HEMODILUTION IN CLINICAL SURGERY - STATE-OF-THE-ART 1996

Acute normovolemic hemodilution entails removal of blood from a patien t either immediately before or shortly after induction of anesthesia a nd simultaneous replacement with cell-free fluid. Nowadays, because of their predictable volume effects, the synthetic colloids (6% dextran 60/70, 6% hydroxyethyl starch 200,000) are preferred as volume substit utes; albumin should be avoided because of its high cost. Hemodilution has experienced a renaissance in recent years, mainly due to the evol ving discussion of legal aspects, immunologic changes, viral infection s, and a potentially higher cancer recurrence rate associated with the transfusion of homologous blood. Hemodilution should be considered fo r elective surgical patients free of contraindications and presenting with an initial hemoglobin concentration greater than or equal to 12 g /dl and an anticipated blood loss of greater than or equal to 1500 ml. The efficacy of this method (judged by the need to give homologous bl ood transfusion) depends on the preoperative (initial) hematocrit, the target hematocrit (to which hemodilution is performed), and the prese t intra- and postoperative transfusion trigger. In the past, data from clinical trials showed that in healthy subjects a target hematocrit o f 20% to 25% (hemoglobin 7.0-8.0 g/dl) is feasible and safe for the pa tient. The lower the target hematocrit accepted, the more extensive is the monitoring required: Intraoperative target hemoglobin concentrati on of 5.0 g/dl and less have been tolerated by surgical patients witho ut adverse effects. The safety and efficacy of acute normovolemic hemo dilution in terms of reducing homologous blood transfusion requirement s has been demonstrated in various clinical studies. Hemodilution ther efore is regarded an integral part of programs aimed at reducing the n eed for homologous blood and can thus be successfully combined with pr eoperative autologous blood deposition, intraoperative blood salvage, and carefully adjusted surgical techniques. Hemodilution is feasible a nd relatively cost-effective, and it minimizes adverse effects associa ted with transfusion of homologous blood, particularly transmission of viral diseases, immunosuppression, and infectious complications.