Blood transfusion Flashcards
What is a blood group system?
Collection of one or more RBC antigens under the control of a single gene or a cluster of closely linked homologous genes
When are antibodies against RBCs clinically significant?
When they can cause haemolysis resulting in…
- haemolytic transfusion reactions
- Haemolytic disease of the foetus and new born (when foetus has a different RBC to mother and mother produced an antibody to it which crossed the plasma
Name the two types of antibodies against RBC antigens
Naturally occurring antibodies
Acquired alloantibodies
What are naturally occurring antibodies?
production of antibodies stimulated by encounters with the missing antigens in food groups or microorganisms - happens at an early age
Usually IgM and remain IgM - can cause HTRs but cannot cross placenta to cause HDFN
*easy agglutination allowing easy blood grouping
What are acquired alloantibodies?
Formed as a result of active immunisation following exposure to non-self RBC antigens in other individuals
Arise due to incompatible blood transfusions (eg RhD positive transfused to RhD negative) or in pregnancy when fetal RBCs can enter maternal blood system
Usually IgG antibodies - do not cause massive HTR but can still cause haemolysis leading to delayed HTRS
Can cross the placenta and cause HDFN
What antigen does a group A RBC have and what antibody is in the plasma?
A-antigen
This anti-B antibodies
What antigen does a group B RBC have and what antibody is in the plasma?
B-antigen
Thus anti-A antibodies
What antigen does a group AB RBC have and what antibody is in the plasma?
Both A and B antigens thus no antibodies
What antigen does a group O RBC have and what antibody is in the plasma?
No antigens
this anti-A and anti-B antibodies
Why do IgM ABO antibodies cause potentially fatal haemolysis
They are capable of fully activating complement
Why do the rare IgG ABO antibodies in plasma not cause HDFN?
Poorly developed ABO antigens so the IgG antibody cannot bind
ABO antigens found on numerous other cells so can be mopped up by binding to those cells instead
Any present in the babies plasma disappear within a few months as they develop their own IgM anti-A and anti-B antibodies
What antigen and antibody to D positive patients have?
D antigen
No antibodies present
What antigen and antibody to D negative patients have?
No antigen
Can develop anti-D antibody if exposed to D positive red blood cells
What can anti-D antibodies cause?
Delayed HTRs - due to extravascular haemolysis often due to transfusions leading to anaemia, jaundice etc
HDFN - severity can vary but can cause either brain damage due to high bilirubin or intra-uterine death
How do you stop pregnant RhD negative women from developing anti-D antibodies?
Given anti-D immunoglobulin which destroys any RhD positive fetal RBCs entering the mothers circulation before she forms her own anti-D antibodies
What are the two methods of ABO grouping?
forward group - using their red blood cells and antibody reagent to test for presence of antigen on rbc
Reverse group - using the patients serum plasma and adding rbc reagent to detect antibodies in the patients plasma
How is RhD grouping done?
Use the patients red blood cells and anti-D antibody reagent to test for antigen D presence on the RBC
What is antibody screening?
Done to detect the presence of any acquired alloantibodies that the patient may develop
Patients serum treated against panels of RBCs which are known clinically relevant antibodies - (anti-human globulin recquired)
What is cross matching?
Done for red blood cell transfusions
after selecting the correct ABO and D group and screening to be negative for any alloantibodies
patient serum mixed with donor RBC and no agglutination should take place if compatible
What two tests do all blood donations undergo?
Group and screen - ABO and RgD determined (often C, c, E, e) and K are also determined
screening for any other clinically relevant ABs
Infection screening -done to reduce the risk of transfusion transmitted infections minimum - Hep B, C and E, HTVL and syphilis
What infection screening tests are performed on all donations?
HIV
Hepatitis B, C and E
Human T-lymphotrophic virus
syphilis
some donations are tested for
Malaria
T. Cruzii
CMV
Why is creutzfeldt Jakob disease tested for prior to donation?
Identify those ineligible to donate - no available blood test
What are the two methods of collecting blood?
Whole blood collection
Apheresis - connected to an apheresis machine which separates out certain components of the blood and collects whats required before returning the rest to the donor
What are the four main blood components?
Red blood cells (packed RBCs)
Platelets
Fresh frozen plasma
Cryoprecipitate
Why are red blood cells transfused?
Increases hb and restores oxygen-carrying capacity in people with anemia due to trauma or other medical problems
Packed red blood cells- as plasma is removed
Stored for 35 days at 4 degrees
Why are platelets transfused?
Treatment of bleeding or reduce risk of bleeding in patients with thrombocytopenia or platelet dysfunction due to drugs
2 methods to produce platelets -
pooled platelets - from 4 donations to make 1 unit of platelets
apheresis platelets - single donor makes 1 unit
7 days at 22 degrees
Why is FFP transfused? What is it?
Contains all the coagulation factors
Treatment of bleeding or reduce risk of bleeding in patients with coagulopathies (clotting factor deficiencies resulting in prolonged PT or APTT)
Frozen when collected to preserve activity of clotting factors
shelf life 3 years at -25 degrees
Why is cryoprecipitate transfused? What is it?
Contains fibrinogen, VIII, von willebrand factor and factor XiII
Given to reduce risk of bleeding when fibrinogen is low due to haemorrhage or disseminated intravascular coagulation (random small clots using up factors)
Made from thawing of FFP till there is a precipitate which is resuspended in small volume of plasma and frozen to maintain activity of clotting factors
3 years at -25 degrees
What are the three plasma derived medicinal products?
Human albumin solution
immunoglobulin solution
clotting factor concentrates
manufactured from pooling of thousands of plasma donations by fractionation
Undergo at least 2 viral inactivation steps - heat treatment and solvent-detergent
What are clinical uses of human albumin solution?
Replace plasma volume in patients with plasma volume loss (due to burns or trauma)
replacing plasma in plasma exchange ie treatment of autoimmune disease
initiate diuresis in patients with low albumin due to liver or kidney disease
What are clinical uses of immunoglobulins
Normal immunoglobulin - ABs to viruses common in population (eg: intramuscular normal to protect against hepatitis A)
-Intravenous Immunoglobulin (ivIg) – can be used in some autoimmune disorders as replacement therapy e.g. immune thrombocytopenia
Specific –fractionated from plasma from selected donors who have a high titre of a specific antibody (from hyperimmune donors) e.g. anti-D, hepatitis B, varicella zoster, rabies, tetanus, CMV.
What are clinical uses of clotting factor concentrates?
patients with the inherited bleeding disorders haemophilia A and haemophilia B are now treated with recombinant synthesised factor concentrates which carry no risk of viral or prion transmission.
Prothrombin complex concentrates (PCCs) contains Factors II, VII, IX and X.
PCCs can be used to reverse the effect of warfarin by replacing these deficient coagulation factors.
PCCs can also be used in the management of patients with major bleeding and haemorrhage who require rapid replacement of coagulation factors (dilutional coagulopathy)
reconstituting and administering PCCs takes less time than the lengthier processes involved in obtaining and thawing FFP.
Replacement of coagulation factors with PCCs should be guided by the results of the coagulation screen (PT and APTT)
Fibrinogen concentrates provide an alternative to cryoprecipitate for replacing fibrinogen
What groups plasma will have no antibodies in it?
AB plasma
Which group is given universally for red blood cell transfusion?
Group O
What is the universal red blood cell donation?
Group O RhD negative
