Kiening K L, Unterberg A W, Bardt T F, Schneider G H, Lanksch W R
Department of Neurosurgery, Virchow Medical Center, Humboldt-University of Berlin, Germany.
J Neurosurg. 1996 Nov;85(5):751-7. doi: 10.3171/jns.1996.85.5.0751.
Monitoring of cerebral oxygenation is considered to be of great importance in minimizing secondary hypoxic and ischemic brain damage following severe head injury. Although the threshold for cerebral hypoxia in jugular bulb oximetry (measurement of O2 saturation in the jugular vein (SjvO2)) is generally accepted to be 50% oxygen saturation, a comparable value in brain tissue PO2 (PtiO2) monitoring, a new method for direct assessment of PO2 in the cerebral white matter, has not yet been established. Hence, the purpose of this study was to compare brain PtiO2 with SjvO2 in severely head injured patients during phases of reduced cerebral perfusion pressure (CPP) to define a threshold in brain PtiO2 monitoring. In addition, the safety and data quality of both SjvO2 and brain PtiO2 monitoring were studied. In 15 patients with severe head injuries, SjvO2 and brain PtiO2 were monitored simultaneously. For brain PtiO2 monitoring a polarographic microcatheter was inserted in the frontal cerebral white matter, whereas for SjvO2 measurements were obtained by using a fiberoptic catheter placed in the jugular bulb. Intracranial pressure was monitored by means of an intraparenchymal catheter. Mean arterial blood pressure, CPP, end-tidal CO2, and arterial oxygen saturation (pulse oximetry) were continuously recorded. All data were simultaneously stored and analyzed using a multimodal computer system. For specific analysis, phases of marked deterioration in systemic blood pressure and consecutive reductions in CPP were investigated. There were no complications that could be attributed to the PtiO2 catheters, that is, no intracranial bleeding or infection. The "time of good data quality" was 95% in brain PtiO2 compared to 43% in SjvO2; PtiO2 monitoring could be performed twice as long as SjvO2 monitoring. During marked decreases in CPP, SjvO2 and brain PtiO2 correlated closely. A significant second-order regression curve of SjvO2 versus brain PtiO2 (p < 0.01) was plotted. At a threshold of 50% in SjvO2, brain PtiO2 was found to be within the range of 3 to 12 mm Hg, with a regression curve "best fit" value of 8.5 mm Hg. There was a close correlation between CPP and oxygenation parameters (PtiO2 and SjvO2) when CPP fell below a breakpoint of 60 mm Hg, suggesting intact cerebral autoregulation in most patients. This study demonstrates that monitoring brain PtiO2 is a safe, reliable, and sensitive diagnostic method to follow cerebral oxygenation. In comparison to SjvO2, PtiO2 is more suitable for long-term monitoring. It can be used to minimize episodes of secondary cerebral maloxygenation after severe head injury and may, hopefully, improve the outcome in severely head injured patients.
监测脑氧合作用对于将严重颅脑损伤后继发性缺氧和缺血性脑损伤降至最低被认为极为重要。尽管颈静脉球血氧饱和度测定法（测量颈静脉血氧饱和度（SjvO2））中脑缺氧的阈值一般认为是血氧饱和度50%，但在脑组织氧分压（PtiO2）监测（一种直接评估脑白质氧分压的新方法）方面，尚未确立类似的值。因此，本研究的目的是比较严重颅脑损伤患者在脑灌注压（CPP）降低阶段的脑PtiO2与SjvO2，以确定脑PtiO2监测的阈值。此外，还研究了SjvO2和脑PtiO2监测的安全性和数据质量。对15例严重颅脑损伤患者同时监测SjvO2和脑PtiO2。脑PtiO2监测时，将极谱微导管插入额叶脑白质，而SjvO2测量则通过置于颈静脉球的光纤导管进行。通过脑实质内导管监测颅内压。持续记录平均动脉血压、CPP、呼气末二氧化碳和动脉血氧饱和度（脉搏血氧饱和度测定）。所有数据均使用多模式计算机系统同时存储和分析。为进行特定分析，研究了全身血压明显恶化和CPP连续降低的阶段。没有可归因于PtiO2导管的并发症，即没有颅内出血或感染。脑PtiO2的“良好数据质量时间”为95%，而SjvO2为43%；PtiO2监测的时间可以是SjvO2监测的两倍。在CPP明显下降期间，SjvO2和脑PtiO2密切相关。绘制了SjvO2与脑PtiO2的显著二阶回归曲线（p < 0.01）。当SjvO2阈值为50%时，发现脑PtiO2在3至12 mmHg范围内，回归曲线“最佳拟合”值为8.5 mmHg。当CPP降至60 mmHg的断点以下时，CPP与氧合参数（PtiO2和SjvO2）之间存在密切相关性，表明大多数患者的脑自动调节功能完好。本研究表明，监测脑PtiO2是一种安全、可靠且敏感的跟踪脑氧合作用的诊断方法。与SjvO2相比，PtiO2更适合长期监测。它可用于将严重颅脑损伤后继发性脑氧合不足的发作降至最低，并有望改善严重颅脑损伤患者的预后。
