Community Acquired Pneumonia (CAP) - Diagnosis and Management



Pneumonia Signs/Symptoms:

 • Confusion/disorientation (LR + 1.9)

 • Cough

 • Dyspnea

 • Pleuritic chest pain (LR + NS)

 • Cachexia (LR + 4.0)



Physical Examination:

 • Temperature > 38.0°C or < 35.1°C (LR + 2.2)

 • Tachypnea with respirations of 30/min or greater (LR + 2.7)

 • Hypoxia with pulse oximetry < 95% (LR + 3.1)

 • Auscultatory findings of pneumonia

 • Heart rate > 100/min (LR + 1.8)

 • Rales/Crackles (LR + 2.3)

 • Rhonchi/Wheezing (LR + 0.8)

 • Dullness of percussion (May appear after day 4 of hospitalization) (LR+ 3.0)

 • Bronchial breath sounds (LR + 3.3)

 • Egophony (May appear 1-3 days after hospitalization) (LR + 4.1)

 • Newly required mechanical ventilation by either intubation or noninvasive ventilation.

 • PaO2/FiO2 ratio ≤250

 • Hypotension requiring aggressive fluid resuscitation



Labs:

 • Total white blood cell count > 10/μL or < 4.5/μL

 • Bands > 15%

 • Uremia (blood urea nitrogen level ≥ 20 mg/dl)

 • Leukopenia (white blood cell count < 4,000 cells/μl)

 • Thrombocytopenia (platelet count < 100,000/μl)



Imaging:

 • New or increasing infiltrate by chest radiograph or CT Scan



Bacterial Pathogens:

 • Streptococcus pneumoniae

 • Haemophilus influenzae

 • Mycoplasmapneumoniae

 • Staphylococcus aureus

 • Legionella species

 • Chlamydia pneumoniae

 • Moraxella catarrhalis

Consider Multidrug-Resistant Organisms (MDRO):

 • Methicillin-resistant S. aureus (MRSA)

 • Pseudomonas aeruginosa



Clinical Prediction Rules:

Pneumonia Severity Index (PSI) (strong recommendation, moderate quality of evidence) over the CURB-65 (low quality of evidence)

 • PSI

 • CURB-65



Predictors of Mortality:

 • Hypotension (LR+ 7.6)

 • Hypothermia (LR + 3.5)

 • HR >100/min (LR + 2.1)

 • RR> 30/min (LR + 2.1)

 • Oxygen < 90% (LR + 2.8)



Testing:

 • Pretreatment Gram stain and culture: Obtain in severe CAP or treated for MDRO or previous PNA with MDRO (MRSA/Pseudomonas)

 • Severe CAP: 

	- Blood cultures

	- Urine for pneumococcal antigen, Legionella antigen

 • Yield of blood CX is low ranging from 2% (outpatients) to 9% (inpatients)

 • MRSA Nares screening: High negative predictive value: RESPIRATORY 96.1%

 • Empiric antibiotic therapy should be initiated in adults with clinically suspected and radiographically confirmed CAP regardless of initial serum procalcitonin level



Treatment:

 • Non-severe Inpatient Pneumonia: β-Lactam + macrolide or respiratory fluoroquinolone

 • Severe Inpatient Pneumonia: β-Lactam + macrolide or β-lactam + fluoroquinolone

 • Prior Respiratory Isolation of MRSA: Add MRSA coverage and obtain cultures/nasal PCR to allow de-escalation or confirmation of need for continued therapy

 • Prior Respiratory Isolation of Pseudomonas Aeruginosa: Add coverage for P. aeruginosa and obtain cultures to allow de-escalation or confirmation of need for continued therapy



Ref: https://doi.org/10.1164/rccm.201908-1581ST



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