When should heparin (unfractionated heparin/low molecular weight heparin) be stopped prior to a surgical procedure?

Timing of Heparin Discontinuation Before Surgical Procedures

For patients receiving heparin therapy who require surgery, unfractionated heparin (UFH) should be stopped at least 4 hours before surgery, and low molecular weight heparin (LMWH) should be discontinued approximately 24 hours before surgery to minimize bleeding risk while maintaining safety. 1

Unfractionated Heparin (UFH) Discontinuation

Intravenous UFH

• Stop IV UFH at least 4-6 hours before surgery to eliminate residual anticoagulant effect 1
• This timing is based on UFH's elimination half-life of approximately 90 minutes (range 30-120 minutes) 1
• The half-life is dose-dependent and varies according to the level of anticoagulation as reflected by aPTT or anti-factor Xa levels 1

Resumption of UFH

• 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

Low Molecular Weight Heparin (LMWH) Discontinuation

Pre-operative Management

• Administer the last pre-operative dose of LMWH approximately 24 hours before surgery rather than 10-12 hours before the procedure 1
• This recommendation is based on LMWH's elimination half-life of 3-5 hours 1
• 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

Resumption of LMWH

• 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

Special Considerations

Bridging Therapy

• For patients on vitamin K antagonists (VKAs) requiring bridging with heparin:
  • Stop VKAs 5 days before surgery 1
  • Begin LMWH or UFH 1-2 days after VKA interruption 1
  • Administer the last dose of LMWH 24 hours before surgery 1
  • For IV UFH, stop 4-6 hours before surgery 1

Risk Stratification

• For high thromboembolic risk patients (mechanical heart valves, recent venous thromboembolism, atrial fibrillation with high stroke risk):
  • Therapeutic-dose bridging is recommended 1
  • When using LMWH, dosing at 70 anti-factor Xa U/kg twice daily is suggested 1, 2
• For low thromboembolic risk patients:
  • Prophylactic once-daily LMWH doses are sufficient 1, 2

Potential Pitfalls and Caveats

• Residual anticoagulant effect: Studies show that 16% of patients receiving bridging anticoagulation with LMWH have a residual anticoagulant effect (anti-Xa level ≥0.10 IU/ml) just before surgery 3
• Higher risk with therapeutic dosing: 30% of patients on therapeutic-dose LMWH have detectable anticoagulant levels pre-procedure compared to only 3% on prophylactic dosing 3
• Advanced age increases the risk of residual anticoagulation 3
• Avoid heparin bridging for patients undergoing colonoscopy with anticipated polypectomy due to increased bleeding risk 1
• For patients with mechanical heart valves requiring IV UFH, some centers hospitalize patients and continue IV UFH until 4 hours before surgery 1

By following these evidence-based recommendations for heparin discontinuation before surgery, clinicians can minimize perioperative bleeding risk while maintaining protection against thromboembolism.