Bammens Bert, Evenepoel Pieter, Verbeke Kristin, Vanrenterghem Yves
Department of Medicine, Division of Nephrology and Laboratory of Radiopharmaceutical Chemistry, University Hospital Gasthuisberg, Leuven, Belgium.
Kidney Int. 2003 Dec;64(6):2238-43. doi: 10.1046/j.1523-1755.2003.00310.x.
Current guidelines for peritoneal dialysis adequacy are based on kinetics of small water-soluble molecules and do not consider the role of other compounds such as middle molecules and protein-bound solutes. Information on the elimination characteristics of the latter solutes by peritoneal dialysis is limited. Moreover, their relation with uremic symptoms remains unclear. The aim of the present study was (1) to investigate the relative contribution of residual renal function to the overall clearances of beta2-microglobulin (beta2m), a middle molecule, and p-cresol, a protein-bound solute, in adults on peritoneal dialysis as compared to small water-soluble molecules and (2) to evaluate relations between serum levels and uremic symptoms.
We performed a cross-sectional observational study, including 30 nonanuric peritoneal dialysis patients. Total, peritoneal, and renal clearances were calculated for urea nitrogen (60 D), creatinine (113 D), phosphate (96 D), beta2m (11.8 kD), and p-cresol (108 D). All patients were asked to complete a uremic symptom questionnaire.
Declining total clearances (L/week/1.73 m2) were measured for urea nitrogen, creatinine, phosphate, beta2m, and p-cresol, respectively: 97.3 +/- 4.6, 98.9 +/- 6.1, 64.0 +/- 3.4, 23.1 +/- 2.6, and 17.5 +/- 2.3 (Friedman test P < 0.001). Conversely, the contribution of residual renal function (%) to the respective solute clearances increased significantly: 31.6 +/- 3.2, 51.0 +/- 4.0, 42.4 +/- 4.0, 68.0 +/- 5.4, 61.9 +/- 4.6 (Friedman test P < 0.001). The serum level of p-cresol, but of none of the other solutes examined, correlated significantly with the symptom score (Pearson r= 0.48, P= 0.008).
During peritoneal dialysis p-cresol behaves like beta2m, probably due to its protein binding. The total clearance of both molecules is significantly lower as compared to water-soluble solutes and mainly depends on residual renal function. Our data further suggest that protein-bound solutes are involved in the pathophysiology of uremic symptoms.
目前的腹膜透析充分性指南基于小水溶性分子的动力学，未考虑其他化合物如中分子和蛋白结合溶质的作用。关于腹膜透析对后一类溶质的清除特性的信息有限。此外，它们与尿毒症症状的关系仍不清楚。本研究的目的是：（1）调查与小水溶性分子相比，残余肾功能对腹膜透析成年患者中分子β2-微球蛋白（β2m）和蛋白结合溶质对甲酚的总清除率的相对贡献；（2）评估血清水平与尿毒症症状之间的关系。
我们进行了一项横断面观察性研究，纳入30例非无尿腹膜透析患者。计算尿素氮（60 D）、肌酐（113 D）、磷酸盐（96 D）、β2m（11.8 kD）和对甲酚（108 D）的总清除率、腹膜清除率和肾脏清除率。所有患者均被要求完成一份尿毒症症状问卷。
尿素氮、肌酐、磷酸盐、β2m和对甲酚的总清除率（L/周/1.73 m²）分别下降：97.3±4.6、98.9±6.1、64.0±3.4、23.1±2.6和17.5±2.3（Friedman检验P<0.001）。相反，残余肾功能对各溶质清除率的贡献（%）显著增加：31.6±3.2、51.0±4.0、42.4±4.0、68.0±5.4、61.9±4.6（Friedman检验P<0.001）。对甲酚的血清水平与症状评分显著相关（Pearson r=0.48，P=0.008），而其他所检测的溶质均无此相关性。
在腹膜透析期间，对甲酚的表现与β2m相似，可能是由于其蛋白结合特性。与水溶性溶质相比，这两种分子的总清除率显著降低，且主要取决于残余肾功能。我们的数据进一步表明，蛋白结合溶质参与了尿毒症症状的病理生理过程。
