Acute kidney injury (AKI) is frequently observed in critically ill patients in intensive care unit (ICU). Extracorporeal blood purification therapies, mainly continuous renal replacement therapy (CRRT), are often used in these patients to support the renal function. These treatments work by removing solutes and waste substances through haemodiafiltration membrane. The amount of purification during CRRT identifies the concept of "dose", that is the amount of clearance desired for a given solute. The ability of solutes to pass through the membrane and be eliminated within the waste fluids is dynamically and unpredictably reduced by “membrane fouling”, i.e. clogging of pores of haemodiafiltration membrane due to several causes.