Purpose

Currently used cannulae for extracorporeal carbon dioxide removal (ECCO₂R) are associated with complications such as thrombosis and distal limb ischemia, especially for long-term use. We hypothesize that the risk of these complications is reducible by attaching hemodynamically optimized grafts to the patient’s vessels. In this study, as a first step towards a long-term stable ECCO₂R connection, we investigated the feasibility of a venovenous connection to the common iliac veins. To ensure its applicability, the drainage of reinfused blood (recirculation) and high wall shear stress (WSS) must be avoided.

Methods

A reference model was selected for computational fluid dynamics, on the basis of the analysis of imaging data. Initially, a sensitivity analysis regarding recirculation was conducted using as variables: blood flow, the distance of drainage and return to the iliocaval junction, as well as the diameter and position of the grafts. Subsequently, the connection was optimized regarding recirculation and the WSS was evaluated. We validated the simulations in a silicone model traversed by dyed fluid.

Results

The simulations were in good agreement with the validation measurements (mean deviation 1.64%). The recirculation ranged from 32.1 to 0%. The maximum WSS did not exceed 5.57 Pa. The position and diameter of the return graft show the highest influence on recirculation. A correlation was ascertained between recirculation and WSS. Overall, an inflow jet directed at a vessel wall entails not only high WSS, but also a flow separation and thereby an increased recirculation. Therefore, return grafts aligned to the vena cava are crucial.

Conclusion

In conclusion, a connection without recirculation could be feasible and therefore provides a promising option for a long-term ECCO₂R connection.

中文翻译：

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用于体外二氧化碳去除的长期静脉连接（ECCO2R）-与普通I静脉连接的数值研究。

目的

当前使用的用于去除体外二氧化碳（ECCO ₂ R）的套管与诸如血栓形成和远端肢体缺血之类的并发症有关，特别是对于长期使用而言。我们假设通过将血液动力学优化的移植物附着到患者​​血管上可以降低这些并发症的风险。在这项研究中，作为迈向长期稳定ECCO ₂ R连接的第一步，我们研究了静脉连接common总静脉的可行性。为了确保其适用性，必须避免回输血液（再循环）和高壁切应力（WSS）。

方法

在分析成像数据的基础上，选择参考模型进行流体动力学计算。最初，使用以下变量进行有关再循环的敏感性分析：血流量，引流和返回return腔交界处的距离以及移植物的直径和位置。随后，针对再循环对连接进行了优化，并对WSS进行了评估。我们验证了在染液穿过的有机硅模型中的仿真。

结果

模拟与验证测量值非常一致（平均偏差为1.64％）。再循环的范围从32.1到0％。最大WSS不超过5.57 Pa。回流移植物的位置和直径对再循环的影响最大。确定了再循环与WSS之间的相关性。总体而言，指向容器壁的流入射流不仅需要较高的WSS，而且还需要分流，从而增加了再循环。因此，与腔静脉对齐的回流移植至关重要。

结论

总之，没有再循环的连接是可行的，因此为长期ECCO ₂ R连接提供了一个有希望的选择。