Noninvasive brain monitoring with near infrared spectroscopy in newborn infants

摘要

The improvements in perinatal care during recent years have increased the number of surviving with low birth weight babies. Approximately 85% of infants born with a birth weight less than 1500 g survive. Follow-up studies have shown that a large majority of the survivors are unimpaired. Among the survivors approximately 5-15% exhibit major neurodevelopmental handicap, while an additional 25% exhibits less prominent developmental disabilities, in particular school failure (Petersen et al 1990, Volpe 1992). The major neuro-pathological causes of the spastic motor deficits, with or without accompanying intellectual deficit, are periventricular leucomalacia (PVL) and intraventricular haemorrhage (IVH). In infants born at full term, birth asphyxia causes hypoxic-ischaemic brain injury, which is the most important avoidable cause of permanent neurological injury (Levene 1993). In order to prevent brain damage and to improve outcome it is important to understand etiology as well as pathogenesis. Numerous risk factors have been identified but the fundamental mechanism seems to be insufficient cerebral oxygen delivery (Greisen 1992). Therefore, knowledge about the balance between oxygen delivery and oxygen consumption, expressed as brain tissue haemoglobin saturation, is important. Near infrared spectroscopy (NIRS) was developed to monitor changes in oxyhaemoglobin [HbO_2], deoxyhaemoglobin [Hb], total cerebral haemoglobin concentration [tHb] and oxidised cytochrome aa_3 [CytO_2]. The measurement can be undertaken in the incubator, shortly after birth. Applying NIRS continuous monitoring is possible, and the measurements can be repeated without risk for the newborn infant.