Transfusion medicine

• Typical RBC unit increases hemoglobin by about 1 g/dL in adults
• For children, 10 mL/kg RBC increases hemoglobin by 2 g/dL(Transfusion 2007;47:212)
• Restrictive hemoglobin thresholds for RBC transfusion have been proven to be as safe or safer than liberal and provide noninferior outcomes in:
  • Intensive care units (7 versus 9 g/dL) (N Engl J Med 1999;340:409)
  • Pediatric intensive care (7 versus 9 g/dL) (N Engl J Med 2007;356:1609)
  • Upper gastrointestinal hemorrhage (7 versus 9 g/dL) (N Engl J Med 2013;368:11)
  • Cardiac surgery (7.5 versus 9.5 g/dL) (N Engl J Med 2018;379:1224)
  • Recovery after hip fracture surgery (8 versus 10 g/dL) (N Engl J Med 2011;365:2453)
  • Bone marrow transplantation (7 versus 9 g/dL) (J Clin Oncol 2020;38:1463)
  • Acute myocardial infarction (7 versus 10 g/dL) (Blood Adv 2020;4:327)
  • Premature neonates (variable thresholds depending on age and the need for respiratory support) (N Engl J Med . 2020;383:2639)
• No particular transfusion trigger based on hemoglobin or any other parameter has been supported by controlled trials in chronic hypoproliferative anemia; transfusion thresholds are based on levels where there is a demonstrated improvement in symptoms for the individual
• Many people with hemoglobin levels below 7 g/dL are able to tolerate anemia well and transfusion is not always required, especially when there is a reversible cause, such as iron deficiency
• Where there is a foreseeable potential need for transfusion, such as elective surgery, optimization of preoperative hemoglobin (consider iron or erythropoiesis stimulating agents as appropriate) is encouraged to reduce transfusion needs
• Where transfusion is indicated for anemia, best practice is to titrate the transfusion volume to needs by giving a single unit and reassessing clinically
• RBC may be transfused in sickle cell disease to prevent sickling in acute chest syndrome, during pregnancy or preoperatively
  • Red cell exchange is preferred over simple red cell transfusion for chronic transfusion therapy or where RBC transfusion is otherwise indicated but there is high hemoglobin (Blood Adv 2020;4:327)

• Leukocyte reduced
  • < 5 x 10⁶ leukocytes per unit
  • Reduce HLA alloimmunization, febrile nonhemolytic transfusion reactions and CMV transmission
• CMV negative
  • Serologically negative; doesn't exclude donors within window periods
  • Leukocyte depleted have very low to negligible CMV risk
  • Recommended during pregnancy or low birth weight premature neonates
  • May be used in CMV negative transplant recipients or during intensive chemotherapy
• Irradiated
  • To 25Gy to prevent transfusion associated graft versus host disease (by preventing the proliferation of immunocompetent donor lymphocytes, which can damage host tissue)
  • Indicated for HLA matched or related donors, intrauterine transfusions or neonates who previously received intrauterine transfusions, stem cell transplant recipients or certain immunocompromised groups (Hodgkin lymphoma, after purine analogue therapy, aplastic anemia treated with antithymocyte globulin and some severe T cell immunodeficiency syndromes)
  • GVHD risk is low but potentially fatal; emergency transfusion need not be delayed if irradiated blood is not immediately available
• Washed
  • Indicated for the removal of plasma proteins associated with severe reactions (e.g. prior anaphylaxis to IgA)
• Deglycerolized
  • Frozen red cell units stored in glycerol have this removed before transfusion, usually from rare donor phenotypes
  • Red cell loss during processing means units are up to 20% smaller
• Whole blood
  • Increasing use in trauma / critical bleeding setting to replace all blood components
  • Rarely used outside this setting
• Reference: AABB: Circular of Information - For the Use of Human Blood and Blood Components [Accessed 26 October 2020]

A 64 year old Caucasian woman has hemoglobin of 8.6 g/dL (12 - 15 g/dL), with an MCV of 72 fL (80 - 100 fL) one day after acute myocardial infarction, treated with left anterior descending stent insertion. She is A RhD negative and has an anti-D and an anti-C on red cell antibody screen. She is asymptomatic, has a blood pressure of 120/75 mmHg, a pulse of 68 bpm and no signs of congestive cardiac failure. You are asked to consult on transfusion management. The best advice is to

1. Advise that alternatives to transfusion should be considered as the multiple antibodies will make it hard to source blood for transfusion
2. Indicate that transfusion is unlikely to be required based on the clinical features and that further investigation for iron deficiency should be considered
3. Advise that transfusion should be undertaken with leukocyte depleted blood to prevent further antibody formation
4. Advise to transfuse 2 units of red cells to bring the hemoglobin up to 10 g/dL and consider the cause for anemia
5. Supply washed red cells to prevent antibodies reacting with red cells

B. Indicate that transfusion is unlikely to be required based on the clinical features and that further investigation for iron deficiency should be considered. Evidence indicates that transfusion with a Hb > 8 g/dL does not improve outcomes, even after AMI. The red cell indices indicate possible iron deficiency anemia, especially in a population with lower thalassemia prevalence. Best practice would indicate treatment of the underlying iron deficiency rather than transfusion and a search for the cause.

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Reference: Red blood cell use

Washed red cells are indicated

1. To prevent HLA alloimmunization in a 16 year old with acute myeloid leukemia
2. To prevent a febrile nonhemolytic transfusion reaction in a patient undergoing partial hepatectomy with a history of a similar reaction 2 years prior following their last transfusion
3. In all people having regular transfusions
4. In a 57 year old having a total hip replacement with IgA deficiency and a history of anaphylaxis to fresh frozen plasma
5. In a 36 year old with severe postpartum anemia who had a red cell transfusion stopped due to urticaria and has an IgA of 30 mg/dL (60 - 400)

D. In a 57 year old having a total hip replacement with IgA deficiency and a history of anaphylaxis to fresh frozen plasma. People with IgA deficiency may develop anti-IgA and anaphylaxis to IgA present in all fresh blood products. Washing aims to remove the small amounts of IgA remaining in RBCs.

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Reference: Red blood cell use