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affecting survival following septic challenge in animal models. Using a pseudomonas contaminated burn model they found that the effect of transfusion was not dose-related (24). They also demonstrated with this model that transfusion within 24 hours of pseudomonas challenge did not affect survival, suggesting that a time dependent interaction of the recipient and the transfused blood takes place resulting in increased susceptibility to bacterial challenge (24). Neither anesthesia (methoxyflurane) nor transfusion affected survival of animals given intravenous injections in comparison to untransfused unanesthesized animals given the same intravenous dose of E. coli (26). Both allogeneic transfusion and anesthesia caused significantly increased mortality compared to controls when 10^ E. coli were injected into the peritoneal cavity. The timing of transfusion relative to septic challenge and the severity of the septic challenge interact in determining the significance of allogeneic blood for increasing susceptibility to infectious agents (27). Immunosuppressive thromboxane and prostaglandins E and Fla production by macrophages is increased following allogeneic transfusion (28) and macrophage migration into the peritoneal cavity is reduced in animals previously transfused with allogeneic blood (29). Macrophages from animals transfused with allogeneic blood also exhibit impaired ability to phagocytose and kill bacteria in culture. Leukotrienes are immunostimulatory metabolites of arachidonic acid and their production is inhibited following allogeneic transfusion. Macrophages and macrophage supernatants from transfused rats suppress lymphocyte responses to PHA (30). Significant elevations of serum corticosterone accompany declines in leukocyte counts in animals transfused with allogeneic blood in comparison to syngeneic recipients (31). The experimental studies reproducibly demonstrate that allogeneic blood transfusion causes inhibition of cellular antibacterial mechanisms which cause increased susceptibility to bacterial pathogens. The models support the hypothesis that transfusion-induced immune suppression leads to enhanced susceptibility to bacterial pathogens in the recipient. CANCER RECURRENCE In 1981 a letter in The Lancet suggested that the immunosuppressive properties of transfusion which are beneficial for dialysis patients may be detrimental for patients with malignancies (32). There are now over one hundred published studies investigating the relationship between homologous blood transfusion and cancer recurrence. Meta-analysis of 20 colorectal studies representing 5,236 patients calculated cumulative odds ratios of 1.8 for disease recurrence, and 1.76 for death from cancer in transfused patients (33). Academicians will never be convinced by retrospective studies that transfusion is anything other than a marker of stage of disease and extent of surgery. Since preoperative anemia often leads to blood transfusion and anemia is often a sign of advanced disease in cancer patients, transfusion would be expected to be associated with early disease recurrence because it is associated with anemia. Advanced malignancies necessitate extensive surgery, require more time and cause greater blood loss. Procedure, duration of surgery and blood loss are associated with transfusion and may account for transfusion's association with recurrence. Prognostic factors cannot be adequately controlled in retrospective studies. The significance of perioperative blood transfusion for patients with malignancies cannot be definitely proven without randomizing patients to receive blood or go untransfused. Given the

• Source: Transfusion Immunology and Medicine ; page 297-297 ; ISBN 9780429082597

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