Santoro A, Tetta C, Mandolfo S, Arrigo S, Berti M, Colasanti G, D'Amico G, Imbasciati E, Mazzocchi C, Pacini G, Spongano M, Thomaseth K, Wratten M L, Zucchelli P
Divisione di Nefrologia e Dialisi, Ospedale S. Orsola-Malpighi, Via P. Palagi, 9, 40138 Bologna, Italy.
Nephrol Dial Transplant. 1996 Jun;11(6):1084-92.
Calculation of Kt/V and assessment of nutrition have so far been dependent upon off-line urea measurements of blood or dialysate samples. Here we describe a biosensor for on-line urea measurement during haemodiafiltration. Methods. The biosensor consisted of a cartridge containing covalently linked urease placed between two conductivity cells. The biosensor was placed on the outlet line of a haemofilter in series with a dialyser in order to obtain an aliquot of plasma ultrafiltrate for on-line measurement of urea.
Urea nitrogen concentrations were highly correlated to the difference (Delta) in conductivity measured by the two conductivity cells both in aqueous solutions (in-vitro studies, y=-6. 676+32.12x, R2=0.998, P<0.0001) and in ultrafiltrates (ex-vivo studies, y=-637+32.01x, R2=0.98, P<0.00001). Delta conductivity was highly reproducible (% variation: ).8-5.3%) and stable (maximal % variation at 150 mg/dl after 100 min. 0.9+/-0.3 vs initial values). The intradialytic plasma water urea profile was obtained in 10 haemodialysis patients. To study recirculation, the plasma water urea profile was analysed before and 3 min after stopping the dialysate flow. The pre- and post-stopped flow ratio (1.21+/-0.1, mean+/-1 SD) was superimposable to conventional blood sampling data (opposite arm venous arterial: 1.22+/-0.11) and allowed correction for recirculation. A novel approach to urea kinetic modelling was described and used to reliably project end-dialysis and post-dialysis rebound urea concentration as early as 90 min. Projected (29.2+/-10.4 g) or measured (29.8+/-10.5 g) net urea removal was highly correlated with the amount of urea collected in the total spent dialysate (29.7+/-10.6 g) (R2=0.99, R2=0.97 respectively).
These results indicate that on-line, real-time analysis of urea kinetics may provide information on delivery of adequate dialysis in high-efficiency techniques.
迄今为止，Kt/V的计算和营养评估依赖于对血液或透析液样本进行离线尿素测量。在此，我们描述一种用于血液透析滤过过程中在线测量尿素的生物传感器。方法：该生物传感器由一个装有共价连接脲酶的试剂盒组成，试剂盒置于两个电导率池之间。生物传感器与透析器串联放置在血液滤过器的出口管线上，以便获取一份血浆超滤液用于在线测量尿素。
在水溶液（体外研究，y = -6.676 + 32.12x，R² = 0.998，P < 0.0001）和超滤液（离体研究，y = -637 + 32.01x，R² = 0.98，P < 0.00001）中，尿素氮浓度与两个电导率池测量的电导率差值（Δ）高度相关。Δ电导率具有高度可重复性（变异百分比：0.8 - 5.3%）且稳定（100分钟后150mg/dl时最大变异百分比为0.9 ± 0.3与初始值相比）。在10例血液透析患者中获得了透析过程中的血浆水尿素曲线。为研究再循环，在停止透析液流动前和停止后3分钟分析血浆水尿素曲线。停止流动前后的比率（1.21 ± 0.1，均值 ± 1标准差）与传统血液采样数据（对侧臂静脉 - 动脉：1.22 ± 0.11）可叠加，并可用于校正再循环。描述了一种尿素动力学建模的新方法，并用于早在90分钟时可靠地预测透析结束时和透析后反跳尿素浓度。预测的（29.2 ± 10.4g）或测量的（29.8 ± 10.5g）净尿素清除量与总用过的透析液中收集的尿素量（29.7 ± 10.6g）高度相关（分别为R² = 0.99，R² = 0.97）。
这些结果表明，尿素动力学的在线实时分析可能为高效技术中充分透析的实施提供信息。
