Pulmonary embolism

Question 1

Definition

Answer 1

Formation of blood clot in the lower limbs due to low pressure system. Clot then travels to pulmonary artery.

Question 2

Investigation

Answer 2

Limited use: 
-CXR
-Blood count, biochemistry , Blood gas count 
-CT angiogram
useful:
-V/Q scan
-D-dimer: breakdown of coagulant test- shows how much fibrin has been broken down by plasmin 
- ECHO 

preventative:

• CT of abdomen and mammogram
• Thrombophilia screening

Question 3

Signs

Answer 3

• Pleural rub, pyrexia, pleural effusion
• Tachypnoea, tachycardia, hypoxia
• tachypnoea, tachycardia, hypoxia and hypotension

Question 4

Symptoms

Answer 4

Pleuritic chest pain 
acute dyspnoea 
cough
Tachycardia 
Haemoptysis 
If severe: cardiac arrest/ syncope 
-cyanosis 
-low BP
-tachycardia 
-Elevated JVP

Question 5

Treatment

Answer 5

Treat underlying condition:

• 02
• Anticoagulants: slow down the process of clot formation e.g. Warfarin,LMW Heparin
• Antiplatelets: slow down the adherence of platelets e.g. aspirin
• Thrombolysis : anteplase
• Pulmonary embolectomy

Question 6

How to test severity

Answer 6

Wells score: signs and symptoms
Geneva score: symptoms and risk factors
pulmonary CT angiogram

Question 7

Well’s score outcome

Answer 7

> 6.5- high probability
4.5-6.0- moderate probability
<4.50- low probability

Question 8

Pulmonary infarction

Answer 8

Rare due to dual supply to the lungs
If clot lodges in pulmonary artery can cause increase in pressure in pulmonary circulation which causes leakage of blood into alveolar spaces
This can lead to pulmonary infarction

Question 9

Risk factors for PE

Answer 9

• Trauma
• Surgery- Pro-coagulants develop
• Pregnancy
• Clotting factor problems
• Cancer
• CVS disease e.g. MI

Question 10

How does PE develop

Answer 10

• Rupture in the endothelium
• platelets bind to damaged section of the endothelium
• platelets become activated by collagen and tissue factor which are usually kept separate from the blood
• platelet plug
• Coagulation cascade causes the clotting factors to become cleaved and fibrinogen to become fibrin
• Fibrin forms a mesh like capsule around the platelet
• The platelet can begin to break itself down which leads to the development of thromboembolism
• Thrombo-embolus can move to the pulmonary arteries and interrupt blood flow
• Alveoli which are fully ventilated become surrounded by capillaries which are not perfused
• This leads to V/Q mismatch
• The body can only withstand small amounts of V/Q mismatch before it can no longer meet the bodies demand

Question 11

How does the body react to V/Q mismatch?

Answer 11

Hyperventilation- causes CO2 to leave the body at a faster rate
This can always cause respiratory alkalosis which leads to an increase in blood Ph

Question 12

Aetiology behind PE

Answer 12

Virchow’s triad:

• Blood flow pattern: status
• Constituency of the blood: hyper coagulability
• Damage to endothelium relating to: infection, chronic inflammation, toxins

Question 13

How is an embolectomy performed?

Answer 13

Balloon embolectomy
-insert catheter with balloon 
-balloon presses clot against wall re-establishing blood flow
-device stabilises into clot 
-device+ catheter removed
Surgical embolectomy: cut into vessel