Ferrari M, Williams M A, Wilson D A, Thakor N V, Traystman R J, Hanley D F
Department of Anesthesiology/Critical Care Medicine, Johns Hopkins Medical Institutions, Baltimore, Maryland 21287, USA.
Am J Physiol. 1995 Aug;269(2 Pt 2):H417-24. doi: 10.1152/ajpheart.1995.269.2.H417.
We used rapid-scanning near-infrared (NIR) spectroscopy (730-960 nm) to study the effects of graded or acute hypoxia on cerebral cytochrome-c oxidase (cyt aa3) redox state in blood-perfluoro-carbon-exchanged cats with somatosensory evoked potential (SEP) monitoring. In graded hypoxia [10 min each at fractional inspiratory O2 concentration (FIO2) 0.9, 0.8, 0.7, 0.6, and 0.5], cyt aa3 reduction occurred at FIO2 0.6 when cerebral O2 delivery was < 3.5 ml.100 g-1.min-1. In acute hypoxia (FIO2 0.6 for 10 min), significant cyt aa3 reduction occurred from 5 to 10 min (cerebral O2 delivery 3.1 +/- 0.3 ml.100 g-1.min-1) and recovered with reoxygenation (FIO2 1.0). Cyt aa3 redox changes preceded or coincided with SEP alterations in both hypoxia protocols. These results demonstrate that cerebral cyt aa3 reduction occurs with severe reduction of cerebral O2 delivery, but no significant change in cerebral cyt aa3 redox state occurs with small reductions of cerebral O2 delivery. We conclude that substantial changes in cerebral cyt aa3 do not occur at physiological levels of O2 delivery and that current NIR clinical instruments would detect oxygen-dependent cerebral cyt aa3 redox changes only when O2 delivery is extremely compromised.
我们使用快速扫描近红外（NIR）光谱法（730 - 960纳米），在监测体感诱发电位（SEP）的全氟碳交换血液的猫身上，研究分级或急性缺氧对脑细胞色素c氧化酶（细胞色素aa3）氧化还原状态的影响。在分级缺氧过程中[每次在吸入氧分数（FIO2）为0.9、0.8、0.7、0.6和0.5的条件下持续10分钟]，当脑氧输送量<3.5毫升·100克-1·分钟-1时，在FIO2为0.6时细胞色素aa3发生还原。在急性缺氧（FIO2为0.6，持续10分钟）过程中，在5至10分钟时细胞色素aa3发生显著还原（脑氧输送量为3.1±0.3毫升·100克-1·分钟-1），并在复氧（FIO2为1.0）后恢复。在两种缺氧方案中，细胞色素aa3的氧化还原变化均先于或与SEP改变同时出现。这些结果表明，脑氧输送量严重降低时会发生脑细胞色素aa3还原，但脑氧输送量小幅降低时脑细胞色素aa3氧化还原状态无显著变化。我们得出结论，在生理水平的氧输送时，脑细胞色素aa3不会发生实质性变化，并且当前的近红外临床仪器仅在氧输送极度受损时才能检测到依赖氧的脑细胞色素aa3氧化还原变化。
