How many hours prior to a procedure should the heparin (unfractionated heparin) drip be stopped?

Stopping Unfractionated Heparin Before Procedures

Stop the unfractionated heparin (UFH) infusion 4-6 hours before the procedure to completely eliminate its anticoagulant effect. 1, 2

Timing Based on Pharmacokinetics

• UFH has an 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
• The 4-6 hour window allows for approximately 3-4 elimination half-lives to pass, ensuring >90% clearance of the drug 3
• Both the American College of Chest Physicians and American Heart Association recommend this 4-6 hour interval to completely eliminate the anticoagulant effect before surgery 1, 2

Procedure-Specific Considerations

Standard Surgical Procedures

• For most elective surgeries, stop UFH infusion at least 4-6 hours before the procedure 1, 2
• If there is concern about residual anticoagulant effect, checking aPTT or anti-factor Xa levels prior to the procedure can confirm adequate clearance 3

Neuraxial Procedures

• Neuraxial procedures (spinal anesthesia, epidurals, lumbar punctures) are contraindicated under active anticoagulation 4
• The same 4-6 hour stopping time applies for UFH before neuraxial procedures 1, 2

Special Situations: Heparin-Induced Thrombocytopenia (HIT)

If the patient has acute HIT (<1 month) and requires alternative anticoagulants 4:

• Argatroban: Stop infusion 4 hours before surgery 4
• Bivalirudin: Stop infusion 2 hours before surgery 4
• These agents have much shorter half-lives (argatroban ~50 minutes, bivalirudin ~20-30 minutes) 4

Common Pitfalls to Avoid

• Do not assume the anticoagulant effect is gone immediately after stopping the infusion - the half-life means residual activity persists for several hours 1, 2
• Be aware that the half-life can vary significantly (30-120 minutes) depending on the dose and level of anticoagulation at the time of discontinuation 1
• For high thrombotic risk patients, consider the timing carefully - stopping too early increases thrombotic risk, while stopping too late increases bleeding risk 1

Postoperative Resumption

• Resume UFH ≥24 hours after elective surgery to reduce bleeding risk 1, 2
• When restarting UFH postoperatively, avoid bolus dosing and begin with a lower-intensity infusion with a lower target aPTT than used for full-dose initiation 1, 2
• For low-bleeding risk procedures, UFH can be restarted without a bolus more than 4 hours after removal of the peripheral venous catheter 1