A continuous renal replacement therapy (CRRT) apparatus comprising: - a filtration unit having a primary chamber and a secondary chamber separated by a semi-permeable membrane; - a blood circuit having a blood withdrawal line connected to an inlet of the primary chamber, and a blood return line connected to an outlet of the primary chamber, said blood circuit being configured for connection to a patient cardiovascular system; - a blood pump to circulate blood in the blood circuit; - a dialysate line connected to an outlet of the secondary chamber; - one or more lines (8; 51; 57; 58; 63; 69; 67; 74) to transfer a respective solution into blood; - at least one fluid source of a solution for each of said one or more lines, wherein said solution comprises at least one buffer agent in the form of bicarbonate or bicarbonate precursor; - a control unit configured to receive a patient prescription including parameters for setting a CRRT blood treatment, characterized in that the control unit is further configured to either • determine a parameter indicative of a steady state acid-base balance in the blood of the patient who has to undergo a CRRT blood treatment, wherein said parameter is the net buffer load in the patient expected at a steady state or the normalized net buffer load in the patient expected at a steady state, and is determined as a function of the concentration of said buffer agent in said fluid source and as a function of the estimated or calculated patient systemic steady state concentration of bicarbonate and/or bicarbonate precursors; or • determine a parameter indicative of a steady state bicarbonate concentration in the blood of the patient who has to undergo the CRRT blood treatment, wherein said parameter is the patient steady state bicarbonate concentration once assuming a default value for the normalized net buffer load, and is determined as a function of the concentration of said buffer agent in said fluid source and as a function of the estimated or calculated net buffer load indicative of a steady state acid-base balance in the blood of the patient, wherein the net buffer load during an extracorporeal blood treatment is the sum of bicarbonate generated from the metabolism of bicarbonate precursors, and bicarbonate balance from the extracorporeal blood therapy (J HCO3_bal), wherein the normalized net buffer load is normalized over a patient body weight. - a filtration unit having a primary chamber and a secondary chamber separated by a semi-permeable membrane; - a blood circuit having a blood withdrawal line connected to an inlet of the primary chamber, and a blood return line connected to an outlet of the primary chamber, said blood circuit being configured for connection to a patient cardiovascular system; - a blood pump to circulate blood in the blood circuit; - a dialysate line connected to an outlet of the secondary chamber; - one or more lines (8; 51; 57; 58; 63; 69; 67; 74) to transfer a respective solution into blood; - at least one fluid source of a solution for each of said one or more lines, wherein said solution comprises at least one buffer agent in the form of bicarbonate or bicarbonate precursor; - a control unit configured to receive a patient prescription including parameters for setting a CRRT blood treatment, • determine a parameter indicative of a steady state acid-base balance in the blood of the patient who has to undergo a CRRT blood treatment, wherein said parameter is the net buffer load in the patient expected at a steady state or the normalized net buffer load in the patient expected at a steady state, and is determined as a function of the concentration of said buffer agent in said fluid source and as a function of the estimated or calculated patient systemic steady state concentration of bicarbonate and/or bicarbonate precursors; or • determine a parameter indicative of a steady state bicarbonate concentration in the blood of the patient who has to undergo the CRRT blood treatment, wherein said parameter is the patient steady state bicarbonate concentration once assuming a default value for the normalized net buffer load, and is determined as a function of the concentration of said buffer agent in said fluid source and as a function of the estimated or calculated net buffer load indicative of a steady state acid-base balance in the blood of the patient,