Estimation of cerebral venous saturation in newborn infants by near infrared spectroscopy.

The purpose of the study was to evaluate the near infrared spectroscopy technique for determination of the cerebral venous oxygen saturation. By tilting the patient's head down 15 degrees, changes in OD may be caused by changes in cerebral blood volume. On the assumption that increases in cerebral blood volume consist of venous blood only, cerebral venous oxygen saturation can be calculated as the measured change in oxygenated Hb divided by the change in total Hb. Two groups of mechanically ventilated, newborn infants were investigated: 10 asphyxiated, term infants and another 22 preterm infants with respiratory distress syndrome. All were monitored by near infrared spectroscopy during tilting, and cerebral blood flow was estimated by the 133Xe clearance technique immediately before tilting. Cerebral venous oxygen saturation could not be calculated in 13 preterm infants, as the blood volume remained constant during tilting. In the remaining 19, cerebral venous oxygen saturation averaged 0.67 (SD = 0.09) in asphyxiated infants and 0.53 (SD = 0.15) in preterm infants (p = 0.03). The corresponding values of cerebral blood flow were closely and inversely related to oxygen extraction calculated from cerebral venous saturation as estimated by near infrared spectroscopy.