Transfusion Flashcards
What blood components are available (one donor)?
Red cells
Platelets
Fresh frozen plasma
Cryoprecipitate
What blood products are available (many donors)?
Human Albumim Intravenous immunoglobulin Human normal immunoglobulin concentrates Specific immunoglobulins (eg tetanus, hepatitis B, varicella-zoster, rabies, immunoglobulins) Anti-D immunoglobulin Prothrombin complex concentrates
What are the ABO groups?
A- A antigen, anti-B antibodies
B- B antigen, anti A antibodies
AB- A and B antigen, no antibodies (universal recipient)
O- No antigens, anti A and anti B antibodies (universal donor)
What are most naturally occurring ABO antibodies?
IgM (pentameric structure)
Some IgG
Describe the genetics behind ABO blood group
Ch 9- A and B Genes
O Gene is silent, A and B is co-dominant
What are the phenotypes of each genotype?
OO-O
AA or AO-A
BB or BO-B
AB-AB
What is the other main blood group type?
Rh (D)
+ or - (most +ve)
Describe the genetics of Rh(D)
Ch 1
2 alleles: D and d
DD and Dd +, dd -
What happens when a Rh(D)- individual is exposed to Rh(D)+ red cells (either pregnancy with + foetus or transfusion)?
One will develop anti-Rh(D) antibody (often shortened to anti-D)
Another exposure may result in reaction
What are some indications for red cell transfusion?
Anaemia
Acute blood loss
What are some possible indications for platelet transfusion?
Low platelet count - how low? Patient age Symptoms of bleeding Direction of change of platelet count Platelet kinetics Underlying infection/ fever Concomitant anaemia Concomitant drugs Requirement for / recovery from surgery Congenital platelet functional defects Acquired platelet functional defects eg myeloma, uraemia
What happens in an acute haemolytic transfusion reaction?
Activation of complement, coagulation and kinin systems
What does the complement cascade causes in transfusion reaction?
Release of C3a and C5a: Powerful anaphylotoxins Increase vascular permeability Dilate blood vessels Cause release of serotonin and histamine – fever, chills, hypotension, shock
Formation of MAC leads to rupture of transfused cells
What does coagulation cause in transfusion reaction?
Thromboplastic material from haemolysed red cells leads to indiscriminate activation of the coagulation
mechanism – Disseminated Intravascular Coagulation
What activates the kinin system in transfusion reaction?
Factor XII
What does the kinin system cause in transfusion reaction?
Formation of bradykinin- arteriolar dilatation, increased vascular permeability
Leads to hypotension, which in turns leads to release of catecholamines- leads to vasoconstriction within kidneys and other organs
What are the features of immediate haemolytic transfusion reaction?
May begin after only 1 ml is transfused Pyrexia / rigors Faintness / dizziness Tachycardia / tachypnoea /hypotension Pallor / sweating Headaches / chest or lumbar pain Local pain at infusion site Cyanosis Patient may say “something is wrong” All of this may be difficult to recognise if patient is unconscious
What is required if an immediate haemolytic transfusion reaction occurs?
Stop transfusion
Start IV fluids to maintain BP and urine output
Obtain samples
What are the features of delayed haemolytic transfusion reaction?
Haemolysis usually 5-10 days post transfusion
Symptoms / signs similar to, but less acute than, a IHTR
Unexplained fall in Hb value as transfused red cells are destroyed
Appearance of jaundice, renal failure or biochemical features associated with IHTRs
Detection of positive DAGT or irregular antibodies in post- transfusion blood samples
What are the lab features of delayed haemolytic transfusion reactions?
Anaemia, spherocytic red cells on blood film
Elevated bilirubin and LDH
Positive DGAT and/or appearance of red cell allo-antibody
+- a degree of renal failure
What are the features of febrile non-haemolytic transfusion reactions?
2% of red cell, and 20% of platelet, transfusions
Rapid temperature rise 1 - 2oC, chills, rigors
Antibodies to contaminating white cells
Release of cytokines and vasoactive substances from white cells during storage
May be difficult to differentiate these symptoms from those of very early acute HTR
How is febrile non-haemolytic transfusion reaction investigated?
HLA antibodies may be detectable
No evidence of red cell incompatibility
How is febrile non-haemolytic transfusion reaction prevented?
Anti-pyretics
Leucodepleted blood cmoponents
Describe urticarial transfusion reactions?
Mast cell - IgE response to infused plasma proteins
Rash / weals within few minutes of starting transfusion
Slow the transfusion
Consider anti-histamines
