Biocompatibility of leukocyte removal filters during leukocyte filtration of cardiopulmonary bypass perfusate

Interaction of Activated Leukocytes with Polymeric Microspheres

Three types of polymeric particles with different surface wettabilities, i.e., poly(methylmethacrylate) (PMMA), poly(methylmethacrylate-hydroxyethylmethacrylate) (P(MMA/HEMA)) and poly(methylmethacrylate)/poly(vinyl alcohol) PMMA/PVAL with a diameter of 1.5 μm were produced in this study. These particles were incubated with blood samples obtained both from three patients undergoing cardiopulmonary bypass. In the blood samples taken before the bypass operations, there was considerable phagocytosis and/or adhesion of the PMMA particles, i.e., 14±4 particles per monocyte and 11±3 particles per neutrophil. While there was almost no phagocytosis and/or adhesion of the P(MMA/HEMA) and PMMA/PVAL particles. In the blood samples which were taken during bypass operations, phagocytosis and/or adhesion of PMMA microspheres increased significantly. The P(MMA/HEMA) and/or PMMA/PVAL particles adhered, or were even phagocytosed by the activated leukocytes in this case. Leukocytes activated during the bypass operations gradually returned to normal in about 24 h.

Extracorporeal tumor cell filtration during extended liver surgery: first clinical use of leukocyte depletion filters--case series

Background

During oncologic surgery, intraoperative manipulation of tumor tissue is almost unpreventable and causes a high risk of tumor cell dissemination into venous blood. A tumor cell-reducing effect of leukocyte adhesion filter systems has been shown under in vitro conditions.

Methods

In a first clinical attempt, leukocyte adhesion filters were integrated into veno-venous bypass systems in four patients undergoing extended liver surgery for secondary hepatic malignancies.

Practicability, handling, and safety aspects as well as potency of cell removal and clinical side effects of the filter system were analyzed.

Results

All patients tolerated the application of the system without problems during operative and postoperative follow-up. Immunohistochemical staining of perioperative blood samples detected cytokeratin positive (CK+) cells in three cases during the hepatic mobilization.

Conclusions

Effectiveness of CK+ cell depletion and safety of the procedure was shown. The presented surgical technique represents a safe and innovative tool; however, clinical significance has to be examined in a larger patient cohort.

Is reduced systemic heparinization justified with heparin-bonded bypass circuits in cardiac surgery?--Experience with and without aprotinin

The effects of aprotinin combined with heparin-bonded bypass circuits and reduced systemic heparinization on haemostasis and inflammatory reactions were measured in patients with elective CABG operation. Patients were randomized to be operated on either without aprotinin (NOAPRO, n=15) or with aprotinin (APRO, n=15) at a low dose of 2 Mio KIU in the priming volume. Activated clotting time was adjusted to 400 +/- 50 s during cardiopulmonary bypass (CPB). Haemostasis (fibrinopeptide A (FPA), thrombin-antithrombin complex (TAT), D-Dimer, plasmin-antiplasmin (PAP), plasminogen-activator inhibitor (PAI)), inflammatory reaction (lactoferrin, IL-6, sTNF-IIR, SC5b-9) and clinical data were evaluated perioperatively. Perioperative clinical and laboratory data including mediastinal drainage volume, postoperative morbidity and mortality were comparable for patients in both groups. FPA was elevated in the APRO group during CPB (P=0.001), D-Dimer in the NOAPRO group after CPB (P=0.002). No differences were seen for TAT, PAP or PAI between the groups. Lactoferrin was elevated in NOAPRO at the end of CPB (P=0.01) and after heparin reversal with protamine sulphate (P=0.02). No intergroup differences were seen for IL-6, sTNF-IIR or SC5b-9 between the groups. In association with reduced heparinization, pump prime aprotinin retains its antifibrinolytic effect in modified bypass equipment with a heparin surface besides an anti-inflammatory effect in terms of inhibition of leukocyte activation. However, thrombin activation may be increased with aprotinin. We therefore recommend sufficient systemic heparinization despite heparin surface modification of bypass equipment.

Bradykinin generation in RC-MAP during storage at 4 degrees C and leukocyte removal filtration

We investigated contact system activation in red cell concentrate in mannitol-adenine-phosphate (MAP) solution (RC-MAP) during storage and leukocyte removal filtration. The contact system activation was assessed in terms of bradykinin (BK) generation. The BK level in the RC-MAP transiently but significantly (p < 0.05) increased at 7 to 14 days of storage. Moreover, the BK level in 21-day-stored RC-MAP was approximately 10 times higher than that in other blood components. The BK level in mannitol-containing MAP solutions, but not that in mannitol-free MAP solution, saline or whole blood, increased during storage. The plasma angiotensin-converting enzyme (ACE) activity decreased significantly only in mannitol-containing MAP solutions. These findings suggest that mannitol plays an essential role in the increase in BK level in RC-MAP. Furthermore, the BK level in RC-MAP increased 10 minutes after the start of filtration through a negatively charged filter, either a BPF-4 or an RN-40, and reached a maximum of 6,000 pg/ml. Hypotensive reactions are rare in RC-MAP transfusion in comparison to their incidence in platelet concentrate (PC) transfusion in spite of the higher BK level in RC-MAP than in PC. Therefore, BK generation in various blood components is not likely to be the main cause of hypotensive reactions. However, the level of BK in RC-MAP is sufficiently high to cause site pain. Further investigation on the clinical significance of a high BK level in blood components is necessary.

Endothelial cell injury in cardiovascular surgery: the systemic inflammatory response

Many of the components currently used to perform cardiovascular operations lead to systemic insults that result from cardiopulmonary bypass circuit-induced contact activation, circulatory shock, and resuscitation, and a syndrome similar to endotoxemia. Experimental observations have demonstrated that these events have profound effects on activating endothelial cells to recruit neutrophils from the circulation. Once adherent to the endothelium, neutrophils release cytotoxic proteases and oxygen-derived free radicals, which are responsible for much of the end-organ damage seen after cardiovascular operations. Recently the cellular and molecular mechanisms of endothelial cell activation have become increasingly understood. It is conceivable that once the molecular mechanisms of endothelial cell activation are better defined, therapies will be developed allowing the selective or collective inhibition of vascular endothelial activation during the perioperative period.

Leukocyte depletion results in improved lung function and reduced inflammatory response after cardiac surgery

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.