• Naomi D Franken, Hugo van Oostrom, Peter J Stienen, Arie Doornenbal, and Ludo J Hellebrekers.
• Department of Clinical Sciences of Companion Animals, Division Anaesthesiology and Neurophysiology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, the Netherlands.
• Vet Anaesth Analg. 2008 Sep 1;35(5):424-31.

ObjectiveTo study, the analgesic and sedative effects of different constant rate infusions (CRI) of dexmedetomidine, in the rat, by measurement of specific electroencephalographic parameters. The recorded parameters were somatosensory-evoked potentials (SEPs) and auditory-evoked potentials (AEPs), which have been shown to be related to analgesia and sedation respectively.AnimalsNine male Wistar rats (HsdCpb:Wu, Harlan Netherlands BV, body weight 300-350 g).MethodsSomatosensory-evoked potentials were recorded from the primary somatosensory cortex and the vertex location (SI/Vx-SEPs). Auditory-evoked potentials were recorded from the primary auditory cortex and vertex location (AI/Vx-AEPs). Primary somatosensory cortex and vertex location recorded SEPs and AI/Vx-AEPs were recorded alternately, during CRI of dexmedetomidine (4.0, 10.0, 20.0 microg kg(-1) hour(-1)) and a control (saline).ResultsThe primary somatosensory cortex-evoked potentials were not affected by the dexmedetomidine CRI, but the other three parameters were significantly affected; although the AI-SEP to a lesser extent than the Vx-SEP and Vx-AEP. A maximum effect on the Vx-AEP was reached at lower doses than on the Vx-SEP.ConclusionsBased on the present findings, it is suggested that CRI of dexmedetomidine provided profound sedation at low doses, whereas higher doses are needed to provide concurrent analgesia.Clinical RelevanceA constant rate infusion of dexmedetomidine can be a valuable adjunct in the provision of sedation and/or analgesia. However, analgesia cannot be produced without sedation, and sedation is not necessarily accompanied by comparative degrees of analgesia.

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