Device for extracorporeal blood treatment comprising: - a filter 102 having a primary and a secondary chamber separated by a semi-permeable membrane, - a withdrawal line connected to the primary chamber of the filter, - the withdrawal line operationally associated to a first means for regulating blood flow rate Q b, - a return line at the outlet of the primary chamber of the filter, - a first pre-infusion line connected to a local anticoagulation substance container and connected to the withdrawal line, and operationally associated to a second means for regulating anticoagulation liquid flow rate Q pre1, - a first post-infusion line connected to a container of a solution at least partially restoring blood ionic balance for infusing the solution in the blood and operationally associated to a third means for regulating the ionic balance restoring solution flow rate Q post1, - an effluent line connected at the outlet of the secondary chamber of filter, connected to a drain pipe and operationally associated to a fourth means for regulating liquid effluent liquid flow rate Q eff, - a CPU including a first means programmed to receive the signal output by at least one of the first, second, third and fourth means for regulating liquid flow rate (115, 119, 121, 123), characterized in that the CPU further includes second means programmed to control at least the third means for regulating the ionic balance restoring solution flow rate Q post1 as a function of the input flow rate equal to blood flow rate Q b, plasma water blood flow rate Q pw, or plasma flow rate Q p, effluent liquid flow rate Q eff, and anticoagulation liquid flow rate Q pre1, wherein second CPU means are programmed to control at least the third means for regulating the ionic balance restoring solution flow rate Qpost1 as a function of the following equation: Q post 1 = α × F dilu × K with: α = constant, A = constant, F dilu = Q b Q b + Q pre 1, or F dilu = Q pw Q pw + Q pre 1, or F dilu = Q p Q p + Q pre 1 K = A x Q eff, Q pw being the plasma water flow rate, Q p being the plasma flow rate, K being a flow parameter (the product of a constant and the effluent liquid flow rate). - a filter 102 having a primary and a secondary chamber separated by a semi-permeable membrane, - a withdrawal line connected to the primary chamber of the filter, - the withdrawal line operationally associated to a first means for regulating blood flow rate Q b, - a return line at the outlet of the primary chamber of the filter, - a first pre-infusion line connected to a local anticoagulation substance container and connected to the withdrawal line, and operationally associated to a second means for regulating anticoagulation liquid flow rate Q pre1, - a first post-infusion line connected to a container of a solution at least partially restoring blood ionic balance for infusing the solution in the blood and operationally associated to a third means for regulating the ionic balance restoring solution flow rate Q post1, - an effluent line connected at the outlet of the secondary chamber of filter, connected to a drain pipe and operationally associated to a fourth means for regulating liquid effluent liquid flow rate Q eff, - a CPU including a first means programmed to receive the signal output by at least one of the first, second, third and fourth means for regulating liquid flow rate (115, 119, 121, 123), characterized in that the CPU further includes second means programmed to control at least the third means for regulating the ionic balance restoring solution flow rate Q post1 as a function of the input flow rate equal to blood flow rate Q b, plasma water blood flow rate Q pw, or plasma flow rate Q p, effluent liquid flow rate Q eff, and anticoagulation liquid flow rate Q pre1, wherein second CPU means are programmed to control at least the third means for regulating the ionic balance restoring solution flow rate Qpost1 as a function of the following equation: Q post 1 = α × F dilu × K with: α = constant, A = constant, F dilu = Q b Q b + Q pre 1, or F dilu = Q pw Q pw + Q pre 1, or F dilu = Q p Q p + Q pre 1 K = A x Q eff, Q pw being the plasma water flow rate, Q p being the plasma flow rate, K being a flow parameter (the product of a constant and the effluent liquid flow rate). α = constant, A = constant, K = A x Q eff, Q pw being the plasma water flow rate, Q p being the plasma flow rate, K being a flow parameter (the product of a constant and the effluent liquid flow rate).