BLOOD BANKING

BLOOD BANKING

A blood bank is a cache or bank of blood or blood components, gathered as a result of blood donation, stored and preserved for later use in blood transfusion. The term “blood bank” typically refers to a division of a hospital laboratory where the storage of blood product occurs and where proper testing is performed to reduce the risk of transfusion related events. It is important for a blood bank to pass all the eligibility guidelines as mandated by theNational Health Service (NHS) and Food and Drug Administration (FDA). The safety and reliability should also be a consideration too. This includes compatibility testing for transfusion and may include blood donation processing, depending on the capabilities of the facility.Transfusion

Most hospital blood banks also perform testing to determine the blood type of patients and to identify compatible blood products for blood transfusions, along with a battery of tests (e.g. disease) and treatments (e.g. leukocyte filtration) to ensure and enhance quality. Some such procedures can be done “upstream” by the collecting agency, or a contracted laboratory. The increasingly recognized problem of inadequate efficacy of transfusion and post-transfusion complications raises the importance of quality testing and screening; U.S. hospitals spend more on dealing with the consequences of transfusion-related complications than on the combined costs of buying, testing/treating, and transfusing their blood.

Donors are sometimes paid; in the U.S. and Europe, most blood for transfusion is collected from volunteers while plasma (specifically blood plasma) for manufacturing is from paid donors.

In the US, certain standards are set for the collection and processing of each blood product. “Whole blood” (WB) is the proper name for one defined product, specifically unseparated venous blood with an approved preservative added. Most blood for transfusion is collected as whole blood. Autologous donations are sometimes transfused without further modification, however whole blood is typically separated (via centrifugation) into its components, with Red Blood Cells (RBC) in solution being a commonly used product. Units of WB and RBC are both kept refrigerated at 1-6 C, with maximum permitted storage periods (shelf lives) of 35 and 42 days respectively.

Red Blood Cell units can also be frozen when buffered with glycerol, but this is an expensive and time consuming process, and is rarely done. Frozen red cells are given an expiration date of up to 10 years and are stored at -65C.

The less-dense blood plasma is made into a variety of frozen components, and is labeled differently based on when it was frozen and what the intended use of the product is. If the plasma is frozen promptly and is intended for transfusion, it is typically labeled as fresh frozen plasma. If it is intended to be made into other products, it is typically labeled as recovered plasma or plasma for fractionation. Cryoprecipitate can be made from other plasma components. These components must be stored at -18C or colder, but are typically stored at -30C.

The layer between the red cells and the plasma is referred to as the buffy coat and is sometimes removed to makeplatelets for transfusion. Platelets are typically pooled before transfusion and have a shelf life of five days, or three days once the transfusion centre that collected them has completed their tests. Platelets are stored at room temperature (20-24C) and must be agitated. Since they are stored at room temperature in nutritive solutions, they are at high risk for growing bacteria.

Some blood banks also collect products by apheresis. The most common component collected is plasma viaplasmapheresis, but red blood cells and platelet can be collected by similar methods. These products have the same shelf life and storage conditions as their manually produced counterparts. An ongoing study allows platelets collected by apheresis to be kept for seven days, but only with specific microbiological testing. The lack of a preservative solution makes a longer shelf life of little use.

Short-term Storage

Routine blood storage is limited to 21 days at 1–6 °C when treated with acid-citrate-dextrose (ACD), citrate-phosphate-dextrose (CPD) or citrate-phosphate-double dextrose (CP2D) and 35 days when treated with citrate-phosphate-dextrose-adenine (CPDA1) (5 weeks for WB, 6 weeks for RBC), and involves refrigeration but usually not freezing. There has been increasing controversy about whether the age of blood is a factor in transfusion efficacy, specifically on whether older blood directly or indirectly increases risks of complications. Studies have not been consistent on answering this question, with some showing that older blood is indeed less effective but with others showing no such difference; nevertheless, as storage time remains the only available way to estimate quality status or loss, a first-in-first-out inventory management approach is standard presently.

Insufficient transfusion efficacy can result from blood product units damaged by so-called storage lesion – a set of biochemical and biomechanical changes which occur during storage. With red cells, this can decrease viability and ability for tissue oxygenation. (Note that upon transfusion, cells have exhibited some degree of ability to reverse their storage lesion, albeit not entirely – and often too slowly to benefit urgent-care patients.) Without a clinically feasible and reliable means to directly measure this phenomenon (during storage), many physicians have adopted a so-called “restrictive protocol” – whereby transfusions are simply being held to a minimum, as delayed recovery times and extended hospitals stays is viewed as the “lesser evil” compared to the harm and thus resulting cost of transfusing blood product of unknown quality.

Long-term Storage

Long-term storage is relatively uncommon, compared to short-term storage. Cryopreservation of red blood cells is done to store rare units for up to 10 years. The cells are incubated in a glycerol solution which acts as a cryoprotectant(“antifreeze”) within the cells. The units are then placed in special sterile containers in a freezer at very cold temperatures. The exact temperature depends on the glycerol concentration.