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The Neural Mechanisms of Anesthesia and Human Consciousness (LOC-2013)

The safety and scientific validity of this study is the responsibility of the study sponsor and investigators. Listing a study does not mean it has been evaluated by the U.S. Federal Government. Read our disclaimer for details. Identifier: NCT01889004
Recruitment Status : Completed
First Posted : June 28, 2013
Last Update Posted : January 11, 2016
Academy of Finland
Hospital District of Southwestern Finland
Information provided by (Responsible Party):
Harry Scheinin, University of Turku

Brief Summary:

The explanation of consciousness poses one of the greatest challenges to science and philosophy in the 21st century. It remains unclear what consciousness is and how it emerges from brain activity. By studying anesthesia and sleep, the investigators aim to reveal what happens in the brain when consciousness is lost and when it returns. During the study, a series of Positron Emission Tomography (PET), Magnetic Resonance Imaging (MRI) and electroencephalography (EEG) studies will be carried out on healthy male subjects to reveal the neural correlates of consciousness. Consciousness of the subjects will be manipulated with normal sleep and anesthetic agents dexmedetomidine and propofol.

First, various neurophysiological tools to separate consciousness, connectedness and responsiveness during normal sleep will be tested. The most suitable methods and subjects will be selected and then tested during anesthetic-induced sedation and loss of responsiveness (LOR). The anesthetics (dexmedetomidine or propofol) will be administered as target-controlled infusions (TCI) with step-wise concentration-increments until LOR is detected. Then, TCIs are repeated in the same subjects but adjusted according to the individual drug target concentrations sufficient for LOR, and a series of PET perfusion imaging measurements will be performed to obtain the brain activity information in various states of consciousness. The same subjects will then be imaged with PET for brain activity after sleep deprivation (awake), during various sleep stages and immediately after awakening. Finally, ten dexmedetomidine subjects will be given the drug once more, and functional MRI (fMRI) data will be collected at various states of consciousness before and during verbal and nonverbal vocalizations. EEG will be continuously collected in all sessions. The depth of anesthesia will be measured using quantitative EEG and bispectral index (BIS) monitoring.

The results may lead to the discovery of new and better objective indicators of the depth of anesthesia and consciousness, and new insights into the understanding of neural mechanisms behind drug-induced loss of consciousness and ultimately the mechanisms of action of (general) anesthetics as well as consciousness itself.

Condition or disease Intervention/treatment Phase
Consciousness, Level Altered Drug: Dexmedetomidine Drug: Propofol Phase 4

Detailed Description:
(not needed)

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Study Type : Interventional  (Clinical Trial)
Actual Enrollment : 47 participants
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)
Primary Purpose: Basic Science
Official Title: The Neural Mechanisms of Anesthesia and Human Consciousness (LOC-2013)
Study Start Date : February 2014
Actual Primary Completion Date : January 2016
Actual Study Completion Date : January 2016

Resource links provided by the National Library of Medicine

Arm Intervention/treatment
Experimental: Dexmedetomidine
Intravenous dexmedetomidine using target controlled infusion
Drug: Dexmedetomidine
Escalating concentrations until loss of responsiveness
Other Name: Dexdor

Experimental: Propofol
Intravenous propofol using target controlled infusion
Drug: Propofol
Escalating concentrations until loss of responsiveness
Other Name: Propofol-Lipuro

Primary Outcome Measures :
  1. Regional cerebral blood flow [ Time Frame: Several measurements during two separate days within 2 months ]
    Altogether 14 PET scans during two separate study days. Cerebral blood flow changes will be used as surrogates for changes in regional brain activity.

Secondary Outcome Measures :
  1. EEG [ Time Frame: Continuous data collection during five separate days within 2 months ]
  2. Functional magnetic resonance imaging (fMRI) [ Time Frame: Several measurements during one day ]
  3. Event related potentials [ Time Frame: Several time points during five separate days within 2 months ]

Other Outcome Measures:
  1. Drug concentration in plasma [ Time Frame: Several times points during two or three separate days within 2 months ]

Information from the National Library of Medicine

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Ages Eligible for Study:   20 Years to 30 Years   (Adult)
Sexes Eligible for Study:   Male
Accepts Healthy Volunteers:   Yes

Inclusion Criteria:

  • Male
  • Age 20-30 years
  • Good general health i.e. American Society of Anesthesiologists (ASA) physical status I
  • Fluent in Finnish language
  • Right handedness
  • Written informed consent
  • Good sleep quality

Exclusion Criteria:

  • Chronic medication
  • History of alcohol and/or drug abuse
  • Strong susceptibility for allergic reactions
  • Serious nausea in connection with previous anesthesia
  • Strong susceptibility for nausea
  • Any use of drugs or alcohol during the 48 hours preceding anesthesia
  • Use of caffeine products 10-12 hours prior the study, 24 hours before sleep studies
  • Smoking
  • Clinically significant previous cardiac arrhythmia / cardiac conduction impairment
  • Clinically significant abnormality in prestudy laboratory tests
  • Positive result in the drug screening test
  • Blood donation within 90 days prior to the study
  • Participation in any medical study with an experimental drug or device during the preceding 60 days
  • The study subject has undergone a prior PET or SPECT study
  • Any contraindication to magnetic resonance imaging (MRI)
  • Hearing impairment
  • Detected unsuitability based on initial electrophysiological measurements
  • Detected unsuitability based on MRI scanning results
  • Sleep disorder or severe sleep problem

Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its identifier (NCT number): NCT01889004

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Turku PET Centre
Turku, Finland, FI-20521
Sponsors and Collaborators
University of Turku
Academy of Finland
Hospital District of Southwestern Finland
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Principal Investigator: Harry Scheinin, MD University of Turku
Additional Information:
Publications automatically indexed to this study by Identifier (NCT Number):
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Responsible Party: Harry Scheinin, Adjunct Professor, University of Turku Identifier: NCT01889004    
Other Study ID Numbers: LOC-2013
266467 ( Other Grant/Funding Number: Academy of Finland )
2013-001496-21 ( EudraCT Number )
KLnro 72/2013 ( Registry Identifier: Finnish Medicines Agency (Fimea) )
First Posted: June 28, 2013    Key Record Dates
Last Update Posted: January 11, 2016
Last Verified: January 2016
Keywords provided by Harry Scheinin, University of Turku:
Cerebral blood flow
Event related potentials
Functional magnetic resonance imaging
General anesthesia
Positron emission tomography
Additional relevant MeSH terms:
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Consciousness Disorders
Neurobehavioral Manifestations
Neurologic Manifestations
Nervous System Diseases
Neurocognitive Disorders
Mental Disorders
Hypnotics and Sedatives
Central Nervous System Depressants
Physiological Effects of Drugs
Anesthetics, Intravenous
Anesthetics, General
Analgesics, Non-Narcotic
Sensory System Agents
Peripheral Nervous System Agents
Adrenergic alpha-2 Receptor Agonists
Adrenergic alpha-Agonists
Adrenergic Agonists
Adrenergic Agents
Neurotransmitter Agents
Molecular Mechanisms of Pharmacological Action