What are the appropriate indications, initiation protocols, dosing regimens, monitoring, and reversal strategies for anticoagulation therapy?

How to Use Anticoagulation

For cancer-associated VTE, use low molecular weight heparin (LMWH) as monotherapy—specifically dalteparin 200 units/kg SC daily for 30 days, then 150 units/kg daily for at least 6 months—as this is the only LMWH with Category 1 evidence and FDA approval for this indication 1.

Indications for Anticoagulation

Treatment of Established VTE

• Proximal DVT or PE: Minimum 3 months anticoagulation required 2, 3
• Cancer-associated VTE: Indefinite anticoagulation while cancer is active, under treatment, or risk factors persist 1
• Catheter-associated thrombosis: Anticoagulate as long as catheter is in place, minimum 3 months total 1

Prophylaxis Settings

• Hospitalized medical patients: Enoxaparin 40 mg SC daily, dalteparin 5,000 units SC daily, or UFH 5,000 units every 8 hours 2
• Surgical patients: Start 2-4 hours preoperatively, continue at least 7-10 days; consider extended prophylaxis up to 4 weeks for high-risk patients 2
• High-risk cancer outpatients: Apixaban 2.5 mg BID or rivaroxaban 10 mg daily 2

Initiation Protocols

For Acute VTE Treatment

LMWH Monotherapy (Preferred for Cancer Patients)

• Dalteparin: 200 units/kg SC daily for 30 days, then 150 units/kg daily 1
• Enoxaparin: 1 mg/kg SC every 12 hours (or 1.5 mg/kg once daily) 2, 1
• Tinzaparin: 175 units/kg SC once daily 2

Direct Oral Anticoagulants (DOACs)

• Rivaroxaban: 15 mg BID for 21 days, then 20 mg daily (with food) 2, 1
• Apixaban: 10 mg BID for 7 days, then 5 mg BID 1
• Edoxaban: Requires at least 5 days parenteral anticoagulation first, then 60 mg daily (30 mg if weight <60 kg, CrCl 30-50 mL/min, or on P-glycoprotein inhibitors) 1, 2, 1
• Dabigatran: Requires at least 5 days parenteral anticoagulation first, then 150 mg BID (only if CrCl >30 mL/min) 1

Unfractionated Heparin (UFH)

• IV: 80 units/kg bolus, then 18 units/kg/hour, target aPTT 2-2.5× control 2, 1
• SC: 333 units/kg load, then 250 units/kg every 12 hours 1

Fondaparinux

• Weight-based: <50 kg: 5 mg; 50-100 kg: 7.5 mg; >100 kg: 10 mg SC daily 2, 1

Dosing Regimens

Special Populations

Obese Patients

• Use actual body weight for LMWH dosing, not a fixed maximum dose 4

Renal Impairment

• CrCl 30-50 mL/min: Edoxaban 30 mg daily; use caution with LMWH and consider dose adjustment 1, 2
• CrCl <30 mL/min: Avoid fondaparinux; dabigatran contraindicated; use UFH or warfarin 1, 5

Elderly (>70 years)

• Avoid tinzaparin with renal insufficiency 5

Monitoring

Baseline Testing

• CBC, renal and hepatic function panel, aPTT, PT/INR 1

Ongoing Monitoring

• Hemoglobin, hematocrit, platelet count: Every 2-3 days for first 14 days, then every 2 weeks or as clinically indicated 1
• Warfarin: Target INR 2.0-3.0 2, 6
• LMWH: Anti-Xa monitoring generally not recommended unless renal dysfunction, extreme body weight, or pregnancy 4
• UFH: aPTT monitoring to maintain 2-2.5× control 2, 1

DOACs

• No routine monitoring required, but DOAC-specific coagulation tests may help in patients at risk for elevated levels 7
• DOAC levels >50 ng/mL considered clinically relevant before urgent procedures 7

Contraindications

Absolute

• Recent CNS bleed, intracranial or spinal lesion at high risk for bleeding 5
• Active major bleeding (>2 units transfused in 24 hours) 5
• Recent spinal anesthesia/lumbar puncture 5

Relative

• Chronic, clinically significant bleeding >48 hours 5
• Thrombocytopenia (platelets <50,000/mcL) 5
• Severe platelet dysfunction 5
• Recent major operation at high risk for bleeding 5

Reversal Strategies

For Major Bleeding

Warfarin

• Vitamin K plus prothrombin complex concentrate (PCC) 8

Dabigatran

• Idarucizumab (specific reversal agent) 8, 7

Apixaban/Rivaroxaban

• Andexanet alfa (specific reversal agent) 8, 7
• Exception: Do not use andexanet alfa before cardiac surgery requiring heparin for extracorporeal circulation 7

LMWH/Fondaparinux

• PCC or recombinant activated factor VII for life-threatening bleeding 9
• Note: Recombinant factor VII at high doses (30-70 mg/kg) associated with dramatically higher thromboembolic events in LVAD patients 9

General Measures

• Stop anticoagulant immediately 8
• Standard resuscitative measures for hemodynamic compromise 8
• Consider transfusion support as needed 8

Restarting Anticoagulation After Bleeding

Delay restart if:

• Bleed occurred at critical site (intracranial, spinal, intraocular, pericardial, retroperitoneal) 8
• High risk of rebleeding or death/disability with rebleeding 8
• Source of bleed not yet identified 8
• Surgical or invasive procedures planned 8

Restart anticoagulation when:

• Bleeding controlled and patient stable 8
• Clinical indication for anticoagulation persists 8
• Risk-benefit assessment favors anticoagulation 8

Common Pitfalls

• Do not use global coagulation tests (PT/aPTT) to exclude clinically relevant DOAC levels 7
• Do not use fixed maximum doses for LMWH in obese patients 4
• Do not start dabigatran or edoxaban without at least 5 days of parenteral anticoagulation first 1
• Do not use concurrent parenteral anticoagulation when transitioning to dabigatran or edoxaban (unlike warfarin) 1
• Do not use 1 mg fixed-dose warfarin for VTE prophylaxis during major orthopedic surgery—it is ineffective 6