• Need for stopping the meeting for coagulation of the circuit of dialysis: -either complete coagulation of the circuit [ Time Frame: during dialises ]
  
• or coagulation partial of the circuit (a clot is noted in the lines or the trap with bubbles [ Time Frame: during dialeses ]
  
• -or increase in the venous pressure (statement) of the circuit of more than 50 that is to say increase in the venous pressure (statement) of the circuit of more than 50 % beyond its initial value [ Time Frame: during the dialeses ]
  

• Loss of effectiveness of dialysis? dialysance of urea during the meeting (online measurement carried out by the generator of dialysis) [ Time Frame: during the dialeses ]
  
• Loss of effectiveness of dialysis overloads hydro-sodic persistent (weight of the patient at the end of the meeting: + 500 grams compared to the basic weight) [ Time Frame: during the dialeses ]
  
• Tolerance of the meeting of dialysis clinical side effects (cephalgias, cramps, arterial hypotension [ Time Frame: during the dialeses ]
  
• Tolerance of the meeting of dialysis hemorrhagic accidents to at the time the 48 hours following the meeting of dialysis [ Time Frame: 48 hours following the meeting of dialysis ]
  

Conventional hemodialysis requires transient systemic anticoagulation to prevent blot clotting after contact with the extracorporeal circuit. However, low molecular weight heparin (LMWH) or unfractioned heparin are contra-indicated in dialysis patients at risk for hemorrhagic complications. In this setting, several procedures theoretically allow dialysis without systemic heparinization, but randomized studies to compare them are lacking. The gold standard is the use of iterative rises of the extra corporeal circuit with isotonic saline (« rises »). Two emerging procedures are increasingly used : continuous pre-dilution of the arterial line (« pre-dilution ») and the use of a specific dialysis membrane (NEPHRAL 400 ST) coated with heparin immediately before use (« heparin adsorption »).

We propose a monocentric prospective randomized open study to compare « rises », « pre-dilution » and « heparin adsorption » in chronic hemodialysis patients with contra-indication to the use of LMWH. Main criteria will be extra-corporeal circuit clotting, with dialysis efficiency and tolerance as secondary criteria. Comparison will be made on grounds of « n-of-1 » trial, i.e. series of randomized cross-over tests in individuals. We have planned to include 75 patients in this study, with 1050 LMWH-free dialysis sessions.

We hope to demonstrate chat by comparison wit rises, pre-dilution and heparin absorption techniques reduce the rate of extra-corporeal circuit by 30 and 50% respectively. We also hope to show that heparin adsorption (i) better preserves membrane integrity throughout the dialysis session, resulting in enhanced dialysis efficiency ; (ii) avoids extra fluid infusion and ultrafiltration, resulting in better dry weigh achievement and better clinical tolerance.