Preservation of the cortical somatosensory-evoked potential during dexmedetomidine infusion in rats

Successful somatosensory-evoked potential (SEP) monitoring has been performed during the administration of dexmedetomidine to patients, but a systematic investigation of the dose response of the SEP to dexmedetomidine has not been reported. In this study, we evaluated the effect of a range of dexmedetomidine doses on the cortical SEP in rats. Twelve rats were initially anesthetized with ketamine and the lungs were mechanically ventilated. Femoral arterial and venous catheters were placed. Anesthesia was maintained with constant infusions of remifentanil (5-15 mug.kg(-1).min(-1))and vecuronium (56 mug.kg(-1).min(-1)). Dexmedetomidine was infuse at 0.1, 0.25, 0.5, 1.0, and 2.0 mug.kg(-1).min(-1) in a step-wise manner with 10-min infusion periods at each step. In eight rats, an additional large-dose infusion of dexmedetomidine at 10 mug.kg(-1).min(-1) was administered for 30 min. The cortical SEPs were recorded after stimulation of the tibial nerve. At all infusion rates, there was a statistically insignificant increase in the SEP amplitude. Dexmedetomidine consistently increased the SEP latency, but these increases were not statistically significant. These data demonstrate that dexmedetomidine maintains technically adequate conditions for SEP monitoring in rats and provides support for future studies of the effect of dexmedetomidine on SEP monitoring in humans.