Evaluation of analgesic and sedative effects of continuous infusion of dexmedetomidine by measuring somatosensory- and auditory-evoked potentials in the rat

Authors

  • Naomi D Franken MSc,

    1. Department of Clinical Sciences of Companion Animals, Division Anaesthesiology and Neurophysiology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, the Netherlands
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  • Hugo Van Oostrom MSc,

    1. Department of Clinical Sciences of Companion Animals, Division Anaesthesiology and Neurophysiology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, the Netherlands
    2. Rudolf Magnus Institute of Neuroscience, Utrecht University, the Netherlands
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  • Peter J Stienen PhD,

    1. Department of Clinical Sciences of Companion Animals, Division Anaesthesiology and Neurophysiology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, the Netherlands
    2. Rudolf Magnus Institute of Neuroscience, Utrecht University, the Netherlands
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  • Arie Doornenbal,

    1. Department of Clinical Sciences of Companion Animals, Division Anaesthesiology and Neurophysiology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, the Netherlands
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  • Ludo J Hellebrekers PhD, DVM, Diplomate ECVAA

    1. Department of Clinical Sciences of Companion Animals, Division Anaesthesiology and Neurophysiology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, the Netherlands
    2. Department of Equine Sciences, Division Anaesthesiology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, the Netherlands
    3. Rudolf Magnus Institute of Neuroscience, Utrecht University, the Netherlands
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H. van Oostrom, Department of Clinical Sciences of Companion Animals, Division Anaesthesiology and Neurophysiology, Faculty of Veterinary Medicine, Utrecht University, P.O. Box 80.154 Yalelaan 108, NL-3508 TD Utrecht, the Netherlands. E-mail: h.vanoostrom@uu.nl

Abstract

Objective  To 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.

Animals  Nine male Wistar rats (HsdCpb:Wu, Harlan Netherlands BV, body weight 300–350 g).

Methods  Somatosensory-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 μg kg−1 hour−1) and a control (saline).

Results  The 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.

Conclusions  Based 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 relevance  A 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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