Jean G, Chazot C, Charra B, Terrat J C, Vanel T, Calemard E, Laurent G
Centre de Rein Artificiel, Tassin, France.
Blood Purif. 1998;16(4):187-96. doi: 10.1159/000014334.
According to previous studies, postdialysis urea rebound (PDUR) is achieved within 30-90 min, leading to an overestimation of Kt/V of between 15 and 40% in 3- to 5-hour dialysis. The purpose of the study was to assess the impact of PDUR on the urea reduction ratio (URR), Kt/V and normal protein catabolic rate (nPCR) with long 8-hour slow hemodialysis.
This study was performed in 18 patients (13 males/5 females), 62.5 +/- 11.7 years of age, hemodialyzed for 3-265 months. Initial nephropathies were: 3 diabetes; 2 polycystic kidney disease; 3 interstitial nephritis; 2 nephrosclerosis; 3 chronic glomerulonephritis, and 5 undetermined. Residual renal function was negligible. The dialysis sessions were performed using 1- to 1.8-m2 cellulosic dialyzers during 8 h, 3 times a week. Blood flow was 220 ml/min, dialysate flow 500 ml/min, acetate or bicarbonate buffer was used. Serial measurements of the urea concentration were obtained before dialysis, immediately after dialysis (low flow at t = 0), and at 5, 10, 20, 30, 40, 60, 90 and 120 min, and before the next session. The low-flow method was used to evaluate the access recirculation, second-generation Daugirdas formulas for Kt/V, and Watson formulas for total body water volume estimation. The difference between the expected urea generation (UG) and urea measured after dialysis (global PDUR) defines net PDUR (n-PDUR).
The n-PDUR usually became stable after 58 +/- 25 (30-90) min. Its mean value was 17 +/- 10% of the 30-second low-flow postdialysis urea (3.9 +/- 2 mmol/l). This small postdialysis urea value and the importance of UG in comparison with shorter dialysis justify the use of n-PDUR. Ignoring n-PDUR would lead to a significant 4% overestimation (p < 0.001) of the URR (79 +/- 7 vs. 76 +/- 8%), 12% of Kt/V (1.9 +/- 0.4 to 1.7 +/- 0.38) and 4% of the nPCR (1.1 +/- 0.3 to 1.05 +/- 0.3). n-PDUR correlated negatively with postdialysis urea (r = 0.45 p = 0.05), positively with URR (r = 0.31 p = 0.01) and Kt/V (r = 0.3 p = 0.03) but not with K, and negatively with the urea distribution volume (r = 0.33 p = 0.05). Mean total recirculation, ultrafiltration rate, predialysis urea levels and urea clearance did not correlate with n-PDUR.
We found a significant PDUR in long-slow hemodialysis after a mean of 1 h after dialysis. This PDUR has a less important impact upon dialysis delivery estimation than short 3- to 5-hour hemodialysis, especially for the lower Kt/V or URR ranges. This is explained by the low-flux, high-efficiency, and long-term dialysis. Its inter-individual variability incites us to calculate PDUR on an individual basis.
根据以往研究，透析后尿素反弹（PDUR）在30 - 90分钟内出现，导致在3至5小时的透析过程中Kt/V被高估15%至40%。本研究的目的是评估在长达8小时的缓慢血液透析中PDUR对尿素清除率（URR）、Kt/V和正常蛋白分解代谢率（nPCR）的影响。
本研究纳入18例患者（13例男性/5例女性），年龄62.5±11.7岁，血液透析3 - 265个月。初始肾病类型为：3例糖尿病；2例多囊肾；3例间质性肾炎；2例肾硬化；3例慢性肾小球肾炎，5例未明确。残余肾功能可忽略不计。透析疗程使用1至1.8平方米的纤维素透析器，持续8小时，每周3次。血流量为220毫升/分钟，透析液流量500毫升/分钟，使用醋酸盐或碳酸氢盐缓冲液。在透析前、透析后即刻（t = 0时低流量）、5、10、20、30、40、60、90和120分钟以及下次透析前连续测量尿素浓度。采用低流量法评估通路再循环，使用第二代Daugirdas公式计算Kt/V，使用Watson公式估算总体液量。预期尿素生成量（UG）与透析后测量的尿素之间的差值定义为净PDUR（n - PDUR）。
n - PDUR通常在58±25（30 - 90）分钟后趋于稳定。其平均值为透析后30秒低流量尿素的17±10%（3.9±2毫摩尔/升）。与较短透析相比，这种较小的透析后尿素值以及UG的重要性证明了使用n - PDUR的合理性。忽略n - PDUR会导致URR显著高估4%（p < 0.001）（79±7%对76±8%）、Kt/V高估12%（1.9±0.4至1.7±0.38）以及nPCR高估4%（1.1±0.3至1.05±0.3）。n - PDUR与透析后尿素呈负相关（r = 0.45，p = 0.05），与URR呈正相关（r = 0.31，p = 0.01）以及与Kt/V呈正相关（r = 0.3，p = 0.03），但与钾无关，与尿素分布容积呈负相关（r = 0.33，p = 0.05）。平均总再循环、超滤率、透析前尿素水平和尿素清除率与n - PDUR均无相关性。
我们发现在长时间缓慢血液透析中，透析后平均1小时会出现显著的PDUR。与3至5小时的短时间血液透析相比，这种PDUR对透析剂量评估的影响较小，尤其是对于较低的Kt/V或URR范围。这是由低通量、高效率和长期透析所解释的。其个体间变异性促使我们基于个体情况计算PDUR。
