The invention relates to a calculation and control system for determining whether a patient intended to follow several sessions of hemodialysis treatment falls or not within one group among several groups of hypertension-affected patients, the system comprising:a) means for determining the value of at least one parameter representing the mass interdialytic evolution of the patient, for at least two sessions,b) means for determining the value of at least one parameter representing the plasmatic conductivity of the patient for at least two sessions,c) means for determining the value of a parameter representing the ionic mass transfer of the treatment for at least two sessions,d) programmed means for determining whether the patient falls or not within a group of hypertension-affected patients as a function of the interdialytic mass evolution of the patient, and/or of the plasmatic conductivity and/or of the ionic mass transfer.
