When to Start VTE Prophylaxis After Surgery
VTE prophylaxis should be initiated as soon as possible after surgery, with mechanical prophylaxis started preoperatively and pharmacological prophylaxis typically started within 24 hours postoperatively when hemostasis is established. 1, 2
Risk Assessment and Timing
Mechanical Prophylaxis
- Start mechanical prophylaxis (sequential compression devices) preoperatively for all surgical patients 2
- Continue until the patient is fully ambulatory 2
Pharmacological Prophylaxis
- Timing of initiation:
- For most surgical patients: Start within 24 hours after surgery when hemostasis is established 2
- For patients receiving neuraxial anesthesia:
- Prophylactic LMWH (e.g., enoxaparin 40mg daily): Start 4+ hours after catheter removal and not earlier than 12 hours after the block was performed 2
- Intermediate LMWH doses: Start 4+ hours after catheter removal and not earlier than 24 hours after the block was performed 2
- Prophylactic UFH: Start as early as 1 hour after removal of neuraxial catheter 2
Risk Stratification
The need for VTE prophylaxis depends on both patient and procedure-specific risk factors:
High-Risk Procedures:
- Major abdominal/pelvic surgery
- Hip or knee arthroplasty
- Major trauma
- Spinal cord injury
- Cancer surgery 2
Patient Risk Factors:
- Age >60 years
- Prior VTE
- Cancer
- Molecular hypercoagulability
- Prolonged immobility
- Obesity
- Heart failure
- Recent MI or stroke 2
Prophylaxis Recommendations by Risk Level
Low Risk (Caprini score 0):
- Early ambulation only 3
Moderate Risk (Caprini score 1-2):
- Mechanical prophylaxis OR pharmacological prophylaxis 3
High Risk (Caprini score 3-4):
- Pharmacological prophylaxis ± mechanical prophylaxis 3
Very High Risk (Caprini score ≥5):
- Combined pharmacological AND mechanical prophylaxis 3
Duration of Prophylaxis
- Standard duration: Continue for at least 7-10 days postoperatively 2
- Extended prophylaxis: For high-risk patients (especially those undergoing major abdominal/pelvic cancer surgery), continue prophylaxis for up to 4 weeks after discharge 2
- Orthopedic surgery: Extended prophylaxis (up to 35 days) should be considered 1
Special Considerations
Cancer Surgery
- Cancer patients have a higher risk of VTE that extends beyond hospitalization
- For major abdominal/pelvic cancer surgery, extended prophylaxis for up to 4 weeks is recommended 2
- More than half of post-radical cystectomy VTEs occur after hospital discharge, with a median of 20 days postoperatively 2
Renal Impairment
- For patients with severe renal impairment (CrCl <30 mL/min), UFH is preferred over LMWH 1
- Consider monitoring anti-Xa levels in patients with renal impairment receiving LMWH 1
Bleeding Risk
- In cases with significant intraoperative bleeding complications, the decision on when to start pharmacologic prophylaxis must be individualized 2
- Consider using UFH (which has a shorter half-life and is reversible) in patients with high bleeding risk 2
Common Pitfalls to Avoid
- Delaying prophylaxis unnecessarily - VTE risk begins during surgery; mechanical prophylaxis should start preoperatively
- Stopping prophylaxis too early - Risk extends beyond hospitalization, especially for high-risk patients
- Overlooking drug-specific timing with neuraxial anesthesia - Different anticoagulants have different timing requirements to prevent spinal hematomas
- Relying solely on pharmacological prophylaxis - Combined approaches (mechanical + pharmacological) may be more effective for highest-risk patients
- Failing to reassess VTE risk daily - Patient risk factors may change during hospitalization 2
By implementing timely and appropriate VTE prophylaxis, you can significantly reduce the risk of this preventable cause of postoperative morbidity and mortality.