2. Definition:
ďPneumonia is an infection of the pulmonary parenchyma.
Despite being the cause of significant morbidity and
mortality, pneumonia is often misdiagnosed, mistreated,
and underestimated.
ďIt is usually caused by bacteria.
ďClinically it presents as an acute illness characterized in
the majority of cases by the presence of cough, purulent
sputum and fever together with physical signs or
radiological changes compatible with consolidation of the
lung.
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3. Classification :
Pneumonia can be classified both anatomically and on the
basis of the aetiology.
Anatomical classification :
ďPneumonias are either localized, with the whole of one or
more lobes affected (lober pneumonia) , or diffuse, when
they primarily affect the lobules of the lung, often in
association with the bronchi and bronchioles - a condition
referred to as 'bronchopneumonia'.
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4. Aetiological classification :
ď An aetiological factor can be discovered in
approximately 75% of patients.
ď The term 'atypical pneumonia' has been used to
describe pneumonia caused by agents such as
Mycoplasma, Legionella, Chlamydia and Coxiella
burnetii.
ďWhile these pneumonias can differ from
pneumococcal disease, there is a considerable
overlap in clinical presentation and as these
agents account for almost one-fifth of the cases of
pneumonia , the term 'atypical' has been dropped.
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5. ď Pneumonias may also result from:
I. chemical causes, such as in the aspiration of
vomitus
II.radiotherapy
III.allergic mechanisms.
Precipitating factors :
ďStrep. pneumoniae - often follows viral infection
with influenza or parainfluenza.
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6. ďHospitalized 'ill' patients - often infected with
Gram-negative organisms.
ďCigarette smoking (the strongest independent
risk factor for invasive pneumococcal disease).
ďAlcohol excess.
ďBronchiectasis (e.g. in cystic fibrosis).
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7. ďBronchial obstruction (e.g. carcinoma) - occasionally
associated with infection with 'non-pathogenic' organisms.
ďImmunosuppression (e.g. AIDS or treatment with
cytotoxic agents) - organisms include Pneumocystis
carinii, Mycobacterium avium-intracellulare,
cytomegalovirus.
ďIntravenous drug abuse - frequently associated with Staph.
aureus infection.
ďInhalation from oesophageal obstruction - often
associated with infection with anaerobes.
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8. ďPathology:
Classic pneumonia evolves through a series of pathologic
changes.
ď The initial phase is one of edema, with the presence of a
proteinaceous exudateâand often of bacteriaâin the
alveoli. This phase so rapidly followed by
ďRed hepatization phase. The presence of erythrocytes in
the cellular intraalveolar exudate gives this second stage
its name, but neutrophils are also present and are
important from the standpoint of host defense. Bacteria
are occasionally seen in cultures of alveolar specimens
collected during this phase.
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9. ďGray hepatization, no new erythrocytes are
extravasating, and those already present have
been lysed and degraded. The neutrophil is the
predominant cell, fibrin deposition is abundant,
and bacteria have disappeared. This phase
corresponds with successful elimination of the
infection and improvement in gas exchange.
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10. ďResolution, the macrophage is the dominant cell
type in the alveolar space, and the debris of
neutrophils, bacteria, and fibrin has been cleared,
as has the inflammatory response.
ďThis pattern has been described best for
pneumococcal pneumonia and may not apply to
pneumonias of all etiologies.
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11. Clinical features:
ďThe clinical presentation varies according to the
immune state of the patient and the infecting
agent. In the most common type of pneumonia -
caused by Strep. pneumoniae - there is often a
preceding history of a viral infection.
Symptoms:
ďThe patient rapidly becomes ill with a high fever
ďpleuritic pain
ďDry cough. A day or two later, rusty-coloured
sputum is produced and at about the same time
the patient may develop labial herpes simplex.
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12. Signs:
ďhigh temperature (up to 39.5°C)
ďRapid and shallow breathing
ďthe affected side of the chest moves less, and signs
of consolidation may be present together with a
pleural rub.
Investigations :
ďChest radiography
ďPlain, X-ray
- confirms the area of consolidation but radiological
changes lag behind the clinical course so that X-ray
changes may be minimal at the start of the illness.
Conversely, consolidation may remain on the chest
X-ray for several weeks after the patient is clinically
cured.
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13. The chest X-ray usually returns to normal by 6
weeks, except in patients with severe airflow
limitation.
- Persistent changes on the chest X-ray after this
time suggest a bronchial abnormality, usually a
carcinoma, with persisting secondary pneumonia.
Chest X-rays should rarely be repeated more
frequently than at weekly intervals during the
acute illness and then at 6 weeks after discharge
from hospital.
- CT,chest may be needed .
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18. ⢠Gram's Stain and Culture of Sputum :
ď§ The main purpose of the sputum Gram's stain is to ensure
that a sample is suitable for culture. However, Gram's
staining may also help to identify certain pathogens (e.g.,
S. pneumoniae, S. aureus, and gram-negative bacteria) by
their characteristic appearance.
ď§ The sensitivity and specificity of the sputum Gram's stain
and culture are highly variable; even in cases of proven
bacteremic pneumococcal pneumonia, the yield of
positive cultures from sputum samples is 50%.
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19. ďBlood Culture in the presence of bacteramia .
ďAntigen Tests
Two commercially available tests detect pneumococcal and
certain Legionella antigens in urine.
ďPolymerase Chain Reaction
Polymerase chain reaction (PCR) tests are available for a
number of pathogens. However, the use of these PCR
assays is generally limited to research studies.
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20. ďSerology
ď§ A fourfold rise in specific IgM antibody titer
between acute- and convalescent-phase serum
samples is generally considered diagnostic of
infection with the pathogen in question, such as
Coxiella burnetii.
ď§ Recently, however, they have fallen out of favor
because of the time required to obtain a final
result for the convalescent-phase sample.
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21. TYPES OF PNEUMONIA
Mycoplasma pneumonia:
⢠Mycoplasma pneumonia is relatively common and often
occurs in patients in their teens and twenties.
⢠Generalized features such as headaches and malaise often
precede the chest symptoms by 1-5 days.
⢠Cough may not be obvious initially and physical signs in
the chest may be scanty.
⢠On chest X-ray, usually only one lobe is involved but
sometimes there may be dramatic shadowing in both
lungs. There is frequently no correlation between the X-
ray appearances and the clinical state of the patient.
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22. ⢠The white blood cell count is not raised.
⢠Cold agglutinins occur in half of the cases.
⢠The diagnosis is confirmed by a rising antibody
titre.
⢠Treatment is with macrolides, e.g. erythromycin
500 mg four times daily for 7-10 days. Tetracycline
is also effective. Although most patients recover in
10-14 days, the disease can be protracted for weeks
and relapses occurring.
⢠Lung abscesses and pleural effusions are rare.
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23. Viral pneumonia
ď Primary viral pneumonia is uncommon in adults,
influenza A virus or adenovirus infection being the
commonest causes.
ďIt predisposes patients to bacterial pneumonia by
damaging the respiratory epithelium and facilitating
bacterial infection. Influenza A (HSNI) normally does not
affect humans but recently has been transmitted from
fowls (Avian flu), crossing the species barrier. Patients
present with fever, breathlessness, cough and diarrhoea.
ď Lymphopenia and thrombocytopenia are present and
pulmonary infiltrates are seen on chest X-ray.
ďThe mortality rate is high.
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24. ďSevere acute respiratory syndrome (SARS) is due to a
novel coronavirus. The incubation period is approximately
5 days with spread between humans mainly by droplet
infection.
ď The outbreak in 2003 affected many healthcare workers.
Fever, malaise, headache and rigors were followed in the
second week by cough, breathlessness and diarrhoea.
ď Lymphopenia, thrombocytopenia and pulmonary
infiltrates (mainly in the lower zones) occur.
ďAt the end of the second week 20% of patients deteriorate,
developing ARDS, and the mortality is high.
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25. ďHaemophilus influenzae
ď§ H. influenzae is a frequent cause of exacerbation of chronic
bronchitis and can cause pneumonia in COPD patients.
ď§ The pneumonia can be diffuse or confined to one lobe.
ď§ There are no special features to separate it from other
bacterial pneumonias.
ď§ It responds well to treatment with oral amoxicillin 500 mg
Ă 4 daily.
ďStaphylococcus aureus
Staph. aureus rarely cause pneumonia except after a
preceding influenzal viral illness.
The infection starts in the bronchi, leading to patchy areas
of consolidation in one or more lobes, which break down
to form abscesses.
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26. ďThese may appear as cysts on the chest X-ray.
ďPneumothorax, effusion and empyemas are
frequent.
ďSepticaemia develops with metastatic abscesses in
other organs.
ďFulminating staphylococcal pneumonia can lead
to death in hours.
ďAreas of pneumonia (septic infarcts) are also seen
in staphylococcal septicaemia. This is frequently
seen in intravenous drug abusers.
ď Pulmonary symptoms are often few but
breathlessness and cough occur and the chest X-
ray reveals areas of consolidation.
ď Abscess formation is frequent.
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27. Gram-negative bacteria These are the cause of many
hospital-acquired pneumonias but they are occasionally
responsible for cases in the community.
Klebsiella pneumoniae:
⢠Pneumonia due to Klebsiella usually occurs in elderly
people with a history of heart or lung disease, diabetes,
alcohol excess or malignancy.
⢠The onset is often sudden, with severe systemic upset.
⢠The sputum is purulent, gelatinous or blood-stained.
⢠The upper lobes are more commonly affected and the
consolidation is often extensive. .
⢠The organism can be found in the sputum or in the blood.
⢠Treatment is dependent on the sensitivity of the organism,
but a cephalosporin is usually required.
⢠The mortality is high, partly owing to the presence of the
predisposing condition.
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28. Pseudomonas aeruginosa
⢠Pneumonia due to Pseudomonas is of considerable
significance in patients with cystic fibrosis, since it
correlates with a worsening clinical condition and
mortality.
⢠It is also seen in patients with neutropenia following
cytotoxic chemotherapy.
⢠The isolation of P. aeruginosa from sputum must be
interpreted with care because may simply represent
contamination from the upper airways.
⢠Treatment with the 4-quinolone antibiotic ciprofloxacin
(200-400 mg i.v. over 30-60 minutes twice daily) or
ceftazidime (2 g bolus i.v. 8-hourly). Ticarcillin (15-20 g
daily i.v. infusion) and piperacillin are active against these
bacilli. These penicillins are usually given in combination
with an aminoglycoside, e.g. gentamicin, for maximum
benefit.
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29. GENERAL MANAGEMENT OF PNEUMONIA:
ď Sputum and blood should always be sent for culture but
antibiotic treatment should not be delayed.
ďSevere cases need to be admitted to hospital and a chest
X-ray performed. Other investigations, e.g. blood gases,
are useful to detect respiratory failure and provide a
baseline for comparison if the patient deteriorates.
ďThe choice of antibiotics is inevitably empirical, and is
largely directed at Strep. pneumoniae infections.
ďThere is no convincing evidence that newer antibiotics
provide any significant therapeutic advantage over
established therapies.
ď For treatment of mild community-acquired pneumonia,
oral amoxicillin at a dose of at least 500 mg 8-hourly. Oral
erythromycin (or clarithromycin, which is better
tolerated) is an alternative choice for those sensitive to
penicillin.
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30. ďFor more severe cases treated in hospital,
combined therapy with amoxicillin and a
macrolide (erythromycin or clarithromycin) is
recommended. When oral therapy is
contraindicated, parenteral ampicillin or
benzylpenicillin should be combined with
clarithromycin.
ďForStaph. aureus infection intravenous
flucloxacillin Âą sodium fusidate should be added.
Fluoroquinolones are recommended for those
intolerant of penicillins or macrolides.
ď For severe cases, parenteral antibiotics should be
given with the combination of a broad-spectrum
lactamase-stable beta-lactam antibiotic (co-
amoxiclav or cefuroxime) and clarithromycin.
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31. ďParenteral antibiotics should be switched to oral
once the temperature has settled for a period of 24
hours and provided there is no contraindication
to oral therapy.
ďThe choice of antibiotics may be narrowed once
microbiological results are available but it should
be remembered that up to 10% of pneumonias
may have mixed infections. .
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32. Criteria for the diagnosis of severe community-
acquired pneumonia:
Clinical features
ďRespiratory rate ⼠30/min
ďDiastolic blood pressure ⤠60 mmHg
ďConfusion
ďHigh mortality particularly in those > 65 years old
ďCo-morbidity
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33. Investigations
ďChest X-ray - more than one lobe involved
ďPao2 < 8 kPa
ďLow albumin (< 35 g/L)
ďWhite cell count (low < 109/L or high > 20 Ă
109/L)
ďRaised serum urea (> 7 mmol/L)
ďBlood culture - positive
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34. ďFor more severe cases treated in hospital in addition to
antibiotic therapy fluids should be given to avoid
dehydration, care of the mouth and skin.
ď Cough should normally be encouraged, but if it is
unproductive and distressing, cough suppressants can be
given.
ď Physiotherapy is needed to help and encourage the
patient to cough.
ďPleuritic pain may require analgesia, but powerful
analgesia (e.g. opiates) should be used with care because
they cause respiratory depression.
ďsevere hypoxia, oxygen therapy should be given.
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35. COMPLICATIONS OF PNEUMONIA
Lung abscess
ďThis term is used to describe severe localized suppuration in the
lung associated with cavity formation on the chest X-ray, often
with the presence of a fluid level.
ďAbscesses may develop during the course of specific pneumonias,
particularly when the infecting agent is Staph. aureus or
Klebsiella pneumoniae. Septic emboli, usually staphylococci,
result in multiple lung abscesses.
ď Infarcted areas of lung occasionally cavitate and rarely become
infected.
ďAmoebic abscesses may occasionally develop in the right lower
lobe following transdiaphragmatic spread from an amoebic liver
abscess.
ďThe patient is often anaemic with a high ESR.
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36. Empyema:
ďEmpyema means the presence of pus within the pleural
cavity.
ďThis usually arises from bacterial spread from a severe
pneumonia or after the rupture of a lung abscess into the
pleural space.
ďTypically an empyema cavity becomes infected with
anaerobic organisms and the patient is severely ill with a
high fever and a neutrophil granulocytosis.
ďEmpyemas should be treated by prompt tube drainage or
by rib resection and drainage of the empyema cavity under
ultrasound control.
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