pneumonia Flashcards
definiton
= acute lower resp tract illness due to infection of distal lung parenchyma
how can pneumonia be classified
- community acquired/ hospital acquired ‘nosocomial’
- aspiration pneumonia
- pneumonia of immunosuppressed
- typical/ atypical pneumonia [latter- more vague symptoms, seen in mycoplasma/chlamydia/legionella infections]
- bronchopneumonia vs lobar pneumonia
- bronchopneumonia = patchy consolidation of different lobes
- lobar pneumonia = fibrosuppurative consolidation of a single lobes occuring in STAGES
- congestion = blood vessels and alveoli get filled with excess fluid [1-2d]
- red = hepatisation exudate [rbcs, np’s, fibrin] fill airspaces making them more solid live like appearance. [3-4th days]
- grey= hepatization, firm still. colour chnage = rbc in exudate breakdown [5-7th days]
- resolution = day 8-3 weeks] as exudate is digested by enzymes/mp’s/coughed up
- Idiopathic interstitial pneumonia
epidemiology
incidence: 1 in 100
mortality- 10% in hosp, 30% in ITU
CAP’s causative organisms
Community acquired pneumonia (CAP) may be caused by the following infectious agents:
- Streptococcus pneumoniae (accounts for around 80% of cases)
- Haemophilus influenzae
- Staphylococcus aureus: commonly after the ‘flu
- atypical pneumonias (e.g. Due to Mycoplasma pneumoniae)
- viruses
[[[[may be 1ry/2ry to underlying disease]]]]]]
Klebsiella pneumoniae is classically in alcoholics
HAP + VAP - define and causative organisms
Hospital acquired pneumonia occurs mostly in patients who are severely debilitated or who are immune suppressed.
Hospital-acquired pneumonia (HAP) is a respiratory infection developing more than 48 h after hospital admission.
in a proportion of patients, HAP is associated with mechanical ventilation, in which case it is termed ventilator-associated pneumonia (VAP)
Most common organisms isolated from respiratory specimens of patients known or suspected to have HAP are
- Pseudomonas aeruginosa,
- Staphylococcal aureus and
- Enterobacteriaceae (especially Klebsiella, E. coli and Enterobacter spp.)
early vs late onset
early-onset HAP or VAP
often caused by typical antimicrobial-susceptible community organisms such as Streptococcus pneumoniae or Haemophilus influenzae
late-onset HAP or VAP
commonly caused by P. aeruginosa or other antimicrobial-resistant opportunistic Gram-negative bacteria or by MRSA
aspiration pneumonia
Aspiration pneumonia is a pneumonia that develops as a result of foreign materials gaining entry to the bronchial tree, usually oral or gastric contents such as food and saliva.
Depending on the acidity of the aspirate a chemical pneumonitis can develop, as well as bacterial pathogens adding to the inflammation.
Aspiration pneumonia often results from an incompetent swallowing mechanism, such as those that occur in
- neurological disease or injury such as stroke, multiple sclerosis and intoxication.
- Iatrogenic causes, such as intubation, can also result in aspiration pneumonia developing.
Risk factors for the development of aspiration pneumonia include:
- Poor dental hygiene
- Swallowing difficulties
- Prolonged hospitalization or surgical procedures
- Impaired consciousness
- Impaired mucociliary clearance
The bacteria often implicated in aspiration pneumonia are aerobic, and often include:
- Streptococcus pneumoniae
- Staphylococcus aureus
- Haemophilus influenzae
- Pseudomonas aeruginosa
Other aerobic, and anaerobic, organisms can also result in aspiration pneumonia, but are less common.
pneumonia of immunocompromised causative organisms
usual suspects
- strept penumoniae
- h. influenzae
- staph aureus
- m catarrhalis
- m pneumoniae
as well as:
- PCP
- TB
- fungi
- CMV/HIV
HIV: Pneumocystis jiroveci pneumonia
Whilst the organism Pneumocystis carinii is now referred to as Pneumocystis jiroveci, the term Pneumocystis carinii pneumonia (PCP) is still in common use
- Pneumocystis jiroveci is an unicellular eukaryote, generally classified as a fungus but some authorities consider it a protozoa
- PCP is the most common opportunistic infection in AIDS
- all patients with a CD4 count < 200/mm³ should receive PCP prophylaxis
Features
- dyspnoea
- dry cough
- fever
- very few chest signs
Pneumothorax is a common complication of PCP.
Extrapulmonary manifestations are rare (1-2% of cases), may cause
- hepatosplenomegaly
- lymphadenopathy
- choroid lesions
Investigation
- CXR: typically shows bilateral interstitial pulmonary infiltrates but can present with other x-ray findings e.g. lobar consolidation. May be normal
- exercise-induced desaturation
- sputum often fails to show PCP, bronchoalveolar lavage (BAL) often needed to demonstrate PCP (silver stain shows characteristic cysts)
Management
- co-trimoxazole
- IV pentamidine in severe cases
- steroids if hypoxic (if pO2 < 9.3kPa then steroids reduce risk of respiratory failure by 50% and death by a third)
s/s
[bro i’m caved *pleural rub*]
symptoms
- fevers, rigors
- malaise, anorexia
- dyspnoea
- cough, purulent sputum, haemoptysis
- pleuritic pain
signs:
bro - bronchial breathing
(i’m)
c- crackles
a - decreased air entry
v- increased vocal resonance ie. cos remember, sound travels better thru fluid than air
e - decreased expansion
d- dull percussion note
*pleural rub* [rub hands together]
ix for pneumonia
First line investigations:
- chest radiology
- FBC differential WCC- neutrophilia in bacterial infections
- urea and electrolytes - check for dehydration
- CRP- raised in response to infection
- sputum and blood culture - especially for pneumococcus, Mycobacterium tuberculosis
- Also pulse oximetry and/or blood gases[if severe pneumonia/pa02 <92%/if pt has pre-existing respiratory disease, for example COPD];
- consider ECG and cardiac enzymes.
Further investigation:
-
serology for atypical organisms - slow, but useful for:
- Mycoplasma pneumoniae,
- Legionella pneumophila,
- Chlamydia psittacosis and
- Chl. pneumoniae,
- Coxiella burnetti,
- viruses
- ====> on admission send clotted 10 ml blood sample with a second sample 10 days later
- Microbiological specimens may be necessary in patients whom fail to respond to conventional treatment - for example, bronchial washings from fibre-optic bronchoscopy, or percutaneous lung aspiration.
- Some centres have countercurrent immunoelectrophoresis available for the identification of pneumococcal antigen from sputum, urine, blood, or CSF. It is not affected by antibiotic therapy.
radiological features of hemophilus influenza
Chest radiology usually shows a lobar pneumonia
Less commonly, a diffuse or bronchopneumonia may be seen.
Pleural effusion and empyema may be seen.
radiological appearance of Legionnaire’s disease
usually, unilateral lobar and then multilobar shadowing
small pleural effusions present in 20 to 50% of cases
uncommonly, cavitation
radiological appearance of mycoplasma pneumonia
Chest radiology is highly variable:
most frequent pattern is one of bronchial thickening with areas of interstitial infiltration and subsegmental atelectasis involving one of the lower lobes
sometimes, there may be dramatic lower lobe shadowing in both lower lobes
Often, there is no correlation between radiologic appearance and the clinical state of the patient.
radiological appearance of pneumococcal pneumonia
classically, shows consolidation with a lobular distribution
note that radiological changes may lag behind the clinical course of the disease and conversely, radiologic features may persist for several weeks after being cured
radiological appearance of staphylococcal pneumonia
The chest radiograph often appears cavitated.
Infection starts in the bronchi, causing areas of patchy consolidation in one or more lobes.
These break down to form multiple thin walled abscesses - pneumatocoeles - which appear as cysts.
Concomitant pathologies such as a pneumothorax, pleural effusion or empyema may be seen depending on the precise aetiology of the disease.
summary of organisms causing pneumonia
Causes
As mentioned before, bacterial pneumonia is by far the most common type of pneumonia seen in clinical practice. Other infective causes include:
- viral
- fungal (e.g. Pneumocystis jiroveci)
