Abstract: Objective To observe the clearance of protein-bound uremic toxins in maintenance hemodialysis (MHD) patients by combination of hemodialysis (HD) and hemoperfusion (HP). Methods A total of 60 MHD patients were randomly divided into 2 groups: HD+HP group (low-flux hemodialysis two times a week and the combined treatment of HD and HP once a week, n=30) and HD group (low-flux hemodialysis three times a week, n=30). High performance liquid chromatography tandem mass spectrometry (HPLC-MS/ MS) method was used to determine the serum concentrations of hippuric acid (HA), indoxyl sulfate (IS), pcresyl sulphate (PCS), and 3-carboxyl-4-methyl-5-2-methyl propyl furfuryl propionate (CMPF) before and after treatment, and the clearance rates of these toxins were calculated. These toxins were also determined in dialysate in HD group and in hemoperfusion apparatus in HD+HP group. Results After the treatment, serum HA decreased from 31.68±19.41mg/L to 11.63±9.48mg/L (t=6.652, P=0.000) in HD group, and from 32.34± 25.60mg/L to 12.60±8.42mg/L (t=6.114, P=0.000) in HD+HP group, with the HA clearance rate of 62.21± 10.01% in HD+HP group and 57.03±18.79% in HD group (t=-1.155, P=0.025). Serum PCS decreased from 28.87±10.51mg/L to 19.05±7.50mg/L (t=8.175, P=0.000) in HD group, and from 31.04±18.93mg/L to 15.61± 10.85mg/L (t=7.738, P=0.000) in HP+HD group, with the PCS clearance rate of 49.92±10.42% in HD+HP group and 34.13±10.13% in HD group (t=-5.302, P=0.003). Serum IS decreased from 31.96±16.30mg/L to 19.98±11.97mg/L (t=8.175, P=0.000) in HD group and from 32.89±16.66mg/L to 16.72±8.02mg/L (t=7.864, P=0.000) in HP+HD group, with the IS clearance rate of 47.67±11.37% in HD+HP group and 37.58±15.13% in HD group (t = -2.754, P = 0.008). Serum CMPF was unchanged in HD group (26.86 ± 19.93mg/L before HD and 28.97±14.40mg/L after HD; t=-2.013, P＞0.05), but decreased from 23.03±18.33mg/L to 11.79±12.07mg/L (t=5.324, P= 0.001) in HP+HD group, with the CMPF clearance rate of -4.79±23.44% in HD group and31.18±11.79% in HD+HP group (t=-3.384, P=0.002). The total solute clearance of HA, PCS, IS, and CMPF were 93.05 ± 61.87mg, 30.57 ± 10.93mg, 27.18 ± 15.55mg, and 0mg, respectively, in HD group, and were 126.14 ± 76.61 mg, 74.95±28.67mg, 82.36±26.96mg and 10.96±6.70mg, respectively, in HD+HP group, higher in HD+HP group than in HD group (P＜0.01). Conclusion HD + HP is better than HD in clearance of proteinbound uremic toxins.

Key words: Hemoperfusion, hemodialysis, protein-bound toxins, total solute removal