Thrombosis Flashcards
What are the causes of hypercoagulability?
Viscosity
- Haematocrit (Polycthaemia)
- Protein/ paraprotein (Myeloma)
Platelet count
- Essential Thrombocythaemia
Coagulation system
- Increased procoagulant factors (factors, fibrinogen, platelets) e.g. raised factor 8
- Decreased anticoagulation factors (protein C, protein S, antithrombin) e.g. thrombophilia, pregnancy
- Decreased fibrinolysis
- Additional Thrombophilic Traits:
- -> Inherited: Factor V Leiden (FV resistant to protein C)
- -> Acquired: Lupus Anticoagulant (autoimmune, isolated or seen in SLE)
What are the factors increasing risk for thrombosis in malignancy?
- Increased coagulability: increased expression of TF, inflammation & increase in factor 8
- Changes to vessel wall: injury to vessel wall during surgery, radiotherapy, chemotherapy
- Stasis: immobility from hospitalization, surgery, fatigue
What are the factors increasing risk for thrombosis in pregnant women?
Increased coagulability: increase in coagulation factors (factors VIII and VII), VWF, fibrinogen
Reduced fibrinolysis: PAI-1 and PAI-2 increases, PAI-2 made by placenta
Venous stasis: Mechanical obstruction of veins by the pregnant ‘gravid’ uterus; obstruction most marked on left common iliac vein; 80-90% pregnancy related DVT occurs on left side
Additional maternal factors: hyperemesis/ dehydration, immobility because of bed rest, obesity (BMI>29 3x risk of PE), pre-eclampsia, operative delivery
Additional risks: previous history of thrombosis/thrombophilia, parity i.e. 4th or 5th child, multiple pregnancy
How is VTE prevented in pregnant patients?
- ASSESS WOMEN FOR RISK FACTORS
- Women with risk factors should receive prophylactic heparin +TED stockings either throughout pregnancy, or in peri/post-partum period
- Highest risk get adjusted dose LMWH heparin
- Mobilize early
- Maintain hydration
In what situations should you avoid LMWH (increased with bleeding)?
- Active bleeding
- Acquired or inherited bleeding disorders
- Anticoagulated
- LP/epidural or spinal anaesthetic within previous 4 hours or expected within next 12 hours
- Acute stroke
- Low platelets <75
- High BP 230/120
In what situations should you avoid the use of compression stockings?
- Peripheral vascular disease: check pulses, inspect limb
- Peripheral arterial bypass grafts
- Stroke
- Peripheral neuropathy or sensory impairment
- Unusual or deformed limb
- Leg edema (e.g. CCF, nephrotic syndrome)
- Delicate skin/ dermatitis/ gangrene/ skin graft
Arterial thrombus (white thrombi) has a high platelet component.
It is unlikely for a thrombus to form within an artery normally as blood flow a lot faster.
Hence, thrombus forms within an atherosclerotic plaque (full of ______________ + ______________).
When the plaque ruptures, the thrombus is formed on site. If the thrombus embolises and occludes the coronary arteries, it leads to myocardial infarction.
white blood cells + lipid components
What are the indications of anticoagulants?
DVT and PE treatment and prophylaxis
- Medical in-patients, Surgical in-patients, Peri-operative
- Peri-partum (pregnancy)
- Pre-long haul flights (esp in high risk patients)
Primary stroke prevention in patients with atrial fibrillation
Secondary stroke prevention (people who had previous stroke or TIA)
Metallic heart valves
Total Hip Replacement/ Knee Replacement
Mural thrombus: Thrombus that adheres to the sides of the vessel. They limit blood flow but does not occlude it altogether
[Vitamin K Antagonists]
Anticoagulation effects through the inhibition of Vitamin K dependent gamma-carboxylation of coagulation factors ____________ e.g. Warfarin, Sinthrome, Phenindone
However, Warfarin also inhibits ____________: shorter half-life than the coagulation factors, creating a pro-thrombotic effect in the first 5 days
Hence need to overlap warfarin and heparin for first 5 days, until _____ for 2 consecutive days (aka stop heparin when INR reaches therapeutic levels)
II, VII, IX and X;
Protein C and S;
INR is >2
[Heparin and its derivatives (UFH and LMWH)]
Anticoagulation effects by binding to and potentiating effects of ___________ and inactivation of ______________ e.g. Unfractionated heparin (UFH), Low Molecular Weight Heparin (LMWH)
anti-thrombin (AT);
thrombin and Factor Xa
Prophylaxis for VTE
- Prophylaxis for VTE: med in-pt LMWH; surgical pts LMWH / DOACs
- Suspected acute VTE: start LMWH in hospital pending confirmation, then upon confirmation initiate or switch to __________________ as patient is discharged
- ______: mainstay for cancer associated thrombosis! (VTE)
- AF (initiate as outpatient): _________________-
- UFH for renal failure (as UFH has short half-life compared to LMWH)/ peri-op if unsure when – however higher risk of ________ than LMWH
- Flights: LMWH prophylaxis
warfarin (majority) /Rivaroxaban/ dabigatran;
LMWH
warfarin / DOACs;
HIT
Which low bleeding risk procedures do NOT require stopping Anticoag if INR is stable (2-3)?
Joint injections, OGD, cataracts, derm procedure, biliary /pancreatic stenting, EUS, dental extraction
Dental extractions:
- No need to stop warfarin provided _______________.
- Avoid NSAIDs and Aspirin.
- Use _______, _______, ___________
recent stable INR <4;
tranexamic acid mouthwash, oxidized cellulose or collagen sponges/sutures
What if peri- operative bridging not required before operation?
- Warfarin stopped ____________
- Do INR _________
- Give oral Vit K if ______
- Restart warfarin ________________(for minor op with no bleeding) or >48hrs post op (if high risk op or bleeding)
- LMWH prophylaxis given as per hospital protocol.
- Duration to withhold DOACs depends on renal function and risk of bleeding (worse renal function require ____________)
5 days before operation;
1 day before op;
INR >1.5;
evening of op or next day
longer duration
If peri-operative bridging REQUIRED
- Warfarin stopped ______________
- LMWH at 9am once INR sub-therapeutic
- Interm Risk: use _____________ for bridging
- High Risk: use ____________ for bridging
- Omit LMWH on day of op (ie last dose ________ before op)
- If high risk op, last dose LMWH should be half dose (if treatment dose)
- Check INR on day of op and give Vit K as required
- Restart LMWH (____ post op) and once haemostasis secured
5 days before operation;
prophylactic dose LMWH ;
treatment dose LMWH;
> 24hrs;
> 6 hrs
