Effects of carotid compression, as assessed by near infrared spectroscopy, upon cerebral blood volume and hemoglobin oxygen saturation.

Near infrared spectroscopy, a recently developed optoelectronic technique, has been studied as a possible method of monitoring the adequacy of cerebral perfusion in 22 patients who were candidates for carotid endarterectomy. Using this technique, changes in haemoglobin volume, haemoglobin oxygen saturation and redox level of cytochrome-c-oxidase were recorded from the frontoparietal region during routine carotid compression tests performed under continuous electroencephalographic (EEG) monitoring. A highly significant association was found between EEG slowing, indicating impaired cerebral function, and a fall in haemoglobin volume and oxygen saturation, indicating a reduced blood and oxygen supply to the brain (Fisher exact test, P less than 10(-5]. In a few tests haemoglobin volume and oxygen saturation were reduced without changes in the EEG recording. This study raises new issues concerning the compensatory mechanisms taking place during carotid occlusion and suggests that near infrared spectroscopy might be useful in monitoring the blood and oxygen supply to the brain during carotid endarterectomy.