Landolt H, Langemann H, Gratzl O
Department of Surgery, Cantonal Hospital, Basal, Switzerland.
Neurosurgery. 1993 Jun;32(6):1000-4; discussion 1004. doi: 10.1227/00006123-199306000-00020.
An on-line pH meter that can be mounted in microdialysis systems is described. The pH monitoring system was tested in rat cortex before and after middle cerebral artery occlusion (focal ischemia model). After probe implantation, pH values in the dialysate quickly reached a stable level that depended on perfusion medium (6.72, Ringer; 6.47, 0.9% saline) and flow rate (2 microliters/min). During ischemia, pH values sank rapidly and significantly, whereas lactic and ascorbic acid levels in the dialysate increased 9- to 12-fold. The pH of the dialysate is lower than that of the extracellular fluid because the relative recovery of carbon dioxide is about twice that of bicarbonate at the flow rate used, as shown in in vitro experiments. The pH meter would provide useful additional information during monitoring for ischemia, not only in experimental situations but also during neurosurgical intensive care. In the latter case, the on-line pH value would be a bedside parameter enabling fast feedback for setting analytical priorities and making therapeutical decisions.
本文描述了一种可安装在微透析系统中的在线pH计。该pH监测系统在大鼠大脑中动脉闭塞（局灶性缺血模型）前后的大鼠皮层中进行了测试。探针植入后，透析液中的pH值迅速达到稳定水平，这取决于灌注介质（林格氏液为6.72，0.9%生理盐水为6.47）和流速（2微升/分钟）。在缺血期间，pH值迅速且显著下降，而透析液中的乳酸和抗坏血酸水平增加了9至12倍。如体外实验所示，在所用流速下，透析液的pH低于细胞外液，因为二氧化碳的相对回收率约为碳酸氢盐的两倍。该pH计不仅在实验情况下，而且在神经外科重症监护期间的缺血监测中都将提供有用的额外信息。在后一种情况下，在线pH值将是一个床边参数，能够为设定分析优先级和做出治疗决策提供快速反馈。
