Change in Brain Perfusion During Induction of General Anesthesia: Relationship Between Transcranial Doppler, Bispectral Index and Cerebral Oximetry : a Prospective Observational Study CERVO2

Main objective: blood pressure target to maintain cerebral perfusion is related to patient's characteristics or comorbidities, it remains uncertain which threshold of blood pressure is to use during general anesthesia in each specific case. Thus, it seems necessary to monitor the cerebral perfusion during anesthesia and to determine the individual dynamic targets of blood pressure. The measure of middle cerebral artery blood flow velocity by transcranial doppler (TCD) is a clinical method to assess cerebral perfusion during general anesthesia and several studies have reported the hemodynamic impact on cerebral blood flow during induction.

Cerebral perfusion can also be approached by near infrared spectroscopy (NIRS) which measures continuously cerebral oxygen saturation. Bispectral index (BIS), which allows a simplified form of continuous electroencephalogram monitoring to assess depth of anesthesia, could also provide the cerebral hypoperfusion assessment quantified by the count of burst suppression ratio (SR). Potentially, those tools need to be combined to assess cerebral perfusion properly.

The goal of this study is to evaluate cerebral perfusion change in adult participants with or without cardiovascular risk factors during a standardized propofol-remifentanil anesthesia induction. Cerebral perfusion will be evaluated and compared using simultaneously the TCD, NIRS and BIS measurements. Those measurements will be also repeated during and after treatment of arterial hypotension episodes in both groups.

Population concerned : the study involves major patients who benefit from intraoperative hemodynamic optimization with norepinephrine (as noradrenaline tartrate) for maintaining blood pressure under general anesthesia during an interventional neuroradiology procedure or orthopedic surgery.

Research Proceedings: all monitoring (TCD, BIS, NIRS) will be collected from the healthy side, contralateral to the interventional side. BIS, NIRS and continuous non-invasive blood pressure measurement will be all connected to the main monitor. For all participants, the data from TCD, NIRS, BIS and the hemodynamic data will be collected over three distinct periods of the interventional procedure : (1) baseline or during preoxygenation at FiO2 of 21% (fraction of inspired oxygen) in awake patients, (2) before Orotracheal Intubation and (3) just after mechanical ventilation.