Clinical Approach to Pneumonia

Question 1

Pneumonia

Definition

Answer 1

An infection of the pulmonary parenchyma.

Caused by bacteria, viruses, fungi, or parasites.

Question 2

Pneumonitis

Definition

Answer 2

Inflammation of the lungs due to non-infectious causes including chemicals. blood, radiation, or auto-immune etiologies.

Question 3

CAP

Answer 3

Infection of the lung parenchyma in pts who acquire the infection in the community.

Question 4

Nosocomial PNA

Answer 4

• Healthcare-associated PNA (HCAP)
  
  • PNA that occurs in a non-hospitalized pt w/ extensive health care contact including recent hospitalization, nursing home, or other long-term care facility or recent IV therapy.
• Hospital-aquired PNA (HAP)
  
  • PNA that occurs 48 hours or more after hospital admission and was not incubating at the time of admission.
• Ventilator-associated PNA
  
  • PNA that develops more than 48-72 hours after mechanical ventilation was started.
  • Subset of HAP

Question 5

PNA

Pathogenesis

Answer 5

• Pathogens gain access to the lungs
  
  • Aspiration of OP secretions ⇒ most common method
  • Extension of normal flora from sinuses, NP, or OP
  • Direct inhalation of organisms
  • Hematogenous or embolic spread from infected heart valves or venous clots
• Pathogens proliferate at the alveolar level
• Host inflammatory response leads to clinical syndrome of PNA

Question 6

CAP

Epidemiology

Answer 6

• Leading cause of death in children worldwide
• 8th leading cause of death in the US
  
  • 30 day mortality 4-15% in adults needing hospitalization
• 4-10 mil infections in US each year
  
  • > 900k cases in adults ≥ 65 y/o per year
• More likely to occur in winter
• Certain populations are at higher risk
  
  • Age extremes: < 5 or > 65
  • Immunosuppressed
  • Underlying lund disease
  • Alcoholics
  • CHF
  • DM
• Environmental exposures
  
  • Birds, farm animals, bat droppings, wild rodens, freshwater exposures ⇒ ass. w/ less common pathogens

Question 7

PNA

Clinical Presentation

Answer 7

• Most have respiratory sx
  
  • Productive cough and SOB ⇒ most common
  • CP
  • Hemoptysis
• Non-specific sx
  
  • Fever, malaise, myalgias, weight loss
• Timing of sx
  
  • Usually acute in bacterial PNA ⇒ days to weeks
  • Can be subacute to chronic ⇒ TB
• Immunocompromised pts can present atypically
  
  • More indolent course or subacute presentation

Question 8

“Typical” CAP

Characteristics

Answer 8

• S. pneumoniae ⇒ most common cause
  
  • Can start w/ URTI
  • Followed by sudden-onset fever, chills, SOB, CP
    
    • Productive cough w/ rust-colored sputum
    • CXR w/ lobar consolidation
    • Sputum culture + less than half the time
    • Blood cultures may be +
• H. influenzae or Moraxella catarrhalis
• S. aureus ⇒ less common cause (~2%)
  
  • Can have a very virulent course
• Gram-neg. organisms ⇒ E. coli, Pseudomonas, Klebsiella
  
  • Rare in CAP
  • Much more common in HAP

Question 9

Typical CAP

CXR

Answer 9

Question 10

“Atypical” CAP

Characteristics

Answer 10

Dx based on presentation.

• Mycoplasma pneumoniae
  
  • Often in children to young adults = ages 5-35 y/o
  • Often present w/ URT sx
    
    • Pharyngitis or otitis media
  • Dry cough, fever, HA, myalgias, GI sx
  • XR w/ fine interstitial infiltrates
• Chlamydia pneumoniae
• Chlamydia trachomatis ⇒ infants
• Legionella species
  
  • Seen in older individuals or pts w/ medical comorbidities
  • Generally ass. w/ water exposure
• Viral PNA ⇒ RSV or influenza

Question 11

Atypical CAP

CXR

Answer 11

Question 12

Lung Abscess

Characteristics

Answer 12

Area of necrosis and cavitation of the lung following infection.

• Can be single or multiple ⇒ usu. one dominant cavity > 2 cm
• Acute (less than 4-6 wks) vs Chronic
• Primary
  
  • 80% of cases
  • Occurs in absence of underlying pulmonary or systemic condition
  • Usually due to aspiration
  • Mostly caused by anaerobic bacteria + strep from oral cavity
• Secondary
  
  • Occurs in setting of underlying condition (tumor/FB) or systemic process (HIV/immunosuppression)
  • Pathogens include S. auresus, GNR, Nocardia, Legionella, fungal pathogens if immunosuppressed

Question 13

Lung Abscess

Pathophysiology

Answer 13

• Bacteria from aspiration enter the lung
• Host defenses unable to clear pathogen
• Aspiration PNA or pneumonitis develops
• Progress to tissue necrosis in ~ 7-14 days ⇒ abscess

Question 14

CAP

Diagnosis

Answer 14

• Dx based on history and physical exam
  
  • Findings varied
  • Fever, tachypnea, hypoxia but VS may be normal
  • Pulmonary exam ⇒ specific but not sensitive
    
    • Asymmetrical chest expansion
    • Chest wall TTP
    • Dullness to percussion
    • Dec. breath sounds
    • Bronchial breath sounds
    • Egophony
    • Rales or wheezing ⇒ neither sensivity or specific
• CXR is necessary but non-specific
  
  • Opacity / infiltrate
• Sputum culture
  
  • Satisfactory sample
    
    • ↑ PMNs
    • Few epithelial cells
    • Organisms present
  • Causative organism only identified in 50% of PNA cases
    
    • Poor sputum sample
    • Organism poorly staining ⇒ Legionella pneumophila, C. pneumoniae, M. pneumoniae
    • Difficult to culture organism
• Biomarkers
  
  • Procalcitonin ⇒ marker of inflammatory response to bacterial infection
    
    • May be used to support dx but not along in making dx
  • CRP ⇒ non-specific marker of inflammation

Question 15

CAP

Admission Considerations

Answer 15

Inc. mortality risk for a number of factors:

• Age ≥ 65 y/o
• Comorbidities ⇒ DM, CKD, CHF
• AMS
• Abnormal VS
  
  • Tachycardia > 125 bpm
  • Tachypnea > 30 rpm
  • High fever > 38.3-40°C
  • Hypotension SBP < 90 mmHg
  • Hypoxia < spO₂ 90%
• Multi-lobar involvement on CXR
• High-risk organism ⇒ gram-neg species or S. aureus

Question 16

PNA

Scoring Indices

Answer 16

• Heckerling Diagnostic Score
  
  • Based on 5 different exam findings and hx
    
    • Temp, HR, Rales/crackles, dec. BS, hx of asthma
  • 0-1 score argues against PNA
  • 4-5 score strongly suggests PNA
• Pneumonia Severity Index
  
  • Includes 20 variables and complicated to use
• CURB-65
  
  • Based on 5 variables
    
    • AMS, BUN, RR, hypotension, age
  • 3+ ass. w/ inc. risk of death

Question 17

PNA

Antibiotic Treatment

Answer 17

• Start abx ASAP ⇒ inc. mortality risk w/ delays
• Sputum & blood cultures before abx started
• Initial therapy empiric
  
  • Target tx based on risk and local abx resistance patterns
  • Up to 15% of CAP may not respond to initial abx
    
    • Wrong abx d/t resistance or coverage
    • Presence of PNA complication
      
      • Parapneumonic effusion/empyema or lung abscess
  • Should show improvement 2-4 days after starting appropriate therapy

Question 18

PNA

Outpatient Therapy

Answer 18

No recent abx ⇒ Macrolide (Azithromycin) OR doxycycline

Recent abx or comorbidities ⇒ Respiratory fluoroquinolone (e.g. Levofloxacin) OR macrolide + B-lactam (e.g. amoxicillin)

Aspiration PNA ⇒ Amoxicllin-clavulanate OR clindamycin

Influenza with bacterial PNA ⇒ cover MRSA

Question 19

PNA

Inpatient Therapy

Answer 19

Respiratory fluoroquinolone OR macrolide + IV cephalosporin (e.g. Ceftriaxone)

Consider nosocomial exposures and other risk factors and target based on risks.

Question 20

Nosocomial PNA

Epidemiology

Answer 20

• 2nd most common infection in hospitalized pts
• Most common infeciton in ICU
• HAP extends hospital stay by 7-9 days
  
  • Costs > 400k/pt
  • Mortality rate as high as 70%

Question 21

Nosocomial PNA

Pathogenesis

Answer 21

• Change in colonization of OP and stomach w/ virulent “hospital-acquired” pathogens
• Organisms aspirated into LRT
• Gastric colonization w/ gram-neg. organism enhanced by neutral pH
• Mechanical ventilation inc. incidence of pneumonia 6-20x
  
  • Disruption of normal ciliary clearance
  • Impaired cough
  • Biofils serve as bacerial reservoir
• Critical illness, poor nutrition, and immobilization lead to inc. susceptibility

Question 22

Nosocomial PNA

Risk Factors

Answer 22

• Mechanical ventilation
• Supine positioning
• Enteral feeding
• AMS ⇒ CNS disease, level of consciousness, sedation
• Duration of hospitalization
• Use of PPI or other gastric acid suppressants
• Patient factors ⇒ older age, lung disease, severity of illness
• Hospital factors ⇒ hospital staff, transportation, environment

Question 23

Nosocomial PNA

Etiologies

Answer 23

Once pt has been hospital for more than 2-3 days, common causative agents change from CAP to HAP associated:

• S. aureus
• Gram negatives:
  
  • Pseudomonas aeruginosa
  • Enterobacteriaceae ⇒ Klebsiella, Enterobacter, E. coli
  • Acinetobacter species
• Anaerobic organisms
• More concern about resistant organisms

Question 24

Nosocomial PNA

Diagnosis

Answer 24

• Clinical signs of PNA are not sensitive or specific in hospitalized pts
• New or progresive radiographic infiltrates
  AND
• Clinical evidence that infiltrate is infectious
  
  • Fever or hypothermia
  • Purulent sputum
  • Leukocytosis
  • Decline in oxygenation
• Microbiology
  
  • Obtain blood and respiratory cultures in all pts where dx is suspected
• Consider Ag testing for S. pneumoniae and Legionella

Question 25

Nosocomial PNA Treatment

Answer 25

* Consider risks for MDR-organisms in VAP * **Prior recent IV abx** ⇒ changes flora * Prolonged hospitalization * Severe illness * Poor functional status * Hemodialysis * _In VAP and HAP, cover for resistant gram ⊕ and gram ⊖ organisms_ * **Vancomycin or linezolid** ⇒ cover for MRSA PLUS * Anti-pseudomonal B-lactam: **Piperacillin-tazobactam, Cefepime, or Meropenem** PLUS * Antipseudomonal quinolone (e.g. **Levofloxacin**) or aminoglycoside (**Gentamicin**) * Narrow-down spectrum and treatment based on susceptibility tests