The effects of on the rheologic properties and oxygen transport capacity of red blood cells processed by 3 different types of cell savers, and its effects on microcirculatory blood flow and tissue oxygenation in vivo

Cell savers are routinely used in our hospital during off-pump coronary artery
bypass grafting to retrieve and wash blood that is lost during the operation.
This washed blood is retransfused to the patient in order to prevent allogeneic
blood transfusion. However, little is known about the rheologic properties and
oxygen transport capacity of the washed red blood cells and the effects of
retransfusion of this blood on microcirculatory blood flow and organ damage in
the patient.
For cell savers 3 different operating principles exist. The most common one
uses discontinuous blood washing with a spinning bowl that is intermittently
filled with blood, processed and emptied. A second one uses a continuous blood
washing principle with a rotational disk. A third one is intermediate using
features of both the discontinuous bowl technology and the continuous
rotational disc technology.
We hypothesize that the operating principle has effects on the rheologic
properties and oxygen transport capacity of the washed blood. Previous research
suggested that in particular the deformability and oxygen carrier properties of
the red blood cells are affected. As a consequence, red blood cells may block
small blood vessels, which affects microcirculatory blood flow and tissue
oxygenation. This may lead to organ damage.

The objective of this study is to determine in vitro the rheologic and oxygen
transport capacity of the washed blood processed by one of 3 different cell
savers and to measure in vivo after retransfusion of this processed blood in
the patient the effects on microcirculatory blood flow and tissue oxygenation
using laser doppler and near infra-red spectroscopy, and on organ damage using
organ specific biomarkers.

Randomized Prospective, interventional trial

randomized to one of the three cellsavers

The microcirculatory blood flow is measured with a small 3 mm thick sensor in
the mouth of the patient. This may be considered as a burden for the patient on
the first postoperative day when they are awake. Blood (30 mL in total) for
analysis of biomarkers will be drawn from an arterial line that is routinely
inserted for these operations. Urine (15 mL in total) will be collected from
the urinary catheter that is routinely inserted for these operations. Due to
the observational character of this study and the non-invasive microcirculatory
measurements, the risks for the patients are negligible. Up to now we are
unaware of adverse events related to the use of the cell savers or the
microcirculatory measurements. Participation will therefore not increase the
risk of the operation, but will also not have immediate benefits for the
individual patient.