Clinical Approach to Pneumonia Flashcards
1
Q
Pneumonia
Definition
A
An infection of the pulmonary parenchyma.
Caused by bacteria, viruses, fungi, or parasites.
2
Q
Pneumonitis
Definition
A
Inflammation of the lungs due to non-infectious causes including chemicals. blood, radiation, or auto-immune etiologies.
3
Q
CAP
A
Infection of the lung parenchyma in pts who acquire the infection in the community.
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
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
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
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
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
9
Q
Typical CAP
CXR
A
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
11
Q
Atypical CAP
CXR
A
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
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
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
-
Satisfactory sample
- 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
-
Procalcitonin ⇒ marker of inflammatory response to bacterial infection
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
