Causes prevention and consequences of DVT/PE

Question 1

Thrombosis

Answer 1

Blood clot within circulation

Question 2

Thrombus

Answer 2

Blood clot in intact blood vessel fixed at a site

Question 3

Thromboembolus

Answer 3

blood clot breaking free and occludes elsewhere in circulation

Question 4

Pulmonary embolism

Answer 4

Deposition of a clot in the main branch/bifurcation of pulmonary artery

Question 5

Patent foramen ovale and pulmonary embolism

Answer 5

Clot can pass from R to L - can enter systemic circulation

Question 6

Virchow’s triad

Answer 6

• Endothelial injury - sepsis/toxins/oedema/trauma
• Blood stasis - impaired muscle pump/proximal occlusion/turbulence
• • hyper-coagulability - protein C deficiency/factor 5 Leiden/pregnancy/hyperviscosity/malignancy

Question 7

haemostasis

Answer 7

• Tissue damage exposes collagen
• Vasoconstriction to decrease blood flow - serotonin, thromboxane A2 etc
• Platelets stick to exposed collagen and release ADP, Ca2+ and serotonin, as well as vWF, fibrinogen and factors V/X111 (a granules)
• Fibrinogen and vWF promote platelet aggregation, ADP, thrombin and TXA2 cause platelet activation, factors V and XIII cause clotting

Question 8

Function of activated protein C

Answer 8

Negative feedback - self-regulation of clotting cascade by inhibiting 5a and 8a

Question 9

How are clots prevented from forming and spreading?

Answer 9

• Prostacyclin (PGI2) and NO from undamaged endothelium prevent platelet adhesion
• Fibrinolysis: plasminogen → plasmin (TPA), plasmin acts on fibrin by creating FDPs

Question 10

Factor 5 leiden

Answer 10

Variant of factor 5 that is resistant to protein C - always activates clotting cascade

Question 11

Treatment for DVTs

Answer 11

Compression stockings + heparin

Question 12

Antidote to unfractionated heparin

Answer 12

Protamine

Question 13

Side effects of heparin

Answer 13

Heparin induced thrombocytopenia - platelet destruction

Question 14

Thrombolytics use

Answer 14

• Used in PE
• Impaired venous return
• Used in significant hypotension and systolic lower than 100

Question 15

Reversal for rivaroxaban and apixaban

Answer 15

Andexanet alfa

Question 16

Sx DVT

Answer 16

• Pain worse on dorsiflexion
• Tender thigh or calf
• Oedema - unilateral
• Venous engorgement - red/purple, warm
• Unexplained tachycardia
• Chest pain/haemoptysis
• Circulatory shock
• Cardiac arrest

Question 17

Investigating DVTs

Answer 17

• D-dimer: sensitive marker for DVT but not specific - varies with age/pregnancy/trauma/surgery etc, used to exclude DVT if normal
• Blood gas: hypoxia (V/Q mismatch) and hypocarbia
• CXR is normally clear
• DVT: use US
• PE: gold standard is CT pulmonary angiogram but can also use V/Q scan with severe CKD