Leukocyte depletion during cardiopulmonary bypass has been demonstrated in animal experiments to improve pulmonary function. Conflicting results have been reported, however, with clinical depletion by arterial line filter of leukocytes at the beginning of cardiopulmonary bypass. In this study, we examined whether leukocyte depletion from the residual heart-lung machine blood at the end of cardiopulmonary bypass would improve lung function and reduce the postoperative inflammatory response. Thirty patients undergoing elective heart operations were randomly allocated to a leukocyte-depletion group or a control group. In the leukocyte-depletion group (n = 20), all residual blood (1.2 to 2.1 L) was filtered by leukocyte-removal filters and reinfused after cardiopulmonary bypass, whereas in the control group an identical amount of residual blood after cardiopulmonary bypass was reinfused without filtration (n = 10). Leukocyte depletion removed more than 97% of leukocytes from the retransfused blood (p < 0.01) and significantly reduced circulating leukocytes (p < 0.05) and granulocytes (p < 0.05) compared with the control group. Levels of the inflammatory mediator thromboxane B2 determined at the end of operation (p < 0.05) were significantly lower in the depletion group than in the control group, whereas no statistical differences in interleukin-6 levels were found between the two groups. After operation, pulmonary gas exchange function (arterial oxygen tension at a fraction of inspired oxygen of 0.4) was significantly higher in the leukocyte-depletion group 1 hour after arrival to the intensive care unit (p < 0.05) and after extubation (p < 0.05). There were no statistical differences between the two groups with respect to postoperative circulating platelet levels and blood loss, and no infections were observed during the whole period of hospitalization. These results suggest that leukocyte depletion of the residual heart-lung machine blood improves postoperative lung gas exchange function and is safe for patients who are expected to have a severe inflammatory response after heart operations.

The method of leucocyte depletion has been recently introduced to the field of cardiopulmonary bypass to reduce leucocyte-mediated organ dysfunction. In this study, we evaluated the efficacy and biocompatibility of the Pall RC400 filters for leucocyte depletion of heparinized cardiopulmonary bypass (CPB) perfusate taken from the heart-lung machine during routine cardiac surgery. For each filter, 700 ml blood were used as filtrate. Filtration was divided into the following groups to study the effect of loading pressure on the efficacy of the filters: under gravity pressure as a control (n = 8), under 100 mmHg (n = 8), 200 mmHg (n = 8), and 300 mmHg loading pressure (n = 8) driven by a roller pump. In addition, heparinized predonation blood taken at the beginning of CPB (n = 8) was filtered under gravity in comparison with the perfusate taken at the end of CPB. The results showed that the average leucocyte removal rate by an RC400 filter for 700 ml of blood was 96.8%. There was no significant difference of leucocyte removal rate between filtration under gravity and under loading pressure up to 300 mmHg. This allows clinical filtration at a speed up to 500 ml/min. The platelet removal rate was significantly higher in blood taken at the beginning of CPB than in blood taken at the end of CPB. Complment split product, C5a, increased only slightly during filtration indicating that this filter, made from polyester, has a good blood compatible characteristic. We conclude that the Pall RC400 leucocyte removal filter is suitable and safe to be used for leucocyte filtration of heparinized CPB perfusate during cardiac surgery.