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[In vitro evaluation of hemolytic effects with use of infusion pumps with finger peristaltic action of blood pumping].

INTRODUCTION
Blood cells pumped by technical systems are exposed to non-physiological mechanical stress. Haemolysis or subhaemolytic damage may occur. Interaction between cells and the artificial material as well as the shear stress are the main reasons for this traumatisation. Up to now in vitro evaluation is the method of choice as no profound theory of mechanical cell damage has existed yet and, furthermore, haemolytic effects exhibit al large biological variability.


METHODS
This study deals with the mechanically induced haemolysis due to blood pumping by infusion pumps (type INCA; Fresenius AG) in dependence on device related as well as blood preserve related (donor, storage time) factors. RBC count, MCV, MCHC, hematocrit, total and extracellular haemoglobin were obtained before and after pumping the blood sample.


RESULTS
At a pump rate of 1000 ml/h, 0.06% of RBC (storage duration of 1-3 days) and 0.3% (storage duration of 34-36 days) were destroyed, respectively. Furthermore, it was shown that only gravity induced perfusion of the Intra-Air-system and the tubing system without any pumping lead to a minor, but significant elevation of extracellular haemoglobin concentration. In contrast, a volume flow rate of 2000 ml/h or the 10 times repeated pump process (1000 ml/h) increases haemolysis by only 27% or 520% respectively.


CONCLUSION
It was concluded that any extrapolation from given experimental conditions to other ones must be performed with great caution due to the complex nature of the haemolysis process. Infusion pumps of the INCA-type stress RBC only slightly and may therefore be used for controlled blood transfusion.