Background: 

The speculation that cerebral tissue oxygen saturation (SctO₂) measured using tissue near-infrared spectroscopy reflects the balance between cerebral metabolic rate of oxygen and cerebral oxygen delivery has not been validated. Our objective was to correlate SctO₂ with cerebral oxygen extraction fraction (OEF) measured using positron emission tomography; OEF is the ratio between cerebral metabolic rate of oxygen and cerebral oxygen delivery and reflects the balance between these 2 variables.

Materials and Methods: 

This cohort study was based on data collected in a previously published trial assessing phenylephrine versus ephedrine treatment in anesthetized patients undergoing brain tumor surgery. The variables of interest were measured twice over the healthy hemisphere before surgery: the first measurement performed after anesthesia induction and the second measurement performed after induction of a ∼20% increase in blood pressure using either phenylephrine or ephedrine.

Results: 

Data from 24 patients were analyzed. The overall vasopressor-induced relative changes in SctO₂ (ΔSctO₂) and OEF (ΔOEF) were 3.16% [interquartile range, −0.73% to 6.04%] and −12.5% [interquartile range, −24.0% to −6.19%], respectively. ΔSctO₂ negatively correlated with ΔOEF after phenylephrine treatment (Spearman rank correlation coefficient [r_s]=–0.76; P=0.007), ephedrine treatment (r_s=–0.76; P=0.006), and any treatment (r_s=–0.79; P<0.001). ΔSctO₂ significantly associated with ΔOEF based on multivariable analysis with ΔOEF, relative changes in mean arterial pressure, arterial blood oxygen tension, and the bispectral index as covariates (P=0.036).

Conclusions: 

The negative correlation between changes in SctO₂ and OEF suggests that SctO₂ may reflect the cerebral metabolic demand-supply balance during vasopressor treatment. The generalizability of our findings in other clinical scenarios remains to be determined.

中文翻译：

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麻醉期间脑组织氧饱和度与氧提取分数之间的相关性：在血管加压药给药期间监测脑代谢供需平衡

背景： 

使用组织近红外光谱测量的脑组织氧饱和度（SctO ₂）反映脑氧代谢率与脑氧输送之间的平衡的推测尚未得到验证。我们的目标是将 SctO ₂与使用正电子发射断层扫描测量的脑氧提取分数 (OEF) 相关联。OEF是脑氧代谢率与脑氧输送量之间的比率，反映了这两个变量之间的平衡。

材料和方法： 

该队列研究基于之前发表的一项试验中收集的数据，该试验评估了接受脑肿瘤手术的麻醉患者中去氧肾上腺素与麻黄碱的治疗效果。手术前在健康半球上对感兴趣的变量进行了两次测量：第一次测量在麻醉诱导后进行，第二次测量在使用去氧肾上腺素或麻黄碱诱导血压增加约 20% 后进行。

结果： 

分析了 24 名患者的数据。_{升压药引起的 SctO 2} (ΔSctO ₂ ) 和 OEF (ΔOEF) 的总体相对变化分别为 3.16% [四分位距，-0.73% 至 6.04%] 和 -12.5% [四分位距，-24.0% 至 -6.19%] ，分别。去氧肾上腺素治疗后， ΔSctO ₂与 ΔOEF 呈负相关（Spearman 等级相关系数 [ r _s ]=–0.76；P =0.007）、麻黄碱治疗（r _s =–0.76；P =0.006）和任何治疗（r _s =–0.79） ；P <0.001）。基于以 ΔOEF、平均动脉压、动脉血氧分压和脑电双频指数作为协变量的相对变化的多变量分析， ΔSctO ₂与 ΔOEF 显着相关（P = 0.036）。

结论： 

_{SctO 2}与OEF变化的负相关提示SctO _{2可能反映}升压药治疗期间脑代谢供需平衡。我们的研究结果在其他临床情况中的普遍性仍有待确定。