Saturday, April 11, 2009

BLOOD TRANSFUSION

Some years back,my father's first question when I'm sick and on admission is "am I on transfusion?"He's probably used to it now and have a better understanding.When it occured to me to write on this topic,can't explain what I felt,but here we are...

Blood transfusion is the transfer of blood or blood products into the blood the blood stream of a patient who has lost blood due to injury,disease or an operation.The amount of blood and blood type of blood transfused depends on the need of the patient.It is the role of biomedical scientist to ensure that the blood being transfused is safe.To ensure safety,the blood is tested to determine its blood group and check that it is not contaminated with harmful micro-organisms.Checks are also made to ensure that the blood to be transfused does not contain antibodies that will destroy the erythrocytes of the recipient and cause death.

The type of blood a needed patient would be transfused with depends on the person's blood group.Blood group system is the classification of blood depending on the characteristics of their erythrocyte and the presence of specific antibodies in their plasma to erythrocyte antigenes.There are different human blood group systems like ABO,Rh,etc.The ABO blood group system classifies people into one of four major blood groups:A,B,O and AB, according to the different types of antigene present on the surfaces of their erythrocytes. The Rh blood group system didvides people into Rh+ or Rh-,depending on whether or not their erythrocytes carry the Rh antigen.The frequencies of these blood groups vary between different populations. AB,A,B and O are universal recipients because they can accept blood from any of the blood groups and O is a universal donor because it can be transfused into persons with other blood group.

The need for blood transfusion is determined by a test known as PCV(Packed Cell Volume).PCV is the measure of the proportion of blood that is made up of cells.The value is expressed in percentage or fraction of cells in 100 millitres of blood,e.g 40% means that there are 40millitres of cells in 100millilitres of blood.When the PCV falls to less than normal, it indicated anaemia. It is normally about 46% for men and 38% for women. It could be a bit lower for people with sickle cell anaemia.

CONSEQUENCIES OF BLOOD GROUP INCOMPATIBLE TRANSFUSION
An example of an incompatible blood transfusion is when a patient of blood group A,the recipient is given blood from a donor who is blood group B.In this case,the anti-B antibodies present in the plasma of the recipient bind to the donated erythrocytes and activate complement.This results in the simultaneous lysis of billions of erythrocytes in the given blood.The lysis of so many erythrocytes,called acute intravascular hemolysis,releases so much haemoglobin that acute renal failure occur and shock result.In addition to the problems caused by the release of haemoglobin, the fragments of erythrocytes memebrane released may also initiate the blood clottings, leading to disseminated intravascular coagulation(DIC).It may also vary according to the blood group involved. Slower destruction of the donated cells may lead to a decreasing haemoglobin concentration, with the patient suffering a fever and general malaise.

HAZARDS OF TRANSFUSION
  • Iron overload: patients who receive many transfusions over long period of time may develop iron overload. The excess of iron,for which there is no excretory route, from transfused blood may cause tissue damage, especially to the heart, liver and endocrine glands. Signs of iron overload can be detected after several transfusions and the condition may be fatal if left untreated. It can be treated with chelating agent to remove unwanted iron.
  • Alloimmunization: patients who receive regular erythrocyte transfusion may become immunized to other blood group antigens present in the ABO compatible cells.This may affect future transfuions.The use of leukodepleted blood, in which leukocytes have been removed prior to transfusion, prevents the immunization of recipient to these antigens.
  • Infection: another potential hazard of transfusion is infection with micro-organisms present in the donor.It has been observed that blood transfusion have spread infections such as HIV and hepatitis C to recipients.For this reason, there is now extensive screening of blood donors.

Even with the the risks involved in blood transfusion, it has save lives, like in the case of anaemia and surgery. I remember my parent got into argument with hospital officials when I had to be transfused sometime ago and there was a delay...my parent wouldn't want to loose their priceless jewel.There was no other option at that point in time than transfusion, and thank God I'm still alive!

To conclude,transfusion scientist must make sure that the process of transfusing blood poses minimal risk to the patient and donor alike. Aside from obvious need for the blood to be carefully matched to avoid possibly fatal transfusion reaction, it is essential that donors are carefully screened to avoid those who are ill or who may be harmed by giving blood, or whose blood poses a health risk beacause, for example, it is contaminated with certain viruses even when the donor shows no sign of ill health.

May the unblemished "BLOOD " of Christ avail for us in all situations.