THROMBOPROPHYLAXIS
VTE Prevention | DVT and PE | Orthopaedic Perioperative Care
VTE Risk by Procedure
Critical Must-Knows
- High Risk Procedures: THA, TKA, hip fracture surgery require extended prophylaxis 28-35 days
- Mechanical: TED stockings + IPC - ALWAYS use with chemical for high-risk procedures
- Chemical Options: LMWH (enoxaparin), DOACs (rivaroxaban, apixaban), aspirin
- Duration: 28-35 days for THA/TKA/hip fracture - NOT just in-hospital
- Timing: Start LMWH 6-12 hours post-op; rivaroxaban 6-10 hours post-op
Examiner's Pearls
- "Extended prophylaxis 28-35 days is MANDATORY
- "LMWH is gold standard but DOACs are equivalent
- "Aspirin is acceptable after initial anticoagulant
- "Mechanical prophylaxis ALWAYS - even if on chemical
Clinical Imaging
Imaging Gallery
Critical VTE Prophylaxis Points
Extended Duration
28-35 days for THA/TKA/hip fracture. VTE risk persists beyond discharge. In-hospital only is INADEQUATE.
Mechanical + Chemical
Always combine methods for high-risk. Mechanical reduces VTE by 50% alone. Adding chemical reduces further.
Aspirin Evidence
EPCAT II: Aspirin non-inferior after initial anticoagulant. Can use aspirin to complete extended course after LMWH/DOAC.
Timing Matters
LMWH: 6-12 hours post-op. DOACs: 6-10 hours post-op. Too early = bleeding. Too late = VTE.
Quick Decision Guide
| Procedure | VTE Risk | Prophylaxis | Duration |
|---|---|---|---|
| THA | Very High | Mechanical + LMWH/DOAC | 35 days |
| TKA | Very High | Mechanical + LMWH/DOAC | 14-35 days |
| Hip Fracture | Very High | Mechanical + LMWH | 35 days |
| Major Trauma | High | Mechanical + LMWH | Until ambulatory |
| Foot/Ankle | Moderate | Mechanical ± aspirin | Until ambulatory |
MCEVTE Prophylaxis Approach
Memory Hook:MCE = Mechanical, Chemical, Extended - the three pillars of VTE prophylaxis in orthopaedics!
HIP HIPHigh-Risk VTE Procedures
Memory Hook:HIP HIP hooray for prophylaxis! These procedures need extended 35-day prophylaxis.
LEADChemical Prophylaxis Options
Memory Hook:LEAD with prophylaxis - LMWH leads as gold standard, DOACs and Aspirin are alternatives!
Overview and Epidemiology
Why VTE Prophylaxis Matters
VTE is the most common preventable cause of in-hospital death. After THA/TKA without prophylaxis, DVT rates are 40-60% and symptomatic PE 1-2%. This is a mandatory exam topic.
Venous Thromboembolism (VTE) includes deep vein thrombosis (DVT) and pulmonary embolism (PE).
Virchow's Triad
- Stasis: Immobility, surgery, prolonged recumbency
- Endothelial injury: Surgical trauma, inflammation
- Hypercoagulability: Surgery-induced, thrombophilia
All three components are present in orthopaedic surgery.
Risk Without Prophylaxis
- THA: DVT 42-57%, PE 0.9-28%
- TKA: DVT 41-85%, PE 1.5-10%
- Hip fracture: DVT 46-60%, fatal PE 3-12%
- Major trauma: DVT 40-80%
These figures demonstrate why prophylaxis is mandatory.
Pathophysiology and Mechanisms
Thrombosis Anatomy
Most clinically significant DVTs originate in the deep calf veins (soleal sinuses) and propagate proximally. Proximal DVT (popliteal, femoral, iliac) carry highest PE risk. Upper limb DVT is uncommon in orthopaedics.
Deep Vein System:
- Calf veins: Posterior tibial, peroneal, soleal sinuses (origin of most DVT)
- Proximal veins: Popliteal, femoral, iliac (highest PE risk)
- Upper limb: Subclavian, axillary (rare in orthopaedics)
Natural History:
- Thrombus forms in calf veins during/after surgery
- May propagate proximally (20-30% if untreated)
- Proximal DVT can embolize to pulmonary circulation
- PE mortality depends on clot burden and cardiopulmonary reserve
Classification Systems
VTE Risk Stratification
| Risk Level | Procedures | Prophylaxis | Duration |
|---|---|---|---|
| Very High | THA, TKA, hip fracture, pelvic trauma | Mechanical + LMWH/DOAC | 28-35 days |
| High | Major trauma, spine fusion, cancer surgery | Mechanical + LMWH | Until ambulatory or 14 days |
| Moderate | Foot/ankle, upper limb, arthroscopy | Mechanical ± aspirin | Until ambulatory |
| Low | Minor procedures, outpatient | Early mobilization | None required |
Risk stratification guides prophylaxis intensity and duration.
Clinical Assessment
DVT Signs
- Calf pain: Worse with dorsiflexion (Homan's sign)
- Swelling: Asymmetric leg swelling
- Warmth: Affected limb warmer
- Erythema: Subtle redness
- Palpable cord: Thrombosed vein
Clinical signs are unreliable - 50% DVTs are asymptomatic.
PE Signs
- Dyspnea: Most common symptom
- Pleuritic chest pain: Sharp, worse on inspiration
- Tachycardia: Heart rate greater than 100
- Hypoxia: SpO2 less than 92%
- Syncope: Massive PE
PE is a clinical emergency - act immediately if suspected.
Clinical Diagnosis is Unreliable
Clinical signs miss 50% of DVTs. Screening is not recommended. Focus on PREVENTION with appropriate prophylaxis rather than detection.
Investigations
Investigation for Suspected VTE
Wells Score for DVT or PE probability. Guides further investigation.
Sensitive but not specific. Useful to rule OUT VTE if negative. Always elevated post-operatively (not useful post-op).
Gold standard for DVT. Non-compressible vein = thrombus. Sensitivity greater than 95% for proximal DVT.
Gold standard for PE. CT pulmonary angiography. V/Q scan if contrast contraindicated.
Note: D-dimer is NOT useful post-operatively as it is always elevated. Use clinical suspicion and imaging.
Management Algorithm
Mechanical Prophylaxis
Mechanical Methods
Graduated compression stockings. Below-knee or thigh-high. Reduces DVT by 50% alone. Proper fit essential.
Sequential calf compression. Apply in OR, continue post-op. More effective than TED alone. Combine with TED for best effect.
Venous foot pump. Alternative to IPC. May be used if calf access limited.
Mechanical prophylaxis is ALWAYS indicated for high-risk procedures, even with chemical prophylaxis.
Surgical Technique
Surgical Strategies to Reduce VTE
- Minimize tourniquet time: Longer tourniquet = higher risk
- Gentle tissue handling: Reduce endothelial injury
- Regional anesthesia: May reduce VTE vs general
- Intraoperative IPC: Start before induction
- Adequate hydration: Avoid hypovolemia
- Avoid hypotension: Maintain perfusion
These strategies complement mechanical and chemical prophylaxis.
Complications
Complications of Anticoagulation
| Complication | Incidence | Management |
|---|---|---|
| Major bleeding | 1-3% | Hold anticoagulant, reverse if severe, mechanical only |
| Wound hematoma | 2-5% | May require washout, balance VTE and bleeding risk |
| HIT (heparin-induced thrombocytopenia) | 0.5-1% | Stop heparin, use fondaparinux or argatroban |
| Spinal hematoma | Rare | Neurological emergency - decompress urgently |
| GI bleeding | 1-2% | PPI cover, balance benefits vs risks |
HIT is a serious complication of heparin products. Check platelets day 5-10 if using LMWH. If suspected, stop heparin and use alternative (fondaparinux, argatroban).
Postoperative Care
Post-Discharge VTE Prevention
Educate on VTE symptoms. Calf pain, swelling, shortness of breath. Seek immediate help if suspected.
Continue LMWH or DOAC as prescribed. Ensure patient understands regimen. Self-injection teaching for LMWH.
May switch to aspirin for completion. Based on EPCAT II evidence. Continue until 35 days total.
Review at follow-up. Stop prophylaxis at 35 days if fully mobile. Continue longer if high-risk or immobile.
Patient compliance with home prophylaxis is essential. Simplify regimens where possible.
Outcomes and Prognosis
With Prophylaxis:
- DVT: Reduced to 2-5%
- Symptomatic PE: Less than 0.5%
- Fatal PE: Less than 0.2%
Prognostic Factors for VTE:
| Factor | Higher Risk | Implication |
|---|---|---|
| Prior VTE | 5-10x baseline | Consider extended prophylaxis beyond 35 days |
| Cancer | 3-5x baseline | LMWH preferred over aspirin |
| Thrombophilia | 2-5x baseline | Hematology input |
| Bilateral surgery | 2x | Higher dose or longer duration |
| Transfusion | 1.5x | Adequate prophylaxis |
Appropriate prophylaxis makes VTE a rare event after modern arthroplasty.
Evidence Base
- Rivaroxaban vs enoxaparin for THA/TKA
- Superior VTE reduction with rivaroxaban
- Similar major bleeding rates
- DOACs are effective alternative to LMWH
- Aspirin vs rivaroxaban to complete extended prophylaxis
- After initial 5-day rivaroxaban
- Non-inferior for symptomatic VTE
- Lower bleeding with aspirin
- Extended prophylaxis 10-35 days for THA/TKA
- LMWH, fondaparinux, DOACs, or aspirin acceptable
- Mechanical prophylaxis recommended for all
- Balance VTE and bleeding risk
- Meta-analysis of VTE prophylaxis trials
- LMWH superior to UFH
- Extended prophylaxis superior to in-hospital only
- Mechanical adds benefit to chemical
- Patients undergoing elective hip/knee arthroplasty should receive prophylaxis
- Multiple pharmacological options acceptable
- Extended duration beyond hospital recommended
- Mechanical prophylaxis recommended
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
Scenario 1: THA Prophylaxis Protocol
"You are planning a primary THA on a 65-year-old man with no prior VTE history. What is your VTE prophylaxis protocol?"
Scenario 2: High Bleeding Risk
"A 70-year-old woman is undergoing TKA. She has a history of GI bleeding and is on aspirin for coronary artery disease. How do you manage VTE prophylaxis?"
Scenario 3: Suspected PE Post-Arthroplasty
"Post-operative day 3 after TKA, the patient develops sudden dyspnea and pleuritic chest pain. HR 120, SpO2 88% on room air. What is your approach?"
MCQ Practice Points
Extended Prophylaxis Duration
Q: How long should VTE prophylaxis continue after THA? A: 28-35 days. VTE risk persists beyond hospital discharge. In-hospital only prophylaxis is inadequate.
LMWH Timing
Q: When should enoxaparin be started after THA? A: 6-12 hours post-operatively. Too early increases bleeding risk. Too late may allow thrombus formation.
Aspirin Evidence
Q: What trial supports aspirin for VTE prophylaxis after arthroplasty? A: EPCAT II (NEJM 2018) showed aspirin is non-inferior to rivaroxaban when used to complete extended prophylaxis after initial anticoagulant.
VTE Risk Without Prophylaxis
Q: What is the DVT rate after THA without prophylaxis? A: 40-60% DVT, 1-2% symptomatic PE. This demonstrates why prophylaxis is mandatory.
Mechanical Prophylaxis Role
Q: What is the role of mechanical prophylaxis in VTE prevention? A: Always use mechanical prophylaxis (TED + IPC) as adjunct. Essential for patients with bleeding contraindications. Start IPC intraoperatively.
HIT Management
Q: How do you manage suspected HIT in a post-arthroplasty patient? A: Stop all heparin immediately. Use non-heparin anticoagulant (fondaparinux, argatroban). Check platelet count and 4T score.
Australian Context
Australian Guidelines:
- NHMRC Clinical Practice Guidelines support extended prophylaxis
- TGA-approved agents: enoxaparin, rivaroxaban, apixaban, dabigatran, aspirin
- Medicare rebates available for VTE prophylaxis agents
State-Specific Protocols:
- Most Australian public hospitals have VTE prophylaxis protocols
- Victoria: VENHa (VTE prevention protocols)
- NSW/QLD: Similar extended prophylaxis recommendations
Medicolegal Considerations:
- VTE prophylaxis failure is a common medicolegal issue
- Document risk assessment and prophylaxis plan
- Document patient education on VTE symptoms
- Ensure discharge prescription includes extended prophylaxis
PBS Prescribing:
- Enoxaparin PBS-listed for VTE prophylaxis in major orthopaedic surgery
- DOACs have specific indications and restrictions
- Aspirin is over-the-counter
Australian surgeons should follow hospital protocols and ensure extended prophylaxis is prescribed at discharge.
THROMBOPROPHYLAXIS
High-Yield Exam Summary
VTE Risk
- •THA/TKA/Hip fracture = very high
- •40-60% DVT without prophylaxis
- •1-2% symptomatic PE
- •Risk persists 35 days post-op
Prophylaxis Approach
- •MCE: Mechanical + Chemical + Extended
- •TED + IPC for ALL high-risk
- •LMWH is gold standard
- •DOACs are equivalent alternatives
Duration
- •THA: 35 days
- •TKA: 14-35 days
- •Hip Fracture: 35 days
- •NOT just in-hospital
Timing
- •LMWH: 6-12 hrs post-op
- •Rivaroxaban: 6-10 hrs post-op
- •Start IPC in OR
- •TED immediately post-op
Complications
- •HIT: Stop heparin, use alternative
- •Major bleeding: 1-3%
- •Balance VTE vs bleeding risk
- •Spinal epidural haematoma with neuraxial anaesthesia