Every patient included in the study will undergo 3 standardised hemodialysis treatments, each using a different dialysis membrane (PMMA, PS, AN69ST). The order of the membranes used will be randomized.

During each conventional and standardised hemodialysis treatment, 6 blood samples will be taken at different time points (T0, T5, T15, T30, T90, T240) to evaluate coagulation activation (TAT, PF1+2, d-dimers, TF) and, more specifically, activation of the contact phase pathway of coagulation (kallikrein, fXIa, fXIIa).

Inclusion Criteria:

• Patients treated with hemodialysis since at least three months.
• Hemodialysis treatment schedule of 3 x 4 hours weekly.
• Arteriovenous fistula (AVF) use for vascular access.
• Treatment with oral acetylsalicylic acid 80 or 100mg q every day.
• ≥ 18 years of age.
• Patients able and agree to provide signed informed consent.

Exclusion Criteria:

• Use of vitamin K antagonists or novel oral anticoagulant therapy.
• Use of chronic heparin treatment, UFH or LMWH.
• Use of clopidogrel.
• Use of ACE-inhibitors.
• Known allergy against one of the dialysis membranes used during this study (PMMA: BKU®, Toray; PS: Phylter®, Bellco; AN69ST: Evodial®, Gambro).
• Known heparin-induced trombopenia type 2.
• Active infection and/or ongoing systemic antimicrobial treatment.
• Presence of central venous catheter, tunnelled or non-tunnelled and/or AV graft.
• Hospitalized patients.
• Planned surgery during study period.
• Mean Qb of <300ml/min during one of the last 3 dialysis sessions before inclusion.
• Vascular access dysfunction defined as (a) known AV access outflow tract stenosis, (b) planned vascular access intervention, (c) planned vascular access conversion.
• Planned conversion of dialysis modality during study period.