Is near-infrared spectroscopy living up to its promises?
Introduction
Transillumination of the head of small animals is possible using near-infrared spectroscopy (NIRS). The first clinical research use of NIRS in 1985 was in newborns,1 and quantitative spectroscopy was subsequently performed in 1986.2 In the following years many papers on NIRS in newborns were published. The purpose of this chapter is to provide a short overview and discuss the potential clinical use of NIRS for neonatal intensive care.
Section snippets
Geometry
The newborn infant's head is ideally suited for NIRS. The overlying tissues are relatively thin, which ensures that the signal is dominated by brain tissue – white as well as grey matter. NIRS recordings can be performed with the light being applied to one side of the head and received on the other side (transmission mode) in low-birth-weight infants with biparietal diameters of 6–8 cm. In this situation a large part of the brain is ‘seen’ during the measurement, and the results may be
Trend monitoring of haemoglobin signals
Near-infrared spectroscopy is a perfect candidate for clinical monitoring of the tiny sick preterm neonates. It is non-invasive, gives real-time information, does not interfere with intensive care, does not affect the underlying skin, and does not remove the infants from the nursery.
In principle, NIRS allows on-line trending of changes in O2Hb and HHb, and hence of tHb (the sum of [O2Hb] and [HHb]), which is proportional to changes in cerebral blood volume, which in turn can be used as a
Clinical correlates of cTOI
In a group of 18 severely asphyxiated term infants, those with poor outcome showed a rise in cTOI during the first day of life.22 This is in agreement with the concept of delayed energy failure and ‘luxury’ perfusion. In a group of 20 newborn infants operated for congenital transposition of the great vessels, those with preoperative cTOI <35% tended to have lower developmental scores at follow-up at 2–3 years of age.23 It should be noted that in both studies the differences were seen at the
Conclusion and the future
NIRS has matured as a method to obtain quantitative measures of cerebral blood volume, flow and oxygenation, and has yielded credible and sometimes important information. These methods are manual, however, and too cumbersome for clinical practice or large-scale research. Second-generation instruments directly quantify a tissue oxygenation index, which is a surrogate measure of venous saturation, an important parameter for judging tissue oxygen sufficiency. The precision of these instruments,
References (23)
- et al.
Quantification of cerebral oxygenation and haemodynamics in sick newborn infants by near infrared spectrophotometry
Lancet
(1986) - et al.
Performance of several published tissue near infrared spectroscopy algorithms
Anal Biochem
(1995) - et al.
Functional brain imaging using fMRI and optical topography in infancy
Sleep Med
(2002) - et al.
Cotside measurement of cerebral blood flow in ill newborn infants by near-infrared spectroscopy
Lancet
(1988) - et al.
Noninvasive monitoring of cerebral oxygenation in preterm infants: preliminary observation
Pediatrics
(1985) - et al.
The effect of PaCO2 induced increase in cerebral blood volume and cerebral blood flow in mechanically ventilated, preterm infants. Comparison of near infra-red spectrophotometry and 133Xenon clearance
Pediatr Res
(1990) - et al.
Near-infrared monitoring of cerebral tissue oxygen saturation and blood volume in newborn piglets
Am J Physiol
(1997) - et al.
Quantification of cerebral hemoglobin as a function of oxygenation using near-infrared time-resolved spectroscopy in a piglet model of hypoxia
J Biomed Opt
(2005) - et al.
Data analysis methods for near infrared spectroscopy of tissue: problems in determining the relative cytochrome aa3 concentration
Proc SPIE
(1991) - et al.
Regional hemodynamic responses to visual stimulation in awake infants
Pediatr Res
(1998 Jun)