Venous Thromboembolism

Question 1

What are the signs and symptoms of DVT?

Answer 1

1. Redness (erythema) of the area
2. Pain
3. Swelling (oedema)
4. Dilation of surface veins
5. Skin warm to touch

Question 2

What are the guideline recommendations for pharmacological VTE prophylaxis?

Answer 2

NICE NG89 recommend prophylaxis of DVT in patients whose risk of VTE outweighs their risk of bleeding (i.e. moderate-high and high-risk patients) or for surgery that requires immobilisation or > 60 minutes tourniquet time or > 90 minutes total anaesthesia time with a fixed bolus dose of 4,500 IU (dosage adjustment for > 100 kg body weight (50 units/kg) with LMWH (e.g. Tinzaparin) or Fondaparinux.

Question 3

What is the D-Dimer test?

Answer 3

D-dimer is a blood test taken commonly from patients with suspected DVT. D-Dimer is normally not detected in blood but once a clot has formed. During the process of breaking down, one of the products of the disintegrating clot is D-Dimer.

Question 4

What is the diagnostic imaging of choice for DVT?

Answer 4

Vein ultrasound. Venography (X-ray) is the current gold standard but is rarely required.

Question 5

What is factor V Leiden?

Answer 5

Factor V Leiden is the name of a specific gene mutation that results in thrombophilia

Question 6

What is thrombophilia?

Answer 6

Thrombophilia is an abnormality of blood coagulation that increases the tendency to form abnormal blood clots

Question 7

When would you consider discontinuing oral contraceptive?

Answer 7

Females with a CHAD VAS score of ⩾ 2 (“moderate-high” risk) undergoing considerable surgery that will require prolonged immobility

Question 8

What are the advantages of LMWH over heparin?

Answer 8

1. No need for lab monitoring
2. Require only a single dose daily by SC injection (until the patient is mobile)
3. Higher bioavailability
4. Longer half-time
5. Lower incidence of heparin-induced thrombocytopenia

Question 9

Why is PT and PTT poor monitors of LMWH?

Answer 9

While unfractionated heparin inhibits factors Xa and IIa, LMWH has more anti-Xa action than anti-IIa activity. The anti-Xa assay would be used instead.

Question 10

What does PT stand for?

Answer 10

Prothrombin Time

Question 11

What does PT test for?

Answer 11

The test measures the activity of prothrombin (clotting factor). Specifically, it measures how long it takes for your blood to begin to form clots. Clotting is caused by a series of clotting factors which activate each other, including the conversion of prothrombin to thrombin.

Question 12

Where is prothrombin produced?

Answer 12

Prothrombin is a plasma protein produced by the liver.

Question 13

What does PTT stand for?

Answer 13

Partial Thromboplastin Time

Question 14

What does PTT test for?

Answer 14

The activated partial thromboplastin time (aPTT) test measures the length of time (in seconds) that it takes for clotting to occur when reagents are added to plasma (liquid portion of blood) in a test tube.

Question 15

What is Tinzaparin?

Answer 15

A low molecular weight heparin anticoagulant with anti-Xa activity that blocks the formation of thrombi

Question 16

What is Apixaban?

Answer 16

A factor Xa inhibitor used to prevent blood clots

Question 17

What is Dabigatran?

Answer 17

A factor II inhibitor used to prevent blood clots

Question 18

What is Warfarin?

Answer 18

A vitamin K inhibitor that limits the activation of vitamin K-dependent coagulant proteins (factors II, VII, IX and X)

Question 19

If Warfarin is to be discontinued, within what timeframe should it be stopped pre-op and resumed post-op? When would its discontinuation not be indicated?

Answer 19

Discontinue Warfarin three to six days prior to surgery (ensure INR < 1.5)—resuming 24 hours post-op—when CHAD VAS score is “low” risk. If discontinuation is not indicated (“moderate-high” risk), bridge patient by ceasing warfarin three to six days before surgery and giving LMWH 4500 IU bolus dose one day before surgery, resuming warfarin 24 hours post-op.

Question 20

Thrombin is known by which clotting factor?

Answer 20

Factor II

Question 21

Why monitor warfarin?

Answer 21

For dose adjustment

Question 22

How do you reverse warfarin overdose?

Answer 22

Discontinue warfarin and receive vitamin K 1-2.5 mg orally

Question 23

What is Virchow’s triad?

Answer 23

1. Circulatory stasis - tourniquet, immobilisation, atrial fibrillation, left ventricular dysfunction, venous insufficiency or varicose veins, venous obstruction from tumour, obesity or pregnancy
2. Endothelial wall damage - trauma or surgery, smoking
3. Hypercoagulable state - thrombophilia, malignancy, oestrogen therapy, trauma or surgery, h/o DVT

Question 24

How does tobacco increase the risk of VTE?

Answer 24

Nicotine has a long-term effect of increased blood viscosity (due to augmentation of platelet adhesiveness and decreased fibrinolytic activity) and atherosclerosis

Question 25

What’s the course of action if DVT is suspected?

Answer 25

Use the Well’s score to assess a patient’s risk. If DVT is suspected, promptly refer the patient to A+E for further assessment (D-Dimer/Ultrasound)