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

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

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.

Study Overview

• Status: Completed
• Conditions: Consciousness, Level Altered
• Intervention / Treatment: Drug: Dexmedetomidine; Drug: Propofol

Detailed Description

(not needed)

• Study Type: Interventional
• Enrollment (Actual): 47
• Phase: Phase 4

Contacts and Locations

Study Locations

• Finland
  • Turku, Finland, FI-20521
    • Turku PET Centre

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 20 years to 30 years (Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: Male

Description

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

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Dexmedetomidine; Intravenous dexmedetomidine using target controlled infusion	Drug: Dexmedetomidine; Escalating concentrations until loss of responsiveness; Other Names: Dexdor
Experimental: Propofol; Intravenous propofol using target controlled infusion	Drug: Propofol; Escalating concentrations until loss of responsiveness; Other Names: Propofol-Lipuro

What is the study measuring?

Primary Outcome Measures

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

Secondary Outcome Measures

Outcome Measure	Time Frame
EEG	Continuous data collection during five separate days within 2 months
Functional magnetic resonance imaging (fMRI)	Several measurements during one day
Event related potentials	Several time points during five separate days within 2 months

Other Outcome Measures

Outcome Measure	Time Frame
Drug concentration in plasma	Several times points during two or three separate days within 2 months

Collaborators and Investigators

• Sponsor: University of Turku
• Collaborators: Academy of Finland; Hospital District of Southwestern Finland
• Investigators: Principal Investigator: Harry Scheinin, MD, University of Turku

Publications and helpful links

General Publications

• Langsjo JW, Alkire MT, Kaskinoro K, Hayama H, Maksimow A, Kaisti KK, Aalto S, Aantaa R, Jaaskelainen SK, Revonsuo A, Scheinin H. Returning from oblivion: imaging the neural core of consciousness. J Neurosci. 2012 Apr 4;32(14):4935-43. doi: 10.1523/JNEUROSCI.4962-11.2012.
• Kallionpaa RE, Valli K, Scheinin A, Langsjo J, Maksimow A, Vahlberg T, Revonsuo A, Scheinin H, Mashour GA, Li D. Alpha band frontal connectivity is a state-specific electroencephalographic correlate of unresponsiveness during exposure to dexmedetomidine and propofol. Br J Anaesth. 2020 Oct;125(4):518-528. doi: 10.1016/j.bja.2020.05.068. Epub 2020 Aug 7.
• Kallioinen M, Scheinin A, Maksimow M, Langsjo J, Kaisti K, Takala R, Vahlberg T, Valli K, Salmi M, Scheinin H, Maksimow A. The influence of dexmedetomidine and propofol on circulating cytokine levels in healthy subjects. BMC Anesthesiol. 2019 Dec 5;19(1):222. doi: 10.1186/s12871-019-0895-3.
• Kallionpaa RE, Scheinin A, Kallionpaa RA, Sandman N, Kallioinen M, Laitio R, Laitio T, Kaskinoro K, Kuusela T, Revonsuo A, Scheinin H, Valli K. Spoken words are processed during dexmedetomidine-induced unresponsiveness. Br J Anaesth. 2018 Jul;121(1):270-280. doi: 10.1016/j.bja.2018.04.032. Epub 2018 May 23.
• Radek L, Kallionpaa RE, Karvonen M, Scheinin A, Maksimow A, Langsjo J, Kaisti K, Vahlberg T, Revonsuo A, Scheinin H, Valli K. Dreaming and awareness during dexmedetomidine- and propofol-induced unresponsiveness. Br J Anaesth. 2018 Jul;121(1):260-269. doi: 10.1016/j.bja.2018.03.014. Epub 2018 May 10.

Helpful Links

• Research Group Home Page

Study record dates

Study Major Dates

• Study Start: February 1, 2014
• Primary Completion (Actual): January 1, 2016
• Study Completion (Actual): January 1, 2016

Study Registration Dates

• First Submitted: June 23, 2013
• First Submitted That Met QC Criteria: June 27, 2013
• First Posted (Estimate): June 28, 2013

Study Record Updates

• Last Update Posted (Estimate): January 11, 2016
• Last Update Submitted That Met QC Criteria: January 8, 2016
• Last Verified: January 1, 2016

More Information

Terms related to this study

• Keywords: EEG; Propofol; Dexmedetomidine; Functional magnetic resonance imaging; Positron emission tomography; Consciousness; Cerebral blood flow; General anesthesia; Event related potentials
• Additional Relevant MeSH Terms: Mental Disorders; Nervous System Diseases; Neurologic Manifestations; Neurobehavioral Manifestations; Neurocognitive Disorders; Consciousness Disorders; Physiological Effects of Drugs; Adrenergic Agents; Neurotransmitter Agents; Molecular Mechanisms of Pharmacological Action; Central Nervous System Depressants; Peripheral Nervous System Agents; Analgesics; Sensory System Agents; Anesthetics, Intravenous; Anesthetics, General; Anesthetics; Analgesics, Non-Narcotic; Adrenergic alpha-2 Receptor Agonists; Adrenergic alpha-Agonists; Adrenergic Agonists; Hypnotics and Sedatives; Propofol; Dexmedetomidine
• 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))