Pneumonias Lec 4
Pneumonias Lec 4
Pneumonias Lec 4
An infection of the lower respiratory tract in an individual who has not been recently
hospitalized
CAUSES
The single leading cause of community-acquired pneumonia is Streptococcus pneumoniae.
Common organisms are S. pneumoniae, Haemophilus influenzae, Staphylococcus
aureus, Peptostretococcus,Fusobacterium,Bacteroides,Prevotella, Mycoplasma
Parainfluenza Influenza
PATHOPHYSIOLOGY
■Decreased mucociliary clearance of airway (eg, cystic fibrosis, smoking, COPD, elderly)
host defenses.
■Relative/absolute immunosuppression (eg, chronic disease, HIV) susceptibility to
bacterial infection.
■ Hematogenous spread of organism to lung
■ Patients at risk for the above pathophysiologic process are most likely to get pneumonia.
SYMPTOMS/EXAM
Fever, dyspnea, or cough productive of purulent or bloody sputum are most common.
Pleuritic chest pain, tachypnea, and abnormal breath sounds
In the elderly, the presenting complaint may be vague and nonspecific, eg, altered mental
status, poor appetite, or a fall.
DIFFERENTIAL
Hospital-acquired pneumonia: Occurs after at least 5 days of inpatient care and frequently
caused by Pseudomonas, Enterobacter, Legionella, or S. aureus. Also consider pulmonary
embolism, bronchiectasis, bronchitis, CHF.
DIAGNOSIS
Suspect based on clinical presentation
It is not possible to differentiate atypical from typical infections based on clinical criteria.
CXR
Radiographic findings cannot accurately predict the microbial cause, but lobar infiltrates are
more likely due to typical bacterial pathogens and interstitial infiltrates due to atypical
pathogens.
The initial CXR may be negative in patients with significant dehydration.
Microbiological diagnosis is reserved for more seriously ill admitted patients:
Blood cultures: Low yield overall but accurately identifies organism when positive
Sputum Gram stain and culture. Diagnostic sample must have <10 epithelial cells and >25
WBC/hpf. See Table 10.9 for Gram stains of common organisms that cause pneumonia.
Specific culture and antigen testing if Legionella suspected
Pleural fluid evaluation, if present.
TREATMENT
■The Pneumonia Patient Outcomes Research Team (PORT) score can help guide decisions regarding the
Demographic factor
THORAC IC AN D RESPI
Age: men Number of years
DISORDE RS
Age: women Number of years minus 10
RATORY
Nursing home resident 10
Comorbid illnesses
Neoplastic diseaseb 30
Liver diseasec 20
CHFd 10
Cerebrovascular diseasee 10
Renal diseasef 10
Physical examination finding
Altered mental statusg 20
Respiratory rate 30 breaths/min 20
Systolic BP 90 mmHg 20
Temperature 35°C or 40°C 15
Pulse 125 bpm 10
Laboratory or radiographic finding
Arterial pH 7.35 30
BUN 30 mg/dL 20
Sodium 130 meq/L 20
Glucose 250 mg/dL 10
Hematocrit 30% 10
Arterial Po2 60 mmHg 10
Pleural effusion 10
Risk Stratification Based on PORT Score
DISORDE RS
71–90 III 0.9–2.8 Outpatient or brief inpatient
■ Usually asymptomatic, but a small number of cases may develop progressive primary
infection.
■ Latent TB
■ No symptoms of active disease,
hemoptysis
■ Extrapulmonary TB: Sites include lymph node (most common), pleura, genitourinary