Timing of Heparin Discontinuation Before Surgical Procedures
For patients requiring surgical procedures, unfractionated heparin (UFH) should be stopped at least 4 hours before surgery, and low molecular weight heparin (LMWH) should be held approximately 24 hours before surgery to minimize bleeding risk while maintaining perioperative safety. 1, 2
Unfractionated Heparin (UFH) Management
Pre-operative Discontinuation
- Stop intravenous UFH at least 4 hours before surgery to eliminate residual anticoagulant effect 1
- UFH has a variable elimination half-life of approximately 90 minutes (range 30-120 minutes), which is dose-dependent and varies according to the level of anticoagulation 1, 2
- For surgical patients receiving prophylactic UFH, the typical regimen is 5,000 U given 2-4 hours preoperatively and every 8 hours thereafter, or 5,000 U 10-12 hours preoperatively and once daily thereafter 1
Post-operative Resumption
- Resume UFH ≥24 hours after surgery rather than within 24 hours to reduce bleeding risk 1
- When restarting UFH post-operatively, avoid bolus dosing and begin with a lower-intensity infusion with a lower target aPTT than used for full-dose initiation 1
- For therapeutic anticoagulation, the maintenance dose typically ranges from 20,000 to 40,000 units/24 hours as a continuous infusion 3
Low Molecular Weight Heparin (LMWH) Management
Pre-operative Discontinuation
- Administer the last pre-operative dose of LMWH approximately 24 hours before surgery rather than 10-12 hours before the procedure 1, 2
- LMWH has a longer elimination half-life (3-5 hours) compared to UFH 4
- Studies show that patients who received their last LMWH dose approximately 12 hours before surgery had detectable anticoagulant effect in >90% of cases, with 34% having therapeutic levels at the time of surgery 1
- For neuraxial anesthesia or analgesia, prophylactic doses of once-daily LMWH should not be administered within 10-12 hours before the procedure 1
Post-operative Resumption
- For high bleeding risk surgeries, resume therapeutic-dose LMWH >24 hours after surgery 1
- For low to moderate bleeding risk procedures, LMWH can be resumed 24 hours after surgery 1, 2
- After catheter removal for neuraxial anesthesia, the first dose of LMWH can be administered no earlier than 2 hours afterward 1
- After surgery, the first dose of LMWH can be administered 6-8 hours postoperatively 1
Special Considerations for Bridging Therapy
- For patients on vitamin K antagonists (VKAs) requiring bridging with heparin, stop VKAs 5 days before surgery 2, 5
- Begin LMWH or UFH 1-2 days after VKA interruption 2, 5
- For high thromboembolic risk patients, therapeutic-dose bridging is recommended with LMWH at 70 anti-factor Xa U/kg twice daily 2, 5
- For moderate to low thromboembolic risk patients, prophylactic once-daily doses are sufficient 5
- Oral anticoagulation can be resumed the day after the procedure 5
Comparative Safety Profile
- Both UFH and LMWH have comparable safety profiles when properly timed around surgical procedures 6, 7
- LMWH may offer advantages over UFH in certain surgical settings due to more predictable dose response and longer half-life 4, 8
- In orthopedic surgery, LMWH has been shown to be more effective than UFH in preventing deep vein thrombosis 8
Common Pitfalls and Caveats
- Failure to account for the variable half-life of UFH (30-120 minutes) can lead to increased bleeding risk if stopped too close to surgery 1, 2
- Administering LMWH too close to surgery (within 12 hours) results in detectable anticoagulant effect in >90% of patients at the time of surgery 1
- Resuming full-dose anticoagulation too early after surgery increases bleeding risk, especially in high bleeding risk procedures 1
- Avoid bolus dosing when restarting UFH post-operatively to reduce bleeding complications 1
- For patients with renal impairment, LMWH dosing may need adjustment as it depends on significant renal clearance 1