Does acute normovolemic hemodilution reduce perioperative allogeneic blood exposure? A systematic review.

The objective of this study was to systematically review the literature and to statistically summarize the evidence evaluating the efficacy of acute normovolemic hemodilution (ANH). Review of 1575 citations identified 24 prospective, randomized, controlled trails of ANH containing a total of 1216 patients. When all trials were pooled ANH reduced the likelihood of exposure to allogeneic blood and the total units of allogeneic blood transfused. Marked heterogeneity of the results was present and adverse events were incompletely reported. Subgroup analyses could not account for all heterogeneity noted in this overview. Under reporting of small trials with negative results was suspected. In trials using a protocol to guide perioperative transfusion, ANH failed to reduce either the likelihood of transfusion or the units administered. It is possible that experimental design bias in favor of reducing transfusion in the ANH group is in part responsible for the reported efficacy of this technique