Depner T A, Rizwan S, Cheer A Y, Wagner J M, Eder L A
Department of Internal Medicine, University of California, Davis, Sacramento 95817.
ASAIO Trans. 1991 Jul-Sep;37(3):M141-3.
Resistance to urea diffusion among body fluid compartments diminishes the therapeutic effectiveness of hemodialysis. Cell membrane or capillary wall resistance is thought to be responsible for hemodialysis-induced urea disequilibrium. The authors examined the possibility that reduced blood flow might contribute to urea disequilibrium in the arm opposite the blood access site. Blood samples were taken simultaneously from a vein in the arm opposite the access site and from the arterial port after occluding the access graft between the needle sites for 1 min. Venous urea nitrogen levels from the opposite arm averaged 10% higher after 5 min, 26% higher after 60 min, and 36% higher after 120 min of dialysis. A three-compartment model of urea kinetics that includes a blood flow term accurately predicted all measured urea nitrogen concentrations in both arms. These data suggest that the opposite arm often behaves as a compartment with high resistance to urea diffusion. Slow diffusion from this compartment is partially due to reduced blood flow/compartment volume, and results in a delayed fall in venous blood urea nitrogen (BUN).
体液各腔室之间对尿素扩散的阻力会降低血液透析的治疗效果。细胞膜或毛细血管壁阻力被认为是血液透析引起尿素失衡的原因。作者研究了血流量减少可能导致血液通路部位对侧手臂出现尿素失衡的可能性。在将穿刺部位之间的血管通路移植物闭塞1分钟后，同时从血液通路对侧手臂的静脉和动脉端口采集血样。透析5分钟后，对侧手臂的静脉尿素氮水平平均高出10%，60分钟后高出26%，120分钟后高出36%。包含血流量项的尿素动力学三室模型准确预测了双臂中所有测量的尿素氮浓度。这些数据表明，对侧手臂通常表现为对尿素扩散具有高阻力的腔室。来自该腔室的缓慢扩散部分是由于血流量/腔室体积减少，导致静脉血尿素氮（BUN）下降延迟。
