Restoration of red blood cell volume following 2-unit red blood cell apheresis

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

BACKGROUND

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.

STUDY DESIGN AND METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Impact of allogeneic 2-RBC apheresis on iron stores of Brazilian blood donors

One limiting factor for automated two-red blood cells collections (2-RBC) is its potential iron depletion. We analyzed hematological parameters and iron balance before, two and four months after 2-RBC of 96 non-supplemented male donors. Four months after 2-RBC, ferritin level was significantly lower (P<0.01) than baseline levels and the number of donors who presented ferritin <30 ng/ml increased from 18 to 47. We concluded that four months was not sufficient for iron recuperation in the population studied. In an attempt to avoid iron depletion after 2-RBC, we recommend augmentation in the interval between blood donations and pre-donation ferritin measurement.

Safety of RBC apheresis and whole blood donation in allogeneic and autologous blood donors

Automated red cell collection is now a well-established technology. As with any new method, the risks and benefits must be weighed against older approaches, in this case manual collection. Although widely perceived to be safe, manual collection is associated with a number of potential complications, some of which can be serious, even debilitating. The safety record of 2-RBC and other RBC automated procedures is excellent. Physiologic, cardiovascular, and neurocognitive responses are modest and fall within those seen for manual collection. The long term effects related to erythropoietic response and iron loss are manageable and are similar to the effects of repeated whole blood donation. The collection of whole blood by manual means has been performed for nearly a century and as result the safety of this procedure is assumed. Conversely, the safety of automated collection in general and particularly RBC has had to "prove" itself, primarily because it is much more recent and is a different paradigm. Millions of procedures have been performed using both approaches. The blood donor, the "raw material" which makes hemotherapy possible, is the essential enabler in these processes. This article examines the complications of both manual and automated RBC collection.