VTE Prevention and treatment Flashcards
Virchow’s triad
Blood Flow
Blood coagulability
Vessel wall damage
What is VTE?
Blood clot starting in veins of calf as DVT
May remain localised
Or may extend proximally and travel through circulation to heart and get pumped to lungs where veins are smaller so gets plugged = PE
Consequences of DVT
PE Post thrombotic syndrome in LT Leg ulcers at most severe Future episodes risk CTEPH
Hypertension associated with PE
CTEPH
Chronic thromboembolic pulmonary HTN
Higher risk in who?
- unprovoked episode vs. causative RF or persisting (surgery)
Post-thrombotic syndrome
Pain, swelling Ulceration, skin discolouration Variable severity Reduced QoL 40% DVT complications
Causes of VTW
- hereditary
- acquired»»
- unprovoked»_space;
(many have hereditary and acquired)
Major RF for VTE
- fracture of hip/pelvis
- hip knee replacement surgery
- major trauma
- major general surgery for malignancy
- spinal cord injury
- hospitalisation with acute medical illness
(anything tthat can happen in hospital or trauma)
Minor RF for VTE
- previous
- malignancy/chemo
- pregnancy or post partum
- COCP or hormone therapy
- central venous line
- thrombophilia
- other conditions = IBD, nephrotic syndrome
Weaker but common RF
- age
- travel
- obesity
- varicose veins
- diet
- smoking
- air pollution
Why do cancer patients have increased risk
- cancer is prothrombotic
- immobility
- surgery and chemo
- central venous catheters
(VTE 2nd equal leading cause of death in cancer patients)
RF for VTE in pregnancy
- obesity
- maternal age >35
- caesarean section (esp emergency)
Prevention
Thromboprophylaxis
NICE VTE Prevention
- all patients on admission assess for VTE and bleeding risk (national risk assessment tool)
- offer verbal and written info on prevention to patients and carers
- provide anti-embolism stocking with right size
- re-assess within 24 hours of admission
- if at risk offer VTE prophylaxis
- offer info on discharge
- offer extended prophylaxis
Methods of thromboprophylaxis
Mechanical = stockings, intermittent pneumatic compression Pharm = UH, LMWH, fondaparinux, DOACs, aspirin
UH dose
5000U
bd or tds
SC
LMWH dose
- enoxaparin 40mg sc od
- dalteparin 5000U sc od
- tinzaparin 4500 u sc od
Fondaparinux dose
synthetic pentasaccharide 2.5mg sc od
Direct thrombin inhibitor
Dabigatran
Factor Xa inhibitor
Rivaroxaban
Apixaban
Mechanism of heparin
Requires binding to antithrombin to work
Speeds up inhibition of activated clotting factors
Factors 2a and 10a and thrombin
To inactivate thrombin needs to bind to thrombin sequence and AT
LMWH
Predominantly inhibit 10a
Most = Not thrombin as not long enough
Fonaparinux
only pentasaccharide sequence
10a inhibition only
no thrombin inhibition
DOACs
Etiher Xa if xa in name of drug
Thrombin = dibigitran
Peak level very rapidly, work very quickly
Half life of 12 hours
Metabolised and eliminated through particular systems so interact with other drugs
DOAC Renal excretion
Dibigatran 80% vs.
Apixiban 25%
CI for compression stockings
- peripheral vascular disease
- leg or buttock pain on exercise
- previous/planned revasc surgery
- massive leg oedema so unable to fit
- interfering dermatitis, recent skin graft, gangrene
Alternative to compression stocking
Intermittent pneumatic compression
Sleeve around calf which blows up
Mimics walking = increases venous return
Treatment
- anticoagulant = prevention extension and recurrence
- LMWH immediate as works quickly
- overlap with warfarin until INR in therapeutic range for 2 days (5 days minimum)
- then stop LMWH
- continue warfarin for 3months
- monitor in anticoagulant clinic
Strengths of warfarin
1mg
3mg
5mg
Warfarin
- long half life = 36 hours
- metabolised in liver
- Vit K antagonist
- prevents synthesis of cofactors which use Vit K as coagonist = 2,7,9.10
- requires regular monitoring of INR
- risk of major bleeding
Pregnancy and warfarin
Avoid = teratogenic and bleeding
Safe for breast feeding
Alternative treatments
5 days LMWH, dabigatran or edoxaban for 3 months
OR
- rivaroxaban or apixaban higher starting dose for 1st week until reach standard dose (no LMWH)
