Intraoperative monitoring of cerebral oximetry and depth of anaesthesia during neuroanesthesia procedures

This review reports recent evidence on intraoperative monitoring of cerebral oximetry and depth of anaesthesia during neuroanaesthesia procedures. The clinical benefits of intraoperative monitoring with cerebral oximetry [near infrared spectroscopy (NIRS) and brain tissue oxygenation monitoring (brptiO2)] and depth of anaesthesia with bispectral index (BIS) have recently been studied in surgical (carotid endarterectomy, cerebral arteriovenous malformations resection and brain tumour resections) and neuroradiological vascular procedures. BrptiO2/PaO2 ratio is much more reliable than absolute brptiO2 readings in detecting hypoxia in arteriovenous malformation resections. NIRS can help clinicians monitor those patients receiving endovascular treatment for acute ischaemic stroke and during carotid endarterectomy, but the value of applying cerebral oximetry in patients with cerebral vasospasm needs to be further evaluated. Awake craniotomy demonstrated that because of considerable pharmacokinetic/pharmacodynamic interindividual variation, BIS titration is recommended. Thus, the presence of a frontal brain tumour did not affect ipsilateral BIS values. Recent studies provide interesting evidence of intraoperative monitoring of NIRS, brptiO2 and BIS. The brptiO2/PaO2 ratio is much more reliable than an absolute brptiO2 reading; NIRS helps clinicians to monitor patients who are undergoing endovascular treatment, and BIS guides the titration of anaesthesia during awake craniotomy; its values are not affected by the presence of a frontal brain tumour.