目的  观察混合稀释血液透析滤过(mixed predilution and postdilution hemodiafiltration，mixed-HDF)对维持性血液透析(maintenance hemodialysis,MHD)患者的溶质清除效果。 方法  采用自身交叉对照研究法，选择符合纳排标准的MHD患者共10例，每周常规血液透析(hemodialysis,HD)治疗3次，每月血液透析滤过(hemodiafiltration，HDF)1次，每次治疗时间4小时，分别完成前稀释血液透析滤过(predilution hemodiafiltration，pre-HDF)、后稀释血液透析滤过(postdilution hemodiafiltration，post-HDF)和mixed-HDF治疗，根据前置换液量和后置换液量的分配情况将mixed-HDF分为2:1、1.5:1和1:1 mixed-HDF组；采集治疗前、后血标本，观察血常规变化，比较血尿素氮(BUN)、血肌酐(Scr)、磷(P)、β2微球蛋白(β2-microglobulin，β2-MG)、甲状旁腺激素(PTH)等清除情况。观察治疗过程中低血压、高血压、肌肉痉挛等不良反应情况，记录透析器和体外循环管路的凝血情况。 结果  共纳入10例患者，均完成5种不同模式HDF治疗。其中2:1、1.5:1、1:1 mixed-HDF的BUN清除率与pre-HDF(t=-0.576,1.150,0.215；P=0.290,0.140,0.417)、post-HDF(t=-1.054,0.243,-1.168；P=0.161,0.407,0.136)比较差异无统计学意义。Scr清除率：1.5:1高于2:1 mixed-HDF(t=1.893,P=0.047)。P清除率：1:1 mixed-HDF对P清除率高于pre-HDF(t=2.171,P=0.029)，2:1、1.5:1 mixed-HDF对比pre-HDF    (t=1.677,1.734；P=0.064,0.058)和post-HDF(t=0.735,0.545；P=0.240,0.300)组间差异无统计学意义。1.5:1 mixed-HDF对β2-MG的清除率高于post-HDF(t=3.314,P=0.005)，2:1、1:1 mixed-HDF对比pre-HDF(t=1.218,0.879；P=0.127,0.201)和post-HDF(t=1.235,0.837；P=0.124,0.212)组间差异无统计学意义。对PTH的清除率，1.5:1 mixed-HDF高于post-HDF(t=1.870,P=0.047)，2:1、1:1 mixed-HDF对比post-HDF(t=1.479,0.974；P=0.087,0.178)及pre-HDF(t=-0.672,-0.833；P=0.259,0.213)组间差异无统计学意义。 结论  mixed-HDF对小分子溶质和中大分子溶质均具有高效清除能力。mixed-HDF对小分子溶质清除率与pre-HDF和post-HDF相当，对中大分子溶质清除率高于post-HDF和pre-HDF。

Objective To observe the effect of mixed predilution and postdilution hemodiafiltration (mixed-HDF) on solute removal in maintenance hemodialysis (MHD) patients.  Methods  Ten MHD patients who met the inclusion and exclusion criteria were selected in this self-cross-control study. They were treated with conventional hemodialysis (HD) three times a week and HDF once a month. Each hemodialysis lasted 4 hours. HDF was performed in the order of predilution hemodiafiltration (pre-HDF), postdilution hemodiafiltration (post-HDF), and mixed-HDF. According to the distribution of pre-displacement fluid volume and post-displacement fluid volume, the mixed-HDF was divided into 2:1 mixed-HDF group, 1.5:1 mixed-HDF group and 1:1 mixed-HDF group. Blood samples before and after the treatment were collected to observe the changes of blood routine, blood urea nitrogen (BUN), serum creatinine (Scr), phosphorus (Phos), β2-microglobulin       (β2-MG) and parathyroid hormone (PTH) before and after the hemodialysis. Adverse reactions during treatment including blood pressure change, muscle spasm, and coagulation in dialyzer and extracorporeal circulation circuit were observed.  Results  The 10 MHD patients completed the 5 different modalities of HDF treatment. The BUN clearance rates of 2:1, 1.5:1, and 1:1 mixed-HDF had no significant differences with the BUN clearance rates of pre-HDF (t=-0.576, 1.150 and 0.215 respectively; P=0.290, 0.140 and 0.417 respectively) and post-HDF (t=-1.054, 0.243 and -1.168 respectively; P=0.161, 0.407 and 0.136 respectively). The Scr clearance rate was higher in 1:1 mixed-HDF than in 2:1 mixed-HDF (t=1.893, P=0.047). The clearance rate of Phos was significantly higher in 1:1 mixed-HDF than in pre-HDF (t=2.171, P=0.029), but had no significant differences as compared with the rates of 2:1 and 1.5:1 mixed-HDF with the rates of pre-HDF (t=1.677 and 1.734; P=0.064 and 0.058) and post-HDF (t=0.735 and 0.545; P=0.240 and 0.300). The clearance rate of β2-MG was significantly higher in 1.5:1 mixed-HDF than in post-HDF (t=3.314, P=0.005), but had no significant differences as compared the rates of 2:1 and 1:1 mixed-HDF with the rates of pre-HDF (t=1.218 and 0.879; P=0.127 and 0.201) and post-HDF (t=1.235 and 0.837; P=0.124 and 0.212). The clearance rate of PTH was higher in 1.5:1 mixed-HDF than in post-HDF (t=1.870, P=0.047), but had no significant differences as compared the rates of 2:1 and 1:1 mixed-HDF with the rates of pre-HDF (t=-0.672 and -0.833; P=0.259 and 0.213) and post-HDF (t=1.479 and 0.974; P=0.087 and 0.178).  Conclusion  Mixed-HDF has the ability of efficient clearance of small molecule solutes as well as medium and large molecule solutes. For clearance of small molecule solutes, mixed-HDF has the similar efficiency as pre-HDF and post-HDF; for clearance of medium and large molecule solutes, mixed-HDF has the efficiencies higher than pre-HDF and post-HDF.