Watzman H M, Kurth C D, Montenegro L M, Rome J, Steven J M, Nicolson S C
Brain Research Laboratory, Departments of Anesthesiology and Critical Care Medicine, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA.
Anesthesiology. 2000 Oct;93(4):947-53. doi: 10.1097/00000542-200010000-00012.
Cerebral oximetry is a noninvasive bedside technology using near-infrared light to monitor cerebral oxygen saturation (Sco2) in an uncertain mixture of arteries, capillaries, and veins. The present study used frequency domain near-infrared spectroscopy to determine the ratio of arterial and venous blood monitored by cerebral oximetry during normoxia, hypoxia, and hypocapnia.
Twenty anesthetized children aged < 8 yr with congenital heart disease of varying arterial oxygen saturation (Sao2) were studied during cardiac catheterization. Sco2, Sao2, and jugular bulb oxygen saturation (Sjo2) were measured by frequency domain near-infrared spectroscopy and blood oximetry at normocapnia room air, normocapnia 100% inspired O2, and hypocapnia room air.
Among subject conditions, Sao2 ranged from 68% to 100%, Sjo2 from 27% to 96%, and Sco2 from 29% to 92%. Sco2 was significantly related to Sao2 (y = 0. 85 x -17, r = 0.47), Sjo2 (y = 0.77 x +13, r = 0.70), and the combination (Sco2 = 0.46 Sao2 + 0.56 Sjo2 - 17, R = 0.71). The arterial and venous contribution to cerebral oximetry was 16 +/- 21% and 84 +/- 21%, respectively (where Sco2 = alpha Sao2 + beta Sjo2 with alpha and beta being arterial and venous contributions). The contribution was similar among conditions but differed significantly among subjects (range, approximately 40:60 to approximately 0:100, arterial:venous).
Cerebral oximetry monitors an arterial/venous ratio of 16:84, similar in normoxia, hypoxia, and hypocapnia. Because of biologic variation in cerebral arterial/venous ratios, use of a fixed ratio is not a good method to validate the technology.
脑血氧饱和度测定是一种无创床边技术，利用近红外光监测动脉、毛细血管和静脉混合血液中的脑氧饱和度（Sco2）。本研究采用频域近红外光谱法测定常氧、低氧和低碳酸血症期间通过脑血氧饱和度测定监测的动脉血和静脉血的比例。
对20例年龄＜8岁、动脉血氧饱和度（Sao2）各异的先天性心脏病麻醉患儿在心脏导管插入术期间进行研究。通过频域近红外光谱法和血氧饱和度测定法在常碳酸血症室内空气、常碳酸血症100%吸入氧气和低碳酸血症室内空气条件下测量Sco2、Sao2和颈静脉球血氧饱和度（Sjo2）。
在各受试者条件下，Sao2范围为68%至100%，Sjo2为27%至96%，Sco2为29%至92%。Sco2与Sao2（y = 0.85x - 17，r = 0.47）、Sjo2（y = 0.77x + 13，r = 0.70）以及二者组合（Sco2 = 0.46Sao2 + 0.56Sjo2 - 17，R = 0.71）显著相关。脑血氧饱和度测定中动脉血和静脉血的贡献分别为16±21%和84±21%（其中Sco2 =αSao2 +βSjo2，α和β分别为动脉血和静脉血的贡献）。该贡献在各条件下相似，但在受试者之间差异显著（范围约为40:60至约0:100，动脉血:静脉血）。
脑血氧饱和度测定监测的动脉血/静脉血比例为16:84，在常氧、低氧和低碳酸血症中相似。由于脑动脉/静脉比例存在生物学差异，使用固定比例并非验证该技术的良好方法。
