Blood transfusion

Blood transfusion

Updated: 07/28/2025

© Jun Wang, MD, PhD

 

Blood type

Commonly used lab tests

  • Forward typing
    • Patient’s RBCs + anti-A or anti-B reagents
    • Agglutination confirm presence of A and/or B antigens
  • Reverse typing
    • Patient’s serum + A or B reagent RBCs
    • Agglutination confirm presence of A and/or B antibodies
  • Screen
    • Identify anti-bodies in patient’s serum
    • Mixing patient’s serum and reagent RBCs with known antigens
    • Agglutination suggest presence of antibodies against one or more antigens on reagent type O RBCs
    • Presence of antibody confirmed by analyzing the agglutination pattern with a panel of reagent cells
  • Cross match
    • Ensure compatibility between recipient’s and donor blood
    • Prevent transfusion reactions
    • Major cross match: mixing patient’s serum with donor RBCs
    • Minor cross match: mixing patient’s RBCs with donor serum
    • Agglutination indicates incompatibility
    • Only compatible blood should be used
  • Direct antiglobulin test
    • AKA direct Coombs test
    • Detect antibodies or complement attached to patient’s RBCs
    • Mix patient’s washed RBCs with antibodies against human antibodies
    • Agglutination indicates attachment of antibodies on RBC surface
    • Positive results indicate immune hemolysis

Auto and allo antibodies

  • Autoantibodies
    • Against self antigens
    • Either warm or cold
    • Commonly seen in hospitalized patients
    • May be clinically significant
  • Alloantibodies
    • Produced against foreign antigens, such as blood type
    • Most commonly anti Rh antigens
    • Only certain types clinically significant for causing hemolysis
    • Usually formed after transfusion, pregnancy or transplant
    • May be naturally occurred (M, N of MNS system)
    • Difficulty finding compatible donor blood
    • May need least incompatible donor blood, especially for patients with long history of transfusion

Hemolytic disease of the fetus and newborn

Transfusible blood products

  • Whole blood: Less commonly used
  • Red cells
    • Packed red cells, leukocyte-reduced red cells, etc
    • For severe anemia, or moderate anemia with symptoms or bleeding
    • Each unit should raise Hb 1-15g/dL
    • Need matched ABO type, or Type O 
  • White cells: leukocytopenia with infection, aplastic anemia, ABO, Rh, and HLA-typing 
  • Platelets
  • Fresh frozen plasma: coagulation factors deficiency, matched ABO type, or type AB
  • Cryoprecipitate: hypofibrinogenemia, dysfibrinogenemia

Massive transfusion 

  • Large amount of RBC transfusion
    • Entire blood replacement within 24 hours
    • Half blood volume replacement in 3 hours
    • >10 RBC in 24 hours 
    • 4-5 RBCs within 1 hour 
    • Ultra-massive transfusion: >20 RBCs in 24 hours 
  • Risks include acidosis, hypothermia, coagulopathy, etc
  • Recommendation: RBC, plasma and platelets in a 1:1:1 ratio 

Risks associated with transfusion 

  • Alloantibody formation
  • Disease transmission, such as HIV, HCV, HBV, etc 
  • Transfusion reactions 

Transfusion reactions

  • Any adverse response to transfusion of blood or blood components
  • May be life-threatening
  • May occur during or days/weeks after transfusion
  • Immunologic or non-immunologic
  • Most common presentations: fever, chills, urticaria, pruritus
  • Transfusion should be immediately stopped when transfusion reaction is suspected
  • Treatments most often supportive
  • Hemolytic transfusion reactions

  

Practice questions I

Practice questions II

 

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Contents

Pathology notes Jun Wang, MD, PhD 1. General information Frequently discussed syndromes Terms of dermatology Terms of hematology 2. Immunodeficiency disorders HIV infection   Primary immunodeficiency disorders 3. Hemodynamic abnormalities Shock Thrombosis and embolism Bleeding disorders Blood transfusion 4.  Benign blood cell disorders Anemia Benign white cell disorders 5. Hematopoietic neoplasms Lymphoid neoplasms Myeloid neoplasms Histiocytic neoplasms: Langerhans cell histiocytosis 6. Cardiovascular system Pulmonary hypertension Cardiovascular system tumors 7. Respiratory tract tumors 8. Gastrointestinal tract Congenital disorders Infectious gastroenteritis Oral cavity Esophagus Stomach Intestinal tumors Salivary glands Exocrine pancreas and gallbladder 9. Urinary system Kidney masses Lower urinary tract 10. Male reproductive system 11. Female genital tract 12. Breast 13. Endocrine organs Pituitary gland Ad...
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Bleeding disorders

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