Pneumonia Flashcards
How does pneumonia rank on the cause of death for world and US
- 3rd most common cause of death in the world
- 6th leading cause of death in US: 50,000 in 2010
Number of cases of community acquired pneumonia (CAP) per year
5 million
Outpatient vs. Inpatient pneumonia stats
- 80% treated as outpatients & 20% as inpatients
- mortality rate among outpatients
Types of pneumonia
- community acquired pneumonia (CAP)
- hospital acquired pneumonia (HAP)
- healthcare associated
Mechanisms of lung to defend against pathogens
- nasal vibrissae and turbinates capture large inhaled particles
- gag reflex and cough protect from aspiration
- branching of tracheobronchial tree traps microbes in airway
- mucociliary escalator sweep entrapped contents up to oropharynx
Role of normal flora that is typically adherent to mucosal cells of oropharynx
- prevent pathogenic bacteria from binding & decreases risk of pneumonia caused by more virulent bacteria
What occurs when barriers are overcome
- alveolar macrophages phagocytize and destroy pathogens
- if not killed, pathogens are eliminated via mucociliary elevator or lymphatics
- macrophages release cytokines & chemokines (TNF, IL-8) and leukotriene B4, which recruit neutrophils from blood stream to alveolar spaces, where they uptake and degrade microorganisms
- specific IgG bind surface of organisms and augment the ability of neutrophils and macrophages to phagocytize the bacteria
How can pathogens reach the lungs
- microaspiration of oropharyngeal contents
- inhalation of small aerosolized droplets that contain microorganisms
- consequence of a bloodstream infection/hematogenous spread
- direct spread from adjacent structures
Most common route to acquire pneumonia
- microaspiration of oropharyngeal contents
Microorganisms associated with microaspiration of oropharyngeal contents
- strep pneumonia, haemophilus influenzae
Microorganisms associated with inhalation of small aerosolized droplets
- mycobacterium tuberculosis, and viral infections
How do patients typically present
- fever, cough, sputum, leukocytosis, radiographic infiltrate, crackles, hypoxemia, hemoptysis, respiratory alkalosis, dyspnea
What causes fever in pneumonia
- IL-1 & TNF
What causes leukocytosis and increased purulent secretions
- chemokines (IL-8, GCSF) stimulate release and migration of neutrophils to the lung
What causes radiographic infiltrate, crackles, and hypoxemia
- inflammatory mediators create alveolar capillary leak
What causes respiratory alkalosis
- increased respiratory drive in the inflammatory response syndrome
What causes dyspnea
- decreased compliance due to capillary leak, hypoxemia, increased respiratory drive, increased secretions, and infection related bronchospasm
What does pneumonia patient become hypoxemic
- alveoli become filled with purulent secretions, which leads to shunts
Steps to diagnosing pneumonia
- evidence of infection: fever, chills, leukocytosis
- signs/symptoms localized to the respiratory system: cough, increased sputum, SOB, angina, abnormal pulmonary exam
- new infiltrate on chest radiograph
Organisms associated with typical pneumonia presentation
- S. pneumonia, haemophilus influenzae, S. aureus
Organisms associate with atypical pneumonia presentation
- mycoplasma pneuminae, chlamydia pneumoniae, legionella
Organisms associated with travel to central US
histoplasma capsulatum
Physical exam findings with pneumonia patient
- use of accessory muscles of respiration
- increased tactile fremitus with dull percussion reflecting consolidation
- crackles, bronchial breath sounds, pleural friction rub
Physical exam sensitivity and specificity
- sensitivity: 58%
- specificity: 67%
What is needed to diagnose pneumonia
Chest Radiograph
Purpose of chest radiograph
- establish diagnosis of pneumonia
- differentiates pneumonia from other conditions
- assesses extent of involvement of lungs
- occasionally suggest an etiologic diagnosis
Possible microbiologic work ups for pneumonia
- sputum gram stain and culture
- blood culture
- urinary antigen tests
- PCR
- Serology
Sputum gram stain and culture: adequacy
- to be adequate: >25 neutrophils,
Limitations of sputum gram stain and culture
- 30% of patients have non productive cough
- only 14% can provide an adequate sample
- 15-30% already received antibiotics
Blood culture: CAP stats
- 5-14% of blood cultures from patients hospitalized with CAP are positive
Blood culture: hematogenous staph aureus pneumonia stats
- nearly always positive blood culture
- positive in only about 25% of cases in which inhalation or aspiration is responsible for the CAP
How often can specific microbiologic cause be established
50%
How antibiotic treatment is chosen
- pathogen is identified
- empiric treatment
Factors that effect antibiotic chosen for treatment
- comorbidities, immunosuppression
- risk factors for multidrug resistant pathogens (MDR): hospital workers
- resistance patterns
- environmental exposures
Importance of timing of treatment
- interval of more than 4 hours b/w initial presentation and first antibiotic dose is associated with increased in hospital mortality
Treatment for patients stable enough to be treated as outpatients
- treated empirically
- cause of infection not sought b/c of substantial cost of testing
- choose antibiotic which covers most common organisms
Treatment for patients being admitted to the hospital
- guidelines recommend empirical therapy with broader spectrum antibiotics
- test for microbial diagnosis
What if influenza is active in the community
- antiviral treatment is recommended as soon as possible for all patients with suspected or confirmed infection
Pneumonia prevention
- pneumococcal vaccination
- influenza vaccination
- smoking cessation
Pneumococcal vaccine
- pneumovax
2. prevnar
Pneumovax
- 23 valent polysachharide
- covers 88% of strains causing bacteremia/meningitis
- indicated for elderly or patients with chronic health conditions
Prevnar
- 13 different strains
- indicated for elderly
Influenza vaccination
- 20,000 deaths annually
- prevention is most effective management strategy
- everyone 6 months of age and older should get vaccine every season
Importance of pneumococcal vaccine
- key to prevent INVASIVE pneumococcal disease
What is the most common infectious cause of death in the world
pneumonia
