Chapter 7-06: Key Medications & Interventions in Hematology

TRANSFUSION MEDICINE

Standard testing

• ABO typing: Determine A/B antigens present on RBCs (blood type A, B, AB, or O)

• Rh(D) typing: Tests for D antigen on RBCs (e.g., A+ vs. A–)

• Type and screen: Tests for unexpected antibodies in patient plasma that might react with transfused product and cause hemolysis. Must be done q72 hrs.

• Type and cross: Final confirmation test that is performed by mixing the patient’s plasma and the donor’s RBCs. Performed when transfusion is imminent/very likely.

Antibody testing

• Direct antiglobulin test (DAT or Coombs): Tests for auto-antibodies on the patient’s RBCs

  • - Mix patient’s RBCs + Coomb’s reagent (anti-IgG, anti-C3)

• Indirect Coombs: Tests for antibodies in the patient’s plasma

  • - Mix patient’s plasma + donor RBCs and Coomb’s reagent

Apheresis (separation of blood)

• Plasmapheresis: Removes high molecular weight proteins from plasma (e.g., antibodies). Used in TTP, hyperviscosity syndrome, cryoglobulinemia, myasthenia gravis, Guillain-Barré syndrome, anti-GBM, some ANCA vasculidities.

• Cytapheresis: Removes cellular components (e.g., leukapheresis: removes WBCs in acute leukemia)

Complications of transfusion

• Hypocalcemia: Citrate used to preserve pRBCs chelates calcium

• Volume overload: Blood products stay mostly intravascular, so 250 cc of pRBCs (1 unit) is equivalent to 1000 cc normal saline. Rapid increase in intravascular volume can lead to circulatory overload and increased hydrostatic pressure, which can worsen active bleeding.

Special preparations of blood

• Leukoreduced: WBCs filtered out

  • - Decreased risk of febrile reaction in patients with prior febrile non-hemolytic transfusion reactions

  • - Deceased risk of HLA/RBC alloimmunization in patients who are chronically transfused (i.e., patients with hematologic malignancies, transplant candidates)

• CMV reduced-risk: Requires CMV-negative donor or leukocyte reduction to remove mononuclear cells; prevents CMV transmission in CMV-negative recipients of bone/organ transplant, pregnant women, HIV+ patients

• Irradiated: Prevents donor T-cells from attacking host marrow

  • - Used to prevent TA-GVHD in 1^st degree–related donors for heme malignancy, bone marrow transplant (not solid tumor transplant or HIV+)

• Washed: Removes anti-IgA antibodies and plasma proteins

  • - Prevents anaphylaxis in severe IgA deficiency

Types of blood products

• Packed red blood cells (pRBCs): 1 unit = 250 cc, expect to increase Hgb by 1 g/dL

  • - Transfusion time: 60–240 min

  • - Transfusion goal: Depends on patient-specific factors

    • Goal: Hgb >7 g/dL in most patients

    • Goal: Hgb >8 g/dL in certain patients with CAD and/or ACS

• Platelets: 1 pheresis (6-pk) = 300 cc, expect to increase platelet by 30K/µl

  • - Transfusion time: 30–60 min

  • - Pooled platelets = platelets removed from whole blood donation from many donors

  • - Apheresis = platelets from a single donor

  • - Transfusion goal: Depends on patient-specific factors

    • Goal: Plt >10K/μl prophylaxis against spontaneous bleeding in most patients

    • Goal: Plt >50K/μl if major bleed

• Fresh frozen plasma (FFP): 1U = 250 cc, contains all coagulation factors

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