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NEUROSURGICAL ANESTHESIA

The Effects of Dexmedetomidine on Myogenic Motor Evoked Potentials in Rabbits

From the Department of Anesthesiology, Nara Medical University, Nara, Japan.

Address correspondence and reprint requests to Masahiko Kawaguchi, MD, Department of Anesthesiology, Nara Medical University, 840 Shijo-cho, Kashihara, Nara 634-8522, Japan. Address e-mail to drjkawa{at}naramed-u.ac.jp.

BACKGROUND: Dexmedetomidine is used in the perioperative management of patients, including as an intraoperative adjuvant. The effects of dexmedetomidine on myogenic motor evoked potentials (MEPs) remain undetermined. We conducted the present study to investigate the effects of dexmedetomidine on myogenic MEPs in rabbits.

METHODS: New Zealand white rabbits were used for the studies. First, to determine appropriate doses of dexmedetomidine as an adjunct for anesthesia in rabbits, the level of anesthesia was evaluated by testing the palpebral and limb withdrawal reflexes, and the reactions to ear pinching and tail clamp at 5, 25, 50, 100 µg/kg/h. Second, in 10 rabbits under ketamine and fentanyl anesthesia, myogenic MEPs in response to single pulse and a train-of-five pulses were recorded from the soleus muscle before, during, and after the administration of dexmedetomidine at 5, 25, and 50 µg/kg/h.

RESULTS: At 50 µg/kg/h of dexmedetomidine, palpebral reflex, limb reflex, and reaction to ear pinching were inhibited in >50% of animals, but the reaction to tail clamp was not reduced. Dexmedetomidine suppressed myogenic MEPs in a dose-dependent manner, but when multipulses were used for stimulation, myogenic MEPs could be recorded in all animals at 50 µg/kg/h.

CONCLUSIONS: As long as multipulse is used for stimulation, the recording of myogenic MEPs is feasible in rabbits under ketamine and fentanyl anesthesia during the administration of dexmedetomidine at doses that are an adjunct to anesthesia.

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