Q. I would like to know the answers to the following two questions: How is blood stored in a blood bank? What are the changes that occur to the erythrocytes during storage?
Blood is collected into a plastic bag for blood collection & storage which contains anticoagulant/buffers etc. which allow storage of blood. These include citrate-phosphate dextrose (CPD), acid-citrate dextrose (ACD), ACD or CPD with adenine to prolong red cell storage, and other preservative solutions like SAGM etc. If red cells are preserved in SAGM solution then their life goes upto 42 days. The CPD solution preserves whole blood for 21 days whereas CPDA solution preserves blood for 35 days. The material of the bag is biocompatible with blood cells and allows diffusion of gases permitting optimal cell preservation. The specimen thus collected is tested for hepatitis B & C, HIV and other infections. The blood is stored in refrigerators at 2 to 6 degrees C. Each unit of whole blood normally is separated into several components. Red blood cells may be stored under refrigeration for a maximum of 42 days, or they may be frozen for up to 10 years. Red cells carry oxygen and are used to treat anaemia. Platelets are important in the control of bleeding and are generally used in patients with leukaemia and other forms of cancer. Platelets are stored at room temperature and may be kept for a maximum of five days. Fresh frozen plasma, used to control bleeding due to low levels of some clotting factors, is kept in a frozen state for usually up to one year. Cryoprecipitate, which contains only a few specific clotting factors, is made from fresh frozen plasma and may be stored frozen for up to one year. Granulocytes are sometimes used to fight infections, although their efficacy is not well established. They must be transfused within 24 hours of donation. Other products manufactured from blood include albumin, immune globulin, specific immune globulins, and clotting factor concentrates. Commercial manufacturers commonly produce these blood products. Stored RBCs develop complex and multiple membrane changes leading to increased osmotic fragility (due to shape change), decrease in the level of 2,3-DPG (increasing the oxygen affinity of haemoglobin), reduced ATP levels, loss of potassium ions with seeping in of sodium ions, loss of deformability of RBCs and reduced life span.