What are the signs and symptoms of DVT?
- Redness (erythema) of the area
- Swelling (oedema)
- Dilation of surface veins
- Skin warm to touch
What are the guideline recommendations for pharmacological VTE prophylaxis?
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.
What is the D-Dimer test?
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.
What is the diagnostic imaging of choice for DVT?
Vein ultrasound. Venography (X-ray) is the current gold standard but is rarely required.
What is factor V Leiden?
Factor V Leiden is the name of a specific gene mutation that results in thrombophilia
What is thrombophilia?
Thrombophilia is an abnormality of blood coagulation that increases the tendency to form abnormal blood clots
When would you consider discontinuing oral contraceptive?
Females with a CHAD VAS score of ⩾ 2 (“moderate-high” risk) undergoing considerable surgery that will require prolonged immobility
What are the advantages of LMWH over heparin?
- No need for lab monitoring
- Require only a single dose daily by SC injection (until the patient is mobile)
- Higher bioavailability
- Longer half-time
- Lower incidence of heparin-induced thrombocytopenia
Why is PT and PTT poor monitors of LMWH?
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.
What does PT stand for?
What does PT test for?
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.
Where is prothrombin produced?
Prothrombin is a plasma protein produced by the liver.
What does PTT stand for?
Partial Thromboplastin Time
What does PTT test for?
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.
What is Tinzaparin?
A low molecular weight heparin anticoagulant with anti-Xa activity that blocks the formation of thrombi
What is Apixaban?
A factor Xa inhibitor used to prevent blood clots
What is Dabigatran?
A factor II inhibitor used to prevent blood clots
What is Warfarin?
A vitamin K inhibitor that limits the activation of vitamin K-dependent coagulant proteins (factors II, VII, IX and X)
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?
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.
Thrombin is known by which clotting factor?
Why monitor warfarin?
For dose adjustment
How do you reverse warfarin overdose?
Discontinue warfarin and receive vitamin K 1-2.5 mg orally
What is Virchow’s triad?
- Circulatory stasis - tourniquet, immobilisation, atrial fibrillation, left ventricular dysfunction, venous insufficiency or varicose veins, venous obstruction from tumour, obesity or pregnancy
- Endothelial wall damage - trauma or surgery, smoking
- Hypercoagulable state - thrombophilia, malignancy, oestrogen therapy, trauma or surgery, h/o DVT
How does tobacco increase the risk of VTE?
Nicotine has a long-term effect of increased blood viscosity (due to augmentation of platelet adhesiveness and decreased fibrinolytic activity) and atherosclerosis
What’s the course of action if DVT is suspected?
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)