Blood Banking, Blood-transfusion and Compatibility Testing, Method of Collecting Blood

Blood Banking

Blood-transfusion

Compatibility Testing

PRE-TRANSFUSION TESTS 

Method of Collecting Blood 

 Blood-transfusion and Compatibility Testing

Therapeutic administration of blood and blood products is indicated in many diseases and other health problems. Loss of blood from the body impairs the ability of the circulatory system to supply adequate amounts of oxygen to body tissues and upsets the delicate water and acid-base balance of the body fluids. This can lead to severe illness and death. Loss of blood may be due to haemorrhage, excessive destruction of red cells or inability of the body to replenish its own blood cells.

The technique of replacing a patient's whole blood or its components is known as blood transfusion. 

The blood used for transfusion should be such that it should not have any harmful effect on the patient. The tests carried out for this purpose are called compatibility tests and are performed on a blood sample of a willing, normal, healthy individual, the donor. 

The procedures involved in collecting, storing, processing and distributing the blood of potential donors is called blood banking.

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Compatibility Testing

Most healthy individuals can donate blood without any ill-effects. However, selection and proper identification of a donor is essential so that the blood collected for transfusion is safe and beneficial to the patient (recipient). Most blood donations are voluntary.

Two basic principles must be kept in mind when the donor is selected:

1. The blood collection procedure should not be harmful to the donor.

2. The donor's blood should not be harmful tothe recipient.

The selection of the blood donor involves a medical history and simple physical examination (pulse rate, blood pressure), and later, screening for transfusion-transmissible diseases.

PRE-TRANSFUSION TESTS :- DONOR'S BLOOD While collecting donor's blood, a small sample of blood should be collected separately for testing before it can be safely transfused into any recipient. The following screening tests must be performed on the donor's blood sample.

Haemoglobin Concentration:- The concentration of haemoglobin may be determined by any method described in this book. It is best to disqualify persons with haemoglobin of less than 12g/100 ml. This rule may be relaxed to permit individuals with 10 g/100 ml haemoglobin to donate blood in emergencies

 Parasites Blood should be screened for blood parasites such as malaria, microfilaria and trypanosomes, especially in endemic areas.

Tests for Syphilis:- A blood sample positive for syphilis may transmit live spirochaetes of Treponema pallidum to the recipient. Therefore, screening tests such as VDRL or RPR should be performed on the donor's sample. The blood should be discarded if found positive. However, T. pallidum cannot survive for more than 48-72 hours at 4°C. Hence, the blood stored for more than 72 hours at 4°C has no risk of transmitting syphilis to the recipient.

Test for Hepatitis B:-Transfusion of blood from a hepatitis B carrier can result in the transmission of the disease to the recipient. Therefore the blood sample of the donor must be screened for the presence of hepatitis B antigen (HBsAg) by one of the various methods available.

Test for Human Immunodeficiency Virus (HIV) :- Human immunodeficiency virus (HIV), the causative agent of acquired immunodeficiency syndrome (AIDS) poses the highest risk of transmission through blood transfusion, and can lead to the fatal disease. Therefore, every blood donor must be screened for HIV by ELISA or other screening tests.

Test for Human Immunodeficiency Virus (HIV):- Human immunodeficiency virus (HIV), the causative agent of acquired immunodeficiency syndrome (AIDS) poses the highest risk of transmission through blood transfusion, and can lead to the fatal disease. Therefore, every blood donor must be screened for HIV by ELISA or other screening tests.

COLLECTION OF BLOOD:-

Blood Containers:-

Method of Collecting Blood:- While collecting blood, the donor should lie down, and a blood pressure cuff should be used on the arm above the venepuncture site. Under aseptic conditions, make a venepuncture using an 18 gauge needle to obtain a faster flow. The collection bag with anticoagulant should be kept below the level of the arm for gravity flow. Swirl the bag intermittently to bring about mixing of blood with the anticoagulant. The donor should gently flex the fingers or clench and unclench the fist to assist the flow of blood from the vein. About 420-450 ml of blood can be collected from a donor at a time. When the full amount of blood has been collected, collect the blood into 2 tubes in 5 ml amounts for various screening tests. Seal the venepuncture site on the donor's arm with a plaster to stop the flow of blood. The donor should be allowed to rest for a while and offered a nourishing drink to adjust for the loss of blood.

Proper labelling of the collecting container is of utmost importance

The label should contain the following information:-

1.Donor       identification	number
2.ABO and Rh type
3.The type and volume of	anticoagulant.
4.Volume and name of the	product (e.g.,whole	blood, red cells.
5.Temperature          for	storage
6. Date         of         expiry.

The blood must be stored in a refrigerator with a constant temperature of 1-6°C. An alarm should sound if the temperature exceeds the limit. The stored blood should be inspected daily for colour, turbidity, haemolysis and clot formation, and should be discarded if there is any evidence of bacterial contamination.

Anticoagulants and PreservativesUsed for Blood Collection:-

COMPATIBILITY TESTING:- Before a donor's blood is transfused into a recipient, there should be no antigens or antibodies in both the donor's blood and

recipient's blood that would react with each other, resulting in the destruction of red cells. In other words, there should be no transfusion reaction. The donor's blood should be compatible with recipient's blood and should give maximum benefit to the recipient.

Compatibility testing involves the following:-

1.    ABO and Rh Typing of the Donor and the Recipient:- ABO and Rh D grouping of the donor and the recipient blood should be done. Both should belong to the same ABO group and Rh-D type to be compatible.

 The methods of ABO TYPING

Crossmatching:- Crossmatching is divided into two parts:

1. Major cross match:- It involves testing donor's red cells with recipient's serum to detect unexpected antibodies in recipient's serum that will destroy donor's red cells.

2. Minor cross match:- It tests recipient's red cells with donor's serum in the same way as the major cross match. These antibodies can also be detected by antibody screening tests.

Major cross match	Donor cells + Recipient serum
Minor cross match	Recipient cell + Donor serum

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BLOOD TRANSFUSION:- There are clinical conditions in which therapeutic replacement of blood is indicated. The potential benefits of transfusion must always be greater than any potential harm to the patient. The indications for blood transfusion may be divided into four major categories:

1. Restoration of oxygen carrying capacity Blood transfusion may be necessary to restore or maintain the oxygen carrying capacity of blood. The best results are achieved by transfusion of red blood cells after removing the plasma. If the plasma is not removed, the increase in total blood volume may result in circulatory overload.

2. Maintenance of blood volume in cases of acute blood loss (e.g., post-operative massive bleeding or bleeding after injury); transfusion of whole blood or plasma gives good results. However, the best results are obtained by replacing the lost volume of blood with an electrolyte solution, followed by packed red cells later.

3. Maintenance of haemostasis It is sometimes necessary to replace coagulation factors to maintain haemostasis. Various blood components or derivatives may be transfused as the situation demands. Examples of such transfusions include platelet concentrates, fresh frozen plasma, cryoprecipitates and factor VIII and IX concentrates.

4. Restoration of leucocyte function The clinical conditions demanding transfusion of leucocytes do not arise very often, but may be necessary in a granulocytopenic patient with infection.

Autologous Transfusion:- Transfusion of blood or blood products previously collected from the same person is called autologous transfusion. Usually such a person expects to undergo a surgical procedure which may involve loss of blood. The patient's own blood is preferred because the hazards of immunisation by foreign material and transmission of disease do not arise. Autologous transfusion may also be necessary when a person is immunised to some antigens. However, autologous transfusion is not a common practice.

Directed Transfusion:-This is elective transfusion of blood to a patient with the blood donated by his family member or a friend. Recently, directed transfusions have become more common due to the fear of transmission of HIV.

USE OF BLOOD COMPONENTS:-

FRACTIONS AND DERIVATIVES:-Each component of whole blood such as the formed elements, proteins and electrolytes, has a different and important function to perform. Therefore, indiscriminate use of whole blood is not justified when most patients can be effectively treated with one or more of the components. Optimum use of every blood donation is achieved when each donor serves more than one patient. It can be accomplished by skilful and intelligent use of proper blood component or derivative for each indication               
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TRANSFUSION REACTIONS

TRANSFUSION REACTIONS:-The term transfusion reaction means an obviously adverse response to transfusion, usually during, or immediately after, the transfusion. The transfusion reactions can be of four main types: haemolytic, febrile, allergic or those due to circulatory overload. However, poor survival of the transfused blood, or failure to achieve the desired clinical effect in the patient, should also be considered as mild forms of transfusion reactions.     

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