Autologous blood transfusion and cardiopulmonary bypass did not have an effect on RBC deformability or aggregation. (Image source: Thinkstock)

Autologous blood transfusion and cardiopulmonary bypass did not have an effect on RBC deformability or aggregation. (Image source: Thinkstock)

Blood delivers oxygen to the body’s tissues.  Wine may improve from aging, but oxygen delivery capacity of blood decreases with age. Oxygen delivery of blood is related to the quality of the red cell membrane. As the membrane stiffens, the cell become less deformable, and less readily traverses small capillary vascular beds.  As it ages, stored blood is also more likely to aggregate, which also compromises blood flow through small capillary vascular beds.  Cardiopulmonary bypass can also affect red blood cell quality.

Dr. Steven M. Frank, Department of Anesthesiology/Critical Care Medicine, The Johns Hopkins Medical Institutions, Baltimore, Maryland, and colleagues used a microfluidic slit-flow ektacytometer to measure deformability and aggregation of red blood cells in patients who underwent cardiac surgery with cardiopulmonary bypass.  The results of their study are published in this month’s issue of Anesthesia & Analgesia in the article “Impaired Red Blood Cell Deformability After Transfusion of Stored Allogeneic Blood but not Autologous Salvaged Blood in Cardiac Surgery Patients.”

In this prospective cohort (not randomized) study, autologous blood was salvaged during and after cardiopulmonary bypass from the surgical field and from the extracorporeal circuit respectively.  Blood samples were obtained from 32 patients through radial artery catheters at different times before, during, and after surgery. Twelve patients received only autologous salvaged red cells, ten patients also received < 4 units of stored allogeneic blood, and ten received autologous salvaged RBCs and 5-12 units of stored allogeneic blood.  Patients whose sternotomy was revised received more stored blood. Cardiopulmonary bypass duration was longer in patients who received more allogeneic blood units.

If patients underwent cardiopulmonary bypass and received autologous blood, RBC deformability did not change. Red cell deformability was decreased, particularly in patients who received more units of allogeneic blood, or in those who received allogeneic blood, compared to those who did not.  By postoperative day 3, for those patients who received less autologous and less allogeneic blood, these changes had mostly reversed. However, reversal was incomplete amongst those who received more allogeneic blood.  Whether deformability of red cells is associated with adverse outcome is not clear, though based on other studies, adverse outcome is higher for those who receive more allogeneic blood.

Red cell aggregation was lowest after cardiopulmonary bypass and after surgery, particularly in patients who did not receive any allogeneic blood.  Red cell aggregation was no different between groups.  Baseline levels returned 48 hours after surgery.

It is unclear what effect cardiopulmonary bypass or allogeneic blood would have alone since all patients who underwent cardiopulmonary bypass also received autologous (i.e., salvaged) blood.  We were also not told how long the blood allogeneic blood was stored.  However, we do know that autologous blood and cardiopulmonary bypass, together, did not have an effect on either RBC deformability or aggregation.