Neuroimaging of Anesthetic Modulation of Human Consciousness

Study Overview
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Brief Summary
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This study's purpose is to see if mental functions take place during different levels of anesthesia, using a commonly used drug (Propofol). fMRI (functional Magnetic Resonance Imaging, or brain imaging) shows areas in the brain involved in thinking at different depths of anesthesia.

Detailed Description
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Administering anesthetic drugs to suppress consciousness is an imperatively important step in major surgical operations. Yet the neurobiological mechanisms that underlie loss of consciousness under general anesthesia remain elusive. Despite advancements in understanding the molecular, synaptic, and cellular effects of anesthetics, the large-scale, systems-level modulation of neuronal processes that support conscious cognitive functions is incompletely understood. While profound decreases in global and regional brain metabolism, blood flow, and functional connectivity have been reported, these changes often fail to correlate with the loss and return of consciousness. To date, there is no consciousness meter or gold standard to objectively assess and monitor the level of consciousness under general anesthesia. Several studies suggest that residual cognitive functions may not completely vanish under general anesthesia; however, the level and complexity of residual information processing in the anesthetized brain remains unknown. Finally, the neurobiological mechanisms that govern anesthesia induction and emergence appear to be partially different, but the relevance of these differences to the modulation of the state of consciousness is unclear.

Official Title
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Neuroimaging of Anesthetic Modulation of Human Consciousness

Conditions
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Healthy

Intervention / Treatment
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* Drug: Propofol


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Must have a body mass index (BMI) less than 30. Must be right handed Must be English speaking Must be capable of giving written informed consent. Must have history of playing tennis (or any type of racquet sport) at least 30 times over lifetime. Exclusion Criteria: History of obstructive sleep apnea; History of a difficult airway with a previous anesthetic; History of neurological disorders; Hypertension or other cardiovascular abnormalities; Pulmonary hypertension or other pulmonary abnormalities; Gastroesophageal reflux disease (GERD) or heartburn; History of significant head injury with loss of consciousness; Learning disability or other developmental disorder; Allergic reactions to eggs; Pregnant or nursing mothers; Contraindications to neuroimaging methods; Inability or unwilling to fast, or withhold food and liquid intake, for 8 hours prior to your scheduled study visit. Unwilling to abstain from alcohol use for 24 hours prior to your scheduled study visit. History of drug use, or have a positive drug screen. Tattoos on the head or neck region - all other tattoos are subject to determination by investigators. Any impairment, activity or situation that in the judgment of the study coordinator or Principal Investigators would prevent satisfactory completion of the study protocol.

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 40 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Propofol Administration<br> | Drug: Propofol<br>* Propofol administration<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change From Baseline in Blood Oxygen Level Dependent (BOLD) Response to Sensory Stimuli During Sedation | Change = BOLD Response During Sedation - BOLD Response During Baseline | Baseline to 90 minutes | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change From Baseline in Squeeze Pressure | Measurements of the force of participants' hand squeezing on a rubber ball in response to instructions. Change = Squeeze Pressure During Sedation - Squeeze Pressure During Baseline. | Baseline to 90 minutes |