VTE Prophylaxis + IVC Filter Flashcards
(24 cards)
Introduction of VTE
- VTE is a serious and potentially fatal complication of surgery
- Almost half of the population undergoing non orthopaedic surgery are at moderate risk of VTE
What is Virchow’s Triad
Virchow’s triad
1) Damage to vs wall
- Compression trauma to veins of soleus plexus in calf
2) Venous stasis
- Immobility, loss of muscle pump
3) Increase coagulability
- Trombocytosis lead to plt adhesion
- Protein S, C deficiency, antithrombine III deficiency
What are the risk factors for VTE?
General
Patient Factor:
* >40 yrs old
* Obesity ( BMI >30)
* Immobilisation
* Previous DVT
* Pregnancy / post partum
* Malignancy , esp ovarian, pancreas
* Hypercoagulability state – protein, C, S and antithrombin deficiency
* Medical illness – include MI, resp insufficiency
Surgery Factor:
* GA
* Major abdominal / ortho surgery
- Duration of operation:
*Minor surgery: duration under 30 minutes.
*Major surgery: duration more than 30 minutes
Incidence of VTE ( location of VTE )
Overview of Risk catergory for VTE
Risk is usually high in patients :
- Undergoing major surgery (surgery longer then 45mins)
- Abdominal and thoracic cavity surgery
- Prolonged surgery (> 2 hours)
- Emergency rather then elective
- Critically ill patients
Scoring to predict incidence of VTE
Use of an objective assessment score, The Modified Caprini Risk Assessment Model
- Patient undergoing surgery classified according to estimated baseline risk (EBR) for VTE in the absence of thromboprophylaxis
- Caveat to the model is its only applicable to patients undergoing general and abdominal/pelvic surgery
- Mechanical and pharmacological prophylaxis in patients with Caprini score more then 3
Recommendation of low risk VTE prophylaxis
Thromboembolism from Thromboembolic Risk Factors (THRIFT) Consensus Group, 1992
- <40 yrs old
- Surgery last <30min, avoiding GA
- Rapid mobilisation post op
- No other risk factors
- Management
o No specific measures
o Aggressive mobilisation
Recommendation of Moderate risk VTE prophylaxis
Thromboembolism from Thromboembolic Risk Factors (THRIFT) Consensus Group, 1992
- > 40 - 60 yrs old without risk factors
- Moderately obese
- Abd surgery req GA
- Management
o Low dose unfractionated Heparin 5000 – 7500IU bd
o LMWH (daily dose according to manufacturer)
o Intermittent pneumatic compression OR Elastic graduated compression stockings
Recommendation of high risk VTE Prophylaxis
Thromboembolism from Thromboembolic Risk Factors (THRIFT) Consensus Group, 1992
- > 60 yrs old age going for major op (cancer / ortho)
- 40-60 yrs old with risk factors
- Prolonged immobilization
- Pelvic trauma / surgery
- Multiple risk factors
- Management
o Unfractionated heparin 5000 - 7500IU tds
o LMWH or Intermittent pneumatic compression
Overview of VTE prophylaxis managment based on Caprini scoring
Overview of VTE management ( according to risks)
THRIFT CONCENSUS
VTE Prophylaxis Mx
Divided into:
- Mechanical
- Pharmacological
Mechanical:
1. Graduated elastic compression stocking ( The Sigel profile, which equates to a graduated compression pressure profile of 18 mmHg at the ankle, 14 mmHg at the mid-calf, 8 mmHg at the knee (popliteal break), 10 mmHg at the lower thigh and 8 mmHg at the upper thigh was found to increase deep venous flow velocity by 75%.) and intermittent pneumatic compression devices.
2. Effective in preventing DVT in moderate-risk surgical patients.
3. One small disadvantage is that some patients can note ffectively wear these
stockings due to unusual limb size or shape.
4. Mechanical methods may also be combined with pharmacological prophylaxis
to increase efficacy in high-risk patients.
5. Preferred in patients at increased risk of bleeding from pharmacological
prophylaxis.
6. Graduated elastic stockings are contraindicated in severe leg ischaemia.
VTE Prophylaxis Mx ( Pharmacological)
S/C: LMWH/Unfractionated heparin/Fundaparinux
ORAL: Warfarin(not commonly used), Dabigatran,Rivaroxaban,Apixaban
Assuming all patients are at low bleeding risk
- Very low risk: mechanical and pharmacological measures are not required as patients are ambulatory
- Low risk: mechanical methods will suffice
- Moderate /High risk: Pharmacological and mechanical
These include:
a. Standard unfractionated heparin(usually in low dosage)
b. Low molecular weight heparins or heparinoids
c. Oral anticoagulants
d. Dextran70
1) Low dose UFH
- Subcutaneously is effective in preventing DVT and PE in a dose of 5000U every 12 hours ( 5000units BD starting 2 or more hours before surgery
- In obesity 5000 – 7500 units BD)
b. Easy to administer and relatively inexpensive, and does not require anticoagulant monitoring.
2) LMWHs and heparinoids
a. Also given subcutaneously for prophylaxis as once-daily injections.
b. Compared to standard heparins, LMWHs are more effective in orthopaedic surgery and slightly more effective in general surgery without increasing the risk of bleeding.
c. Much less likely to produce heparin-induced thrombocytopaenia and osteoporosis than unfractionated heparin.
d. Addvantages include its ease of administration using pre-filled syringes, non-requirement for monitoring and once-daily injection
e. Main disadvantage is that it is porcine-based
Enoxaparin(1mg/kg)
- Started 2 hours before abdominal surgery and once daily after surgery
- In cancer surgery : 10-12 hours prior to surgery
Tinzaparin
- 4500 units 12 hrs before surgery and OD after surgery
3) Oral Anticoagulant
a. may sometimes be used as prophylaxis especially when heparin is contraindicated.
b. The advantages are its ease of administration, low cost and safety.
c. The disadvantages are they require daily monitoring of the INR
d. The recommended therapeutic range is 2.0 to 2.5
e. There is little rationale for this therapy to be used routinely as prophylaxis.
4) The pentasaccharide fondaparinux sodium
a. The first of a new class of synthetic antithrombotic agents that acts through selective inhibition of factor Xa.
b. Fondaparinux contains no animal sourced components and has been designed to bind selectively to a single target in plasma, antithrombin III
how to weigh the risk of bleeding and thrombosis?
An objective assessment of bleeding is required when weighing up the risk of thrombosis versus bleeding events.
The IMPROVE bleeding risk score
Types of Surgeries ( Bleeding risks)
Time of initiation of VTE Prophylaxis
- Low bleeding risk start within 6-12 hours post operatively
- High bleeding risk upto 48 hours post operatively
- In patients whom risk of bleeding is low, mechanical methods should start before surgery and pharmacological methods 2-12 hours preoperatively.
- In high bleeding risk patients mechanical prophylaxis to be started preoperatively and pharmacological postoperatively as soon as haemostasis is secured and considered safe (generally 2-72 hours post operation)
- Pharmacological prophylaxis to be continued until patient is fully ambulatory (averaging 10 days)
- Extended prophylaxis (> 10 days) up to 3 – 4 weeks typically with LMWH not routinely recommended except for those undergoing major abdominal surgery (eg. CRS & HIPEC)
Well’s score for PE
DVT well’s score
Duration for anticoagulation in VTE patient
Overview of IVC filter
Complication of VTE
The most common complication of VTE is chronic venous insufficiency (CVI) leading to post thrombotic syndrome (PTS)
Post thrombotic syndrome results in debilitating pain, swelling, and ulceration and is asignificant cause of loss of working days. It can contribute to an increase in recurrent DVT and PE.Prevention of PTS will significantly reduce the morbidity and late mortality of DVT.
Wearing graduated elastic compression stockings with an ankle pressure greater than 23 mmHg following a proximal DVT have been shown to reduce post thrombotic complications.
Patients are advised to continue wearing the stockings on the affected leg for at least 2 years and also to ensure that they are replaced 2 to 3 times per year
Overview of Heparin Induced Thrombocytopenia (HIT)
If heparin induced thrombocytopenia (HIT) develops, the platelet count typically begins to fall5 to 10 days after starting heparin, although in patients who have received heparin in the previous 3 months it can have a rapid onset due to pre existing antibodies.
If the platelet count falls by 30% or more and/or the patient develops new thrombosis or skin allergy or any of the other rarer manifestations of HITT between days 4 to 14 of heparin administration, HITT should be considered and heparin should be stopped and an alternative anticoagulant started in full dosage e.g. danaparoid, argatroban or fondaparinux
Treatment for DVT
- In patients with confirmed DVT or PE, offer a choice of LMWH, fondaparinux or rivaroxaban, taking into account comorbidities, contraindications and drug costs.
- Offer warfarin within 24 hours of diagnosis in combination with LMWH or fondaparinux.
- For rivaroxaban, no overlap with LMWH or fondaparinux is needed as rivaroxaban has a rapid onset of action and predictable bioavailability.
- In patients with severe renal impairment or established renal failure (eGFR <30 mL/min) offer UFH with dose adjustments based on APTT or LMWH with dose adjustments based on anti Xa assay
- For patients with PE and hemodynamic instability, offer IV UFH and consider systemic thrombolytic therapy
Low molecular weight heparin is continued for at least 5 days or until the INR is above 2 for at least 24 hours, whichever is longer.
⏳ Why 5 Days of LMWH Before Switching to Oral Anticoagulants (e.g., warfarin):
✅ 1. Immediate Anticoagulation
* LMWH (Clexane) works within hours, rapidly reducing clot propagation.
* Oral warfarin takes ~3–5 days to become therapeutic (INR 2–3).
⛔ 2. Warfarin’s Delayed Onset
* Warfarin initially depletes Protein C & S (natural anticoagulants) faster than clotting factors, causing a temporary hypercoagulable state.
* LMWH bridges this risky period.
🧪3. Overlap Ensures Therapeutic INR
* LMWH is continued for at least 5 days AND until INR ≥2.0 for 2 consecutive days.
* This ensures safe transition to full anticoagulant effect with warfarin.
