What is the protocol for managing anticoagulation with Coumadin (warfarin) and a Lovenox (enoxaparin) bridge in a patient with thrombocytosis and anemia undergoing surgery?

Perioperative Warfarin Management with Lovenox Bridging

For most patients requiring surgery while on warfarin, bridging with Lovenox should NOT be performed—only those at highest thromboembolic risk (mechanical mitral valve, recent stroke/TIA with mechanical valve, or VTE within 3 months) should receive therapeutic-dose bridging, as bridging increases major bleeding 2-3 fold without proven benefit in the majority of patients. 1, 2

Critical Context: Thrombocytosis and Anemia

Your patient's thrombocytosis and anemia require special consideration:

• Anemia is an independent risk factor for warfarin-associated bleeding and should lower your threshold for avoiding bridging or delaying postoperative anticoagulation resumption 2
• Thrombocytosis after enoxaparin administration has been documented (paradoxically increasing platelet counts, sometimes >600 G/L), though this did not correlate with thrombotic complications in prospective studies 3
• Monitor platelet counts on postoperative days 5,7,11, and 15 if bridging is used 3

Risk Stratification: Who Needs Bridging?

HIGH RISK - Bridge with Therapeutic-Dose LMWH:

• Mechanical mitral valve OR any mechanical valve with prior stroke/TIA 1, 2
• Atrial fibrillation WITH rheumatic mitral stenosis 1
• VTE within the past 3 months 1, 2
• Active cancer with high VTE risk (selected cases) 1

LOW-TO-MODERATE RISK - DO NOT Bridge:

• Non-valvular atrial fibrillation (even with CHADS₂ 5-6) 1, 2
• Bileaflet mechanical aortic valve without additional risk factors 4
• VTE >3 months ago 1, 2
• Thrombophilia without active thrombosis 1

Preoperative Protocol (If Bridging Required)

Warfarin Discontinuation:

• Stop warfarin 5 days before surgery to allow INR to decrease to ≤1.5 2, 5, 2
• Alternative: Stop warfarin 2 days preoperatively with vitamin K 2.5 mg orally, though this provides only 2 days of unprotected time 2

LMWH Initiation:

• Start therapeutic-dose enoxaparin 3-4 days before surgery (approximately 36 hours after last warfarin dose) when INR falls below 2.0 5, 2
• Dosing: Enoxaparin 1 mg/kg subcutaneously twice daily OR 1.5 mg/kg once daily 2, 5, 2
• Last preoperative LMWH dose: 24 hours before surgery (NOT 12 hours—the 24-hour timing is safer) 5, 2

Preoperative INR Check:

• Check INR on the day before or morning of surgery to confirm ≤1.5 5, 2
• If INR 1.5-1.8, consider low-dose oral vitamin K 1-2.5 mg 5, 2
• Draw INR at least 10-12 hours after last enoxaparin dose to avoid falsely elevated readings 5

Postoperative Protocol

Timing Based on Bleeding Risk:

HIGH-BLEEDING-RISK PROCEDURES (cardiac, intracranial, spinal surgery, major vascular surgery, extensive cancer surgery):

• Delay therapeutic-dose LMWH for 48-72 hours postoperatively 5, 2
• Consider stepwise approach: Start prophylactic-dose enoxaparin 40 mg daily for first 24-48 hours, then increase to therapeutic dose if hemostasis adequate 2, 1
• Given your patient's anemia, strongly consider the 72-hour delay before therapeutic dosing 2

LOW-TO-MODERATE-BLEEDING-RISK PROCEDURES:

• Resume therapeutic-dose LMWH 24 hours post-procedure if adequate hemostasis achieved 5, 2
• Assess surgical hemostasis before ANY postoperative heparin—examine wound drainage (amount, type, progression) 2, 1

Warfarin Resumption:

• Resume warfarin the evening of surgery or next morning at usual maintenance dose 5, 2
• Alternative: Give 1.5x maintenance dose for 2 days to accelerate therapeutic range 5
• Continue enoxaparin bridging until INR ≥2.0 on two consecutive measurements 5
• Check INR daily after resuming warfarin until therapeutic (2.0-3.0) 5

Renal Dosing Adjustment:

• If CrCl <30 mL/min, use IV unfractionated heparin instead of LMWH 5, 2

Critical Pitfalls to Avoid

• DO NOT give therapeutic-dose enoxaparin within 24 hours after high-bleeding-risk procedures—this increases major bleeding risk to 20% 5, 6
• DO NOT bridge based solely on anticoagulation indication—the BRIDGE trial definitively showed harm without benefit in most AF patients 1, 4
• DO NOT resume therapeutic heparin without assessing hemostasis—major bleeding requires prolonged anticoagulation interruption, paradoxically increasing thrombotic risk 2, 1
• DO NOT overlook your patient's anemia—this significantly increases bleeding risk and should bias toward conservative postoperative resumption 2

Monitoring During Bridging

• Platelet count: Baseline, then days 5,7,11, and 15 postoperatively (especially important given thrombocytosis) 3
• Hemoglobin: Monitor closely given baseline anemia 2
• INR: Day before surgery, then daily after warfarin resumption 5
• Clinical hemostasis: Wound drainage assessment before each therapeutic-dose LMWH administration 2, 1