Perioperative Medicine  |   August 2019
Propofol Sedation Alters Perceptual and Cognitive Functions in Healthy Volunteers as Revealed by Functional Magnetic Resonance Imaging
Author Notes
  • From the Departments of Anesthesiology (W.L.G., K.K.L., C.J.R., S.L., S.G.), Radiology (X.L.), and Neurology (J.R.B., S.-J.L.), Medical College of Wisconsin, Milwaukee, Wisconsin; and the Department of Anesthesiology, University of Michigan, Ann Arbor, Michigan (A.G.H.).
  • Partial results of this article were presented at the American Society of Anesthesiologists conference in San Diego, California, on October 25, 2015.
    Partial results of this article were presented at the American Society of Anesthesiologists conference in San Diego, California, on October 25, 2015.×
  • Submitted for publication May 1, 2018. Accepted for publication February 1, 2019.
    Submitted for publication May 1, 2018. Accepted for publication February 1, 2019.×
  • Address correspondence to Dr. Gross: Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, Wisconsin, 53226. bgross@mcw.edu. Information on purchasing reprints may be found at www.anesthesiology.org or on the masthead page at the beginning of this issue. Anesthesiology’s articles are made freely accessible to all readers, for personal use only, 6 months from the cover date of the issue.
Article Information
Perioperative Medicine / Clinical Science / Pharmacology / Radiological and Other Imaging
Perioperative Medicine   |   August 2019
Propofol Sedation Alters Perceptual and Cognitive Functions in Healthy Volunteers as Revealed by Functional Magnetic Resonance Imaging
Anesthesiology 8 2019, Vol.131, 254-265. doi:10.1097/ALN.0000000000002669
Anesthesiology 8 2019, Vol.131, 254-265. doi:10.1097/ALN.0000000000002669
Abstract

Editor’s Perspective:

What We Already Know about This Topic:

  • Loss of consciousness during anesthesia is associated with a loss of anterior–posterior connectivity

  • However, during anesthesia local sensory cortex function may be preserved

What This Article Tells Us That Is New:

  • During propofol sedation, activation on functional magnetic resonance imaging in higher cognitive areas, such as semantic and phonologic processing, is abolished with deep sedation and only partially suppressed with light sedation

  • Activation related to lower sensory processing continues with deep and light sedation

Background: Elucidating networks underlying conscious perception is important to understanding the mechanisms of anesthesia and consciousness. Previous studies have observed changes associated with loss of consciousness primarily using resting paradigms. The authors focused on the effects of sedation on specific cognitive systems using task-based functional magnetic resonance imaging. The authors hypothesized deepening sedation would degrade semantic more than perceptual discrimination.

Methods: Discrimination of pure tones and familiar names were studied in 13 volunteers during wakefulness and propofol sedation targeted to light and deep sedation. Contrasts highlighted specific cognitive systems: auditory/motor (tones vs. fixation), phonology (unfamiliar names vs. tones), and semantics (familiar vs. unfamiliar names), and were performed across sedation conditions, followed by region of interest analysis on representative regions.

Results: During light sedation, the spatial extent of auditory/motor activation was similar, becoming restricted to the superior temporal gyrus during deep sedation. Region of interest analysis revealed significant activation in the superior temporal gyrus during light (t [17] = 9.71, P < 0.001) and deep sedation (t [19] = 3.73, P = 0.001). Spatial extent of the phonologic contrast decreased progressively with sedation, with significant activation in the inferior frontal gyrus maintained during light sedation (t [35] = 5.17, P < 0.001), which didn’t meet criteria for significance in deep sedation (t [38] = 2.57, P = 0.014). The semantic contrast showed a similar pattern, with activation in the angular gyrus during light sedation (t [16] = 4.76, P = 0.002), which disappeared in deep sedation (t [18] = 0.35, P = 0.731).

Conclusions: Results illustrate broad impairment in cognitive cortex during sedation, with activation in primary sensory cortex beyond loss of consciousness. These results agree with clinical experience: a dose-dependent reduction of higher cognitive functions during light sedation, despite partial preservation of sensory processes through deep sedation.