What is the initial workup and management for a patient presenting to the emergency department with community-acquired pneumonia (CAP) versus hospital-acquired pneumonia?

Emergency Department Workup and Management: Community-Acquired Pneumonia vs Hospital-Acquired Pneumonia

Critical Distinction

Community-acquired pneumonia (CAP) and hospital-acquired pneumonia (HAP) require fundamentally different approaches in the emergency department, with CAP being the primary focus of ED management since HAP by definition occurs ≥48 hours after hospital admission and would not typically present as a new ED case. 1

Initial Assessment for CAP in the Emergency Department

Severity Assessment Tools

Use objective severity scoring systems immediately upon diagnosis to guide disposition and treatment decisions. 1, 2

• CURB-65 score (Confusion, Uremia, Respiratory rate ≥30, Blood pressure <90 systolic or ≤60 diastolic, age ≥65): Simple bedside tool for rapid risk stratification 1
• Pneumonia Severity Index (PSI): More comprehensive 20-variable prediction rule that identifies low-risk patients (classes I-III) suitable for outpatient management 1, 2
• Modified BTS severity score: Performs best across multiple outcomes including mortality and ICU need 3

Three-Step Disposition Process

Follow this algorithmic approach for every CAP patient: 1, 2

1. Step 1 - Assess contraindications to home care:

   • Severe hemodynamic instability (systolic BP <90 mmHg despite fluids) 1
   • Acute hypoxemia (oxygen saturation <90% on room air) 1, 2
   • Inability to take oral medications 1
   • Active coexisting conditions requiring hospitalization 1

2. Step 2 - Calculate PSI score:

   • Risk classes I-III: Consider outpatient management 1, 2
   • Risk classes IV-V: Hospitalization recommended 1

3. Step 3 - Apply clinical judgment:

   • Frail physical condition 1
   • Severe social/psychiatric problems 1
   • Unstable living situation 1
   • Admission from long-term care facility (high risk for resistant pathogens) 4

Diagnostic Workup in the Emergency Department

For Outpatient Management

Routine investigations including chest radiography are NOT necessary for most patients managed as outpatients. 1

• Pulse oximetry should be performed to assess oxygenation 1
• Microbiological investigations are not routinely recommended 1

For Hospitalized Patients

Obtain the following investigations before antibiotic administration when feasible: 1

• Chest radiograph: Mandatory to confirm pneumonia diagnosis 1
• Pulse oximetry: Essential for all patients 1
• Blood cultures: The evidence is mixed on routine use, but should be obtained in severe CAP or ICU admission 5
• Sputum culture: Consider for patients not responding to empirical therapy or with risk factors for resistant organisms 1
• Point-of-care CRP testing: May improve antibiotic decision-making when available 1
• Complete blood count, basic metabolic panel: For severity assessment and PSI calculation 1

Common pitfall: Blood cultures are frequently obtained but have low yield in non-severe CAP; prioritize them for severe cases or those with specific risk factors. 5

Antibiotic Management in the Emergency Department

Timing of First Dose

Administer the first antibiotic dose while the patient is still in the emergency department. 1, 2, 5

• Target administration within 8 hours of hospital arrival 2
• For patients with severe sepsis, initiate immediately upon diagnosis 1
• Critical caveat: While early administration improves outcomes, the specific 4-hour window previously emphasized lacks strong mortality benefit in non-severe CAP 5

Empirical Antibiotic Selection for CAP

Outpatient Treatment (Low-Risk, PSI I-III)

For previously healthy adults without comorbidities: 2

• First choice: Amoxicillin 1g three times daily 2
• Alternative: Macrolide (azithromycin or clarithromycin) 1

For patients with comorbidities or recent antibiotic use: 2

• Advanced macrolide OR respiratory fluoroquinolone (levofloxacin, moxifloxacin) 1, 2

Non-Severe Inpatient (Medical Ward)

Preferred regimen: β-lactam PLUS macrolide 1, 2

• β-lactam options: Ceftriaxone, cefotaxime, ampicillin-sulbactam, or ceftaroline 1, 2
• Macrolide: Azithromycin or clarithromycin 1, 2, 6
• Alternative: Respiratory fluoroquinolone monotherapy (levofloxacin 750mg daily or moxifloxacin) 1

Severe CAP Requiring ICU Admission

For patients WITHOUT Pseudomonas risk factors: 1, 2

• β-lactam (ceftriaxone, cefotaxime, or ampicillin-sulbactam) PLUS either azithromycin OR respiratory fluoroquinolone 1, 2

For patients WITH Pseudomonas risk factors (structural lung disease, recent hospitalization, recent broad-spectrum antibiotics): 1, 2

• Antipseudomonal β-lactam (piperacillin-tazobactam, cefepime, meropenem, or imipenem) 1, 2
• PLUS ciprofloxacin or levofloxacin 750mg 1, 2
• OR antipseudomonal β-lactam PLUS aminoglycoside PLUS macrolide 1

For suspected MRSA (recent hospitalization, IV drug use, known colonization): 1, 2

• Add vancomycin or linezolid to above regimens 1

Special Pathogen Considerations

Legionella pneumophila: 2, 6

• Preferred: Respiratory fluoroquinolone (levofloxacin) 1, 2
• Alternative: Azithromycin 2, 6

Atypical pathogens (Mycoplasma, Chlamydophila): 2

• Macrolide, doxycycline, or respiratory fluoroquinolone 1, 2

Hospital-Acquired Pneumonia (HAP) Considerations

HAP would not typically present to the ED as a new case, but if a recently discharged patient returns with pneumonia: 4

• High suspicion for resistant organisms including MRSA and Pseudomonas 4
• Risk factors include: admission from long-term care, antibiotic exposure in previous 30 days, COPD 4
• Empirical coverage should be broader than standard CAP regimens 4
• Consider antipseudomonal β-lactam PLUS coverage for MRSA 1

Disposition and Follow-Up

Discharge Criteria from ED/Hospital

Patients can be discharged when they meet ALL of the following for 24 hours: 1, 2

• Temperature ≤37.8°C 1
• Heart rate ≤100 beats/min 1
• Respiratory rate ≤24 breaths/min 1
• Systolic blood pressure ≥90 mmHg 1
• Oxygen saturation ≥90% on room air 1
• Able to maintain oral intake 1

Duration of Therapy

Treat for minimum 5 days, with patient afebrile for 48-72 hours before discontinuation. 1, 2

• Most patients: 5-7 days for responding patients 1, 2
• Longer duration needed for Legionella, S. aureus, or complications 1

Follow-Up

Arrange clinical review at 6 weeks post-treatment: 2

• Chest radiograph if persistent symptoms or high malignancy risk 2
• Pneumococcal and influenza vaccination counseling 2

Common Pitfalls to Avoid

• Over-admission of low-risk patients: Comorbid illness alone does not mandate admission if PSI score is low and patient is clinically stable 7
• Inadequate pathogen coverage: Healthcare-associated risk factors (long-term care, recent antibiotics, recent hospitalization) require broader empirical coverage 4
• Delayed ICU transfer: Patients meeting severe CAP criteria should be admitted directly to ICU rather than medical ward 1
• Premature switch to oral therapy: Ensure hemodynamic stability and clinical improvement before transitioning 1, 2
• Inappropriate antibiotic treatment increases 30-day readmission rates and hospital length of stay 4