[Two cases of extreme hemodilution caused by massive hemorrhage immediately after start of operation]

We describe two cases of extreme hemodilution due to large amounts of fluid infusion for unexpected massive hemorrhage. In both cases, unexpected hemorrhage with difficult hemostasis occurred within 60 min after the start of the operation. For lack of transfused blood, large amounts of fluid infusion using crystalloid and colloid solutions including 5% albumin, plasma expander and lactated Ringer's solution were administered to maintain circulatory blood volume. The hemoglobin concentration and hematocrit had been below 2.0 g.dl-1 and 10% for approximately one hour, respectively. The extreme hemodilution improved by the urgent blood transfusion. In one case, intraoperative autotransfusion with Cell-Saver was performed. In spite of intraoperative extreme hemodilution, their postoperative courses were uneventful. Intraoperative awareness was present in both cases.