The invention relates to a method and an apparatus for monitoring the autonomous nervous system of a sedated patient. A skin conductance signal is measured at an area of the patient's skin during a measurement interval. A first measure and a second measure, both reflecting the state of the autonomous nervous system of the patient, is calculated by means of certain integral functions. The largest one of the first and second measures is then selected as the output signal (Y) that reflects the state of the autonomous nervous system of the sedated patient.