317.1 🎓 醫孞生版

317.1.0.1 📌 䞀頁重點

317.1.0.1.1 Definition + Epidemiology
317.1.0.1.1.1 CAP
  • Pneumonia acquired outside hospital OR within 48 hours of admission
  • Excludes recent hospitalization, nursing home (used to be HCAP — now subset of CAP per 2019 IDSA)
317.1.0.1.1.2 Epidemiology
  • 5-10 cases per 1,000 adults annually
  • Increasing with age
  • Mortality: outpatient < 1%, hospitalized 5-15%, ICU 20-50%
  • Top infectious cause of death globally
317.1.0.1.1.3 Risk Factors
  • Age > 65
  • Chronic diseases (COPD, asthma, HF, DM, CKD, immunocompromised)
  • Smoking + alcohol
  • Aspiration risk
  • Recent viral URI
  • Crowding (military, prison, dormitories)
317.1.0.1.2 Pathogens
317.1.0.1.2.1 Common Bacterial
  • Streptococcus pneumoniae (most common bacterial, ~ 30-50%)
  • Mycoplasma pneumoniae (young, atypical)
  • Chlamydia pneumoniae (atypical)
  • Legionella pneumophila (water-borne, severe)
  • Haemophilus influenzae
  • Moraxella catarrhalis
  • Staphylococcus aureus (post-influenza, IVDU)
  • Klebsiella pneumoniae (alcoholic, currant jelly sputum)
  • Mixed bacterial + viral
317.1.0.1.2.2 Viral (Increasingly Recognized with Molecular Testing)
  • Influenza A/B
  • Respiratory Syncytial Virus (RSV)
  • COVID-19 / SARS-CoV-2
  • Rhinovirus
  • Adenovirus
  • Parainfluenza
  • Metapneumovirus
317.1.0.1.2.3 Other
  • Anaerobes (aspiration risk)
  • Tuberculosis (atypical presentation; need exclude)
  • Endemic fungi (Histoplasma, Coccidioides, Blastomycosis)
  • Pneumocystis jirovecii (PCP) (HIV, immunocompromised)
317.1.0.1.2.4 Risk-Based Pathogen Considerations
  • Alcohol: Klebsiella, anaerobes, S. pneumoniae
  • Post-influenza: S. aureus (esp MRSA), S. pneumoniae
  • COPD: H. influenzae, Moraxella, S. pneumoniae
  • Aspiration: anaerobes, GNR, S. aureus
  • Cystic fibrosis: Pseudomonas, S. aureus
  • HIV: PCP, S. pneumoniae, M. tuberculosis, H. influenzae
  • IVDU: S. aureus, anaerobes
  • Animal exposure: Coxiella (Q fever, livestock), Francisella (rabbits, tularemia), Chlamydia psittaci (birds, psittacosis)
317.1.0.1.3 Clinical Presentation
317.1.0.1.3.1 Classic Symptoms
  • Fever, chills
  • Productive cough
  • Pleuritic chest pain
  • Dyspnea
  • Tachycardia, tachypnea
317.1.0.1.3.2 Atypical Pneumonia (“Walking Pneumonia”)
  • Mycoplasma, Chlamydia, Legionella, virus
  • Dry cough
  • Headache, myalgia, sore throat
  • Less leukocytosis
  • Extrapulmonary symptoms (Legionella: GI, hepatic, renal, neurologic)
  • More gradual onset
317.1.0.1.3.3 Severe / ICU Features
  • Septic shock
  • Respiratory failure requiring NIV/ventilation
  • Multi-lobar / bilateral infiltrates
317.1.0.1.4 Diagnosis
317.1.0.1.4.1 Clinical + Radiographic
  • CXR: infiltrate (consolidation, ground-glass, bronchopneumonia)
  • CT chest: better for ILD, abscess, mass; PCP, cavitation
  • Ultrasound: bedside; consolidation, effusion
317.1.0.1.4.2 Laboratory
  • CBC + differential
  • BMP, LFTs
  • Blood cultures × 2 (for severe, high-risk)
  • Sputum Gram + culture (good quality + before antibiotics)
  • Urine antigens: pneumococcal, Legionella
  • Procalcitonin (bacterial vs viral; stewardship)
  • Multiplex respiratory PCR: viral panel + atypicals
  • COVID-19 PCR / antigen
  • HIV testing (in selected high-risk)
  • Lactate, ABG (severity)
317.1.0.1.4.3 Severity Scoring

CURB-65: - Confusion - Urea > 7 mmol/L (BUN > 19 mg/dL) - Respiratory rate ≥ 30 - BP < 90/60 - 65 = age ≥ 65 - Score 0-1: outpatient - 2: short hospital stay or close observation - ≥ 3: hospitalize; consider ICU at ≥ 4

PSI (Pneumonia Severity Index): - 20-variable score; complex - Class I-V - More accurate than CURB-65 for low risk

SMART-COP: - Predicts need for intensive respiratory or vasopressor support - Useful for severity stratification

IDSA/ATS Severe CAP Criteria (2019):

Major (any 1 = severe): - Mechanical ventilation - Septic shock requiring vasopressors

Minor (≥ 3 = severe): - RR ≥ 30 - PaO2/FiO2 ≀ 250 - Multilobar infiltrates - Confusion - Uremia (BUN ≥ 20) - Leukopenia - Thrombocytopenia - Hypothermia - Hypotension requiring aggressive fluid

317.1.0.1.5 Treatment — IDSA/ATS 2019 + 2024 Updates
317.1.0.1.5.1 Outpatient (Healthy, No Comorbidities)

First-Line: - Amoxicillin 1 g PO TID (high-dose for S. pneumoniae) - OR - Doxycycline 100 mg PO BID - OR - Macrolide (azithromycin, clarithromycin) — only if local resistance < 25%

317.1.0.1.5.2 Outpatient (Comorbidities: COPD, DM, CKD, HF, malignancy, alcohol, asplenia)

Options: - Combination: amoxicillin-clavulanate OR cephalosporin (cefuroxime, cefpodoxime) + macrolide OR doxycycline - Monotherapy: respiratory fluoroquinolone (levofloxacin, moxifloxacin, gemifloxacin)

317.1.0.1.5.3 Inpatient Non-ICU

First-Line: - Combination: - β-lactam (ceftriaxone, cefotaxime, ampicillin-sulbactam) + macrolide (azithromycin) OR - β-lactam + doxycycline (if macrolide CI) - Monotherapy: - Respiratory fluoroquinolone (levofloxacin, moxifloxacin)

317.1.0.1.5.4 ICU Treatment

First-Line: - β-lactam (ceftriaxone, cefotaxime, ampicillin-sulbactam) + macrolide (azithromycin) OR - β-lactam + respiratory fluoroquinolone

Pseudomonas Risk (severe COPD, structural lung, recent antibiotics): - Anti-pseudomonal β-lactam (piperacillin-tazobactam, cefepime, ceftazidime, imipenem, meropenem) + macrolide OR - Anti-pseudomonal β-lactam + fluoroquinolone (ciprofloxacin or levofloxacin)

MRSA Risk (recent influenza, IVDU, recent hospitalization): - Add vancomycin or linezolid

317.1.0.1.5.5 Severe CAP — 2024 Updates

Adjunctive Corticosteroids (CAPE COD 2023): - N = 800 severe CAP (mechanical ventilation OR high-flow + FiO2 ≥ 0.5) - Hydrocortisone 200 mg/d × 4-8 days - ↓ 28-day mortality (6.2% vs 11.9%) - Now Class IIa in selected severe CAP - Caution: viral CAP (especially influenza), hyperglycemia, immunocompromised

317.1.0.1.5.6 Specific Pathogens

Legionella: - Severe + atypical - Azithromycin OR levofloxacin × 7-14 days - Urinary antigen for serogroup 1 (70%)

Mycoplasma + Chlamydia (atypicals): - Macrolide or doxycycline or fluoroquinolone

S. aureus / MRSA: - Vancomycin or linezolid

Pseudomonas: - Anti-pseudomonal β-lactam (combo with aminoglycoside or fluoroquinolone)

Influenza Co-Infection: - Oseltamivir within 48 hours - May benefit even after 48 hours in severe

COVID-19: - Dexamethasone 6 mg × 10 days (RECOVERY) if requires O2 - Remdesivir - Tocilizumab/baricitinib for severe (REMAP-CAP) - Anticoagulation

317.1.0.1.5.7 Duration
  • Most CAP: 5 days (if clinically improving by day 3-5, afebrile 48 hours)
  • Severe / complicated: 7-14 days
  • Legionella: 7-14 days
  • S. aureus or Pseudomonas: 14+ days
  • Procalcitonin-guided: helps shorten duration
317.1.0.1.6 Adjunctive + Supportive
317.1.0.1.6.1 Oxygen Therapy
  • Maintain SpO2 88-92% (COPD) or 94-98% (others)
  • HFNC for hypoxemic RF
317.1.0.1.6.2 Mechanical Ventilation
  • For respiratory failure
  • Lung-protective if ARDS develops
317.1.0.1.6.3 Vasopressors
  • Norepinephrine first-line in septic shock
317.1.0.1.6.4 IV Fluids
  • Initial resuscitation in shock
317.1.0.1.6.5 Adjunctive Steroids
  • Severe CAP (CAPE COD 2023)
  • Hydrocortisone 200 mg/d
317.1.0.1.6.6 DVT Prophylaxis
317.1.0.1.6.7 Nutrition + Glycemic Control
317.1.0.1.7 Outcomes + Follow-Up
317.1.0.1.7.1 Failure to Improve
  • Within 72 hours
  • Causes:
    • Wrong organism
    • Resistance
    • Complication (empyema, abscess)
    • Wrong diagnosis (PE, malignancy, ILD)
  • Re-evaluate clinically + imaging + cultures
317.1.0.1.7.2 Treatment Response Monitoring
  • Clinical: vital signs, oxygenation, mental status, leukocyte count
  • Imaging follow-up: 4-6 weeks for resolution (older patients may take longer)
  • Mortality: 28-day or 1-year
317.1.0.1.7.3 CAP Complications
  • Pleural effusion (parapneumonic) → empyema
  • Lung abscess
  • Bacteremia / sepsis
  • Cardiac (MI, AF — increased risk during CAP)
  • ARDS
317.1.0.1.8 Prevention
317.1.0.1.8.1 Vaccinations (2024 Updated)

Pneumococcal (CDC 2023-2024): - PCV20 (Prevnar 20): single dose for adults ≥ 19 with high-risk OR ≥ 65 - PCV15 (Vaxneuvance) + PPSV23 (Pneumovax 23): alternative; PPSV23 ≥ 1 year after PCV15 - For immunocompromised: PCV20 + PPSV23

Influenza: annual

COVID-19: annual + boosters

RSV (2023 NEW): - Adults ≥ 60 + risk factors - Two products: Arexvy (GSK), Abrysvo (Pfizer)

Pertussis (Tdap): every 10 years

317.1.0.1.8.2 Smoking Cessation
  • Major modifiable RF
317.1.0.1.8.3 Alcohol Reduction
317.1.0.1.9 Special Populations
317.1.0.1.9.1 Elderly
  • Atypical presentations (confusion, falls without fever)
  • Higher mortality
  • Aspiration risk
  • Pneumococcal + RSV vaccines particularly important
317.1.0.1.9.2 Immunocompromised
  • Wider pathogen consideration (PCP, fungal, mycobacterial)
  • Bronchoscopy + BAL for diagnosis often needed
  • Specific treatment
317.1.0.1.9.3 Pregnancy
  • Influenza vaccination + treatment important (severe in pregnancy)
  • COVID-19 vaccination
  • Avoid teratogenic antibiotics (e.g., tetracyclines, fluoroquinolones)

317.1.0.2 🩺 床邊速查

  • CURB-65 ≥ 2: hospitalize; ≥ 4: ICU
  • Outpatient healthy: amoxicillin OR doxycycline OR macrolide
  • Inpatient non-ICU: β-lactam + macrolide OR fluoroquinolone
  • ICU: β-lactam + macrolide OR β-lactam + fluoroquinolone
  • Pseudomonas risk: anti-pseudomonal β-lactam + aminoglycoside / fluoroquinolone
  • MRSA risk (post-flu, IVDU): vanc / linezolid
  • Severe CAP: hydrocortisone 200 mg/d (CAPE COD 2023)
  • Duration: 5-7 days typical
  • Vaccines 2024: PCV20, RSV ≥ 60 + risk factors