When should heparin (subcutaneous, 5000 units, every 12 hours) be held before a scheduled surgery?

Timing of Prophylactic Heparin Hold Before Surgery

For prophylactic-dose unfractionated heparin 5000 units subcutaneous every 12 hours, hold the medication 4-6 hours before surgery. 1

Preoperative Management

Hold prophylactic UFH 4-6 hours before the surgical incision to allow adequate clearance of anticoagulant effect while minimizing thrombotic risk. 1 This timing is based on UFH's elimination half-life of approximately 90 minutes (range 30-120 minutes), which allows for near-complete clearance of anticoagulant activity by the time of surgical incision. 2, 1

Key Distinction: Prophylactic vs. Therapeutic Dosing

• Prophylactic UFH (5000 units q8-12h): Hold 4-6 hours before surgery 1
• Therapeutic UFH (IV infusion): Hold ≥4 hours before surgery 2
• Prophylactic LMWH: Hold 12 hours before surgery 1
• Therapeutic LMWH: Hold 24 hours before surgery 2

The 5000 units q12h regimen you're asking about is clearly prophylactic dosing, not therapeutic. 2

Postoperative Resumption

Resume prophylactic UFH ≥24 hours after surgery for high-bleeding-risk procedures, or approximately 24 hours after low-to-moderate-bleeding-risk surgery, contingent on adequate surgical hemostasis. 2, 1

Resumption Guidelines by Surgical Risk:

• High-bleeding-risk surgery: Resume 48-72 hours postoperatively 2
• Low-to-moderate-bleeding-risk surgery: Resume 24 hours postoperatively 2
• Neuraxial procedures: Resume ≥4 hours after catheter removal 1

When resuming UFH postoperatively, avoid bolus dosing and use the same or lower infusion rate as preoperatively to minimize bleeding risk. 2

Duration of Prophylaxis

Continue prophylactic heparin for at least 7-10 days postoperatively, or until the patient is fully ambulatory, whichever is longer. 2, 3 Extended prophylaxis for up to 4 weeks should be considered in high-risk patients (e.g., cancer surgery, major orthopedic procedures). 2, 1

Common Pitfalls to Avoid

• Do not confuse prophylactic with therapeutic dosing: The 4-6 hour hold time applies specifically to prophylactic UFH; therapeutic anticoagulation requires different timing 2, 1
• Avoid premature resumption: Resuming heparin too early postoperatively (within 12-24 hours) significantly increases major bleeding risk, particularly after major surgery (up to 20% bleeding rate). 2
• Consider neuraxial anesthesia: If epidural or spinal anesthesia is planned, coordinate timing with anesthesia team, as needle/catheter placement should not occur within 4-6 hours of the last prophylactic UFH dose 1
• Monitor for heparin-induced thrombocytopenia (HIT): Obtain baseline and periodic platelet counts during therapy 3

Special Populations

Patients over 60 years may require lower doses or more conservative timing, though the standard 4-6 hour hold remains appropriate. 3 For patients with severe renal insufficiency, UFH is preferred over LMWH, and the standard timing applies. 2