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2. HDS Pulmonary > Clinical Approach to Pneumonia > Flashcards

Clinical Approach to Pneumonia Flashcards

1
Q

Pneumonia

Definition

A

An infection of the pulmonary parenchyma.

Caused by bacteria, viruses, fungi, or parasites.

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2
Q

Pneumonitis

Definition

A

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

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3
Q

CAP

A

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

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4
Q

Nosocomial PNA

A
  • 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
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5
Q

PNA

Pathogenesis

A
  • 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
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6
Q

CAP

Epidemiology

A
  • 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
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7
Q

PNA

Clinical Presentation

A
  • 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
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8
Q

“Typical” CAP

Characteristics

A
  • 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
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9
Q

Typical CAP

CXR

A
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10
Q

“Atypical” CAP

Characteristics

A

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
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11
Q

Atypical CAP

CXR

A
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12
Q

Lung Abscess

Characteristics

A

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
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13
Q

Lung Abscess

Pathophysiology

A
  • 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
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14
Q

CAP

Diagnosis

A
  • 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
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15
Q

CAP

Admission Considerations

A

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
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16
Q

PNA

Scoring Indices

A
  • 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
17
Q

PNA

Antibiotic Treatment

A
  • 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
18
Q

PNA

Outpatient Therapy

A

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

19
Q

PNA

Inpatient Therapy

A

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

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

20
Q

Nosocomial PNA

Epidemiology

A
  • 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%
21
Q

Nosocomial PNA

Pathogenesis

A
  • 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
22
Q

Nosocomial PNA

Risk Factors

A
  • 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
23
Q

Nosocomial PNA

Etiologies

A

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
24
Q

Nosocomial PNA

Diagnosis

A
  • 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
25
Q

Nosocomial PNA

Treatment

A
  • 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

2. HDS Pulmonary (28 decks)

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