Key Points
- Stabilize ABCs; begin targeted evaluation without delaying life-saving therapy.
- Use system-specific risk tools to guide testing and disposition.
- Order high-yield tests first; escalate imaging when indicated.
- Start evidence-based initial therapy and reassess frequently.
Algorithm
- Primary survey and vitals; IV access and monitors.
- Focused history/physical; identify red flags and likely etiologies.
- Order system-appropriate labs and imaging (see Investigations).
- Initiate guideline-based empiric therapy (see Pharmacology).
- Reassess response; arrange consultation and definitive management.
Clinical Synopsis & Reasoning
CAP diagnosis rests on compatible symptoms plus new infiltrate on chest imaging; integrate epidemiology and exposures to refine atypical and resistant pathogen risk. Use PSI or CURB‑65 to guide site of care and adjunctive testing. Consider aspiration, viral etiologies, and complications (effusion, empyema) when clinical course deviates from expected.
Treatment Strategy & Disposition
Start guideline‑concordant empiric antibiotics tailored to comorbidities and local resistance, avoid unnecessary MRSA/Pseudomonas coverage, and transition to oral therapy after clinical stability. Provide supplemental oxygen to maintain SpO₂ targets, treat sepsis physiology when present, and encourage early mobilization. Arrange follow‑up for clinical reassessment and pneumococcal/influenza vaccination; admit if hypoxemic, unstable, or high risk by PSI/CURB‑65.
Epidemiology / Risk Factors
- Immunosuppression, devices; recent hospitalization
Investigations
| Test | Role / Rationale | Typical Findings | Notes |
|---|---|---|---|
| CBC | Inflammation/infection | Leukocytosis/leukopenia | |
| Lactate | Hypoperfusion | Elevated | Trend |
| Blood cultures | Pathogen ID | Positive/negative | Before antibiotics if feasible |
Common Outpatient Regimens
| Setting | Regimen | Notes |
|---|---|---|
| Healthy adult | Amoxicillin high dose OR doxycycline | Add macrolide only in atypical-predominant regions |
| Comorbidities | Amox/clav OR cefuroxime + azithro/ doxy | Fluoroquinolone monotherapy alternative |
| Severe beta-lactam allergy | Respiratory fluoroquinolone | Use stewardship safeguards |
Pharmacology
| Medication | Mechanism | Onset | Role in Therapy | Limitations |
|---|---|---|---|---|
| Ceftriaxone + azithro | β-lactam + macrolide | Hours | Non-severe inpatient | QT; biliary sludging; ED use |
| Doxycycline | 30S ribosomal inhibition | Hours | Outpatient alternative/atypical coverage | Photosensitivity; avoid pregnancy; ED use |
| Amox/clav or cefuroxime + azithro | β-lactam ± macrolide | Hours | Comorbid outpatient | GI upset; QT with macrolides; ED use |
| Amoxicillin (high dose) | Cell-wall inhibition | Hours | Healthy outpatient first-line | Allergy; ED use |
| Levofloxacin | DNA gyrase inhibition | Hours | Monotherapy in select cases | Tendinopathy; QTc; ED use |
Prognosis / Complications
- Depends on host and source control; sepsis/organ failure risk
Patient Education / Counseling
- Explain red flags and when to seek emergent care.
- Reinforce medication adherence and follow-up plan.
Notes
Avoid routine corticosteroids. Consider coverage for MRSA/Pseudomonas only with specific risk factors (prior isolation, recent IV antibiotics, severe disease).