Intraoperative monitoring usually does not assess intravascular blood volume of the patient. The variations of the systolic blood pressure and the right auricular pressure allow to appreciate the intravascular blood volume changes and their consequences on the cerebral perfusion pressure. However, when the autoregulation of the cerebral blood flow is strongly depressed, the evaluation of the cerebral perfusion pressure alone is inadequate. In this case, the optimal monitoring should be metabolic (jugular bulb venous oxygen saturation) to finally assess the cerebral flow-metabolic coupling.