Application of Electroretinogram to Anesthetic Depth Monitor

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Our study using rabbits showed that volatile anesthetics and hypoxia alter the rabbit ERG inthe different manner and it seemed to be possible to apply ERG to clinical practise as an intraoperative monitoring of anesthetic depth and brain hypoxia. Then, we have made intraoperative erg monitoring device. This device is composed of personal computer, hpotostimulator, electrode of contactlens form and amplifier. Photostimulator and electrode are linked with fiberoptics. Using this device, we made the followoing study. The effects of enflurane on ERG was studied in 12 patients undergoingsurgical procedures. Recordings were made at 0%, 0.8%, 1.7% end-tidal enflurane concentration. There were statistically significant increases in the latencies of the a-waves, b-waves, ops with increasing concentrations of enflurane. The amplitudes of the a-waves were reduced with increasing concentrations of enflurane, but the amplitudes of the b-waves did not chage. The latencies of OP were thougt to be the most sensitive indicator of the anesthetic depth among these parameters. Some problems were found during this study. One of these problems is electrical interference of many electric device s in the operating room. Another problem is a shift of the electrode during operation. The Quantity of light through the fiberoptics may not be sufficient. To apply this technique to clinical practise, there were many problems to be solved. However, this may be one of the possible monitor of anesthetic depth and brain hypoxia in future.