What is the recommended anticoagulation regimen, including heparin (unfractionated heparin), in patients undergoing Coronary Artery Bypass Grafting (CABG) with endarterectomy?

Anticoagulation Regimen for CABG with Endarterectomy

For patients undergoing Coronary Artery Bypass Grafting (CABG) with endarterectomy, weight-adjusted unfractionated heparin (UFH) at 300-400 units/kg should be administered during the procedure, with a target activated clotting time (ACT) of 300-350 seconds using the Hemochron device or 250-300 seconds using the HemoTec device. 1

Preoperative Anticoagulation Management

Antiplatelet Therapy

• Aspirin (81-325 mg daily) should be administered preoperatively and continued until the day of surgery 1, 2
• P2Y12 inhibitors should be discontinued before elective CABG:
  • Clopidogrel and ticagrelor: at least 5 days before surgery 1
  • Prasugrel: at least 7 days before surgery 1
• For urgent CABG, P2Y12 inhibitors should be discontinued for at least 24 hours to reduce major bleeding 1

Bridging Therapy

• If anticoagulation is needed preoperatively (e.g., for high-risk patients with mechanical valves or recent thrombosis):
  • UFH: Stop 4-6 hours before surgery 1
  • LMWH: Administer last dose 24 hours before surgery 1
  • Avoid crossing between different anticoagulants (e.g., from LMWH to UFH) as this increases bleeding risk 1

Intraoperative Anticoagulation

UFH Dosing During CABG with Endarterectomy

• Initial bolus: 300-400 units/kg for procedures estimated to last longer than 60 minutes 3
• Target ACT: 300-350 seconds (Hemochron) or 250-300 seconds (HemoTec) 1
• Monitor ACT regularly during the procedure to maintain therapeutic anticoagulation

Special Considerations

• Weight-adjusted heparin dosing provides more predictable anticoagulation than fixed dosing 1, 4
• For patients with heparin-induced thrombocytopenia (HIT), alternative anticoagulants such as bivalirudin, lepirudin, or danaparoid should be used 5, 6

Postoperative Anticoagulation

Immediate Postoperative Period

• Routine use of UFH after uncomplicated CABG is not recommended and may increase bleeding events 1
• If continued anticoagulation is necessary due to residual thrombus or significant dissections, subcutaneous UFH may provide a safer alternative to intravenous administration 1

Long-term Anticoagulation

• Aspirin (100-325 mg daily) should be initiated within 6 hours postoperatively and continued indefinitely to prevent graft closure 2
• Consider dual antiplatelet therapy (DAPT) with aspirin plus a P2Y12 inhibitor for patients at increased risk of graft occlusion who are not at high bleeding risk 1

Monitoring and Complications

Monitoring Parameters

• Monitor activated partial thromboplastin time (aPTT), platelet count, hematocrit, and occult blood in stool during heparin therapy 3
• For patients on LMWH, standard ACT monitoring is not effective as LMWH has little effect on ACT measurements 1

Bleeding Risk Management

• Careful hemostasis and meticulous surgical technique are essential to minimize bleeding risk
• Protamine can be used to reverse heparin effects if excessive bleeding occurs, but should be used selectively 7
• Monitor for neck swelling or symptoms of airway compromise that may indicate hematoma formation 7

Special Considerations

Atrial Fibrillation After CABG

• Transient new-onset AF occurs in approximately one-third of patients 2-3 days after CABG 1
• If AF persists for >48 hours, warfarin anticoagulation (target INR 2.0-3.0) should be considered 1
• In high-risk patients with history of stroke or TIA who develop AF, heparin should be considered despite increased bleeding risk 1

Practical Pitfalls to Avoid

• Avoid routine postoperative heparin infusions when using glycoprotein IIb/IIIa inhibitors 1
• Avoid crossing between different anticoagulants (e.g., from LMWH to UFH) as this increases bleeding risk 1
• Do not use ACT to guide anticoagulation therapy in patients currently being treated with LMWH 1
• Remember that impaired atrial contraction can persist for several weeks after AF resolves, potentially increasing thrombosis risk 1

By following these evidence-based recommendations for anticoagulation during CABG with endarterectomy, clinicians can optimize outcomes while minimizing the risks of both thrombotic and bleeding complications.