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Abstract: TH-PO350

Middle Molecules Elimination in Expanded Hemodialysis: Only Convective Transport?

Session Information

Category: Dialysis

  • 701 Dialysis: Hemodialysis and Frequent Dialysis


  • Macías, Nicolás, Hospital Gregorio Marañón., Madrid, Spain
  • Vega, Almudena, Hospital Gregorio Marañón., Madrid, Spain
  • Abad, Soraya, Hospital Gregorio Marañón., Madrid, Spain
  • Garcia Prieto, Ana M., Hospital Gregorio Marañón., Madrid, Spain
  • Torres aguilera, Esther, Hospital Gregorio Marañón., Madrid, Spain
  • Santos, Alba, Gregorio Mara?on Hospital, Madrid, Spain
  • Aragoncillo, Ines, Hospital Gregorio Marañón, Madrid, Spain
  • Luno, Jose, Hospital General Universitario Gregorio Marañón, Madrid, Spain

Hemodialysis using high flux membranes leads to convective transport by internal filtration(IF) [Direct Filtration(DF)/Backfiltration(BF)] and allows middle molecules(MM) elimination. The development of High Retention Onset dialyzers has achieved greater elimination of MM and their depurative capacity could be similar to high convective volumes of online hemodiafiltration. The aim of the study was to assess solute transport mechanisms in expanded hemodialysis(HDx) with Theranova 500(Baxter).


We analyzed fourteen HDx sessions with similar dialysis conditions: blood flow 400 ml/min, dialysate flow 700 ml/min, dialysate temperature 35.5C and 240 minutes length. Pressures at the inlet and the output of both dialyzer compartments(Pbi, Pbo, Pdi, Pdo) were collected hourly with DBB-EXA monitor(Nikkiso) to estimate convective volume(CV) using different semi-empirical methods previously used to model IF. Blood viscosity data and uremic toxins with various molecular weight were measured pre-dialysis, at 1 hour(pre-filter and post-filter) and post-dialysis to calculate molecules reduction over time and dialyzer in vivo clearances.


Ultrafiltration was 1.47±0.9 L and Kt/V 1.74±0.3. Hydrodynamic data (average Pbi:259±39, Pbo:155±27, Pdi:271±30, Pdo:145±29 mmHg, monitor TMP 1.8±4 mmHg, oncotic pressure 20,8±3,4 mmHg, blood viscosity 1,51±0,10 cP) allowed to estimate DF and BF rates and volumes. Models showed a DF flow range from 18.2±4.5 to 29.8±3.1 ml/min and BF flow range from 16.8±1.8 to 26.6±2.3 ml/min. The highest calculated CV was 7160.2±738.9 ml/session.
Global, convective and diffusive clearances and molecules RR are summarized in Table.
CV was correlated with urea(r:-0.785,p=0.001), creatinine(r:-0.675,p=0.008) and myoglobin(r:0.587,p=0.027) clearances.


Results suggest that diffusive transport is a main mechanism of middle molecules elimination in HDx with Theranova 500. HDx offers a potential advantage achieving efficient depuration of middle molecules without the need for high convective transport volumes.