CONTINUOUS NONINVASIVE MEASUREMENT OF CEREBRAL ARTERIAL AND VENOUS OXYGEN-SATURATION AT THE BEDSIDE IN MECHANICALLY VENTILATED NEONATES

Objectives: To test the practicability of a new spectrophotometric met hod using pulse oximetric techniques in combination with special filte rs for the noninvasive determination of cerebral arterial and venous o xygen saturation and oxygen extraction in neonatal intensive care unit patients. The spectrophotometer used three different wavelengths at a sampling rate of 100 Hz. Design: Clinical evaluation of a new method and comparison with previously published data. Setting: Design and con struction of the special spectrophotometer at the Biomedical Engineeri ng Laboratory of the Swiss Federal Institute of Technology. Measuremen ts in the neonatal intensive care unit of the University Hospital, Zur ich, Switzerland. Patients: Convenience sample of 15 clinically stable newborn infants, who were mechanically ventilated and receiving suppl emental oxygen. Median gestational age was 29 5/7 wks (range 26 3/7 to 36 0/7), median birth weight was 1555 g (720 to 2500), median postnat al age was 4 days (1 to 10). Interventions: The emitter and receiver w ere placed on the forehead near the sagittal sinus, between 2 and 2.8 cm apart, and the pulsating light attenuations (arterial and venous pu lse waves) were recorded. Measurements and Main Results: Arterial and venous pulse waves were satisfactory in 10 of 15 infants. Mean cerebra l arterial oxygen saturation was 89.9 +/- 5.4% (SD), mean cerebral ven ous oxygen saturation was 73.0 +/- 8.9%, and mean cerebral oxygen extr action was 16.9 +/- 11.7%. A linear regression analysis demonstrated a significant correlation between mean PCO2 and venous oxygen saturatio n (slope 1.0%/torr, p < .05) and between mean PCO2 and cerebral oxygen extraction (slope -1.3%/torr, p < .05). Conclusion: This new method h as the potential for monitoring continuously, noninvasively, and simul taneously cerebral arterial and venous oxygen saturation and oxygen ex traction in mechanically ventilated preterm infants.