Goal
Minimize symptomatic DVT / PE while limiting postoperative bleeding
Options
Mechanical compression - graduated stockings, pneumatic compression, foot pumps
Aspirin
Low molecular weight heparin (LMWH)
Oral factor Xa inhibitors - Rivaroxaban, Apixaban
Warfarin - usually used for treatment
Contraindications to chemoprophylaxis
Active bleeding
High risk bleeding
- hemophilia
- thrombocytopenia - platelets < 50
- history GI bleeding
Severe hepatic disease (INR < 1.3)
Renal impairment
- must adjust LMWH and oral factor Xa inhibitor doses
History of HITT (heparin induced thrombocytopenia)
Recent neurosurgery or eye surgery
Spinal anesthesia
Queensland Health Guidelines for Prevention of DVT
LMWH
- prophylaxis 12 hours after insertion
- typically withhold for 4 - 6 hours after removal
Oral Factor Xa inhibitors
- 24 hours minimum after insertion
- 6 hours after withdrawal
Timing
Queensland Health Guidelines for Prevention of DVT
Onset
Hemostasis obtained
Heparin / LMWH - 12 hours post op
Oral factor Xa inhibitors
- Rivaroxaban 6 - 10 hours post op
- Dabigatran 4 hours postop
- Apixaban 12 - 24 hours post op
Duration
TKA - 10 - 14 days
THA - 4 - 5 weeks
Low Molecular Weight Heparin (LMWH)
| Definition | Types | Mechanism | Advantage | Disadvantage |
|---|---|---|---|---|
|
Fractionated heparin Molecular weight < 5000 |
Enoxeparin / Clexane - 0.5 mg/kg od - 40 mg od
Dalteparin / Fragmin - 5000IU od |
Antifactor Xa |
Longer half life than heparin Decreased bleeding due to reduced platelet effect No monitoring required Antidote: Protamine sulfate |
Given by injection Reduce dose with low GFR Increase dose BMI > 40 Difficult to reverse HITT |
Direct oral Factor Xa inhibitors
| Definition | Types | Mechanism | Advantage | Disadvantage |
|---|---|---|---|---|
| Act directly on Factor X |
Rivaroxaban 10 mg od
Apixaban 2.5 mg bid
Dabigatran 220 mg od |
Factor Xa inhibitor |
Oral dosing No monitoring required |
Interact with statins |
Aspirin
| Definition | Types | Mechanism | Advantage | Disadvantage |
|---|---|---|---|---|
|
Acetylsalicyclic acid |
Aspirin 80 - 300mg |
COX inhibitor |
Oral form No monitoring required |
GI bleeding / stomach upset
|
Mechanism
- irreversibly inhibits cyclo-oxygenase in platelets
- blocks thromboxane A2 formation
Results
Mechanical compression
- 540 THA treated only with graduated stockings and pneumatic compression
- routine ultrasound day 4 and 7
- incidence proximal DVT 1%
Warfarin v LMWH
- RCT of 1000 THA of warfarin v dalteparin
- warfarin: DVT 24%, proximal DVT 1%, symptomatic DVT 4.5%
- dalteparin: DVT 13%, proximal DVT 1%, symptomatic DVT 1.5%
Aspirin v LMWH
- RCT 100mg aspirin v 40 mg enoxeparin / LMWH in 9711 THA and TKA patients
- symptomatic VTE in aspirin group was 3.5%
- symptomatic VTE in enoxeparin group was 1.8%
- no difference in mortality
Oral Factor Xa inhibitors versus LMWH
- 4500 THA RCT to either rivaroxaban or enoxeparin
- enoxeparin: DVT/PE 3.7%, major bleeding 0.1%
- rivaroxaban: DVT/PE 1.1%, major bleeding 0.3%
- Swedish registry
- 5,700 THA with oral anticoagulants: symptomatic DVT 0.3%, symptomatic PE 0.1%
- 27,000 LMWH: symptomatic DVT 0.6%, symptomatic PE 0.4%
- reduced risk of DVT / PE with oral factor Xa inhibitor
- no difference in bleeding
- 5400 THA RCT either apixaban or enoxeparin 35 days
- enoxeparin: DVT/PE 3.9%
- rivaroxaban: DVT/PE 1.4%
Aspirin versus Oral Factor Xa inhibitors
- 3500 patients
- rivaroxaban 5 days + aspirin 9 days TKA or 30 days THA
- rivaroxaban 14 days TKA or 30 days THA
- no difference DVT or major bleeding
Preoperative
- RCT of 1500 THA of warfarin v LMWH / dalteparin
- dalteparin given preoperatively had slightly decreased rates of total DVT but increased bleeding
Duration
- RCT of 2500 THA patients
- 30 days of rivaroxaban v 14 days enoxeparin
- rivaroxaban: DVT 2%, PE 0.1%, bleeding 7%
- enoxeparin: DVT 8%, PE 0.5%, bleeding 6%