The effect of prolonged perfusion with a membrane oxygenator (PPMO) on white blood cells

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Abstract
Preserving the rheological properties of whole blood cells is vital for their smooth passage in the capillaries without causing blockage and disturbances in the microcirculation. To evaluate the effect of mechanical trauma on the rheology of white blood cells during prolonged perfusion with membrane oxygenation (PPMO), 16 in vitro experiments were conducted for 72 hours. The St George Carrimed Filtrometer was used to estimate the plasma white cell filtration rates (P-WFR). Also an in vitro estimation of the ability of individual cells to pass through capillaries, the white blood cell clogging rate (WBC-CR), the number of clogging particles (WBC-CP), the total white blood cell count (T-WBC) and two in vitro estimations to assess the effect of aggregates and stiff cells in blocking the microcirculation were performed. The traumatized white cells reduced their mean P-WFR by 37% ± 9, 72% ± 2 and 76% ± 2 at 24, 48 and 72 hours respectively (p < 0.001). The mean WBC-CR was increased to 15.2 ± 1.5, 32.6 ± 2.2 and 40.3 ± 8.3 x 102%/ml at 24, 48 and 72 hours respectively (p < 0.001). The mean WBC-CP was increased to 6.6 ± 1.5, 9.7 ± 1.2 and 13.9 ± 2.1 x 106/ml at 24 hours (p < 0.05), 48 and 72 hours respectively (p < 0.001). The T-WBC was decreased to 55% ± 0.3, 23% ± 0.2 and 14% ± 0.1 at 24,48 and 72 hours respectively (p < 0.001). This study showed a serious loss in white cell rheology during PPMO, which may contribute to the plugging effect of the microvessels in clinical use and may explain the organ dysfunction seen during ECMO on the basis of inadequate tissue oxygenation and nutrition due to areas of reduced perfusion, which results in increased frequency of morbidity.