Department of Medicine, National University Health System, Singapore.
Faculty of Medicine, Institute of Health and Science Technology, Aalborg University, Aalborg, Denmark.
Crit Care Med. 2020 Jul;48(7):e592-e598. doi: 10.1097/CCM.0000000000004351.
We designed a novel respiratory dialysis system to remove CO2 from blood in the form of bicarbonate. We aimed to determine if our respiratory dialysis system removes CO2 at rates comparable to low-flow extracorporeal CO2 removal devices (blood flow < 500 mL/min) in a large animal model.
Experimental study.
Animal research laboratory.
Female Yorkshire pigs.
Five bicarbonate dialysis experiments were performed. Hypercapnia (PCO2 90-100 mm Hg) was established in mechanically ventilated swine by adjusting the tidal volume. Dialysis was then performed with a novel low bicarbonate dialysate.
We measured electrolytes, blood gases, and plasma-free hemoglobin in arterial blood, as well as blood entering and exiting the dialyzer. We used a physical-chemical acid-base model to understand the factors influencing blood pH after bicarbonate removal. During dialysis, we removed 101 (±13) mL/min of CO2 (59 mL/min when normalized to venous PCO2 of 45 mm Hg), corresponding to a 29% reduction in PaCO2 (104.0 ± 8.1 vs 74.2 ± 8.4 mm Hg; p < 0.001). Minute ventilation and body temperature were unchanged during dialysis (1.2 ± 0.4 vs 1.1 ± 0.4 L/min; p = 1.0 and 35.3°C ± 0.9 vs 35.2°C ± 0.6; p = 1.0). Arterial pH increased after bicarbonate removal (7.13 ± 0.04 vs 7.21 ± 0.05; p < 0.001) despite no attempt to realkalinize the blood. Our modeling showed that dialysate electrolyte composition, plasma albumin, and plasma total CO2 accurately predict the measured pH of blood exiting the dialyser. However, the final effluent dose exceeded conventional doses, depleting plasma glucose and electrolytes, such as potassium and phosphate.
Bicarbonate dialysis results in CO2 removal at rates comparable with existing low-flow extracorporeal CO2 removal in a large animal model, but the final dialysis dose delivered needs to be reduced before the technique can be used for prolonged periods.
我们设计了一种新型呼吸透析系统，以碳酸氢盐的形式从血液中去除 CO2。我们旨在确定我们的呼吸透析系统是否以与低流量体外 CO2 去除装置（血流<500ml/min）相当的速度从大型动物模型中去除 CO2。
实验研究。
动物研究实验室。
雌性约克夏猪。
进行了 5 次碳酸氢盐透析实验。通过调整潮气量，在机械通气的猪中建立高碳酸血症（PCO2 90-100mmHg）。然后用新型低碳酸氢盐透析液进行透析。
我们测量了动脉血中的电解质、血气和血浆游离血红蛋白，以及进入和离开透析器的血液。我们使用物理化学酸碱模型来了解碳酸氢盐去除后影响血液 pH 的因素。在透析过程中，我们去除了 101（±13）ml/min 的 CO2（归一化到静脉 PCO2 为 45mmHg 时为 59ml/min），对应于 PaCO2 降低 29%（104.0±8.1 与 74.2±8.4mmHg；p<0.001）。透析过程中分钟通气量和体温不变（1.2±0.4 与 1.1±0.4L/min；p=1.0 和 35.3°C±0.9 与 35.2°C±0.6；p=1.0）。尽管没有尝试重新碱化血液，但碳酸氢盐去除后动脉 pH 升高（7.13±0.04 与 7.21±0.05；p<0.001）。我们的模型表明，透析液电解质组成、血浆白蛋白和血浆总 CO2 准确预测了透析器出口血液的实测 pH。然而，最终的透析剂量超过了常规剂量，耗尽了血浆葡萄糖和电解质，如钾和磷酸盐。
在大型动物模型中，碳酸氢盐透析以与现有低流量体外 CO2 去除相当的速度去除 CO2，但在该技术可用于延长时间之前，需要减少输送的最终透析剂量。
