This study aims to demonstrate equivalence in terms of molecule removal between continuous hemodialysis using an "enhanced middle molecule clearance" membrane(Ultraflux EMiC2) and continuous hemofiltration using a standard membrane (Ultraflux AV1000S) in ICU patients requiring continuous renal replacement therapy.

In sepsis, the removal of middle molecular weight molecules such as cytokines (also called blood purification), has shown a great interest in intensive care during the last decades. Indeed, these cytokines are involved in the development of the multi-organ failure syndrome when patients are in septic shock. There is some evidence to suggest that extracorporeal therapies (hemofiltration-hemodialysis)are interesting tools to modulate the inflammatory response and to restore the immune homeostasis.

However, hemodialysis using "conventional" membranes does not allow the removal of middle molecules. Conversely, high-volume hemofiltration is an appropriate therapy but it has a lot of drawbacks due to the high ultrafiltration rates (removal of beneficial small molecules, technical and economical issues due to the use of large amounts of fluid replacement). Finally, high cut-off hemofiltration has been reported to be associated with significant albumin loss.

Therefore, continuous "enhanced middle molecule clearance" hemodialysis could be an interesting alternative, making possible the removal of these middle molecules without significant albumin loss and with some theoretical advantages (reduced cost due to the possibility to produce the dialysate from a water circuit, decreased nursing workload).

The aim of this study is to assess the clearances of different kind of molecules (small, middle and large) when continuous enhanced middle molecule clearance hemodialysis is applied to septic patients.

Inclusion Criteria:

• Male or female aged over 18 years.
• ICU patients with septic shock and AKI requiring continuous renal replacement.
• Patient able to agree to be enrolled in the study with informed consent. If the patient can not provide consent, only the consent of family members will be sought if they are present and, to default, the opinion of trustworthy person under article L.1111-6 of the French Health Code. If there is no family present, or trustworthy person designated, the subject will not be included in the study.

Exclusion Criteria:

• Pregnancy or lactation.
• Participation in another research protocol.
• People particularly vulnerable as defined in Articles L.1121-5, L.1121-6, L.1121-7, L.1121-8 et L.1122-1-2 of the French Health Code.