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Abstract

The Noninvasive ICP (Intracranial Pressure) Monitoring System NIP-200/210 has been used in several hospitals with more than 2000 patients since March 2002. It is based on the N2 wave response to flash visual evoked potentials (FVEP). According to our data, the mean latency period for the FVEP-induced N2 wave in healthy controls was 126.61 +/- 14.64 ms, in which that of females was shorter than that of males (123.95 +/- 10.345 ms vs. 130.75 +/- 14.632 ms; p < 0.05). There was no significant difference between the left or right side response (126.71 +/- 14.91 ms vs. 124.468 +/- 15.043 ms, p > 0.05). No significant difference in latency was found across age groups in our patient pool. In general, the N2 wave was stable and easily identified in most of the patients or healthy controls. When the data obtained with the NIP-200/210 Noninvasive ICP Monitoring System was compared with that from invasive techniques, the results were quite consistent (correlation index 0.651-0.97, standard error 8-15%). From our clinical trial results, we conclude that the latency periods for the FVEP-induced N2 wave reflected ICP values. However this technique is not suitable in patients with bifrontal hematoma, retinal concussion, or contusion of the optical nerve, because an FVEP value cannot be measured accurately in these cases. In our clinical trials, we used the FVEP technique to determine the effectiveness of mannitol in decreasing the ICP. The data revealed that ICP values decreased significantly within 20 minutes after a mannitol injection, and reached a minimum level at 40 minutes. For a single bolus of mannitol, the duration of the ICP decrease ranged from 30-210 minutes. Elevated ICP is one of the most important clinical issues in neurosurgery and neurology. The present noninvasive technique is safe and easy to perform, with a minimal risk of complications.