Week 4 - Immunocompromised Host Flashcards
Name three risk factors that make a host immunocompromised:
1) chemotherapy
2) immunosuppresive drugs (systemic steroids, post-transplant drugs, rheumatologic meds)
3) acquired immunodeficiency (AIDS, post-splenectomy)
what are the three categories of acquiring PNA?
1) community acquired
2) hospital acquired
3) ventilator associated
What are two clinical parameters that gauge severity of PNA?
PSI (pneumonia severity index), CURB-65
Describe typical vs atypical PNA presentation
- typical: fever, rigors, chills, productive cough, pleurisy, dyspnea
- atypical: low-grade fevers without typical PNA sxs
What are the main pathogens of CAP?
Streptococcus pneumoniae, Mycoplasma pneumoniae, Chlamydia pneumoniae, Haemophilus influenzae, Legionella, viral
What are the main pathogens of VAP?
Gram negatives (Pseudomonas aeruginosa, E coli, Klebsiella, Acinetobacter) and S aureus
What are the most common pulmonary infections in the early stages of immunosuppression?
Bacterial, isolated commonly are Legionella, Mycoplasma and Chlamydia
What are the predominant viral agents in early stages on immunosuppression?
Rhinovirus, adenovirus, coronavirus, influenza, ESV, parainfluenza (post-transplant, include CMV)
What are the most frequent opportunistic pulmonary pathogen in the ICH?
Pneumocystis jiroveci is the most frequent, also Aspergillus fumigatus, Candida albians, Cryptococcus neoformans
For non-resolving PNAs, what noninfectious etiologies must be considered?
Organizing pneumonia, drug-toxicity, cardiac causes
What types of pathogens most commonly cause lobar/bronchopneumonia?
Bacterial
What types of pathogens most commonly cause interstitial pneumonias?
Viral, parasitic, fungal
Radiographically, what constitutes a lobar pneumonia?
Homogenous consolidation with air bronchogram
How long does radiologic resolution of a PNA lag behind the clinical improvement of a patient?
6-8 weeks
Radiographically, what constitutes a bronchopneumonia
patchy appearance with peribronchial thickening and poorly defined airspace opacities. Airbronchograms typically absent
What are the CT findings of severe staph infection?
Lobar enlargement with bulging interlobular fissures c/b abscess/cavitation/pneumoatocele/empyema
What pathogens typically cause an interstitial PNA image?
The atypical bugs: Legionella, Mycoplasma, Chlamydia
What is the typical radiographic appearance of Legionella?
Patchy, localized infiltrate in the lower lobes +/- hilar adenopathy +/- pleural effusion. Rarely with cavitation
What is the typical radiographic appearance of Mycoplasma pneumoniae?
Unilateral, multilobar, or bilateral +/- pleural effusion in 20% of pts
What are the five categories of pulmonary aspergillosis?
1) aspergilloma (saphrophytic)
2) ABPA (hypersensitivity)
3) chronic necrotizing (semi-invasive)
4) Airway-invasive
5) IPA (invasie pulmonary aspergillosis)
What virus accounts for the majority of viral PNAs in immunoCOMPETENT hosts?
Influenza A/B
What viral PNAs are ICH pts more suspectible to?
CMV, HSV, measles, adenovirus
T/F - the diagnosis of viral PNA can be made on the basis of radiographic appearance alone
FALSE - viral PNA chest imaging is variable and overlapping
What infections are typically reactivation?
TB, PCP, toxoplasmas gondii, VZV – hx is key in diagnosis
Humoral immunodeficiency increases risk of what kind of pathogen?
Encapsulated bacteria (S aureus, S pneumoniae, H influenza, PJP)
Cell-mediated or T-cell defects increases risk of what kind of pathogens?
Opportunists (CD4< 100 = viral and fungal ,CD4>100 PCP and mycobacterium)
s/p splenectomy or hyposplenism pts are predisposed to what kinds of pathogens?
Encapsulated bacteria (S aureus, S pneumoniae, H influenza)
What types of pathogens are ICH pts more likely to have in early vs late neutropenia?
Early: bacterial, late: viral or fungal predominates
What is the air bronchogram sign?
represents consolidation – opacification of the air spaces but the bronchioles (air tracks) can still be visualized
What is the bulging fissure sign?
in conjunction with air bronchogram suggests pneumonia, usually upper lobe Klebsiella and pneumococcal infections. DDx neoplasia, large abscesses, infected bullae
What is the silhoutte sign?
obscuring of normal air interfaces of the thorax (thoracic aperture, thoracic wall, paramediastinal spaces, and pericardiac spaces)
What is the feeding veseel sign?
indicates septic emboli when cavtating or noncavtating nodules are associated with a pulmonary vessel
What is the air fluid level sign?
Suggestive of abscess or empyema, mainly caused by S aureus and Klebsiella
What is the split pleural sign?
Normally suggestive of empyema, can also be seen with hemothorax, pleurodesis, post-lobectomy
T/F – ground glass opacities (GGOs) are very specific for lung infection
FALSE - can represent infection, vasculitis, ILD, pulmonary congestion. More helpful is the distribution
GGOs with central/upper lobe predominance sparing the subpleural spaces is indicative of what infection?
PCP
Why is the tree-in-bud sign signify pathology?
These are terminal bronchioles and should not be able to be perceived on CT scan because of their thin walls/caliber
What is the halo sign?
Is always suggestive of invasive aspergillosis with neutropenic fever – it is a good prognostic indicator for response to therapy
What is the air crescent sign?
Separation of the necrotic infective fungal mass by a crescent air space in response to therapy – suggests good response
What is monad’s sign?
Air crescent sign resulting from secondary fungal infection with mycetoma (fungal ball) in a preexisting cavity – this is a bad sign requiring surgical vs other intervention
What is crazy paving sign?
Due to alveolar opacity resulting from exudates accompanied by septal thickening leading to “pedestrian path pattern” – usually seen in pulmonary aveolar proteinosis but is not pathognomonic
What are contraindications to bronchoscopy
1) results won’t change mgmt
What are minor complications of flex bronch?
laryngospasm, bronchospasm, epistaxis, transient hoarseness, fever, nausea, cough, mild airway bleeding
What are major complications of flex bronch?
severe airway hemorrhage, PTX, severe hypercapnia/hypoxemia, arrhythmias, seizure, cardiac arrest
What is the reported incidence of major complications from flex bronch?
1-5%, with most major complications 2/2 TBBx
What is the mortality associated with flexible bronch?
Rare, <0.04%
There are few absolute contraindications to flex bronch – name them
Refractory hypoxemia, HD instability, life threatening arrhythmias, lack of informed consent, inexperience operator, inadequate equipment/facility
What are relative contraindications to bronchoscopy?
Severe hypoxemia (~PO2<70), pulmonary HTN, recent MI ~4-6 wks, coagulopathy, increased intracranial pressure, pregnancy
For autologous SCT, what are the common infections PRE-engraftment?
HSV, Candida, Bacterial, respiratory virus
For autologous SCT, what are the common infections POST-engraftment?
Still bacterial and respiratory viruses. Added risk for CMV, VZV, PCP. Less risk HSV or Candida.
For allogeneic SCT, what the common infections pre-engraftment
Bacterial: gram neg bacilli, gram pos, GI streptococcus
Viral: HSV, respiratory and enteric viruses, HHV in late pre-engraftment
Fungal: Candida, Aspergillus
For allogeneic SCT, what the common infections POST-engraftment (day 15-45) thru day 100?
Bacterial: Gram pos and GI strep, less risk gram neg
Viral: Added risk CMV, HHV6, EBV
Fungal: Added risk PCP, less risk aspergillus. Same risk Candida
For allogeneic SCT, what the common infections POST-engraftment day 100 and beyond?
Bacterial: Encapsulated bacteria
Viral: Added risk VZV. Same risk CMV, HHV6, EBV
Fungal: No longer at risk Candida. Same risk aspergillus and PCP
