Transfusion Medicine PDF

Transfusion Medicine – Prof B Fernandopulle Transfusion Medicine Prepared by Prof B Fernandopulle Department of Pathology , Faculty of Medical Sciences , USJ 1 ...

Transfusion Medicine – Prof B Fernandopulle Transfusion Medicine Prepared by Prof B Fernandopulle Department of Pathology , Faculty of Medical Sciences , USJ 1  Transfusion Medicine – Prof B Fernandopulle Transfusion Medicine Blood Groups There are many blood group systems. The most commonly known and clinically significant are the ABO system and Rh system. The red cells carry blood group antigens on the cell surface. Most blood group antigens are proteins or glycoproteins. ABO system Three allelic genes – A , B , O code for the ABO system. The ABO genes are located on chromosome number 9 These genes follows mendelian principles and A and B genes are co – dominant. The O gene is amorphic in that it does not result in a significant blood group antigen.Thus a person can inherit A , B or O from each of his parents and be of different genotypes.(AA, AO, BB,BO,AB,OO). However if tou receive the A gene you code for the A antigen expression on your red cells, If you get the B gene then you code for the B antigen expression. A person who gets an A gene from one parent and B gene from the other parent will have both A and B antigen expression on red cells. Group A – genotype may be AA or AO Group B – genotype may be BB or BO Group AB – genotype is AB Group O – genotype is OO 2  Transfusion Medicine – Prof B Fernandopulle The above picture demonstrates the acquisition of antigens. All humans will be born with H antigen. If you are OO genotype you do not code for any more changes in the antigenic structure and remain with H antigen. People with A gens will code for deposition of N-acetyly – D – glactosamine to be added to H antigen and then this will become A antigen. Like wise the B gene will code for a Galactose to be added that will change the H antigen to be changed to a B antigen. Bombay O individuals do not express the H antigen also. Therefore they will have in their serum Anti A , antiB and also anti H ( which is not seen in normal O group individuals ) The antibodies of the ABO system are naturally occurring antibodies. That is they are not present in the serum of people when they are born but are produced after the first few months of life. Therefore the antibody can be too low in concentration to be detected until 3 – 6 months of age. ABO antibodies are of usually IgM and a few IgG. They Activate compliment and this is the reason for haemolytic transfusion reactions. Blood Group Antigen on RBC Antibody in plasma A A Anti – B B B Anti – A AB A,B No antibodies O No antigens Anti –A , Anti - B Bombay O No antigens , not even Anti A , Anti B, Anti H H antigen 3  Transfusion Medicine – Prof B Fernandopulle Rh System Blood group antigens of the Rh system are D,C,c,E and e. The Antibodies are anti D , anti C , anti c , anti E and anti e. They are not naturally occurring antibodies and individuals will not naturally have the antibody to lacking antigens. However they are formed when exposed to red cells with the corresponding antigen if the persons own cells lack that antigen. For example a D antigen negative person will not have natural anti D but will form anti D when exposed to the D antigen.These antibodies are Ig G and therefore can cross the placenta. Blood group predominance varies from country to country & ethnic groups. In Sri Lanka it is as follows Group O 45.5% A 22% B 27% AB 5.5% Apart from the major ABO and RH there are any minor Blood group systems. Given are a few, Lewis – Cold Kell -warm Kidd - Warm Duffy - Warm I – Cold P - Cold MNSs - MN Cold Ss Warm Lutheran – Cold Warm - React at 370 C ; Cold react at Room Temperature or less Blood Grouping The test consists of two parts Cell Grouping ( forward grouping ) - To detect the presence or absence of A , B and Rh (D) Antigens on the red cells (Tests RBC with standard monoclonal antibodies) Serum grouping (reverse grouping)- To detect the presence or absence of anti A , anti B in the serum Label four tubes and add one/two drops of anti A, B , AB and anti D to each Add one drop of 2-5 % cell suspension of red cells to the tubes Add 2 drops of patients serum/plasma to tubes labeled as A , B cells Add two drops of A1 ,B reagent cells to these tubes 4  Transfusion Medicine – Prof B Fernandopulle Mix contents and centrifuge Examine for haemolysis or agglutination Grade and record the results Scale according to clumping seen 1+ to 4+ (4+ One very large clump seen ,1+ presence of many small clumps) Cell grouping Serum grouping Anti A Anti AB Anti B Anti D A cells B cells Blood group + + – + – + A+ – + + + + – B+ + + + + – – AB + – – – + + + O+ + + + – – – AB – – – – – + + O– – – – – – – Cord O – Cross matching For cross matching donor red cells are tested against patients serum Principle of cross match ( Not the SOP ) Mix patients serum with donor red cells Centrifuge immediately (immediate spin) and look for haemolysis and agglutination Incubate at 37 0 c.Centrifuge and observe for haemolysis and agglutination Add coomb’s – look for haemolysis and agglutination Thereby we methodically check if donor red cells react with patient sera antibodies and give rise to haemolysis or agglutination. If either are seen the donor pack is mismatched. To be a proper match there has to be NO Agglutination or haemolysis at any stage. Principle of the Coomb’s test The Direct (DAT ) and indirect coomb’s (IAT ) tests are carried out to identify antibodies which are either coating red cells (direct) or in the serum (indirect ). The Coomb’s reagent contains anti human immunoglobin. That is anti IgG or anti C3d. Direct Coomb’s: 5  Transfusion Medicine – Prof B Fernandopulle Above diagram shows red cells coated with antibody when reacted with AHG give rise to agglutination. So if the donor red cells had an antigen that reacted with antibodies in patients sera ,They might show agglutination. Even if they did not show agglutination at this stage when we add coomb’s reagent the AHG in that will bind the antibodies on red cells and cause an agglutination. The second row shows a negative reaction. In the indirect Coomb’s (IAT ) test the patient’s sera is incubated with known red cells and thereafter reacted with Coomb’s reagent. This identifies any antibodies in the patient sera. Blood Donation To donate blood the donor has to fullfill certain criteria. There are permanent and temporary deferral criteria and the donor has to answer a questionnaire and be interviewed by a medical officer. (you are expected to witness this on your visit to the NBTS ) Blood needs to be screened for transfusion transmitted infections and the donated blood is held in quarantine while tests are performed at NBTS for following diseases, HIV ,Malaria,Syphilis,Hepatitis B,Hepatitis C 6  Transfusion Medicine – Prof B Fernandopulle Blood products What is acquired into the CPD /CPDA bags is whole blood. From whole blood the following blood components are prepared by different processes. ( observe this at the NBTS ) Red cell concentrates ,Platelets ,Fresh frozen plasma, Cryoprecipitate, Cryo poor plasma, Albumin, Immunoglobulin , Plasma derived clotting factors Red cell concentrates Red cell concentrates are used to increase haemoglobin in acute and chronic anemia.There is no consensus on precise cut offs for transfusion but usually try to maintain Hb > 7 g/dl. The idea is to prevent symptomatic anemia. However in certain instances like cardiorespiratory compromise , elderly a higher Hb ( 7-10 g/dl ) may be appropriate. Platelet concentrates Platelet concentrates are produced from whole blood using the buffy coat method of preparation or Platelet pharesis from a single donor. Platelets are stored at 220C ± 20C with continual gentle agitation for up to 5-7 d. Compatibility for transfusion -- ABO compatibility , RhD-negative platelet concentrates should be given, where possible, to RhD-negative patients Platelet concentrates should be inspected with particular attention to: The integrity of the pack, checking for leaks at the ports and the seams; unusual colour or turbidity which might suggest bacterial contamination. Usually maintain platelet counts above 10 x 109 ⁄ L in the absence of bleeding but >20 x 10 9 /L if the patient is febrile Bone marrow aspiration and biopsy may be performed in patients with severe thrombocytopenia without platelet support, providing that adequate surface pressure is applied. For lumbar puncture, epidural anaesthesia at least 80x10 9 /L. Gastroscopy and biopsy, insertion of indwelling lines, transbronchial biopsy, liver biopsy, laparotomy or similar procedures, platelet count should be raised to at least 50 x 109 ⁄ l For operations in critical sites such as the brain or eyes, platelet count should be raised to 100 x 109 ⁄ l Preoperative platelet count should be checked to ensure that the above thresholds have been reached. 7  Transfusion Medicine – Prof B Fernandopulle Contraindications to platelet transfusions Thrombotic thrombocytopenic purpura (TTP) Heparin-induced thrombocytopenia (HIT) ITP is not a definite contraindication.In ITP platelets can be given with steroids and IvIg when count is very low and there is life threatening bleeding. Giving platelets to ITP patients otherwise is of no use as the antibodies in the patient will destroy the transfused platelets. Fresh Frozen Plasma (FFP) After removal of the red cells by centrifugation the plasma is rapidly frozen to a temperature that will maintain the activity of labile coagulation factors (– 30 0 C). FFP contains all coagulation factors including varying levels of vitamin K+-dependent factors II, VII, IX, and X. Frozen plasma products must be thawed at 37 0 C prior to be given. Indications for FFP Single coagulation factor deficiencies -Fresh-frozen plasma should only be used to replace single inherited clotting factor deficiencies for which no virus-safe fractionated product is available. Currently applies mainly to factor (F) V. Multiple coagulation factor deficiencies-disseminated intravascular coagulation Reversal of warfarin effect Liver disease Surgical bleeding and massive transfusion Thrombotic thrombocytopenic purpura (TTP)- for plasma exchange Cryoprecipitate and cryosupernatant (‘cryo-poor plasma’) The cryoglobulin fraction of plasma obtained by thawing a single donation of FFP at 4 ± 2 0C. When you thaw FFP slowly at 40C , some clotting factors will precipitate. When you take this precipitated factors suspended in a small volume of plasma it is called Cryoprecipitate. The plasma above is cryoprecipitate depleted’ (also known as ‘cryo-poor plasma’ or ‘cryosupernatant’) The Cryoprecipitate is rich in FVIII, von Willebrand factor (VWF), FXIII, fibronectin and fibrinogen. Cryosupernatant plasma is depleted in FVIII and fibrinogen;is deficient in high molecular weight(HMW) multimers of VWF, but contains VWF metalloproteinase and factor 1X Uses for cryoprecipitate As an alternative to factor VIIl when FVIII is not available As a source of fibrinogen in acquired or inherited hypofibrinogenemia , afibrinogenemia or dysfibrinogenemia 8  Transfusion Medicine – Prof B Fernandopulle Acquired hypofibrinogenaemia is seen in liver disease, massive transfusion and DIC. Uses for cryo poor plasma TTP – Plasma exchange with FFP or cryosupernatant (cryo-poor plasma) Massive transfusion May be defined as the replacement of a patient’s total blood volume with stored blood in less than 24 h, alternative definitions allow more anticipation (such as 50% blood volume loss within 3 h, or a loss of 150 ml/min). As large volumes of (crystalloid re suspended)red cells are used there the dilution of platelets and clotting factors. Therefore Platelet transfusions and Plasma components are recommended. Platelet transfusion is indicated if counts fall below 50 x 109/l. FFP and cryoprecipitate may be given so that the PT and APTT ratios are shortened to within 1.5, and a fibrinogen concentration of at least 1.0 g/l in plasma obtained. Transfusion Reactions will be done in another lecture and Clinical use of blood products will be done in a PBL. Prepared as a handout for the power point presentation – Transfusion Medicine By Dr. Bernadene Fernandopulle , Senior Lecturer /Consultant Haematologist , Department of Pathology , Faculty of Medical Sciences , USJP 9