Investigating Near-Threshold Perception During Anesthetic Sedation

University of Michigan36 enrolled

Overview

The researchers expect to gain a deeper understanding of mental function during different levels of anesthesia, and to evaluate if the use of ultrasonic brain stimulation accelerates return to consciousness. Propofol is FDA approved for use in patients undergoing an anesthetic for medical treatment but is not approved for use in healthy volunteers.

The stimulus set will include real and scrambled images, where the scrambled images will be created by phase-shuffling a randomly chosen real image from each category to preserve category specific low-level image features. Because scrambled images do not include an object stimulus, the images are used as "catch trials" to determine the subjects' baseline tendency to give positive responses to a question about the subjects' recognition experience. Each object category will include four unique real images and one scrambled image. Each image will be repeated 10 times (i.e., trials) for each 16-min session. The pre-stimulus interval will vary randomly from trial to trial between 4 and 8 seconds to prevent stimulus timing predictability. The stimuli will be presented in a randomized order to prevent category predictability.

Study Type

INTERVENTIONAL

Allocation

Purpose

BASIC_SCIENCE

Masking

NONE

Enrollment

Conditions

Propofol Anesthesia fMRI

Interventions

Functional Magnetic Resonance Imaging (fMRI) with propofolCOMBINATION_PRODUCT

Three 16-min sessions in wakeful baseline, light sedation, and recovery will be conducted (Fig. 2). Light sedation will be achieved by IV infusion of propofol to achieve effect-site concentrations of 1.0 μg/ml. Infusion rate will be manually controlled. An initial bolus dose (525 µg/kg) and subsequent infusion rate (82 µg/kg/min) for each participant

Eligibility

Sex: ALLMin age: 18 YearsMax age: 40 YearsHealthy volunteers:

Medical Language ↔ Plain English

Inclusion Criteria: * Healthy study subjects with American Society of Anesthesiologists (ASA)-1 status. * Right-handed * Body mass index (BMI) less than 30. * All subjects will be English speakers. Exclusion Criteria: * Medical contraindication to magnetic resonance imaging (MRI) scanning; are unable to undergo MRI scanning because of possible pregnancy or currently breastfeeding, BMI\>30, metallic substances in the body, claustrophobia, anxiety, or cardiopulmonary disease; or have an intracranial structural abnormality on T1-weighted MRI scans. * History of allergy to propofol, eggs or egg products, soybean or soybean products, neurological, cardiovascular, or pulmonary illness; significant head injury with loss of consciousness; learning disability or other developmental disorder; sleep apnea or any severe snoring history; gastroesophageal reflux disease (GERD) or heartburn; pancreatitis or a history of pancreatitis, or sensory/motor loss sufficient to interfere with performance of the study. * Tattoos in the head or neck region will be excluded from study; other tattoos are subject to determination by investigators based on their assessment regarding participant safety. To eliminate aspiration risk subjects will also be excluded if they have had recent food or liquid intake (within 8 hours). * History of drug use, have a positive drug screen, are unwilling to abstain from alcohol for 24 hours prior to dosing, or have a current history of nicotine use. * Pregnancy

Locations (1)

University of Michigan

Ann Arbor, Michigan, United States

Outcomes

Primary Outcomes

Blood Oxygen Level Dependent (BOLD) response to visual stimuli

Visual stimuli evoked activity was quantified by measurements of the fMRI BOLD signal. Neural response to a natural visual stimulus will be assessed during both conscious and anesthetized states.

Time frame: Up to 90 minutes

Secondary Outcomes

Perceptual criterion (c) derived from the Signal Detection Theory (SDT)

Time frame: Up to 90 minutes

Sensitivity (d') criterion derived from the Signal Detection Theory (SDT)

Time frame: Up to 90 minutes

Data from ClinicalTrials.gov

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