2 g every 24 hours OR cefotaxime 1-2 g every 8 hours OR ampicillin-sulbactam 1.5-3 g every 6 hours) PLUS macrolide (azithromycin 500 mg daily OR clarithromycin 500 mg twice daily) 1

Alternative monotherapy: 1, 3

• Respiratory fluoroquinolone alone (levofloxacin 750 mg daily OR moxifloxacin 400 mg daily) 1

Route of administration: Start with intravenous antibiotics for hospitalized patients, then switch to oral when clinically improved and afebrile for 24 hours. 3

Severe CAP/ICU Patients

For patients WITHOUT Pseudomonas risk factors: 1

• Beta-lactam (ceftriaxone 2 g every 24 hours OR cefotaxime 2 g every 8 hours) PLUS EITHER macrolide (azithromycin 500 mg daily) OR respiratory fluoroquinolone (levofloxacin 750 mg daily OR moxifloxacin 400 mg daily) 1

For patients WITH Pseudomonas risk factors: 1, 3

Risk factors include: structural lung disease (bronchiectasis, COPD), recent hospitalization, recent broad-spectrum antibiotic use. 3

• Antipseudomonal beta-lactam (piperacillin-tazobactam 4.5 g every 6 hours OR cefepime 2 g every 8 hours OR meropenem 1 g every 8 hours) PLUS EITHER:
  • Ciprofloxacin 400 mg IV every 8 hours OR levofloxacin 750 mg daily 1
  • OR Aminoglycoside (gentamicin, tobramycin, or amikacin) PLUS azithromycin 500 mg daily 1

For suspected MRSA: 3

• Add vancomycin 15-20 mg/kg every 8-12 hours OR linezolid 600 mg every 12 hours 3
• Risk factors: prior MRSA infection, recent hospitalization, recent antibiotic use, injection drug use 3

Duration of Therapy

Treatment should generally not exceed 8 days in a responding patient. 1

Minimum duration is 5 days, provided the patient: 3, 4

• Is afebrile for 48-72 hours
• Has no more than one sign of clinical instability
• Can take oral medications
• Has normal mentation

Extended duration (14-21 days) required for: 3

• Legionella pneumonia 1
• Staphylococcal pneumonia 3
• Gram-negative enteric bacilli 3
• Pathogens causing pulmonary necrosis 1

Biomarkers, particularly procalcitonin, may guide shorter treatment duration in responding patients. 1

Common Pitfalls to Avoid

• Do not rely solely on PSI: Clinical judgment must supersede the score when social factors, comorbidities, or clinical instability suggest hospitalization is safer. 1, 5
• Do not delay antibiotics: The first dose should be administered in the ED; delays increase mortality, particularly in severe pneumonia. 1, 3
• Do not use macrolide monotherapy in areas with high resistance: Pneumococcal macrolide resistance exceeds 25% in most U.S. regions. 1, 3
• Do not overuse fluoroquinolones: Reserve for specific indications to prevent resistance development. 3
• Do not forget atypical coverage: Inadequate coverage for Mycoplasma, Chlamydophila, and Legionella leads to treatment failure. 3
• Do not continue antibiotics beyond clinical stability: Adjust therapy based on culture results and discontinue when criteria are met to avoid unnecessary prolonged therapy. 3