Sakaki T, Graf R, Nozaki H, Rosner G, Heiss W D
Max-Planck-Institut für neurologische Forschung, Cologne, Germany.
J Neurosurg. 2001 Sep;95(3):495-9. doi: 10.3171/jns.2001.95.3.0495.
Neurosurgically induced temporary occlusion of intracranial arteries carries the risk of cerebral ischemic damage. Because negative shifts in the cortical direct-current (DC) potential indicate tissue depolarization and, thus, critical ischemic stress, the authors hypothesized that recordings of these potentials could help to determine the optimal duration and frequency of induced intermittent focal ischemia to prevent brain injury. The investigators related the results of DC recordings both to simultaneously recorded decreases in extracellular Ca++ concentration ([Ca++]o), which reflect Ca++ entry into cells, and to histological outcome.
In cats anesthetized with halothane the effects of intermittent brief (10 minutes long, six times [6 x 10-min group]) and prolonged (20 minutes long, three times [3 x 20-min group]) episodes of middle cerebral artery occlusions were compared with those of a single continuous episode (1 x 60-min group). Laser Doppler flow probes and ion-selective microelectrodes were used to measure cerebral blood flow, DC potentials, and [Ca++]o in cortical tissues of ectosylvian gyri. Negative shifts in DC potential were evaluated in the three groups during the entire 60-minute-long period of ischemia and were smallest in the 6 x 10-min group, larger in the 3 x 20-min group, and largest in the 1 x 60-min group. Accordingly, infarct volumes were smallest in the 6 x 10-min group, intermediate in the 3 x 20-min group, and largest in the 1 x 60-min group. Decreases in ischemic [Ca++]o were significantly greater in the 1 x 60-min group than in the two groups in which there were repetitive occlusions, and recovery of [Ca++]o after reperfusion normalized only in the 1 x 60-min group.
The DC potential may provide a reliable measure to optimize intermittent ischemia and to achieve minimal ischemic brain injury during temporary neurosurgical occlusion of cerebral arteries.
神经外科手术诱导的颅内动脉临时闭塞存在脑缺血损伤风险。由于皮层直流（DC）电位的负向偏移表明组织去极化，进而提示严重缺血应激，作者推测记录这些电位有助于确定诱导间歇性局灶性缺血的最佳持续时间和频率，以预防脑损伤。研究人员将DC记录结果与同时记录的细胞外Ca++浓度（[Ca++]o）降低相关联，[Ca++]o降低反映Ca++进入细胞情况，还与组织学结果相关联。
在氟烷麻醉的猫中，将大脑中动脉间歇性短暂闭塞（每次10分钟，共6次[6×10分钟组]）和延长闭塞（每次20分钟，共3次[3×20分钟组]）的效果与单次连续闭塞（1×60分钟组）的效果进行比较。使用激光多普勒血流探头和离子选择性微电极测量大脑外侧裂回皮质组织中的脑血流量、DC电位和[Ca++]o。在整个60分钟的缺血期内评估三组的DC电位负向偏移，6×10分钟组最小，3×20分钟组较大，1×60分钟组最大。相应地，梗死体积在6×10分钟组最小，3×20分钟组居中，1×60分钟组最大。1×60分钟组缺血时[Ca++]o的降低明显大于有重复闭塞的两组，再灌注后[Ca++]o仅在1×60分钟组恢复正常。
DC电位可能为优化间歇性缺血以及在脑动脉临时神经外科闭塞期间实现最小缺血性脑损伤提供可靠指标。
