CEREBRAL HEMODYNAMICS DURING CARDIOPULMONARY BYPASS IN CHILDREN USING NEAR-INFRARED SPECTROSCOPY

We describe a new noninvasive method using near-infrared spectroscopy for monitoring cerebral hemodynamics during cardiopulmonary bypass in children. All patients were undergoing open heart operations for repair of congenital heart defects. Standardized anesthesia, an alpha-stat method of blood gas management, and nonpulsatile flow were used in all cases. All measurements during bypass were made after steady-state conditions had been reached. Cerebral blood now was measured on 13 occasions in 4 children, aged between 4 and 10 months (median, 5 months). Values of 15.9 to 53.5 mL.100 g(-1) min(-1) were obtained. Cerebral blood volume was measured in 1 patient, aged 4 months. Volumes of 4.3 to 8.0 mL.100 g(-1) were obtained on bypass at full pump flow (2.4 L.min(-1).m(-2)). On bypass at half flow, the volume increased to 14.7 mL.100 g(-1). Change in cerebral blood volume with changing carbon dioxide tension (CBVR) was measured in 13 patients aged from 1 to 90 months (median, 13.5 months). Preoperatively, CBVR was 0.12+/-0.07 mL.100 g(-1).kPa(-1) and was independent of mean arterial pressure, which remained between 40 and 80 mm Hg in all cases. During hypothermic bypass (25 degrees C), CBVR was significantly reduced to 0.05+/-0.02 mL.100 g(-1).kPa(-1). In addition, there were three values at mean arterial pressure of lower than 40 mm Hg in which CBVR was negative (-0.04+/-0.01 mL.100 g(-1).kPa(-1)). We conclude that near-infrared spectroscopy is useful for the noninvasive investigation of cerebral hemodynamics during cardiopulmonary bypass.