Ann Thorac Surg 2001;72:S1806-S1807
© 2001 The Society of Thoracic Surgeons
Supplement: Mechanisms and attenuation of abnormalities in hemostasis/inflammation and neurologic injury: implications for patient outcomes
Red blood cells: an analysis of risk versus benefit
Norig Ellison, MD*a
a Department of Anesthesia, Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania, USA
* Address reprint requests to Dr Ellison, Department of Anesthesia, Hospital of the University of Pennsylvania, 3400 Spruce St, 413 Ravdin Courtyard, Philadelphia, PA 19104, USA
e-mail: ellisonn{at}uphs.upenn.edu
Presented at Mechanisms and Attenuation of Abnormalities in Hemostasis/Inflammation and Neurologic Injury: Implications for Patient Outcomes, Vancouver, BC, Canada, May 6, 2001.
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Abstract
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The value of red blood cell administration to increase oxygen carrying capacity is obvious to all clinicians. Nevertheless, there has never been a prospective, randomized, controlled study documenting the efficacy or conclusively defining the indications for red blood cell use. Considering the risks associated with allogeneic blood, careful consideration must be given before the administration of each unit of blood product.
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Introduction
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At the federal level, there are two advisory committees that are concerned with blood products. In the United States Department of Health and Human Services, the Advisory Committee on Blood Safety and Availability (BSA) provides advice to the Secretary and Assistant Secretary for Health on a broad range of issues to include the following: (1) implications for blood safety and availability of various economic factors affecting product cost and supply; (2) definition of public health considerations for safety and availability of the blood supply, and (3) broad public health, ethical, and legal issues related to blood safety [1]. Within the United States Food and Drug Administration, the Center for Biologics Evaluation and Research (CBER) is charged with ensuring the safety of the nation’s blood supply. This charge includes regulating the collection of blood and blood components used for transfusion or manufacture of pharmaceuticals; related devices such as cell separators and blood collection containers; and human immunodeficiency virus (HIV) screening tests [2]. To assist the CBER in its mission, the Blood Products Advisory Committee (BPAC) was created. There is obviously considerable overlap in the interests and issues of BS&A and BPAC. Frequently, at their meetings, each committee is informed of the actions of the other committee at its last meeting.
For BPAC meetings, CBER staff prepare issues for discussion in considerable detail, ensuring that knowledgeable authorities from federal agencies as well as industry make presentations on each issue. In addition, there is time set aside for public comment and committee discussion. In arriving at decisions regarding a given blood product or device BPAC discusses not only the purported benefit, but the potential risks of said product or device. As a member of BPAC I have often mused, "How would BPAC vote if the product in question were red blood cells?" Weiskopf [3] has pointed out, "Although approximately 12 million units of blood are transfused per year in the United States, the efficacy of this biological has not been demonstrated in an appropriately controlled, prospective study, nor other clear criteria by which one would judge the efficacy of red blood cells (RBC)." Although no one can seriously question the value of RBC, considerable debate does ensue regarding specific indications for their use.
Clearly, the risks of transfusion are considerable (Table 1). What are the benefits?
The one absolute indication for RBC transfusion is to provide adequate oxygen carrying capacity [4]. Nevertheless, the minimum hemoglobin level tolerated without organ dysfunction (often referred to as a "critical hemoglobin") has not been defined. Indeed, Spahn and Cassut [5] have suggested, "The critical hemoglobin level can only be defined for certain organs, specific situations, and disease states, and particular age groups."
This suggestion is based on studies in human volunteers showing that extreme hemodilution to hemoglobin concentration of 5 g/dL was well tolerated with no signs of compromised oxygen delivery such as decreased oxygen consumption or increased lactate production [6]. The principal means of compensating for an acute decrease in hemoglobin concentration are an increased cardiac output and increased oxygen extraction. As every clinician knows, the maintenance of normovolemia during this period of acute hemodilution is essential to avoid adverse hemodynamic and metabolic changes that would decrease the ability to increase cardiac output.
Although there may be no criteria on which to judge efficacy, there are a multitude of guidelines promulgated by various organizations concerning the use of various blood products. The three National Institutes of Health Consensus Conferences on fresh frozen plasma, platelets, and RBC are the best known and acknowledged as definitive statements [4, 7, 8]. A similar troika of papers has been published in Britain addressing fresh frozen plasma, platelets, and transfusion in infants and neonates [9–11]. Several specialty societies have also addressed various aspects of transfusion, from type of surgery to type of patient [12–15].
The recognition of transfusion-associated acquired immunodeficiency syndrome in the early 1980s and the epidemic of cases of this disease over the following decade had a profound impact on the practice of transfusion medicine. Patients came to the operating room expressing more concern about their possible need for blood transfusion than about surviving a major cardiac operation or the surgeon finding an inoperable malignancy. This concern was translated, among other things, into a demand for directed donations and—more importantly, and of lasting effect—a more conservative approach to the administration of allogeneic blood. Blood conservation techniques were (and still are) actively being sought (Table 2). It is in the context of promoting effective hemostasis as an alternative to allogeneic transfusion that this symposium is held.
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References
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Advisory Committee on Blood Safety, and Availability. Available at: http//www.hhs.gov/bloodsafety/charter.html.
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Center for Biologics Evaluation, and Research. Available at: http//www.fda.gov/cber/blood.htm.
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Weiskopf R.B. More on the changing indications for transfusion of blood and blood components during anesthesia. Anesthesiology 1996;84:498-501.[Medline]
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Consensus conference. Perioperative red blood transfusion. JAMA 1988;260:2700-2703.[Abstract/Free Full Text]
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Spahn D.R., Casutt M. Eliminating blood transfusions; new aspects and perspectives. Anesthesiology 2000;93:242-255.[Medline]
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Weiskopf R.B., Viele M.K., Feiner J., et al. Human cardiovascular and metabolic response to acute, severe isovolemic anemia. JAMA 1998;279:217-221.[Abstract/Free Full Text]
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Consensus conference. Fresh-frozen plasma: indications and risks. JAMA 1985;253:551-553.[Abstract/Free Full Text]
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Consensus conference. Platelet transfusions therapy. JAMA 1987;257:1777-1780.[Abstract/Free Full Text]
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Contreras M., Ala F.A., Greaves M., et al. Guidelines for the use of fresh frozen plasma: British Committee for Standards in Haematology. Working Party of the Blood Transfusion Task Force. Transfusion Med 1992;2:57-63.[Medline]
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Murphy M.F., Brozovic B., Murphy W., et al. Guidelines for platelet transfusion: British Committee for Standards in Haematology. Working Party of the Blood Transfusion Task Force. Transfusion Med 1992;2:311-318.[Medline]
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Voak D., Cann R., Finney R.D., et al. Guidelines for the administration of blood products: transfusion of infants and neonates: British Committee for Standards in Haematology Blood Transfusion Task Force. Transfusion Med 1994;4:63-69.[Medline]
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American College of Obstetricians, and Gynecologists. Blood component therapy, technical bulletin no. 78. Washington, DC: American College of Obstetricians and Gynecologists, 1984.
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Goodnough L.T., Johnston M.F., Ramsey G., et al. Guidelines for transfusion support in patients undergoing coronary artery bypass grafting; Transfusion Practices Committee of the American Association of Blood Banks. Ann Thorac Surg 1990;50:675-683.[Abstract]
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American College of Physicians. Practice strategies for elective red blood cell transfusion. Ann Intern Med 1992;116:403-406.
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Practice guidelines for blood component therapy: a report by the American Society of Anesthesiologists Task Force on Blood Component Therapy. Anesthesiology 1996;84:732-747.[Medline]
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Abstract
Introduction
