Washing

Blood products are often washed in normal saline or other media to remove the contaminants from blood cells. The process of washing limits the amount of plasma within a blood product, as RBC products would otherwise contain small amounts of residual plasma proteins. These proteins have the potential to cause allergic or other reactions in the recipient. Washing reduces the risk of allergic transfusion reactions and can limit the effects of incompatible antibodies related to incompatible ABO blood types. The mixture is then centrifuged to separate the blood cells from the solution. Specific indications for washing include a history of severe or recurrent allergic reactions associated with RBC transfusions, IgA deficiency (when IgA deficient blood is unavailable), red-cell T activation, and complement-dependent autoimmune hemolytic anemia.

Volume and Pathogen Reduction

Volume reduction is typically performed via centrifuge to isolate blood cells from their medium. This process reduces excess potassium and cytokines, thereby reducing the risk of electrolyte imbalance or febrile non hemolytic transfusion reactions. Volume reduction also simply reduces the total volume of the final blood product, which can be used to titrate blood cell concentration as needed.

Pathogen reduction or inactivation reduces the risk of transmission of infectious agents including viruses, bacteria, and parasites. Current processes that reduce the infectious risk of blood transfusion include donor deferral, product testing procedures, and filtration. Nucleic acid testing is commonly employed to detect various pathogens. The U.S. Food and Drug Administration (FDA) requires blood products be tested for human immunodeficiency virus (HIV), hepatitis B virus (HBV), hepatitis C virus (HCV), human T-lymphotropic virus (HTLV), Treponema pallidum (syphilis), West Nile virus, and Zika (WNV) virus. The risk of bacterial
contamination is especially important for platelets, since they are stored at room temperature and more susceptible to bacterial contamination. For plasma products, solvent-detergent agents and nanofiltration are effective, but are not suitable for the cellular components. Cellular products can be treated with visible or ultraviolet light and irradiation. These processes damage nucleic acids and, thus, inhibit transcription and translation in active pathogens and WBCs. With these advancements in blood banking, infectivity of blood is now an uncommon cause of transfusion-related morbidity and mortality.

Delivery of Blood Products to the Operating Room

Blood products are stored in plasticized polyvinyl chloride or polyolefin bags. The storage temperature for red cells is between 2°and 6°C while platelets are stored at room temperature (20-24°C). Plasma products are kept frozen (below −18°C) until needed. Once blood products are requested, the blood bank will prepare the products for transportation to the operating room or intensive care units. Plasma products, such as fresh frozen plasma (FFP) or cryoprecipitate must be thawed prior to administration. Platelets and cryoprecipitate can be
transported at room temperature prior to transfusion, while PRBCs and FFP are transported in coolers with ice packs or other cooling methods. Once delivered to the operating room, the products are verified and then transfused.

It is important for the anesthesiologist to understand the processes that occur in the blood bank, as it allows them to be better stewards of these limited resources. Maintaining proper protocols for these blood products can significantly decrease the waste that can be associated with transfusion medicine due to failure to properly order the products or failure to properly maintain the strict temperature parameters. Understanding the risks that some patients have for transfusion related illnesses allows us to better identify these patients and to work with our blood bank colleagues to mitigate those risks.