Effects of Carotid Compression, as Assessed by near Infrared Spectroscopy, upon Cerebral Blood Volume and Haemoglobin Oxygen Saturation

Abstract

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.

The roles of changes in deoxyhemoglobin concentration and regional cerebral blood volume in the fMRI BOLD signal

“…To (Ferrari et al, 1986(Ferrari et al, , 1987(Ferrari et al, , 1992. This agrees with the known fact that under normal conditions in healthy subjects the ratio of the [tHb] to rCBV (the hematocrit) does not change significantly during short periods of time such as the duration of typical functional activation experiments.…”

Measurement of Optical Path Length for Cerebral Near-Infrared Spectroscopy in Newborn Infants

“…Several groups of investigators have used NIR spectroscopy to observe changes in in tracerebral haemoglobin and cytochrome aa3 oxygenation on an arbitrary scale in ex perimental animals [11] and human subjects [1,6,7]. In studies of newborn infants, we have recently shown that quantitative mea surements of the chromophores are feasible (by application of the Beer-Lambert law) and that a number of additional haemody namic indices including cerebral blood flow and blood volume may be derived [5,13], NIR spectroscopy thus offers the prospect of monitoring cerebral oxygenation and hae modynamics in sick infants.…”

Tissue Oxygen Index

“…1 Applications include monitors of fetal physiology, 2-4 during cardiac surgery, 5,6 muscle function, 7-10 and neonatal, 11 pediatric, 12 and adult brain. [13][14][15][16][17][18][19] A number of NIRS instruments are now available that detect changes in optical attenuation from several wavelengths of light, and although a variety of algorithms have been applied to attempt quantification, accuracy of these instruments remains a concern.The NIRO 300 (Hamamatsu Photonics) provides a continuous online measurement of tissue oxygen index (TOI) using spatially resolved spectroscopy. 20,21 We have previously determined that TOI reflects cerebral oxygenation to a high degree of sensitivity and specificity during carotid surgery, 20 an indication that NIRS can show clinically relevant estimations of cerebral hemodynamic and oxygen changes in the adult head (Figure 1).…”

“…In adults, normal TOI values have been reported to range from 65% to 85%. 14,36 -41 Although a number of authors have compared NIRS with other techniques such as jugular bulb oxygen saturation (SjO 2 ), transcranial Doppler ultrasonography and somatosensory-evoked potential 15,37,[42][43][44][45][46][47][48][49][50][51][52][53][54][55][56] or with neurologic events, few have attempted to define an absolute threshold for ischemia. 13,14,16,17,46,[57][58][59] Most studies of this type using NIRS make no attempt to correct for extracranial contributions to signal changes.…”

“…1 Applications include monitors of fetal physiology, [2][3][4] during cardiac surgery, 5,6 muscle function, [7][8][9][10] and neonatal, 11 pediatric, 12 and adult brain. [13][14][15][16][17][18][19] A number of NIRS instruments are now available that detect changes in optical attenuation from several wavelengths of light, and although a variety of algorithms have been applied to attempt quantification, accuracy of these instruments remains a concern.…”