12.2 Pulmonary embolism

Question 1

Explain the role of the lungs (brief) - PE

Answer 1

• Ventilation
• Gas exchange
• Is an immune organ (anti-inflammatory)

In ~45s ALL blood goes through the lungs

Question 2

What are the different types of embolisms & briefly explain them?

Answer 2

1. Mycotic
   
   • ​​Transfer of infective pathogen TO lungs from DISTANT source
     
     • e.g. Roth spots (infarction of retina e.g.due to diabetes)
     • e.g. splinter haemorrhages (usually traumatic & are perpendicular to the nail)
2. Fat
   
   • ​​From long bone fractures
     
     • Fat causes MULTIFOCAL inflammation in lungs
3. Air
   
   • ​​Due to gas in veins (e.g. cannulations)
4. Thrombotic
   
   • ​​Usually from deep veins in leg (can be from IV lines)
   • Caused by VIRCHOW TRIAD –> causes DVT
     
     1. Venous stasis (e.g. long flights)
     2. Endothelial disruption/inflammation (e.g. damage to circulation)
     3. Hypercoagulation/absence of clotting inhibition (e.g. during infection/cancer)

Question 3

What are the risk factors of a pulmonary embolism?

Answer 3

• 90% from a DVT (deep vein thrombosis) e.g. post pelvic surgery
• Is age dependent (INCREASE age = INCREASE risk)
• Being male
• Having cancer, heart failure, chronic lung disease

Question 4

What happens when someone has a pulmonary embolism?

Answer 4

• Impairs gas exchange
• DECREASED cross-sectional area of pulmonary arterial bed
  
  • INCREASED pulmonary arterial pressure
    
    • DECREASED cardiac output
      
      • ​Can lead to cardiac arrest
  • Alveolar collapse
    
    • Could cause hypoxaemia
• Can lead to INFARCTED lung NOT often as should be a continued supply of oxygen from bronchial circulation & airways
• MOST PE aren’t diagnosed prior to death
  
  • RAPIDLY detriorate prior to death

Question 5

Explain the process following endothelial damage

Answer 5

Question 6

What is a d-dimer test?

Answer 6

• Is +ve if above the threshold
• Is 95% sensitive
• Is 50% specific
• Is NOT used to prove pulmonary embolism
• It proves that there is an INCREASE in inflammation, infection, cancer

Question 7

How do you diagnose someone with a pulmonary embolism?

Answer 7

• Use a Wells scoring
• Doppler USS (ultrasound)
  
  • GOOD
    
    • Measures compressibility
    • ​Assessment of venous system
    • INCREASE specificity & sensitivity
    • Can use colour (to help)
  • BAD
    
    • Is operator dependent
• V/Q scan (ventilation/perfusion scan)
  
  • GOOD
    
    • Evaluates pulmonary vasculature perfusion & segmental bronchoalveolar tree ventilation
    • LOW dose
      
      • Is GOOD for pregnancies
  • BAD
    
    • INCREASE dependant on reporter (confidence & expertise)
• MRI
  
  • BAD
    
    • ​LESS accurate than V/Q
    • Need EXPERTISE help & long scan times (unsuitible if acutely ill)
• Echocardiography
  
  • ​GOOD
    
    • Assessing haemodynamic effects of embolism (suggest coexisting heart disease)
  • BAD
    
    • LESS sensitive & specific (for PE)
• CTPA
  
  • ​GOOD
    
    • 16 sliced CT scan
    • INCREASE sensitivity & specificity
    • Reporters are more confident & better expertienced
  • BAD
    
    • Presentation often UNCLEAR
    • Doses used are LOW but HIGH doses = INCREASE radioactivity

Question 8

Explain the treatment of PE

Answer 8

1. LMWH (low molecular weight heparin)
2. Warfarin
   
   • A vitamin K inhibitor
   • INCREASE risk of bleeding (can cause death if haemorrhage & INCREASE risk of GI bleeding)

Question 9

What is subsegmental PE & what is the treatment for it?

Answer 9

• It is a peripheral emboli LIMITED to subsegmental pulmonary arteries (involves 1 or more subsegmental branches)
• TREATMENT
  
  • Anti-coagulants

Question 10

What is the assessment criteria for someone with a PE?

Answer 10

• Using a pulmonary embolism severity index (table) & using a criteria table

Question 11

What is the treatment for a massive PE?

Answer 11

GOOD (better clinical outcome)

• Streptokinase & heparin

BAD

• Heparin alone

Question 12

What are the cardiac biomarkers od a submassive PE?

Answer 12

Submassive PE = intermediate PE

Cardiac Biomarkers:

• Beta naturetic peptide (BNP)
• N terminal pro BNP (NpBNP)
• Troponin assay (TnT/TNI)