An apparatus for determining physiologic parameters of a patient (6) comprises a pressure sensor adapted to provide readings of a blood pressure of said patient (6), which are stored as at least one pressure curve over time or a derivative thereof with respect to time, and evaluation means (4) adapted to determine, from said pressure curve or said derivative, at least one cardiac activity state variable representing cardiac activity over time and/or variation of cardiac activity over time, and to determine at least one cardiac preload state variable representing cardiac preload over time and/or variation of cardiac preload over time. The evaluation means (4) are further adapted to determine said physiologic parameter as a sum of a plurality of sum terms, at least one of which is a monotonous function of a cardiac activity state variable and at least another one of which is a monotonous function of a cardiac preload state variable.
