What is the preferred anticoagulant, heparin or bivalirudin, for patients on Extracorporeal Membrane Oxygenation (ECMO)?

Heparin vs Bivalirudin for ECMO Anticoagulation

Unfractionated heparin (UFH) is the recommended first-line anticoagulant for patients on Extracorporeal Membrane Oxygenation (ECMO), while bivalirudin should be reserved as an alternative in specific clinical scenarios such as heparin-induced thrombocytopenia (HIT) or heparin resistance. 1

First-Line Anticoagulation: Unfractionated Heparin

Rationale for UFH as First Choice

• UFH is the standard anticoagulant for ECMO supported by strong guideline recommendations 1
• Extensive clinical experience with UFH in ECMO settings
• Well-established monitoring protocols using aPTT or anti-factor Xa
• Reversibility with protamine if bleeding complications occur

UFH Dosing and Monitoring

• Initial dosing: Continuous IV infusion after administration of a bolus dose
• Target: aPTT 1.5-2 times above normal level
• Alternative monitoring: Anti-factor Xa levels
• Dose adjustments based on institutional protocols

Alternative Anticoagulation: Bivalirudin

Indications for Bivalirudin

• Confirmed or suspected heparin-induced thrombocytopenia (HIT)
• Heparin resistance not responding to antithrombin supplementation 2
• Patients with significant bleeding complications on heparin

Bivalirudin Dosing and Monitoring

• Starting dose: 0.02-0.05 μg/kg/min (significantly lower than doses used for other indications) 1
• Target: aPTT 1.5-2 times above normal level
• Requires institutional protocols for dosing and monitoring 1
• Alternative monitoring: Chromogenic anti-IIa testing or diluted thrombin time if available 1
• Dose adjustments needed for patients with renal impairment or postcardiotomy 1

Comparative Efficacy and Safety

Potential Advantages of Bivalirudin

• More predictable pharmacokinetics than heparin
• Shorter half-life (25 minutes with normal renal function)
• May reduce thrombotic events and major bleeding compared to heparin in some studies 3
• Potential reduction in in-hospital mortality reported in some meta-analyses 3

Limitations of Bivalirudin

• Limited high-quality evidence supporting routine use
• Higher cost compared to heparin
• No specific reversal agent
• Evidence primarily from small retrospective studies
• Inconsistent findings regarding superiority over heparin 3

Clinical Decision Algorithm

1. For initial ECMO anticoagulation:

   • Start with UFH as first-line therapy
   • Use institutional protocols for dosing and monitoring

2. Consider switching to bivalirudin if:

   • Confirmed or suspected HIT develops
   • Persistent heparin resistance despite antithrombin supplementation
   • Recurrent thrombotic complications despite therapeutic heparin levels

3. When using bivalirudin:

   • Start at lower doses (0.02-0.05 μg/kg/min)
   • Use institutional protocols for monitoring
   • Adjust dose based on renal function
   • Monitor for bleeding complications

Important Caveats

• No anticoagulation is not recommended for routine ECMO management 1
• Temporarily pausing anticoagulation may be necessary during periods of active bleeding
• Heparin-coated ECMO circuits are generally used when anticoagulation must be paused 1
• Monitoring strategies should be consistent within institutions to ensure standardized care

While some recent meta-analyses suggest potential benefits of bivalirudin over heparin 3, the quality of evidence remains limited, and current guidelines still recommend UFH as the first-line anticoagulant for ECMO patients with bivalirudin reserved for specific clinical scenarios.