Mulvihill J, Crost T, Renaux J L, Cazenave J P
INSERM U.311, Laboratoire de Biologie et Pharmacologie des Interactions du Sang avec les Vaisseaux et les Biomatériaux, Etablissement de Transfusion Sanguine, Strasbourg, France.
Nephrol Dial Transplant. 1997 Sep;12(9):1968-73. doi: 10.1093/ndt/12.9.1968.
Precise evaluation of the haemocompatibility of prototype membranes, flow configurations and anticoagulant regimens is an essential step in the development of dialysis systems minimizing blood activation. An ex vivo model in humans currently employed in our laboratory has recently been adapted to allow the parallel evaluation of two minimodule dialysers with blood from a single donor, thus eliminating differences due to donor variability in the comparison of test and control dialysis modules.
The ex vivo flow system is designed to reproduce the haemodynamic conditions of clinical dialysis on a 1/50 scale. A blood line from the forearm vein of the volunteer donor is divided at a Y-shaped junction, two roller pumps assure equivalent blood flow (5 ml/min) in the branches leading to two minimodule dialysers and heparin (0.1 IU/ml final concentration) is injected into each branch immediately after the Y junction. Samples for analysis of blood activation markers are collected at the exits of the two minimodules over a test period of 27 min. In the present series of tests, a new polyacrylonitrile membrane (PAN) was evaluated relative to standard commercial polysulphone (PS), acrylonitrile copolymer (AN 69) and cuprophan (CUP) membranes.
A steady minimal level of anticoagulation corresponding to a slightly less than two-fold prolongation of APTT (activated partial thromboplastin time) was maintained throughout testing in both branches of the ex vivo flow system. Time curves for the accumulation of activation markers (thrombin-antithrombin III complexes, prothrombin fragment 1 + 2, platelet beta-thromboglobulin, and complement fragment C3a) showed all four types of minimodule dialyser to induce comparable low levels of activation of coagulation parameters and platelets, together with similar mild activation of complement for AN 69, PAN, and PS dialysers as compared to stronger activation for CUP modules. Overall results thus confirmed the acceptable haemocompatibility of the prototype polyacrylonitrile (PAN) membrane.
Among current methods for evaluation of the biocompatibility of haemodialysis systems, ex vivo flow models in humans avoid problems arising from species differences and may be designed to closely reproduce the conditions of clinical dialysis. A parallel configuration eliminates artefacts due to individual variations in donor response. This not only facilitates the direct comparison of test and control membranes under close to identical experimental conditions, but also provides a model particularly well adapted to studies of the effects of different anticoagulation regimens, flow configurations, and dialysates, or alternative methods of sterilization, rinsing, and priming of the dialysers.
准确评估原型膜、血流配置和抗凝方案的血液相容性是开发使血液激活最小化的透析系统的关键步骤。我们实验室目前使用的人体离体模型最近进行了改进，以允许使用来自单一供体的血液对两个小型透析器进行平行评估，从而消除了在比较测试和对照透析模块时由于供体差异而产生的差异。
离体血流系统设计为按1/50比例再现临床透析的血液动力学条件。来自志愿供体前臂静脉的一条血路在一个Y形连接处分开，两个滚轴泵确保在通向两个小型透析器的分支中血流相等（5毫升/分钟），并且在Y形连接处之后立即将肝素（最终浓度为0.1国际单位/毫升）注入每个分支。在27分钟的测试期内，在两个小型透析器的出口处采集用于分析血液激活标志物的样本。在本系列测试中，相对于标准商用聚砜（PS）、丙烯腈共聚物（AN 69）和铜仿膜（CUP），对一种新型聚丙烯腈膜（PAN）进行了评估。
在离体血流系统的两个分支的整个测试过程中，维持了稳定的最低抗凝水平，对应于活化部分凝血活酶时间（APTT）延长略少于两倍。激活标志物（凝血酶 - 抗凝血酶III复合物、凝血酶原片段1 + 2、血小板β - 血小板球蛋白和补体片段C3a）积累的时间曲线显示，所有四种类型的小型透析器诱导的凝血参数和血小板激活水平相当低，与CUP模块较强的激活相比，AN 69、PAN和PS透析器的补体激活程度相似且较轻。总体结果因此证实了原型聚丙烯腈（PAN）膜具有可接受的血液相容性。
在当前评估血液透析系统生物相容性的方法中，人体离体血流模型避免了物种差异引起的问题，并且可以设计成紧密再现临床透析的条件。平行配置消除了由于供体反应的个体差异而产生的假象。这不仅便于在几乎相同的实验条件下直接比较测试膜和对照膜，而且还提供了一个特别适合研究不同抗凝方案、血流配置和透析液的影响，或透析器的替代灭菌、冲洗和预充方法的模型。
