Lower respiratory tract infection and pneumonia: Difference between revisions

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*'''Chest symptoms'''  are: [[shortness of breath]], [[cough]], purulent [[sputum]], [[pleuritic pain]] and [[haemoptysis]].  
*'''Chest symptoms'''  are: [[shortness of breath]], [[cough]], purulent [[sputum]], [[pleuritic pain]] and [[haemoptysis]].  
*'''Chest signs''' include: tachypnoea, dyspnoea, [[pleural rub]], consolidation (reduced [[chest expansion]], dull on [[percussion]], [[bronchial breathing]] and increased [[vocal resonance]]/vocal and [[tactile fremitus]]).
*'''Chest signs''' include: tachypnoea, dyspnoea, [[pleural rub]], consolidation (reduced [[chest expansion]], dull on [[percussion]], [[bronchial breathing]] and increased [[vocal resonance]]/vocal and [[tactile fremitus]]).
In the community, the important thing is to differentiate between LRTI and pneumonia. '''Purulent sputum''' is usually the best way to do this.
In the community, the important thing is to differentiate between viral and bacterial LRTI. '''Purulent sputum''' is usually the best way to do this.


===Investigations===
===Investigations===

Revision as of 10:31, 22 May 2012

Definition

Lower respiratory tract infection - an infection of the lower respiratory tract without radiological change.

Pneumonia - an infection of the lower respiratory tract with radiological change.

Epidemiology

Common.jpgHas incidence of 1-3/1000 and, of those admitted to hospital the mortality is 10%

Pathophysiology

Basically, viruses or bacteria gets into your lower respiratory tract and you get an infection. Go figure. Here are the different types which have different bacteria:

Lower respiratory tract infection (LRTI)

90% of these are caused by viral infections including rhinovirus, adenovirus and influenza and usually do not need antibiotics. Bacterial causes are similar to those for community-acquired pneumonia.

Community-acquired (CAP)

This one is acquired in the community, the most common pneumonia and the most common cause is Strep. pneumoniae. Other common pathogens are H. influenzae and M. pneumoniae. 15% are viral. Of the remaining bacteria, staph. aureus, legionella species, Moraxella catarrhalis, and Chlamydia are the most common. Everything else is rare.

Hospital-acquired (HAP or nosocomial)

The most common are enterobacteriaceae or Staph. aureus. Pseudomonas, Klebsiella, Bacteriodes and Clostridia can be the culpirts too.

Aspiration

Likely in those with stroke, myasthenia, bulbar palsies, reduced consciousness, oesophageal disease (achalasia, GORD), or poor dental hygeine (aspirate anaerobic bacteria).

Immunocompromise

All those bacteria in CAP are common. Others are gram negative bacteria and Pneumocystis jiroveci. Fungi, viruses (CMV, HSV) and mycobacteria are also far more common.

Risk Factors

Being old but besides that, not a lot else.

Clinical Features

In the community, the important thing is to differentiate between viral and bacterial LRTI. Purulent sputum is usually the best way to do this.

Investigations

You're basically trying to see how bad the pneumonia is.

Bloods

Imaging

  • Chest X-Ray - this is really important. Technically, if there is no radiological abnormality, it's not a pneumonia.

Others

You may consider pleural fluid and bronchoscopy if the patient is really ill. To that end....

Assessing severity

Use the CURB65 score. A positive criterion is +1:

  • Confusion
  • Urea > 7mmol/l
  • Respiratory rate >/= 30/min
  • Blood pressure < 90 systolic
  • </=65 years old

0-1 can be managed at home; 2 indicates hospitalisation; >/=3 indicates severe pneumonia. Other things that make it worse are: comorbidity, multilobar/bilateral, PaO2<8kPa OR SaO2<92%.

Management

Essentially, it's antibiotics, oxygen and fluids.

Antibiotics

The treatments vary on where you got the infection. These lists are all alternatives:

Community

If it's mild and had NO previous treatment use ONE of:

  • Amoxicillin 500-1000mg/8h po
  • Erythromycin 500mg/6h po

If it's mild but has been previously treated use ONE of:

  • Amoxicillin + Erythromycin (see above for doses)
  • Fluoroquinolone
  • If IV required use ampicillin 500mg/6h + erythromycin 500mg/6h IVI

If it's severe:

  • Erythromycin 1g/6h IV

WITH one of:

  • Co-amoxiclav IV
  • Cefuroxime 1.5g/8h IV

If it's atypical use ONE of:

  • Clarithromycin 500mg/12h po/IVI +/- rimfampicin - Legionella pneumophilia
  • Tetracycline - Chlamydia species
  • Co-trimoxazole - Pneumocystis jiroveci

Hospital

Use:

  • Aminoglycoside IV (gentamicin)

WITH one of:

  • Antipseudomonal penicillin
  • 3rd generation cephalosporin IV

Aspiration

Use cefuroxime 1.5g/8h IV + Metronidazole 500mg/8h IV

Neutropenic

Use: Aminoglycoside IV WITH one of

  • Antipseudomonal penicillin IV
  • 3rd generation cephalosporin IV

Consider using antifungals after 48h of infection.

Oxygen and fluids

Basically keep the PaO2>8kPa and/or O2>92%. With regards to IV fluids, give if there is anorexia, dehydration or shock

Prognosis

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