Original Article

Poor Blood Mixing in the Shiley Hardshell Venous Reservoir Proven by Changes in Hematological Data on Different Volume Levels

¹ Departments of Extra-Corporeal Circulation, University of Limburg, Academic Hospital, Maastricht, The Netherlands
² Departments of Cardiology, University of Limburg, Academic Hospital, Maastricht, The Netherlands
³ Departments of Cardiothoracic Surgery, University of Limburg, Academic Hospital, Maastricht, The Netherlands

^* Direct communications to: Ellen Retera E.K.P., Department of Extra-Corporeal Circulation, University of Limburg, Academic Hospital, Maastricht, The Netherlands.

Abstract

Low values in hematological data at the end of cardiopulmonary bypass (CPB) brought us to the hypothesis that this could be caused by a visible poor blood mixing phenomenon in the Shiley Hardshell Venous Reservoir (HSVR). To study this phenomenon, we designed an instrument enabling us to take blood samples from the venous reservoir at a level of 1000 ml (A), 500 ml (B) and 100 ml (C). Besides this blood sampling during CPB, we also took samples from the venous line (D). Twenty patients were studied during CPB. The first set of samples was taken 10 minutes after the aorta was occluded and cardioplegia was administered. Successive sampling took place at half hour intervals. The last set of samples were taken shortly after removal of the aortic crossclamp. We observed a marked decrease in the value of the hematocrit (Ht) at level A in the venous reservoir within 30 minutes. The Ht at this level dropped from 23.7% (SD± 2.8) to 6.5% (SD ± 7.3). This showed to be a significant difference in comparison with the values at the other sampling points after 30 minutes (P<0.001) which were respectively at level B: 24.7% (SD ± 2.9), C: 25.1% (SD ± 2.8) and D: 24.9% (SD ± 2.6). The differences between the Ht-values of B, C, and D showed no significant changes. The difference in Ht at level A versus level B, C and D remained until removal of the aortic crossclamp, at which time mixing in the reservoir appeared, due to short time volume changes. It is concluded that poor mixing of blood occurs in the Shiley HSVR depending on the amount of volume. However we could not prove in this study that unexpectedly low values in hematological data at the end of CPB are due to this phenomenon.