Ranking the effectiveness of autologous blood conservation measures through validated modeling of independent clinical data

Abstract

Future supply with allogeneic blood transfusions faces several crucial challenges that warrant thorough (re-)evaluation of existing alternatives. Meta-analyses have indicated a significant potential for autologous blood conservation (ABC) measures to reduce the need for allogeneic blood transfusions. The quality of currently available studies, however, prohibits definite conclusions. Under these circumstances, mathematical modeling offers unique opportunities to compare various ABC measures and to test the impact of different variables on efficacy and effectiveness. We performed an extensive search for clinical ABC studies, focusing on acute normovolemic hemodilution (ANH), intraoperative blood salvage (IBS), or preoperative autologous deposit (PAD). Only ABC studies providing a minimum set of clinical variables were included. Using a clinically validated mathematical model, we then calculated maximal allowable blood loss (efficacy) and increase in red blood cell (RBC) mass (effectiveness) to rank the three techniques. We identified 21 clinical ABC studies, including 3926 patients, as suitable for our model. Our model shows that IBS with high recovery rates is the most efficacious and effective ABC measure. PAD will reveal nearly similar efficacy and effectiveness, only if sufficient time for RBC regeneration has passed and if 4 PAD units or more are available. Our model further demonstrates that ANH as well as IBS with low recovery rates are the least efficacious and effective alternatives. IBS appears to be the most efficacious and effective ABC measure. PAD can only reduce the need for allogeneic blood transfusions under certain circumstances. ANH does not appear to play an important role in ABC.