When should injection heparin (unfractionated heparin or low molecular weight heparin) be stopped in a preoperative patient with an undisplaced calcaneal fracture and possible osteoporosis?

When to Stop Heparin Before Surgery for Calcaneal Fracture

For unfractionated heparin (UFH), stop the infusion 4-6 hours before the surgical incision; for low-molecular-weight heparin (LMWH), administer the last dose at least 12 hours before surgery. 1

Unfractionated Heparin (UFH) Timing

• Stop intravenous UFH infusion 4-6 hours prior to the surgical incision to allow complete elimination of anticoagulant activity, as UFH has a half-life of approximately 60-90 minutes. 1

• This 4-6 hour window allows for approximately 3-4 elimination half-lives to pass, ensuring >90% clearance of the drug. 2

• When UFH is given subcutaneously (rather than as an infusion), the anticoagulant effect is more prolonged and may require longer discontinuation times. 3

Low-Molecular-Weight Heparin (LMWH) Timing

• The last dose of LMWH should be administered at least 12 hours before the surgical procedure. 3

• For patients receiving therapeutic-dose LMWH (such as 70 U/kg twice daily), ensure the 12-hour minimum interval is strictly observed. 3

• For prophylactic-dose LMWH, the same 12-hour minimum applies before any surgical intervention. 3

Critical Considerations for Neuraxial Anesthesia

• Neuraxial procedures (spinal or epidural anesthesia) are absolutely contraindicated under active anticoagulation. 1

• If spinal or epidural anesthesia is planned for the calcaneal fracture surgery, ensure UFH has been stopped for the full 4-6 hours and coagulation parameters have normalized before proceeding. 1

• For LMWH patients requiring neuraxial anesthesia, the 12-hour minimum stopping time must be confirmed before needle placement. 3

Special Considerations for Osteoporosis Context

• While long-term UFH use carries a 2.2-5% incidence of osteoporotic fractures, and LMWH appears to have lower bone density effects, this does not alter the preoperative timing recommendations. 4, 5

• The presence of possible osteoporosis in your patient does not change the standard heparin discontinuation protocol, but it may influence postoperative thromboprophylaxis choices. 4

Postoperative Resumption Guidelines

• Resume heparin at least 6 hours after the end of the surgical procedure once hemostasis is confirmed and there are no surgical contraindications. 3

• For UFH specifically, restart without a bolus dose more than 4 hours after removal of any epidural catheter or surgical drain. 1

• For standard orthopedic surgery with controlled hemostasis, restart UFH at ≥24 hours postoperatively using a lower-intensity infusion without bolus dosing. 1

• If using LMWH postoperatively, the first therapeutic dose should be administered 12 hours after the last prophylactic LMWH dose to avoid overlapping anticoagulant effects. 3

Common Pitfalls to Avoid

• Do not restart heparin too early postoperatively—major bleeding rates can reach up to 20% when bridging therapy is given too close to surgery. 1

• Do not use bolus dosing when restarting UFH after major orthopedic surgery, as this significantly increases bleeding risk. 1

• Do not assume subcutaneous UFH has the same clearance time as intravenous UFH—subcutaneous administration has a more prolonged anticoagulant effect. 3

• Avoid measuring heparin levels preoperatively if the recommended stopping times are followed, as routine monitoring is unnecessary when standard intervals are observed. 3