Pulmonary Embolism

Question 1

What is a PE? What are VTEs?

Answer 1

Pulmonary embolism (PE) describes a blood clot (thrombus) in the pulmonary arteries. An embolus is a thrombus that has travelled in the blood, often from a deep vein thrombosis (DVT) in a leg. The thrombus will block the blood flow to the lung tissue and strain the right side of the heart.

DVTs and PEs are collectively known as venous thromboembolism (VTE).

Question 2

What are the risk factors for DVT or PE?

Answer 2

• Immobility
• Recent surgery
• Long-haul travel
• Pregnancy
• Hormone therapy with oestrogen (e.g., combined oral contraceptive pill or hormone replacement therapy)
• Malignancy
• Polycythaemia (raised haemoglobin)
• Systemic lupus erythematosus (SLE)
• Thrombophilia

Question 3

What are the available VTE prophylaxis treatments? and what are their counterindications.

Answer 3

1) low molecular weight heparin- enoxaparin, dalteparin; counterindications- active bleeding or existing anticoagulants such as warfarin or DOACs (rivaroxaban, apixaban)

2) anti-embolic compression stockings; counterindication- peripheral arterial disease

Question 4

How does PE present?

Answer 4

• SOB
• Cough
• Hemoptysis
• Pleuritic chest pain
• hypoxia
• tachycardia
• tachypnoea
• low grade fever
• hemodynamic instability causing hypotension

Question 5

Which scoring systems are used to predict PEs?

Answer 5

• PERC rule
• Wells score

Question 6

How do you diagnose a PE?

Answer 6

• wells score, the outcome decides the next steps:
• CTPA (CT pulmonary angiogram)
• D-dimer, if positive then CTPA

D-dimer is sensitive but not specific for a VTE, other conditions that cause raised D-dimer:
- pneumonia
- malignancy
- HF
- Surgery
- Pregnancy

Question 7

How does D-dimer indicate a DVT/PE?

Answer 7

D-dimer is a small protein fragment present in the blood after a blood clot dissolves. D-dimer is not a direct indicator of the presence of a clot; rather, it indicates that clots have formed and are being broken down.

Question 8

What do patients with PE show on ABGs? Explain why. What happens in hyperventiliation and hypoventilation syndrome?

Answer 8

Patients with a pulmonary embolism often have respiratory alkalosis on an ABG. Hypoxia causes a raised respiratory rate. Breathing fast means they “blow off” extra CO2. A low CO2 means the blood becomes alkalotic.

The other main cause of respiratory alkalosis is hyperventilation syndrome. Patients with PE will have a low pO2, whereas patients with hyperventilation syndrome will have a high pO2.

Question 9

What is the management for PE?

Answer 9

• oxygen, analgesia
• anticoagulation- DOACs such as apixaban or rivaroxaban as first-line
• LMWH such as enoxaparin, dalteparin should be started immediately when PE is suspected
• Massive PE with haemodynamic compromise is treated with a continuous infusion of unfractionated heparin and considering thrombolysis.

Question 10

What is thrombolysis? What are the risks involved? What are some examples of it? What are the two ways that it can be performed?

Answer 10

Thrombolysis involves injecting a fibrinolytic (breaks down fibrin) medication that rapidly dissolves clots.

There is a significant risk of bleeding with thrombolysis, making it dangerous. It is only used in patients with a massive PE where the benefits outweigh the risks.

Some examples of thrombolytic agents are streptokinase, alteplase and tenecteplase.

Two ways it can be performed:
1) Intravenously using a peripheral cannula
2) Catheter-directed thrombolysis (directly into the pulmonary arteries using a central catheter.

Question 11

What is the long term anticoagulation treatment for VTE?

Answer 11

• DOACs- counterindicated in severe renal impairment
• Warfarin (VIT K antagonist)
• LMWH- first line in pregnancy