Pneumonia (CAP and HAP)

Question 1

Pneumonia

Answer 1

Pneumonia is characterised by acute inflammation with an intense infiltration of neutrophils in and around the alveoli and the terminal bronchioles.

The affected bronchopulmonary segment or the entire lobe may be consolidated by the resulting inflammation and oedema

Question 2

Risk factors for pneumonia

Answer 2

Age: especially infants, young children and the elderly.

· Lifestyle: smoking, alcohol.

· Preceding viral infections - eg, influenza predisposing toStreptococcus pneumoniaeinfection.

· Respiratory: asthma, chronic obstructive pulmonary disease (COPD), malignancy, bronchiectasis, cystic fibrosis.

· Immunosuppression, AIDS, cytotoxic therapy - increased risk of infection withStaphylococcusspp., tuberculosis, Gram-negative bacilli andP. jirovecii.

· Intravenous drug abuse, often associated withStaphylococcus aureusinfection.

· Hospitalisation - often involving Gram-negative organisms.

· Aspiration pneumonia: patients with impaired consciousness, neurological disease such as cerebrovascular or Parkinson’s disease, or patients with oesophageal obstruction are at risk of aspiration pneumonia which usually affects the right lung and is caused by anaerobes from the oropharynx.

· Underlying predisposing disease: diabetes mellitus, cardiovascular disease.

Question 3

CAP

Answer 3

This is defined as the presence of symptoms and signs consistent with acute lower respiratory tract infection in association with new radiographic shadowing for which there is no alternative explanation

Question 4

Pathogens that cause CAP

Answer 4

The most likely organisms are:S. pneumoniae, S. aureus,Mycoplasma pneumoniae,Haemophilus influenzae,Chlamydophila pneumoniaeand respiratory viruses.

Mixed pathogens occur up to 25% of the time.

Question 5

Presentation of CAP

Answer 5

• cough, purulent sputum which may be blood-stained or rust-coloured, breathlessness, fever, malaise

Question 6

What do elderly cap patients mainly present with

Answer 6

• The elderly may present with mainly systemic complaints of malaise, fatigue, anorexia and myalgia. Young children may present with nonspecific symptoms or abdominal pain.

Question 7

Pneumonia associated signs

Answer 7

Signs: tachypnoea, bronchial breathing, crepitations, pleural rub, dullness with percussion

Question 8

Assessing the need for CAP patients to be admitted to hospital

Answer 8

CRB-65

• A 4-point score system is used, one point for each of:
• Confusion (abbreviated mental test score 8 or less, or new disorientation in person, place or time).
• Respiratory rate 30 breaths/minute or more.
• Systolic blood pressure below 90 mm Hg (or diastolic below 60 mm Hg).
• Age 65 years or older.
• Patients who have a CRB-65 score of 0 are at low risk of mortality and should be considered for home care.
• Consider hospital admission for all other patients, particularly those who have a CRB-65 score of 2 or higher.

Question 9

Management of CAP

Answer 9

Patients with suspected CAP should be advised not to smoke and to rest and drink plenty of fluids. Other general measures include:

• Oxygen for hypoxia; ventilation if there is severe hypoxia.
• Fluids for dehydration.
• Analgesics: non-steroidal anti-inflammatory drugs (NSAIDs) and paracetamol - for mild pleuritic pain; more severe pain may require opiate analgesia but care is needed not to aggravate CO2retention.
• Nebulised saline may help expectoration.
• Chest physiotherapy has doubtful benefit. Physiotherapy may be more important in helping to mobilise the patient
• Antibiotics

Question 10

Antibiotic usage for CAP

Answer 10

• Antibacterials are recommended in all suspected cases of pneumonia, starting as soon as possible.
• Antimicrobial therapy should be based on the patient’s characteristics, the setting in which aspiration occurred, the severity of pneumonia, and available information regarding local pathogens and resistance patterns.

Question 11

Antibiotics for low-severity cap

Answer 11

• Offer a five-day course of amoxicillin, reserving clarithromycin, erythromycin (in pregnancy) or doxycycline for patients allergic to penicillin or if atypical pathogen suspected. Stop antibiotic after five days unless microbiology results suggest a longer course or the patient is not clinically stable.

Question 12

Antibiotics for moderate-to-severe CAP

Answer 12

• Patients with moderate-to-severe CAP are normally treated in hospital. However, there may be occasions (eg, refusal of a patient to be admitted) when the GP will be required to provide treatment.
• For moderate-severity CAP, treatment should be as per low-severity CAP pending microbiology results.

Question 13

Antibiotics for high severity CAP

Answer 13

• For high-severity CAP a five-day course of co-amoxiclav with clarithromycin or erythromycin (in pregnancy) should be offered. The oral or intravenous route can be used. Obviously the latter may prove challenging in the community.
• Levofloxacin orally or IV is an option for patients allergic to penicillin.

Question 14

Atypical pathogens that cause pneumonia

Answer 14

• M. pneumoniae
• C. pneumoniae
• Legionella pneumophila
Other micro-organisms that cause similar patterns of presentation via pulmonary infection include:
• Chlamydophila psittaci(exposure to birds, particularly ill ones, is a useful clue in the history).
• Coxiella burnetii(presenting as Q fever).
• Viral pneumonias including influenza A, severe acute respiratory syndrome (SARS), respiratory syncytial virus (RSV), adenoviridae and pneumonitis due to varicella (chickenpox pneumonitis).

Question 15

Risk factors for spread of pneumonia by atypical pathogens

Answer 15

• Mycoplasma and chlamydophila spread by person-to-person contact and spread is most common in closed populations - eg, schools, offices.
• Legionellae are found most commonly in fresh water and man-made water systems.

Question 16

M pneumoniae presentation

Answer 16

• Vague and slow-onset history over a few days or weeks of constitutional upset, fever, headache, dry cough with tracheitic ± pleuritic pain, myalgia, malaise and sore throat.
• This is like many of the common viral illnesses but the persistence and progression of symptoms is what helps to mark it out.
• In otherwise healthy individuals, it usually resolves spontaneously over a few weeks.
• The hacking, dry cough can be very persistent.
• Extra-respiratory features include rashes such as erythema multiforme, erythema nodosum and urticaria; neurological complications like Guillain-Barré syndrome, transverse myelitis, cerebellar ataxia and aseptic meningitis; haematological complications such as cold agglutinin disease and haemolytic anaemia; joint symptoms like arthralgia and arthritis; cardiac complications such as pericarditis and myocarditis; rarely, may cause pancreatitis.

Question 17

C. pneumoniae presentation

Answer 17

• Gradual onset, which may show improvement before worsening again; incubation period is 3-4 weeks.
  
  • Initial nonspecific upper respiratory tract infection symptoms lead on to bronchitic or pneumonic features.
  • Most of those infected remain quite well or are asymptomatic.
  • Cough with scanty sputum is a prominent feature.
  • Hoarseness is a common feature.
  • Headache affects the majority of symptomatic sufferers.
  • Fever is relatively unusual.
  • Symptoms may drag on for weeks or months, despite a course of appropriate antibiotics.
  • Where it causes significant problems, this may be due to secondary infection or co-existing illness - eg, diabetes.

Question 18

L. pneuophila presentation

Answer 18

• This tends to be the most severe of the pneumonias due to atypical pathogens. See the separateLegionnaires’ Diseasearticle.
• Focal outbreaks centred around poorly maintained air-conditioning or humidification systems (although this is often noted retrospectively by public health physicians).
• 2-10 days’ incubation period.
• Initial mild headache and myalgia leading to high fever, chills and repeated rigors; non-chest symptoms often predominate early on.
• Cough is nearly always present, initially unproductive but may lead to expectoration later.
• Dyspnoea, pleuritic pain and haemoptysis are not uncommon.
• Gastrointestinal upset, such as diarrhoea, nausea and vomiting or loss of appetite/anorexia, may occur.
• There may be neurological complications such as confusion, disorientation and focal neurological deficit.
• Arthralgia and myalgia are often reported.
Severe complications include pancreatitis, peritonitis, pericarditis, myocarditis, endocarditis and glomerulonephritis.

Question 19

Specific signs to look for with atypical pneumonia causing pathogens

Answer 19

• Vital signs should be checked.
  
  • Look for evidence of extra-thoracic involvement if an atypical pathogen is suspected.
  • On the whole, chest signs are not helpful. Indeed, it is often the discordance between the chest signs and the illness of the patient, or the floridity of initial CXR appearance, that raises the suspicion of an atypical pathogen.
  • Nonspecific chest signs and evidence of consolidation may be found but this is much less common than in the ‘standard’ pneumonias.
  • There may be signs in other systems, due to complications of the infection.

Question 20

Management of CAP caused by atypical pathogens

Answer 20

Pneumonias due to atypical pathogens are usually treated as for other CAP, at least initially. There is little value in serological testing for most patients with CAP

* Macrolides, such as doxycycline, clarithromycin and erythromycin (the preferred option in pregnancy), have been shown to be effective in the treatment of all three most common infective organisms. They should be considered in all cases of pneumonia (including community-acquired) where atypical pathogens are suspected. Resistance to macrolides is a growing concern
* Severe legionella infections may require rifampicin as well as a macrolide

Fluoroquinolones are also effective against all three of the common infective organisms

Question 21

HAP

Answer 21

This is defined as a new infection of lung parenchyma appearing more than 48 hours after admission to the hospital.

Question 22

Which patients are more susceptible to HAP

Answer 22

• It occurs mostly in patients who are severely debilitated, immunocompromised or mechanically ventilated.

Question 23

What is HAP occuring in less than 5 days usually caused by

Answer 23

• Infection occurring less than five days after hospital admission is usually caused byS. pneumoniae.

Question 24

What is HAP occuring after 5 days usually caused by

Answer 24

• Infection occurring after this time is usually caused byH. influenzae,methicillin-resistantStaphylococcus aureus(MRSA),Pseudomonas aeruginosaand other non-pseudomonal Gram-negative bacteria.
  
  • Hospital-acquired pneumonia is often caused by multiple organisms.

Question 25

HAP differential diagnosis

Answer 25

• Different organism responsible.
  
  • Pulmonary oedema.
  • Pleural effusion.
  • Pneumothorax.
  • Pulmonary embolus.
  • Asthma.
  • COPD.
  • Bronchiectasis.
  • Fibrosing alveolitis.
  • Neoplasm.
  • Sarcoidosis.
  • Pneumonia complication - eg, empyema, lung abscess.

Question 26

HAP investigations

Answer 26

General investigations are not necessary for the majority of patients who are managed in the community. Pulse oximeters allow for simple assessment of oxygenation. When a patient is admitted to hospital:
• FBC with differential white cell count.
• CRP (to aid diagnosis and as a baseline measure).
• Renal function and electrolytes.
• LFTs.
• Blood cultures.
• Pneumococcal and legionella urinary antigen tests.
• CXR. (A follow-up CXR six weeks after recovery from pneumonia is recommended.)
• Sputum examination and culture.
• Pulse oximetry or blood gases.
• Aspiration of pleural fluid (for biochemistry and culture).

Question 27

Complications of HAP

Answer 27

• Pleural effusion that is usually sterile.
  
  • Empyema: a reactive effusion can occur but is trivial. Empyema is potentially more serious and presents as the persistence of fever and leukocytosis after 4-5 days of appropriate antibiotic therapy.
  • Lung abscess: can occur in disease due toS. pneumoniaeand is classically seen in patients with klebsiella or staphylococcal pneumonia.
  • Pneumatocele.
  • Pneumothorax.
  • Pyopneumothorax - eg, following rupture of a staphylococcal lung abscess in the pleural cavity.
  • Deep vein thrombosis.
  • Septicaemia, pericarditis, endocarditis, osteomyelitis, septic arthritis, cerebral abscess, meningitis (particularly in pneumococcal pneumonia).
  • Postinfective bronchiectasis.
  • Acute kidney injury.

Question 28

Which pathogen has the most severe course

Answer 28

Legionella has the most severe course and may cause significant morbidity if not treated early

Question 29

Pneumona prevention

Answer 29

• Early appropriate antibiotic therapy reduces mortality and morbidity.
  
  • Influenzaandpneumococcal vaccination.
  • Targeted risk reduction, such assmoking cessation.