USE OF NEAR-INFRARED SPECTROSCOPY IN THE ADULT

Adult near-infrared spectroscopy is a potential method for observing c hanges in cerebral oxygenation non-invasively. Access of light to the adult brain requires penetration through extracranial tissues; hence t he detection of changes in cerebral chromophore concentration can only be achieved by using near-infrared spectroscopy in the reflectance-mo de thereby adding variables which are difficult to control. These incl ude the effects of variable anatomy, different intra-optode distances and the presence of an extra- to intracranial collateral blood supply. Although movements of oxygenated haemoglobin concentration following specific cerebral stimuli can be demonstrated, the challenge of separa ting changes which occur within the extracranial compartment from thos e occurring in the intracranial compartments remains. Our experience w ith near-infrared spectroscopy in the three adult clinical scenarios o f carotid endarterectomy, head injury and carbon dioxide stress testin g will be presented. The influence of extracranial contamination is de monstrated, as are the methods Me have developed to help control for e xtracranial contamination. Provisional experience with spatially resol ved spectroscopy technology will also be presented.