The authors investigated, in a multicenter, double-blind, randomized trial, whether diaspirin-crosslinked hemoglobin (DCLHb) could reduce the use of allogeneic blood transfusions. This is a very interesting study for several reasons.
First, the study is one of the very few in the area of transfusion medicine that was able to implement and maintain a double-blind study design. DCLHb or packed red blood cells (PRBC) were administered in such a manner that neither the blinded investigative team nor the perioperative medical staff caring for the patient were aware of the solution given. Blinding was successful in over 80% of patients.
Second, the methods and the endpoints of the study were clinically relevant: these were patients undergoing major surgery (as evidenced by the high rate of adverse events in both groups) likely to require transfusions; patients were randomized once the decision to transfuse had been made; and the endpoints included avoidance rate within 7 days after surgery (not only the postponement of transfusion) and the number of units transfused.
Despite the interruption of the study midway into recruitment (Baxter, on FDA recommendation, suspended patient enrollment in the trial), the results show that DCLHb was able to avoid allogeneic blood transfusion completely in 23% of patients and that the median number of units transfused decreased from 3 to 2. The results are even more convincing when one considers that this was an effectiveness study (the intervention works in real life: there was no strict transfusion protocol). Nevertheless, there were major concerns with the safety of the product: it is the FDA’s opinion that DCLHb might have contributed to serious patient morbidity (MOF and ARDS) in two patients undergoing aortic surgery. Eventually, in light of this and other studies with DCLHb, development of the product was stopped.
These are promising results. The authors have shown, convincingly for once, that hemoglobin solutions can effectively reduce the transfusion of allogeneic blood. Clinicians now await second generation products with an improved safety profile.
– Jean-Franois Hardy