Blood transfusions

• Platelets =

  • produced from whole blood donations or by apheresis
  • higher risk of bacterial transmission - stored at room temperature
• FFP =

  • male donors only to reduce risk of TRALI
  • needs to be thawed before transfusion
  • highest rate of severe allergic reaction + TRALI
• Cryoprecipitate=

  • obtained by slowly thawing FFP
  • enriched in fibrinogen
• Blood groups

  • inherited character of red cell surface - detected by specific allo-antibody
  • ABO blood group antigens - oligosaccharides - anchored on glycolipid substrate
• ABO blood group antigens = acute haemolytic transfusion reactions

  RhD blood group antigen = haemolytic disease of foetus and newborn
• ABO system =

  A and B alleles code for transferases - modify precursor called H substrate on red cell membrane

  A and B are dominant over O

  A and B are codominant
• ABO - antigens and antibodies

  A) A

  B) anti-B

  C) B

  D) anti-A

  E) A and B

  F) none

  G) none

  H) anti-A and anti-B

  
• phenotype and genotype

  A) OO

  B) AA or AO

  C) BB or BO

  D) AB

  
• Landsteiner’s law =

  When an individual lacks A or B antigen = corresponding antibody is produced in the plasma

  Naturally occurring complement fixing IgM antibodies cause haemolysis of red cells expressing specific antigen
• ABO mismatch =

  Naturally occurring IgM antibodies to A and B antigen

  Antigen-antibody complexes = initiate complement cascade

  Fromation of membrane attack complex = intravascular haemolysis
• Symptoms and signs of ABO mismatch =

  • heat along transfusion arm
  • back pain
  • flushing + fever
  • nausea + diarrhoea
  • tachycardia + hypotension = circulatory shock
  • thick black urine to haemoglobinuria
• RhD antigen =

  85% of population = RhD positive

  2 alleles D and d - d is silent
• Anti-D antibody is produced on exposure to RhD+ blood through transfusion or pregnancy.

  Can cause haemolytic disease of foetus and newborn
• Haemolytic disease of foetus and newborn

  RhD- mother carrying RhD+ foetus

  First pregnancy = fine

  Small amount of foetal-maternal haemorrhage at time of late miscarriage or childbirth = stimulates anti-D production

  Subsequent pregnancy with RhD+ foetus = materbal anti-D antibodies cross placenta - cause of haemolysis of foetal RBCs
• Features of haemolytic disease of foetus and newborb =

  • foetal anaemia
  • heart failure
  • hydrous foetalis
• Prevention of haemolytic disease of foetus and newborn =

  Prophylactic anti-D given to women from first pregnancy - stop development of immune anti-D
• ABO grouping =

  • use reagents with known antibody specificity - identify antigens present on red cell = Antisera
  • use red cells with known antigen specificity to identify antibodies present in plasma
• ABO/D grouping =

  1. test patients red cells with anti-A + anti-B and anti-D antisera - identify antigens on red cells
  2. test patients plasma against reagent red cells of group A and group B - identify antibodies in plasma
• Agglutination with antisera =

  Positive result

  Indicates presence of antibody
• IAT crossmatch =

  • aggulation indicates donor cells are incompatible with patients plasma

  Uses donor red cells with patient plasma + add anti-human globulin
• Indications for red cell transfusion =

  acute blood loss - with circulatory compromise

  symptomatic anaemia Hb < 70

  Peri-operative
• Red cell transfusion in B12/folate deficiency = can precipitate heart failure - replace haematinics
• Patient declines transfusion due to religious reasons =

  IV iron + erythropoietin
• CKD treatment instead of transfusion =

  iron

  erythropoietin
• Indications for platelet transfusion =

  Prophylaxis in patients with reversible bone marrow failure undergoing chemotherapy

  Treatment of bleeding/ before surgery in thrombocytopenic patient

  Management of massive haemorrhage
• Standard dose of platelet transfusion = 1 pool
• Platelet transfusions not indicated =

  Auto-immune thrombocytopenia

  TTP or HUS

  Before renal biopsy in patients with renal failure
• Indications for FFP transfusion =

  • treatment of bleeding patient with coagulopathy
  • management of massive haemorrhage
  • transfuse early in trauma
  • plasma exchange in TTP
• FFP not indicated for =

  • volume replacement
  • warfarin reversal
• Cryoprecipitate indications =

  • in major haemorrhage - to keep fibrinogen levels up
  • prophylaxis in APML
  • In patients with DIC - low fibrinogen

  Standard dose = 2 pools
• Prothrombin complex concentrate =

  Vitamin K dependent clotting factors

  Used to reverse warfarin if bleeding
• Irradiated blood =

  • risk of graft vs host disease - transfused lymphocytes recognise recipient organs as foreign

  Indications =

  Intra uterine transfusions

  neonatal exchange transfusions

  infants who previously received IUT

  severe T cell immunodeficiency

  Hodgkin’s lymphoma

  Stem cell transplants
• All pregnant women/inra-uterine transfusions/premature infusions of cellular products must be CMV negative.

  CMV can cause miscarriage + birth defects.
• Two sample rule -

  • patient with no blood group needs 2 separate samples for G&S before blood products can be issued
  • needs 2 venepuncture events - taken by 2 different people
• Rate of transfusion =

  RBCs = over 90-120 min. Completed with 4 hours.

  Platelet transfusion = over 30-60 mins

  FFP = 20-30 mins

  Cryoprecipitate = 20-30 mins
• Major haemorrhage definition =

  Loss of one blood volume with 24 hours

  50% blood volume loss within 3 hours

  150ml per minute

  Bleeding leads to HR > 110 bpm or sBP < 90
• Major haemorrhage packs =

  • replace clotting factors and fibrinogen FFP:RBC ratio of 1:2
  • add platelets and cryoprecipitate after 1st major haemorrhage pack
• Haemorrhage packs

  A) 4 units RBCs

  B) 4 units FFP

  C) 4 units RBCs

  D) 4 units FFP

  E) 1 unit platelets

  F) cryoprecipiate

  
• Tranexamic acid =

  Antifibrinolytic drug - inhibits plasminogen conversion to plasmin

  Not recommended in patients with GI bleed
• Heparin reversal = protamine

  Warfarin reversal = PCC and vitamin K