How are blood transfusions managed in patients with polycythemia?

Blood Transfusion Management in Polycythemia Vera

Blood transfusions are generally contraindicated in polycythemia vera patients as they would further increase red cell mass and exacerbate hyperviscosity, potentially increasing thrombotic risk. 1

Understanding Polycythemia and Transfusion Considerations

• Polycythemia vera (PV) is characterized by excessive red blood cell production leading to increased blood viscosity, which is the limiting factor in oxygen delivery to tissues 2
• The primary treatment goal in PV is to reduce hematocrit below 45% through phlebotomy and cytoreductive therapy to prevent thrombotic complications 1, 3
• Increased blood viscosity is a major factor in thrombogenesis in PV, leading to impaired capillary blood flow 4

When Transfusions May Be Necessary in PV Patients

• Transfusions should only be considered in exceptional circumstances:
  • Perioperative blood loss requiring immediate replacement 1
  • Development of secondary bone marrow failure 1
  • Transformation to myelofibrosis with cytopenias 1

Special Transfusion Considerations

• When transfusion is absolutely necessary:
  • Use leukoreduced blood products to minimize inflammatory reactions 1
  • Administer small-volume transfusions with careful monitoring of hematocrit levels 1
  • Perform therapeutic phlebotomy before transfusion if the clinical situation allows, to maintain hematocrit below 45% 1

Managing Thrombotic Risk During Necessary Transfusions

• Low-dose aspirin therapy should be continued during the perioperative period to reduce thrombotic risk 1, 3
• Monitor for signs of hyperviscosity, which can manifest as neurological symptoms and increased bleeding risk 4
• Closely monitor hematocrit levels before, during, and after transfusion 1

Platelet Transfusions in PV

• Platelet transfusions should be avoided in PV patients with thrombocytosis 1
• PV patients may have qualitative platelet defects that can contribute to bleeding risk despite normal or elevated platelet counts 1
• Decreased platelet number and function have been described in cyanotic congenital heart disease with polycythemia 2

Common Pitfalls to Avoid

• Avoid routine transfusions that would counteract the therapeutic goal of maintaining hematocrit <45% 1, 5
• Do not use standard transfusion thresholds for PV patients; higher hemoglobin thresholds for transfusion should be applied 1
• Recognize that phlebotomy, not transfusion, is the cornerstone treatment for PV 3, 6
• Be aware that polycythemia reduces the amount of plasma in a given volume of whole blood, which affects anticoagulant dosing for blood samples 2

Alternative Management Approaches for PV

• Phlebotomy to maintain hematocrit <45% (or approximately 42% for women and African Americans) 5
• Low-dose aspirin (81-100 mg/day) for all patients without contraindications 3, 5
• Cytoreductive therapy (hydroxyurea or interferons) for high-risk patients (age >60 years and/or history of thrombosis) 3
• Ruxolitinib for patients who are resistant to or intolerant of hydroxyurea 2, 7