ANESTHETIC EFFECTS ON MOTOR EVOKED-POTENTIALS IN DOGS

The effects of the various anesthetic agents on the production of tran scranial magnetic motor evoked potentials (tcMMEP) were studied in a c anine model. Pre-anesthetic baseline tcMMEPs demonstrated consistency in onset latency measurements and variability in measurement of peak-t o-peak amplitudes. Changes in tcMMEPs were evaluated following the ind ividual administrations of sodium pentothal, etomidate, halothane, fen tanyl, and ketamine. For induction of anesthesia, etomidate was compat ible with tcMMEP production, whereas sodium pentothal resulted in loss of hindlimb potentials for a period of 45 minutes.For maintenance of anesthesia, halothane was incompatible with the measurement of tcMMEPs . Fentanyl administration was consistent with the recording of reliabl e tcMMEPs, with consistent onset latencies but widely variable peak-to -peak amplitudes. Ketamine was compatible with stable and reproducible tcMMEP production. The results of this study suggest that anesthetic agents have a predictable and consistent effect on tcMMEP responses.