Thiele Robert H, Ikeda Keita, Wang Yunzhen, Bartz Raquel R, Zuo Zhiyi
Department of Anesthesiology, University of Virginia, P.O. Box 800710-0710, Charlottesville, VA, USA.
Department of Anesthesiology, Duke University, Durham, NC, USA.
Can J Anaesth. 2017 Apr;64(4):376-384. doi: 10.1007/s12630-016-0803-y. Epub 2016 Dec 22.
Clinically available near-infrared spectroscopy (NIRS) devices use two to five wavelengths of light to measure the relative amounts of oxyhemoglobin and deoxyhemoglobin in tissue to determine tissue hemoglobin oxygen saturation (StO). In addition to StO, broadband NIRS devices (using hundreds of wavelengths of light) may be able to measure the oxidation state of mitochondrial cytochrome aa (Cyt) which reflects the subcellular energetic state. We hypothesize that broadband NIRS devices can measure Cyt independent of changes in hemoglobin saturation.
In this prospective non-randomized study, 20 male Sprague-Dawley rats (300 g) were anesthetized with isoflurane, tracheally intubated, and ventilated with 100% O containing 2% isoflurane. They were subsequently instrumented with a broadband NIRS device that used a halogen light source coupled to an emitting fibreoptic cable. Three receiving fibreoptic cables were utilized; one analyzed the light source and the other two were directed at the base of the skull. Each receiving fibre was connected to a spectrometer to measure light intensity. Sodium cyanide (NaCN) 5 mg·kg iv was injected in order to produce cytochrome aa reduction. Two to three minutes after injection, oxygen was eliminated and 100% nitrogen (i.e., anoxia) was used for ventilation in order to induce a reduction in both cytochrome aa and hemoglobin desaturation. Changes in the cytochrome oxidation state and hemoglobin oxygenation were calculated using a broadband algorithm and compared before and after both the NaCN and anoxia interventions.
The NaCN injection resulted in a decrease in median [interquartile range (IQR)] deoxyhemoglobin (-0.014 [-0.29 to -0.005] arbitrary units [AU]; P < 0.001), an increase in oxyhemoglobin (0.013 [-0.011 to 0.031] AU; P < 0.001), and a reduction in cytochrome aa (-0.015 [-0.020 to -0.011] AU; P < 0.001). Anoxia resulted in an increase in median [IQR] deoxyhemoglobin (0.13 [0.11 to 0.18] AU; P < 0.001), a decrease in oxyhemoglobin (-0.17 [-0.22 to -0.15] AU; P < 0.001), and a reduction in cytochrome aa (-0.04 [-0.06 to -0.03] AU; P < 0.001).
Broadband NIRS can effectively measure the directionality of changes in both Cyt and StO by uncoupling the cytochrome and hemoglobin signals through inhibition of the electron transport chain and anoxia.
临床可用的近红外光谱（NIRS）设备使用两到五个波长的光来测量组织中氧合血红蛋白和脱氧血红蛋白的相对含量，以确定组织血红蛋白氧饱和度（StO）。除了StO之外，宽带NIRS设备（使用数百个波长的光）或许能够测量线粒体细胞色素aa（Cyt）的氧化状态，这反映了亚细胞能量状态。我们假设宽带NIRS设备能够独立于血红蛋白饱和度变化来测量Cyt。
在这项前瞻性非随机研究中，20只雄性Sprague-Dawley大鼠（300克）用异氟烷麻醉，气管插管，并使用含2%异氟烷的100%氧气进行通气。随后给它们配备一台宽带NIRS设备，该设备使用与发射光纤电缆耦合的卤素光源。使用了三根接收光纤电缆；一根分析光源，另外两根指向颅骨底部。每根接收光纤都连接到一台光谱仪以测量光强度。静脉注射5毫克·千克的氰化钠（NaCN）以产生细胞色素aa还原。注射后两到三分钟，去除氧气并使用100%氮气（即缺氧）进行通气，以诱导细胞色素aa和血红蛋白去饱和的降低。使用宽带算法计算细胞色素氧化状态和血红蛋白氧合的变化，并在NaCN和缺氧干预前后进行比较。
注射NaCN导致脱氧血红蛋白中位数[四分位间距（IQR）]降低（-0.014[-0.29至-0.005]任意单位[AU]；P<0.001），氧合血红蛋白增加（0.013[-0.011至0.031]AU；P<0.001），以及细胞色素aa降低（-0.015[-0.020至-0.011]AU；P<0.001）。缺氧导致脱氧血红蛋白中位数[IQR]增加（0.13[0.11至0.18]AU；P<0.001），氧合血红蛋白降低（-0.17[-0.22至-0.15]AU；P<0.001），以及细胞色素aa降低（-0.04[-0.06至-0.03]AU；P<0.001）。
宽带NIRS可以通过抑制电子传递链和缺氧来解耦细胞色素和血红蛋白信号，从而有效地测量Cyt和StO变化的方向性。
