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NHLBI Working Group on Strategies to Optimize RBC Products
The National Heart, Lung, and Blood Institute (NHLBI) convened a Working Group (WG) of invited external experts including transfusion medicine, hematology, and immunology research scientists, blood service executives and blood bank directors, as well as end users of transfusion including intensivists and trauma experts. The meeting was held in conjunction with the annual NHLBI RFA 08-005 "Immunomodulatory, inflammatory and vasoregulatory properties of transfused red blood cell units as a function of preparation and storage" grantee's meeting at the Bethesda offices of the NHLBI on August 30 and 31, 2011. The purpose of this Working Group was to provide recommendations to the NHLBI that guide informed decisions on research objectives and priorities in the field of Transfusion Medicine with particular emphasis on the emerging questions related to the optimal storage of red blood cell products. The Working Group was responsive to NHLBI Strategic Plan Goals 2 and 3.
In 2010, NHLBI funded eight teams of investigators to conduct basic and translational research including animal models and/or basic human physiologic studies aimed at further characterizing the storage lesion and understanding the interaction between the storage lesion components and recipient/host cells such as endothelial and hematopoietic cells. In day 1 of the meeting, these investigators reported on the progress of these studies.
Four of the teams have proposed that transfusion damage from stored blood is a result of suboptimal tissue oxygenation engendered by a loss of proper control of blood flow. Drs. Gladwin and Kim-Shapiro provided evidence that the red cell storage lesion is driven by increased nitric oxide (NO) catabolism and loss of NO generating functionality mediated by cell free hemoglobin and red blood cell microparticles which increase over time during storage. The team of Drs. Patel, Barnum and Weinberg have proposed that stored RBC may fail to improve tissue oxygen availability due to alterations that impact microcirculatory perfusion following blood transfusion. They presented evidence that two mechanisms contribute to these age-related changes to stored blood: higher rates of NO-dioxygenation and nitrite oxidation by older RBC; as well as complement activation during RBC storage. Dr. Roback also presented evidence that stored RBCs can inhibit NO signaling. In agreement with Dr. Patel's research these effects were not removed by washing the cells prior to study. Drs. Stamler and Reynolds reported on their studies investigating the loss of S-nitrosylated hemoglobin during RBC storage with a subsequent impaired ability of banked RBCs to induce vasodilation and deliver oxygen to tissues.
Dr. Jy presented his work examining the development of RBC, leukocyte and platelet microparticles and the influence of product processes such as leukoreduction on their accumulation in the blood unit. Drs. Blumberg and Phipps described their studies examining the development of cell free hemoglobin and lipid mediators in the supernatant. Drs. Norris and Sparrow presented the status of their studies investigating the inflammatory and immunomodulatory effects of stored blood. Dr. Spitanik presented on studies performed with Dr. Hod that examine the changes in circulatory iron load following transfusion of stored RBCs with evidence that RBCs, and not free hemoglobin or microparticles in the unit, are responsible for these results.
The day concluded with status reports on several ongoing and proposed large randomized trials that test the hypothesis that transfusion of blood that has been stored for shorter periods may be more beneficial clinically than transfusions of RBCs that have been stored for longer periods.
Dr. Simone Glynn, Chief of the Transfusion Medicine and Cellular Therapeutics Branch, NHLBI, began the working group on day 2 of the meeting by summarizing the current state of translational and clinical research aimed at understanding the RBC storage lesion that was described in the presentations and discussion on the previous day. She charged the group to identify the major areas of research needed to optimize preparation and storage of RBC products considering the nature of the storage lesion elements identified so far and the potential detrimental impact on blood availability that would currently result with a sudden shift to use of fresher blood.
Working group presentations were organized to highlight the recent progress and to identify barriers to future advances in the implementation of three general strategies currently in pre-clinical and clinical testing (renitrosylation, washing prior to transfusion, and novel storage solutions and conditions). Each of the various strategies target different aspects of the stored RBC product that are thought to contribute to the RBC storage lesion. In addition, an assessment of shortened RBC shelf life on a large community blood program was presented to the group.
The working group agreed that the so-called "storage lesion" is most likely a result of changes in multiple parameters leading to the development of numerous intermediates in the blood bag over time. Based on the studies presented in the first day of the meeting, targeting any single parameter would likely have only a fractional improvement on the quality of the blood product. Thus, multiple strategies will be needed to improve the safety and efficacy of transfused red blood cell components.
The working group discussions also drew attention to the multiple gaps in knowledge in areas that will be fundamental for the successful development and assessment of these anticipated changes to red blood cell storage and transfusion practices. These gaps could be divided into the need to gain a better understanding of red blood cells and the effects of storage on these properties; gaining better insight into the benefits and adverse outcomes associated with the age of the transfused red blood cell units; and determining where the scientific and blood management communities can impact the field.
Consensus and Recommendations
The Working Group made a series of recommendations to NHLBI, which can be broadly categorized into:1) a need for methodologies, biomarkers, and animal models to measure the clinical benefits of RBC transfusions; 2) a need for research to optimize RBC products and develop new and improved preparations and solutions for RBC products, and 3) a need for a multidisciplinary approach to transfusion medicine research.
Simone Glynn, MD, MPH
Lisbeth Welniak, PhD
Workshop Group Participants
Last Updated November 2011