Phasic pupil dilation response to noxious stimulation in normal volunteers: Relationship to brain evoked potentials and pain report

Authors

  • C. Richard Chapman,

    Corresponding author
    1. Department of Anesthesiology, School of Medicine, University of Washington, Seattle, USA
    2. Pain and Toxicity Research Program, Division of Clinical Research, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
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  • Shunichi Oka,

    1. Department of Anesthesiology, School of Medicine, University of Washington, Seattle, USA
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  • David H. Bradshaw,

    1. Department of Anesthesiology, School of Medicine, University of Washington, Seattle, USA
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  • Robert C. Jacobson,

    1. Department of Anesthesiology, School of Medicine, University of Washington, Seattle, USA
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  • Gary W. Donaldson

    1. Pain and Toxicity Research Program, Division of Clinical Research, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
    2. Department of Statistics, University of Washington, Seattle, USA
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Address reprint requests to: Dr. C. Richard Chapman, Department of Anesthesiology, University of Washington, Box 356540, Seattle, WA 98195-6540. E-mail: crc@u.washington.edu.

Abstract

Pupillary response to noxious stimulation was investigated in men (n= 11) and women (n= 9). Subjects experienced repeated trials of noxious electrical fingertip stimulation at four intensities, ranging from faint to barely tolerable pain. Measures included pupil dilation response (PDR), pain report (PR), and brain evoked potentials (EPs). The PDR began at 0.33 s and peaked at 1.25 s after the stimulus. Multivariate mixed-effects analyses revealed that (a) the PDR increased significantly in peak amplitude as stimulus intensity increased, (b) EP peaks at 150 and 250 ms differed significantly in both amplitude and latency across stimulus intensity, and (c) PR increased significantly with increasing stimulus intensity. Men demonstrated a significantly greater EP peak amplitude and peak latency at 150 ms than did women. With sex and stimulus intensity effects partialled out, the EP peak latency at 150 ms significantly predicted PR, and EP peak amplitude at 150 ms significantly predicted the PDR peak amplitude.

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