Flashcards in Respiratory - Pneumonia and lung abscesses Deck (56):
What is pneumonia? What are the clinical features?
An acute LOWER respiratory tract infection causing consolidation of the lung tissue by the presence of an intra-alveolar inflammatory exudate.
Signs: - pyrexia, cyanosis, confusion, tachypnoea, tachycardia, hypotension, signs of consolidation and a pleural rub
Symptoms: - dyspnoea, fever, rigors, malaise, productive cough, haemoptysis, pleural chest pain (worse on inspiration)
What are the typical examination findings in pneumonia?
Pnuemonia causes consildation, so examination findings include:
- coarse crepitations/ crackles
- reduced chest expansion
- bronchial breathing
- dull percussion note
- increased vocal fremitus/ vocal resonance
What is the most common cause of community acquired pneumonia?
CAP may be primary or secondary to underlying disease. Agents that cause CAP can be divided into typical and atypical.
- Strep pneumoniae
- Mycoplasma pneumoniae
- Chlamydial spp
What are the most common causes of hospital acquired pneumonia?
HAP is defined as pneumonia contracted > 48 hours following hospital in patient admission. It is also called a nosocomial infection.
Gram negative bacilli (e.g. enterobacteraciae), staph aureus and anaerobes (e.g. bacteroides, clostridia) are common. Pseudomonas and Klebsiella should also be considered.
What patients are at risk of aspiration pnuemonia? What agents cause these?
- Bulbar palsies
- Decreased GCS (e.g. head injury, drunk)
- Oesophageal disease (e.g. achalasia, reflux)
- Poor dental hygeine
...risk aspirating oropharyngeal anaerobes.
The main agents responsible for aspiration pneumonia are Strep pneumoniae and anaerobic bacteria (e.g. bacteroides, clostridia, enterobacteraciae)
What are the possible outcomes of aspiration pneumonia?
1) Sterile aspiration: often complicated by a secondary pneumonia
2) Infected aspiration: often results in extensive necrotizing bronchopneumonia with abscess formation
3) Other effects include:
- asphyxia --> death due to massive aspiration
- diffuse alveolar damage/ ARDS
- bronchiolitis obliterans from recurrent gastric acid aspiration
- localised pneumonia
- lipid pnuemonia
What factors predispose to pneumonia?
1) Suppression of cough reflex - e.g. coma, anaesthesia (esp. opioids)
2) Impaired mucociliary apparatus - smoking, genetics (Kartageners syndrome), viral disease (e.g. influenza)
3) Impaired alveolar macrophages - smoking, oxygen toxicity
4) Impaired immune response - drugs, AIDS, leukaemias, congenital immunodeficiencies
5) Pulmonary oedema
6) Retention of secretions
7) Indwelling devices - ET tube, mechanical ventilation
8) Drugs - previous broad spectrum antibiotics
9) Prior viral respiratory tract infection - e.g. post influenza
How can pathogens reach the lung parenchyma and cause infection?
1) Inhalation from the environment - e.g. nebuliser circuit
2) Aspiration of oropharyngeal flora
3) Colonisation of a diseased lower respiratory tract - e.g. bronchiectasis
4) Direct spread from adjacent focus of infection
5) Blood spread - bacteraemia and sepsis
What investigations should be performed in a case of suspected pneumonia?
- CXr: lobar or multilobar infiltrates, air bronchogram, pleural effusion
- Assess oxygenation: oxygen saturation (ABG if sats below 92%)
- Bloods: FBC, U+E, LFT, CRP, Blood cultures
- Sputum: MC&S - in some cases check for Legionella (sputum culture AND urinary antigen)
- Pleural fluid aspiration: MC&S
- Bronchoscopy or bronchoalveolar lavage: if patient immunocompromised or ITU
How is the severity of pneumonia stratified?
Risk assessment can be made using CURB-65. The patient receives 1 point for each of the following:
- Confusion (abbreviated mental test <8)
- Urea > 7mmol/L
- Respiratory rate >30/min
- BP <90 systolic
- age >65
0-1: home treatment possible
2: hospital therapy
>3: severe pneumonia indicates mortality 15-40% - consider ITU
What is one of the problems with CURB-65 risk stratification tool?
It "underscores" the young - i.e. these patients compensate in severe infection so may seem more stable than they actually are. Treat the patient not the score.
What is the antibiotic treatment of choice for CAP?
Typical CAP is caused by either Strep pneumoniae, Haemophilus or Mycoplasma pneumoniae.
Treatment of choice is oral amoxicillin or clarithromycin (in penicillin allergic patients) or doxycycline provided the patient is not vomiting and only has mild or moderate pneumonia (CURB-65). If the patient has moderate pneumonia a loading dose of 200mg of the antibiotic of choice is given followed by maintenance dose over a longer period of time.
How is severe CAP treated?
Severe typical CAP is caused by the same agents as mild to moderate disease. Severe patients should be admitted to hospital and started on IV antibiotics.
Co-amoxiclav or 2nd generation cephalosporin (e.g. cefuroxime) AND clarithromycin should be used.
How is Legionella pneumonia treated?
Legionella pneumonia is an atypical cause of CAP.
Fluoroquinolone combined with clarithromycin is the treatment of choice.
How is chlamydia pneumonia treated?
Tetracycline - e.g. doxycycline
How is Pneumocystis pneumonia treated?
Remember that pneumocystis pneumonia is highly suggestive of immunocompromise and should be treated with high doses of co-trimoxazole.
How are hospital acquired pneumonias treated?
HAP can be caused by gram negative bacilli, gram positive cocci and anaerobes (e.g. bacteroides, clostridia, legionella etc) so broad antibiotic coverage is needed.
An aminoglycoside (e.g. gentamicin) + antipseudomonal penicillin (e.g. Tazoscin)
How are aspiration pneumonias treated?
Cephalosporin IV (e.g. cefuroxime) + metronidazole (for anaerobes)
What is lobar pneumonia?
Pneumonia can be classified by either anatomical location (e.g. broncho or lobar pneumonia) or clinically (e.g. HAP, CAP, recurrent pneumonia, aspiration, immunocompromised etc)
Lobar pneumonia is characterised by large areas of uniform consolidation of a part of a lobe or entire lobe of the lung.
What agents most commonly cause lobar pneumonia?
Lobar pneumonia is the commonest cause of CAP. It usually affects healthy adults and rarely the very young or old.
90% are due to pneumococcus (e.g. strep pneumoniae). The pathogenicity of subtypes depends on virulence factors - e.g. pneumolysin, resistance to phagocytosis - capsular polysaccharide etc
Other gram negative organisms - e.g. Klebsiella, Haemophilus and Legionella - account for other cases but are in the minority.
What is the macroscopic appearance of lobar pneumonia?
The classic appearance is for pneumococcal infection: consolidation that is sharply defined to the lobes which are diffusely affected.
Describe the stages of lobar pneumonia?
The progession of lobar pneumonia is as follows:
Stage 1 - congestion: lungs are heavy, red and boggy. There is alveolar wall congestions and early acute inflammatory changes (e.g. polymorphs)
Stage 2 - red hepatization: lung are firm, deep red and airless. A fibrinous pleurisy is often seen. Increased alveolar exudate of fibrin, polymorphs and phagocytosed organisms with some red cell extravasation
Stage 3 - grey hepatization: lungs are firm, grey//brown and airless. The intra-alveolar exudate is still present but red cells have lysed and alveolar walls are no longer congested
Stage 4 - resolution: exudate is digested and absorbed rapidly so that the lungs return to normal without parenchymal destruction. Pleural inflammation often organises with fibrosis and adhesions.
What is a common feature of Staphylococcal and Klebsiella infections?
These bacteria cause suppurative (pus forming) lung infection with abscess formation. Klebsiella also produces a mucoid appearance on cut surface and thick bronchial secretions.
What is bronchopneumonia?
This is patchy infective consolidation of the lungs in a predominantly bronchial or peribronchial "lobular" distribution.
It is an extremely common form of pneumonia particularly in hospital patients.
Organisms include gram negatives - e.g. Klebsiella, Pseudomonas, E.coli, Proteus - Strep pneumoniae, influenza and anaerobes.
What are the pathological features of bronchopneumonia?
There is a suppurative bronchitis and bronchiolitis with acute inflammatory exudate or pus within the lumen. Alveoli are filled with polymorphs, fibrin and organisms and show destruction of their walls and suppuration.
What are the typical features of pneumococcal pneumonia?
Pneumococcal pneumonia usually caused CAP and is commonest in the elderly, alcoholics, immunosuppressed, post splenectomy and patients pre existing lung disease.
It causes lobar pneumonia. If severe check for urinary antigen.
Treatment is with amoxicillin or clarithromycin
This pneumonia is commonly secondary to prior viral upper respiratory tract infection and affects the young, elderly, IV drug users or patients with underlying diseases (e.g. lymphoma). It causes bilateral cavitating bronchopneumonia with abscess formation...
It is treated with Flucloxacillin (penicillinase resistant penicillin - oral) +/- rifampicin or vancomycin if MRSA suspected.
In what group of patients does Klebsiella affect?
Klebsiella pneumonia is rare. It typically effects the elderly, diabetics and alcoholics (this is an important group). It causes cavitation in the upper lobes primarily and patients often complain of "red current jelly" haemoptysis.
Treatment is with cefotaxime or imipenem.
Pseudomonas typically affects what group of patients? How is it treated?
It is a common pathogen in bronchiectasis and CF. It also causes hospital acquired infections particularly on ITU or after surgery.
Treatment is with an anti-pseudomonal penicillin - e.g. Tazoscin
Which group of patients are affected by mycoplasma?
Mycoplasma infections occur in epidemics about every 4 years and accounts for 15-20% of CAP. It can affect any age group, is more common between 5 and 15 years but more serious in adults.
Describe the course of mycoplasma infection? How is it treated?
It presents insidiously with flu like symptoms (headache, myalgia, arthralgia) followed by a dry cough.
Cold agglutinins may also cause an autoimmune haemolytic anaemia. CXr shows reticulo-nodular shadowing or patchy consolidation often of 1 lower lobe and worse than the signs suggest.
Treatment is with clarithromycin or doxycycline.
What is the usual source of legionella pneumonia?
Legionella pneumonia is usually caused by legionella pneumophila. The main source of infection is the environment, especially piped hot water systems, water reservoirs and cooling units of air conditioning systems. These are colonized by Legionella and overgrowth of organisms is probably important.
There is NO case-to-case transmission.
What are the clinical features of Legionella pneumonia?
Legionella causes a range of illness from subclinical infection to Pontiac fever - a flu like illness - or pneumonia.
Typically, it presents with flu like symptoms (headache, myalgia, arthralgia) followed by a dry cough and dyspnoea.
Extra-pulmonary manifestations include anorexia, D&V, hepatitis, renal failure, confusion and coma. CXr often shows bi-basal consolidation.
How is Legionella pneumonia diagnosed and treated?
Legionella pneumonia is diagnosed by legionella urine antigen/ culture.
Treatment is with a fluoroquinolone (e.g. cipro) for 2-3 wks or clarithromycin.
How can chlamydia affect the lung?
Chlamydial spp. can cause 2 main lung infections:
1) Chlamydiophila pneumoniae - is the commonest chlamydial infection. Person to person spread occurs causing a biphasic illness: pharyngitis, hoarseness, otitis, followed by pneumonia. Dx: chlamydophila complement fixationtests. Rx: doxycycline
2) Chlamydiophila psittaci - causes psittacosis, an ornithosis acquired from infected birds (typically parrots). Symptoms include headache, fever, dry cough, lethargy, anorexia, and D&V. Rx: doxycycline
What viruses commonly cause pneumonia?
Viruses are a common cause of pnuemonia in early childhood but they are much less frequent in healthy adults. They can also be important in certain immunocompromised patients - e.g. organ transplantation
Healthy adults - influenza
Young children - RSV
Previously healthy adults - adenovirus
Immunocompromised - many but esp CMV
What is the macroscopic appearance of viral pneumonia?
Appearance is variable. There can be multiple small foci or extensive haemorrhagic consolidation of both lungs. The areas are firm and congested. There is also congestion of the trachea and bronchi.
What are the microscopic features of viral pneumonia?
1) Trachea and bronchi: intense vascular congestion with mononuclear inflammatory cell infiltrate
2) Lungs: dependent on severity, ranging from interstitial congestion and oedema to widespread changes or ARDS. In some cases viral inclusion bodies are seen - e.g. CMV or giant cells - e.g. measles
What are the effects of viral pneumonia?
These can be divided into primary and secondary effects.
Primary: clinical disease ranges from extremely mild pulmonary involvement to fulminating lethal forms. Influenzal pneumonia is particularly serious.
Secondary: secondary infection with pyogenic bacteria transforms the disease into a severe suppurative bronchopnuemonia. This is common in influenza.
What parasites and helminths cause pneumonia? What patient groups are they primarily associated with?
The patients are almost ALWAYS immunocompromised. The commonest parasitic infection is Pneumocystis. Strongyloides is the most frequent worm causing pulmonary symptoms.
Both are important in AIDS.
What is the course of Pneumocystis pneumonia?
Pneumocystis carinii (formerly jirovecii) is the causative organism. It is extremely common in AIDS where it affects 25-30% of cases.
A high percentage of the population is exposed to pneumocystis and infection results from reactivation of latent organisms.
Patients present with a dry cough, exertional dyspnoea, fever and bilateral crepitations.
What fungi can cause pneumonia?
Similar to parasites and helminths, fungal pneumonia occurs exclusively in immunocompromised patients (e.g. AIDS, cytotoxic drugs, malignancy, connective tissue disease etc).
Several fungi are implicated but there is a wide geographical variation:
- Zygomycetes (group of fungi that may cause lesions similar to aspergillus)
Infections that are common in immunosuppression are: Pneumocystis (most common), Cryptococcus, atypical mycobacterial infection, TB, CMV, pyogenic bacteria
Name the pulmonary manifestations of Aspergillus infection?
1) Bronchial asthma: exposure to high levels of spores can induce typical asthma
2) Extrinsic allergic alveolitis: farmers*, malt workers
3) Allergic bronchopulmonary aspergillosis: a clinical syndrome usually in asthmatics, resulting from combined types I, III and IV hypersenitivities. Pathological components seen in association are:
- eosinophilic pneumonia
- mucoid impaction of bronchi - i.e. mucus plugs in large bronchi
- bronchocentric granulomatosis - a granulomatous infiltrate around bronchi
- proximal bronchiectasis - chronic cases
4) Aspergilloma (mycetoma) - a fungus ball in a pre-existing cavity (mostly TB or sarcoidosis) by Aspergillus. Causes haemoptysis but mostly asymptomatic. Occurs in immunocompetent individuals and is non invasive
5) Invasive pneumonia - occurs almost exclusively in immunocompromised individuals. Invasiveness varies from slowly progressive to fulminant pnuemonia. Fungal hyphae can often be seen invading blood vessels walls and there is little or no inflammatory response. Mortality is high.
What is histoplasmosis?
H.capsulatum is worldwide in distribution but heavily endemic in the central USA. In the immunocompetent it is usually a subclinical infection somewhat similar to primary TB but occasionally has a more acute pneumonic course.
Dissemination often from reactivation of dormant granulomas is frequently seen in the immunocompromised.
Methamine silver stain is used in the diagnosis.
What is coccidiomycosis?
This disease is restricted to the Western hemisphere, largely the south-western USA and usually manifests as a localised "coccidioma".
What is a lung abscess?
A localised area of pulmonary parenchymal suppurative necrosis due to infection by pyogenic organisms (usually bacteria).
What are the causes of lung abscesses?
3) Pre-existing lung disease
How can aspiration lead to lung abscess?
Oropharyngeal secretions normally contain a large number of organisms. Inhalation of this material into the lung predisposes to infection. The infections are often mixed, usually contain anaerobes and occur in the following situations:
i) Inhalation of infected material - e.g. from nasal sinuses
ii) Impaired conscious state - e.g. head injury, alcohol, intoxication, epilepsy, stroke
iii) Disturbance of swallowing - e.g. strictures of the oesophagus, achalasia and pseudobulbar palsy (MND). Secretions cannot be swallowed so accumulate and spill over into the lungs, particularly at night. They can become infected either within the lung or within the oesophagus
What infections cause lung abscesses?
1) Pneumonia: abscess can occur as a complication of primary necrotizing pneumonia - e.g. Staph, Klebsiella, Strep
2) Local spread: from spinal or subphrenic abscess, empyema
3) Blood borne: from any infectious focus, can localize in the lung by septicaemia, bacteraemia or septic embolism
What pre-existing lung diseases cause abscesses?
1) Tumours: obstruction of a bronchus by a tumour produces retention of secretions, parenchymal collapse and colonisation by organisms causing suppuration. This is common in bronchial carcinoma.
2) Others: bronchiectasis, and congenital abnormalities - e.g. bronchogenic cyst
Where are abscess most commonly located?
This is somewhat dependent on the cause. Abscesses associated with aspiration are usually solitary, occur more on the right (vertical right main bronchus) and involve predominantly the posterior segment of the upper lobe and apex of the lower lobe.
Postpneumonic and bronchiectatic abscesses are often multiple and basal. They are filled with pus, and sometimes air (causing an air-fluid level).
What are the clinical features of lung abscesses?
Swinging pyrexia; cough; purulent, foul smelling sputum; pleuritic chest pain; haemoptysis; malaise; weight loss
What are the complications of lung abscesses?
There are several possible outcomes:
1) Scarring: the abscess may resolve with fibrous obliteration
2) Empyema (pus in the pleural space): due to extension of infection or rupture into the pleural cavity
3) Bronchopleural fistula
4) Haemoptysis: due to erosion of vessels in the abscess wall
5) Pneumonia: by local extension into the adjacent parenchyma
6) Metastatic abscesses: due to blood spread - e.g. to brain
7) Amyloidosis: rare and of the reactive systemic type when chronic abscesses persist
What are the x ray findings suggestive of a pulmonary abscess?
Coin and cavitating lesions can be difficult to interpret on chest x ray.
A discrete approximately circular area of whiteness seen within a lung field is termed a coin lesion. If the edge is spiculated, irregular or lobulated it suggests a MALIGNANT lesion. If the centre of the lesion is more lucent than the edge it suggests a cavitating process.
Abscesses often appear as wall cavities with a fluid level.
Name some complications of pneumonia?
1) Respiratory failure: type 1 failure is most common due to consolidation affecting the alveolar capillary diffusion barrier (rather than a problem with ventilation ccausing type 2 failure)
2) Hypotension: combined effects of dehydration and vasodilation due to sepsis. Try and maintain systolic above 90mmHg
3) Atrial fibrillation: common, esp. in elderly. Treat with beta blocker or digoxin
4) Pleural effusion: inflammation of the pleura by adjacent pneumonia may cause fluid exudation into the pleural space. If this is produced faster than it can be reabsorbed an effusion develops (infection causes exudative effusion with high protein)
5) Empyema: is pus in the pleural space. It should be suspected if a patient with resolving pneumonia develops a recurrent fever
6) Lung abscess
7) Sepsis: bacterial spread from the lung parenchyma into the bloodstream. This may cause metastatic infction - e.g. infective endocarditis, meningitis
8) Pericarditis and myocarditis
9) Jaundice: usually cholestatic and may be due to sepsis or secondary to antibiotic treatment (esp. flucloxacillin and co-amoxiclav)