Cerebral hemodynamics during cardiopulmonary bypass in children using near-infrared spectroscopy

Abstract

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 flow 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 −1). 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 preasure, which remained between 40 and 80 mm Hg in all cases. During hypothermic bypass (25 °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.