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Journal of Clinical Monitoring and Computing

, Volume 33, Issue 2, pp 317–323 | Cite as

Suppression of pupillary unrest by general anesthesia and propofol sedation

  • Matthias Behrends
  • Merlin D. LarsonEmail author
  • Andrew E. Neice
  • Michael P. Bokoch
Original Research
  • 98 Downloads

Abstract

The pupil undergoes irregular oscillations when exposed to light. These oscillations, known as pupillary unrest in ambient light, originate from oscillatory activity within the Edinger–Westphal nucleus in the midbrain. The midbrain and upper pons also contain nuclei known to be very sensitive to the effects of anesthetics that play a central role in maintaining wakefulness. We hypothesized that anesthetics may display similar effects on wakefulness and pupillary unrest. Repeat measurements of pupillary unrest using infrared pupillometry were performed in 16 patients undergoing general anesthesia and 8 patients undergoing propofol sedation. Pupil scans were analyzed using fast Fourier transformation to quantify the effects of the anesthetics on pupillary unrest. During general anesthesia and deep sedation, observed pupillary unrest values below 0.1 (AU) indicate complete suppression of pupillary oscillations. Pupillary unrest decreased more during general anesthesia [to 24% of baseline (95% CI 17–30%)] than pupil size [51% of baseline (95% CI 45–57%)]. Sedation with propofol was associated with a reduction in pupillary unrest that was correlated to the depth of sedation as assessed by the Richmond Agitation–Sedation Scale and the processed electroencephalogram. Pupillary unrest is caused by oscillatory activity within the midbrain that is affected by the state of wakefulness or by hypnotics directly. Increased sedation and general anesthesia reduce and then abolish pupillary unrest as wakefulness decreases. We speculate that midbrain nuclei responsible for wakefulness and pupillary unrest are either communicating or share a similar sensitivity to the effects of commonly used anesthetics.

Keywords

Pupillary Eye Anesthesia Propofol 

Notes

Acknowledgements

The present investigation was supported by departmental funding.

Compliance with ethical standards

Conflict of interest

Author Neice holds a patent related to signal processing of pupillary oscillations. No other authors have conflicts of interest.

Supplementary material

10877_2018_147_MOESM1_ESM.mp4 (6.3 mb)
Supplementary material 1. Supplemental video file 1: A video recording of PUAL. Note the size of the pupil is smaller compared to the measurement in darkness (Supplementary File 3). With the addition of light, the fluctuations in pupil size (y axis) are readily observed. Pupil size versus time is shown by the yellow line. Recording is in slow motion; scale at the bottom is in seconds (MP4 6456 KB)
10877_2018_147_MOESM2_ESM.mp4 (1.2 mb)
Supplementary material 2. Supplemental video file 2: Pupillary measurement of a metal hole. Note absence of oscillations (MP4 1262 KB)
10877_2018_147_MOESM3_ESM.mp4 (4.3 mb)
Supplementary material 3. Supplemental video file 3: A video recording of pupillary unrest in darkness. Notice that there is white noise from the recording device but pupillary unrest is essential absent. The recording of pupil size versus time is flat. A blink occurs at 5 s. Recording is in slow motion; scale at the bottom is in seconds (MP4 4412 KB)

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Copyright information

© Springer Science+Business Media B.V., part of Springer Nature 2018

Authors and Affiliations

  • Matthias Behrends
    • 1
  • Merlin D. Larson
    • 1
    Email author
  • Andrew E. Neice
    • 2
  • Michael P. Bokoch
    • 1
  1. 1.Department of Anesthesia and Perioperative CareUniversity of California, San FranciscoSan FranciscoUSA
  2. 2.Department of AnesthesiaOregon Health and Science UniversityPortlandUSA

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