Q What is blood and what are its components?

A Blood is the red fluid which circulates in our body. A normal adult male has about five litres of blood and a female about 4.5 litres. It consists of liquid plasma and the solid cellular part. The cellular component is made up of red blood cells which contain haemoglobin that carries oxygen to the different tissues of the body. White blood cells act as the body’s defence force to fight against germs and the platelets repair injury to vessel walls, thus controlling bleeding. Plasma carries nutrition to all tissues in the body. It also contains blood-clotting factors, immunoglobulins and albumin.

Q Why should we donate blood?

A Although our body produces enough blood for our requirements, there are situations when blood is not sufficiently available in the body to cope with. This may be in acute conditions of blood loss such as accident, trauma, surgery or in disease states where the body is not producing enough to fulfil the requirements such as anaemias and leukaemias. In these situations, when extra blood is required for the suffering individual, one cannot walk into a shop and buy blood because blood is neither manufactured nor can it be obtained from an animal source for human use. Hence it has to be received as a gift from fellow human beings.

Q Who can donate blood?

A Any person more than 17 years of age and less than 65 years of age can donate blood. A male should weigh a minimum of 110 lbs and a female 90lbs. A male donor should have Hb-13.5 gm% or more and a female donor 12.5 gm% or more. All donors must pass the physical and health history examination given prior to blood donation.

Q What precautions are taken during the donation?

A A complete aseptic set up is used. Disposable needles and tubes are needed.

Q How much time does donation take?

A The actual donation time is just about 10 to 15 minutes. Some more time is required for registration, physical tests and health information.

Q Is the blood donation procedure painful?

A It is an absolutely painless procedure. The only time you feel a little pain is when the needle is inserted into your vein. The use of a spray of local anaesthesia can be used at the site of the needle prick.

Q How much blood can one donate at one time?

A A male donor can donate around 500 ml and a female donor around 450 ml.

Q How long does it take to build up the blood you have donated?

A The donated volume of blood is replenished within 24 hours and the red blood cells are normal in a few weeks.

Q What happens to the blood you have donated?

A Blood is tested and typed for blood groups and also for any unexpected red cell antibodies that may cause problems in the recipient. Screening tests are also performed for the possible evidence of donor infection with the hepatitis virus B and C the human immunodeficiency viruses (HIV) I and II (for AIDS) and syphilis. some labs also look for human T-lymphotropic viruses (HTLV) I and II.

Q What are blood groups and their importance in blood transfusion?

A Blood groups are characters present on the red cells which make them specific. The commonest varieties used are A, B, AB and O groups and Rh groups. Because of specificity of these blood groups, only compatibly matched blood can be transfused.

Q How is blood stored?

A Each unit of blood is normally separated into its components such as plasma, red cells, platelets etc. Red blood cells may be stored under refrigeration for a maximum of 42 days or kept frozen for upto 10 years. Platelets are stored at room temperature and may be kept for a maximum of five days. Fresh plasma is usually kept in a frozen state for up to one year. Cryoprecipitate (the anti-anemophilic factor) is usually made from fresh frozen plasma and may be stored frozen for up to one year. While blood cells, when separated, must be transfused within 24 hours.

Q How is blood used?

A Whole blood is mostly used in exchange transfusions for new borns in cases of Rh incompatibility. Packed red cells are used in acute blood loss following accidents trauma or surgery and in cases of chronic anaemia of any origin where sufficient blood is not produced by the body. Platelets are generally used in the patients who bleed from platelet deficiencies as in leukaemias and other forms of cancer. Fresh frozen plasma is used as blood volume expander for the control of bleeding due to the deficiency of clotting factors, for plasma exchange to remove unwanted antibodies, etc. Cryoprecipitate is used for haemophilia cases and granulocytes are used to fight infections.

Q How frequently can one donate blood?

A One can donate one unit of blood every three months.

Dr Sumitra Dash is Additional Professor of Haematology at the PGI, Chandigarh. She worked as a consultant in haematology and was in charge of the Central Blood Bank at the Salmanya Hospital, Bahrain, from 1991-99.