Visual evoked potentials during thiopentone-fentanyl-nitrous oxide anaesthesia in humans.
Visual evoked potentials (VEP) during thiopentone-fentanyl-nitrous oxide anaesthesia were studied in 15 healthy patients undergoing non-neurosurgical procedures. The VEP was recorded before and at 1 and 2 min after induction of anaesthesia with 5-6 mg.kg-1 of thiopentone. After recording the 1 and 2 min VEPs, anaesthesia was maintained with a fentanyl-nitrous oxide-oxygen combination, and further recordings were made at 5, 10, 15 and 20 min after induction. The 1 and 2 min VEPs showed a marked decrease in the amplitudes. Latencies were increased. The amplitudes gradually returned to the control level at 15 min, while the latencies remained increased throughout the study period. In conclusion, thiopentone should be avoided during the critical period of VEP recording. Once it is given, at least 15 min should elapse before an appropriate interpretation of the VEP can be made. Thiopentone-fentanyl-nitrous oxide anaesthesia slightly increases the latencies of the VEP. These effects should be considered in the interpretation of the VEP when thiopentone-fentanyl-nitrous oxide anaesthesia is used.
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Department of Anesthesia, University of Medicine and Dentistry, New Jersey-Robert Wood Johnson Medical School, Robert Wood Johnson University Hospital, New Brunswick 08903-0019.
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D000328:Adult; D000768:Anesthesia, General; D005074:Evoked Potentials, Visual / Q000187:drug effects*; D005283:Fentanyl; D006801:Humans; D008991:Monitoring, Physiologic / Q000379:methods; D009609:Nitrous Oxide; D011930:Reaction Time / Q000187:drug effects; D013874:Thiopental
D013874:Thiopental; D009609:Nitrous Oxide; D005283:Fentanyl