When should heparin (unfractionated heparin) drip be stopped prior to surgery?

Timing of Unfractionated Heparin Discontinuation Before Surgery

Unfractionated heparin (UFH) infusion should be discontinued 4-6 hours before surgery to minimize bleeding risk while maintaining adequate perioperative anticoagulation. 1

Pharmacokinetics and Rationale

• UFH has a relatively short elimination half-life of approximately 90 minutes (range 30-120 minutes), which allows for predictable clearance when stopped before surgery 1
• The anticoagulant effect of IV UFH diminishes rapidly after discontinuation due to its short half-life, making the 4-6 hour window appropriate for most surgical procedures 1
• The American College of Chest Physicians guidelines specifically recommend stopping IV UFH 4-6 hours before surgery to eliminate residual anticoagulant effect and reduce bleeding risk 2

Timing Considerations Based on Surgical Bleeding Risk

• For standard-risk procedures, the 4-6 hour discontinuation window is sufficient to normalize coagulation parameters 1
• For high bleeding risk procedures (neurosurgery, ophthalmic surgery), consider confirming normalization of aPTT before proceeding with surgery 2
• For procedures with lower bleeding risk or where bleeding can be easily controlled (such as dental procedures), a shorter discontinuation period may be acceptable 2

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 1
• Use a lower target aPTT initially when resuming therapy compared to the target used for full-dose initiation 1

Special Considerations

• For patients on bridging therapy (transitioning from oral anticoagulants), the timing remains the same - stop UFH 4-6 hours before surgery 2
• Patients with high thromboembolic risk may benefit from minimizing the time off anticoagulation, but the 4-6 hour window should still be respected to prevent excessive surgical bleeding 2, 1
• Studies have shown that preoperative heparin administration (1-10 hours before incision) is associated with >2-fold reduction in thromboembolic events without significantly increasing bleeding risk 3

Comparison with LMWH

• Unlike UFH, low molecular weight heparin (LMWH) should be discontinued 24 hours before surgery due to its longer half-life (3-5 hours) 1
• Studies show that patients who received LMWH approximately 12 hours before surgery still had detectable anticoagulant effect in >90% of cases 1, 4
• When bridging with LMWH instead of UFH, the last dose should be administered approximately 24 hours before surgery rather than 10-12 hours 1

Common Pitfalls to Avoid

• Stopping UFH too early (>6 hours) may increase thromboembolic risk unnecessarily 3
• Stopping UFH too late (<4 hours) may lead to increased surgical bleeding 2
• Failing to adjust the discontinuation time based on the patient's renal function (impaired renal function may prolong UFH effect) 1
• Restarting UFH too soon after surgery or at full dose with bolus can significantly increase bleeding risk 1