Life-saving transaction

By Kumudini Hettiarachchi

There is a tiny window through which a slip of paper is passed in and after a while a transaction takes place. It is no ordinary transaction - for in some hospital lying in desperate need is a patient. A patient who needs blood.

MediScene checked out the detailed process after which such needy patients are able to get this life-giving liquid.

A potential donor walks in, through the main entrance of the National Blood Transfusion Service and is given a 'donor declaration form' with several searching and at the same time confidential questions. All donors should be above 18 years and weigh more than 50 kilos.

A donor can give blood every four months and voluntary donations are encouraged as opposed to donations by people who come in to replace the blood a patient requires, stresses Dr. Neetha Manthriratne, explaining that 'replacement blood' could be infected as the donor is desperate and may not disclose if he/she is ill. A donor can give blood at hospital-based Blood Banks or through mobile units too.

With the calculated requirement of the country being about 300,000 units (one unit is equivalent to about 500 ml) of blood per year, the aim is to collect all blood requirements through 100% voluntary donations by 2008.

Once the form is filled, the potential donor is ushered into a room where a doctor has a leisurely chat with him/her counselling them and at the same time conducting a thorough physical examination. The counselling is a way of advising them that if they have had multiple sexual partners or have had or are having a major illness such as HIV, Hepatitis B, syphilis or malaria they should refrain from donating blood. The doctor will then decide whether the potential donor is fit to donate blood. The age, weight and also the haemoglobin level, through a simple prick on the finger of the donor, are checked.

"If everything is okay, the donor is taken to the 'bleeding area' where 'whole blood' is collected into a set of bags, the number of bags varying from 2-4. In one bag, there is a solution to keep the red cells viable and prevent clotting," says Dr. Manthriratne adding that 450 ml is collected and with the solution make up about 500 ml.

Thereafter, the 'whole blood' is taken to the component laboratory to be separated into the different components. 'Whole blood’ can be divided into two major components - liquid and cells, with the cells being categorized as red, white (buffy coat) and platelets. The 'whole blood' is then placed in containers and put into the centrifuge machine and the temperature regulated. When the machine revolves, the different components of 'whole blood' settle at different levels. The liquid at the top and the cells at the bottom.

The window through which requests are made.

The liquid is then made into fresh, frozen plasma. However, when the liquid is being transfused to a patient, it has to be thawed before transfusion.

Plasma components stored frozen below -30 0C, can be kept up to one year. Another component which is separated from fresh frozen plasma called Cryo precipitate is used mainly for Haemophilia patients.

Meanwhile, the cells of the blood are then subjected to certain screening tests for HIV, Hepatitis B and C, syphilis and malaria and also to identify the blood group. During the screenings, the units of blood are placed in a quarantine refrigerator and only when the tests come as negative are they stored, ready for use.

"In HIV, there is a window period in the first few months, when the tests cannot detect the disease because the virus could be in the blood without producing antibodies at a detectable level," says Dr. Manthriratne.

After the tests come in negative, the different blood groups are clearly labelled and stored in different fridges, according to the date of collection. Blood is issued on a 'first in first issued basis', she says, to prevent the samples getting outdated.

Blood storage temperatures vary too, with red cells which have a shelf-life of only 35-42 days (depending on the additive solution) being stored at 2-60C.

For the preparation of platelets, fresh blood should be used within 12 hours of collection. Platelets stored at a temperature of 21-24 0C, under continuous agitation (as they aggregate or clot) can only be kept for five days.