Memory & Conditioning Under Anesthesia (MCA)

  • STATUS
    Recruiting
  • End date
    Jun 1, 2023
  • participants needed
    150
  • sponsor
    Keith M. Vogt, MD, PhD
Updated on 12 May 2022
anesthesia
dexmedetomidine
propofol
intravenous anesthetics
acute pain
Accepts healthy volunteers

Summary

The purpose of this study is to determine the effects of pain on long-term memory and conditioned physiologic responses in the presence and absence of distinct intravenous anesthetics. Functional magnetic resonance imaging will be used to identify the neural correlates of these phenomena The study will occur over 5 visits and involves no long-term follow up.

Description

Purpose: Sedative-hypnotic and analgesic agents (termed "anesthetics") are routinely used during medical procedures to prevent or ease suffering, suppressing the conscious experience of pain and its encoding into memory. While overt awareness under general anesthesia is a rare clinical event, implicit memory may still form. Further, at sub-hypnotic anesthetic doses, animals show enhanced fear conditioning and humans may have enhanced amygdala activity. This motivates the investigator's study, as poorly-contextualized aversive memories are theorized to initiate anxiety-spectrum disorders, which may explain the high incidence of post-traumatic stress disorder after anesthetic awareness.

Objective: How anesthetics facilitate or inhibit poorly-contextualized aversive memories is incompletely understood, with little mechanistic work done in human subjects. Thus, there is a critical need to understand how anesthetics modulate the memory and threat response systems during painful stimulation. The overall scientific objective is to determine the memory-modulating effects of propofol, dexmedetomidine, and fentanyl in the context of periodic painful stimulation.

Aim 1: Determine how behavioral and physiologic measures of memory are modulated by pain and the individual effects of three pharmacologically distinct drugs: propofol, dexmedetomidine, and fentanyl. Hypotheses: Based on previous results, 1a) explicit memory will be significantly reduced by propofol and dexmedetomidine, but only modestly by fentanyl. Consistent with my preliminary data, 1b) priming effects will be seen for pain-paired words under all drugs. Electrodermal activity changes still occur with opioids and propofol, thus 1c) pain-related physiologic responses will persist with these two drugs but be blunted by the anti-adrenergic effect of dexmedetomidine.

Aim 2: Determine the brain structures differentially engaged in memory encoding under pain and drug conditions. Task-related functional magnetic resonance imaging (MRI) activity for behavioral measures of explicit or implicit memory will be determined, comparing pain-paired vs non-pain items across drug and no-drug datasets. Functional connectivity (FC) MRI (fcMRI) will be compared between task and drug conditions. The entire brain will be explored, but predictions for key structures follow. Hypotheses: 2a) Hippocampal activity, will be blunted by propofol and dexmedetomidine, while fentanyl will have minimal effect. 2b) Amygdala activity, responsible for physiologic responses, will parallel the predictions in 1c across drug and pain conditions. 2c) Insula activity will be greater for pain-paired items, and this will be attenuated by fentanyl > dexmedetomidine > propofol, corresponding to their anticipated analgesic effect. 2d) Pain has been shown to affect fcMRI during a cognitive task, and thus FC between the key regions in 2a-c will be reduced by all three drugs, in characteristic patterns.

Details
Condition Anesthesia, Pain
Treatment Dexmedetomidine, Fentanyl, Placebo, Propofol, Peripheral Nerve Stimulation
Clinical Study IdentifierNCT04062123
SponsorKeith M. Vogt, MD, PhD
Last Modified on12 May 2022

Eligibility

Yes No Not Sure

Inclusion Criteria

Adults, age 18-39, who are native English speakers with at least a high school education
have normal hearing and memory
be of normal body-weight
be generally healthy (free from significant chronic disease)

Exclusion Criteria

have a valid email address and valid phone number throughout the study
anticipate ability to participate in all visits required for the phase of the study in which they are enrolled
Exclusion Criteria
Pregnancy
Body mass index > 35 (obese) or < 18 (underweight)
Use of psychotropic medications, including anti-epileptics, anti-psychotics, anxiolytics, anti-depressants, stimulants, sleep-aids, anti-histamines, or analgesics
History of adverse reaction to OR abuse of: dexmedetomidine (Precedex), propofol (Diprivan) or the opioids class of medications (fentanyl, morphine, hydromorphone, etc)
History of clinically significant memory or hearing loss
History of obstructive sleep apnea
History of neurologic or psychiatric disease, including benign tremor
History of significant cardiac disease, including high blood pressure or arrhythmia
History of significant pulmonary disease
History of diabetes or neuropathy
History of chronic pain, or other pain processing disorder
Have an implanted medical electronic device
Have indwelling or implanted metal in their body that is not MRI-compatible
Have claustrophobia
Have a history of drug abuse
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