Pulmonology / Infectious Disease
Community-Acquired Pneumonia (Adult)
Acute lower respiratory tract infection acquired outside hospital; severity drives site of care and antibiotic choice.
J18.9
J15.9
J13
Reviewed 2026-09-12- SpO2 < 90% on room air, RR ≥ 30, SBP < 90 mmHg → resuscitation bay, consider ICU
- Septic shock requiring vasopressors or need for mechanical ventilation = severe CAP (major ATS/IDSA criterion)GRADE 1A
- New confusion, urea > 7 mmol/L, multilobar infiltrates → admit
- Start O2 to target SpO2 92–96% (88–92% if COPD/hypercapnia)
- Chest X-ray PA/lateral — gold standard for diagnosisGRADE 1A
- CBC, BMP, urea, lactate, procalcitonin (adjunct, not to withhold antibiotics)
- Blood + sputum cultures if severe CAP or prior MRSA/PseudomonasGRADE 1B
- Urinary pneumococcal & Legionella antigen in severe CAP
- SARS-CoV-2 / influenza PCR during respiratory season
CURB-65
0–1 outpatient · 2 consider admission · ≥3 inpatient, assess ICU
PSI / PORT
Class I–II outpatient · III observation · IV–V inpatient
- Outpatient, no comorbidities: amoxicillin OR doxycyclineGRADE 1B
- Inpatient non-severe: β-lactam + macrolideGRADE 1A
- Severe CAP: β-lactam + macrolide; add MRSA/Pseudomonas cover only if risk factorsGRADE 1B
Amoxicillin
PO
- Adult
- 1 g TID
- Renal
- CrCl 10–30: 500 mg BID–TID; <10: 500 mg daily
- Duration
- 5 days (min), afebrile 48 h
Ceftriaxone
IV
- Adult
- 1–2 g q24h
- Renal
- No adjustment
- Duration
- 5–7 days
Azithromycin
IV/PO
- Adult
- 500 mg daily
- Renal
- No adjustment; caution CrCl < 10
- Duration
- 3 days
10/kg
- Severe β-lactam allergy: respiratory fluoroquinolone (levofloxacin 750 mg daily)GRADE 1A
- Pregnancy: avoid doxycycline & fluoroquinolones; ceftriaxone + azithromycin preferred
- MRSA risk: add vancomycin (AUC-guided) or linezolid 600 mg q12h
- Pseudomonas risk: piperacillin-tazobactam 4.5 g q6h or cefepime 2 g q8h
- Non-response at 72 h: re-image, assess empyema, resistant organism, alternative diagnosis
- Vitals q4h; SpO2 continuous if on O2
- Expect defervescence in 48–72 h; cough may persist 2–6 weeks
- Complications: parapneumonic effusion/empyema, ARDS, sepsis, AKI
- Discharge when clinically stable ≥ 24 h (HR ≤ 100, RR ≤ 24, SBP ≥ 90, SpO2 ≥ 90%, eating)
- Follow-up CXR at 6–8 weeks only if > 50 yrs smoker or persistent symptoms
- guidelineDiagnosis and Treatment of Adults with CAP — ATS/IDSA, 2019
- trialCAP-START: β-lactam monotherapy vs combinations — NEJM, 2015
- trialPTC trial: 3 vs 8 days β-lactam — Lancet, 2021
- fda labelCeftriaxone for injection — prescribing information — DailyMed, 2024
Decision support only. Verify against local protocols and current labeling.