What is the dose of Fresh Frozen Plasma (FFP) for treating heparin resistance?

Fresh Frozen Plasma Dosing for Heparin Resistance

The recommended dose of Fresh Frozen Plasma (FFP) for treating heparin resistance is 10-15 ml/kg of body weight, which typically corresponds to 2-4 units of FFP for an average adult. 1, 2

Understanding Heparin Resistance

Heparin resistance is defined as:

• Inability to achieve an Activated Clotting Time (ACT) >300 seconds after administration of >600 U/kg heparin 1
• Often caused by antithrombin III (AT III) deficiency (congenital or acquired)
• Other causes include preoperative heparin treatment, extreme thrombocytosis, septicemia, and hypereosinophilic syndrome 1

Treatment Algorithm for Heparin Resistance

1. First-line approach:

   • Identify heparin resistance (ACT <300 seconds despite adequate heparin dosing)
   • Consider FFP administration at 10-15 ml/kg 1, 2
   • For an average adult, this typically means 2-4 units of FFP (each unit averages ~300 ml) 2

2. Alternative approach:

   • Antithrombin III (AT III) concentrate (if available)
   • More effective than FFP in achieving adequate anticoagulation 3
   • Avoids risks associated with FFP (transfusion reactions, volume overload, viral transmission)

Evidence Supporting FFP Use in Heparin Resistance

The evidence supporting FFP for heparin resistance comes primarily from observational studies and case reports:

• FFP contains approximately 1 unit/ml of antithrombin III (AT III) 1
• FFP appears to "normalize" the heparin-ACT dose-response curve in heparin-resistant patients 4
• After FFP administration, patients typically require less total heparin during cardiopulmonary bypass 4
• Protamine sulfate requirements are substantially lower after FFP administration 4

Practical Considerations

• Timing: FFP should be administered early when heparin resistance is identified, typically before or at the beginning of cardiopulmonary bypass 4
• Monitoring: Repeat ACT measurement 15-30 minutes after FFP administration to assess response
• Storage and compatibility: FFP should be ABO compatible with the patient 2
• Thawed FFP usage: Once thawed, FFP must be used within 24 hours if stored at 4°C, and within 30 minutes if removed from refrigeration 2

Cautions and Limitations

• FFP carries risks including transfusion-related acute lung injury (TRALI), volume overload, and viral transmission 3
• AT III concentrate may be more effective than FFP for treating heparin resistance 3
• FFP may not always restore ACT to therapeutic levels 3
• Patients receiving FFP for heparin resistance should be monitored for transfusion reactions, which occur in approximately 5% of patients 1

Special Populations

• Neonates and infants: Typically have lower levels of AT III (20-80% of adult levels) until approximately 6 months of age 1
• Patients with hereditary AT III deficiency: May require higher doses of FFP or preferably AT III concentrate 1

By following this approach to FFP dosing for heparin resistance, clinicians can effectively manage this challenging clinical scenario while minimizing risks associated with inadequate anticoagulation during cardiopulmonary bypass.