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Department of Anesthesiology, Mayo Clinic, Jacksonville, FL
To the Editor:
In August 2003, Schubert et al. (1) showed through a multicenter trial that allogenic blood transfusion requirements could be reduced by using the blood substitute diaspirin cross-linked hemoglobin (DCLHb). While this may seem worthy of sharing with the medical community, the adverse effects of DCLHb should not be taken lightly. The adverse effect profile of this substance included urinary problems, jaundice, and pancreatitis, and the study was terminated because of safety concerns (1). Another trial by Sloan et al. (2) showed significantly increased mortality when DCLHb was used in trauma patients, which should negate any benefit that DCLHb could offer in terms of reducing the amount of transfused bank blood.
Our compliments to Schubert et al. (1) for their efforts in conducting a multicenter trial, which can be a monumental task, but the positive findings of decreased usage of blood bank products should have been overshadowed by the fact that the product was discontinued for safety concerns before publication of their article. Research into other hemoglobin substitutes should focus not only on short-term answers but also on patient safety and longer-term outcomes.
References
Department of General Anesthesiology, Cleveland Clinic Foundation, Cleveland, OH
In Response:
We appreciate the interest in and comment on our recent publication about the prospective multicenter randomized controlled trial (RCT) of diaspirin cross-linked hemoglobin (DCLHb) in elective surgical patients (1). We agree completely with Bloomfield and Leone that further development in hemoglobin oxygen carriers (HBOC) needs to focus on improving their safety profiles. In our concluding statement, we emphasized this point in particular.
With regard to DCLHb, it should be noted that, while more frequent mortality was reported for patients randomized to DCLHb in the trauma study mentioned by Bloomfield and Leone, this was not the case in other multicenter RCTs (1–3), including in trauma patients (4). A substantial amount of clinical safety data had indeed been accumulated even before we began our trial. Its purpose was to investigate whether DCLHb could lead to significant avoidance or reduction or allogeneic blood transfusion. This was consistent with guidelines for evaluation of HBOC efficacy published by the Center for Biologies Evaluation and Research of the U.S. Food and Drug Administration (5).
It has become clear that administration of HBOC can result in substantial avoidance of blood transfusion. We must now go beyond simply comparing safe hemoglobins to blood and look at their potential to rescue ischemic tissue and to deliver oxygen reliably to that area of the microcirculation where oxygen is needed most. New modified hemoglobins may indeed facilitate oxygen release into capillary beds (6,7), preventing precapillary loss of oxygen, which is associated with the vasoconstrictive effect of earlier species.
References
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