Near-infrared spectroscopy as a hemodynamic monitor in critical illness

BACKGROUND: Near-infrared spectroscopy has moved from a research tool to a widely used clinical monitor in the critically ill pediatric patient over the last decade. The physiological and clinical evidence supporting this technology in practice is reviewed here. METHODOLOGY: A search of MEDLINE and PubMed was conducted to find validation studies, controlled trials, and other reports of near-infrared spectroscopy use in children and adults in the clinical setting. Guidelines published by the American Heart Association, the American Academy of Pediatrics, and the International Liaison Committee on Resuscitation were reviewed including further review of references cited. RESULTS: The biophysical properties of near-infrared spectroscopy devices allow measurement of capillary-venous oxyhemoglobin saturation in tissues a few centimeters beneath the surface sensor with validated accuracy in neonates, infants, and small patients. The biologic basis for the relationship of capillary-venous oxyhemoglobin saturation to cerebral injury has been described in animal and human studies. Normal ranges for cerebral and somatic capillary-venous oxyhemoglobin saturation have been described for normal newborns and infants and children with congenital heart disease and other disease states. The capillary-venous oxyhemoglobin saturation from both cerebral and somatic regions has been used to estimate mixed venous saturation and to predict biochemical shock, multiorgan dysfunction, and mortality in different populations. The relationship of cerebral capillary-venous oxyhemoglobin saturation to neuroimaging and functional assessment of outcome is limited but ongoing. Although there are numerous conflicting reports in small populations, expert opinion would suggest that special use may exist for near-infrared spectroscopy in patients with complex circulatory anatomy, with extremes of physiology, and in whom extended noninvasive monitoring is useful. CONCLUSIONS: Class II, level B evidence supports the conclusion that near-infrared spectroscopy offers a favorable risk-benefit profile and can be effective and beneficial as a hemodynamic monitor for the care of critically patients.