Loss of ConsciousnessNCT04502550
Brain Networks and Consciousness
An observational study of Loss of Consciousness and Parkinson Disease, run by University of Texas Southwestern Medical Center at 1 site in United States.
Trial summary
General anesthesia (GA) is a medically induced state of unresponsiveness and unconsciousness, which millions of people experience every year. Despite its ubiquity, a clear and consistent picture of the brain circuits mediating consciousness and responsiveness has not emerged. Read more about this study
- Who is it for?
- Ages 18 years and older
- Conditions the study is for
- Loss of Consciousness, Parkinson Disease, Essential Tremor
- What is being tested?
- Propofol
- Type of treatment
- Injection or infusion
- How many people
- 57 participants
- Where
- 1 siteUnited States
- Study dates
- 15 Oct 2020to 31 Dec 2025
- Phase
- Observational
- Are there results?
- Yes, posted in the registrySummary in the doctors' view
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 years and older
- All sexes
- No healthy volunteers
- Adult, Older adult
Study population: Study participants are Parkinson's disease and essential tremor patients undergoing revision/replacement of an implantable pulse generator for DBS, or initial DBS implantation.
Who may be able to join
- Willingness and ability to cooperate during conscious operative procedure for up to 40 minutes
- Clinical diagnosis of Parkinson's disease or essential tremor
- Preoperative MRI without evidence of cortical or subdural adhesions or vascular abnormalities
Who cannot join
- Patients with recent use (within one week) of anticoagulant or antiplatelet agent use
- Neurocognitive testing indicating amnestic cognitive deficits
- History of intolerance of propofol or medical indications to use an anesthetic other than propofol
Trial locations and contacts
1 site in 1 country.
About this study
Official title: Subcortical-cortical Network Dynamics of Anesthesia and Consciousness
General anesthesia (GA) is a medically induced state of unresponsiveness and unconsciousness, which millions of people experience every year. Despite its ubiquity, a clear and consistent picture of the brain circuits mediating consciousness and responsiveness has not emerged. Studies to date are limited by lack of direct recordings in human brain during medically induced anesthesia. Our overall hypothesis is that the current model of consciousness, originally proposed to model disorders and recovery of consciousness after brain injury, can be generalized to understand mechanisms of consciousness more broadly. This will be studied through three specific aims. The first is to evaluate the difference in anesthesia sensitivity in patients with and without underlying basal ganglia pathology. Second is to correlate changes in brain circuitry with induction and emergence from anesthesia. The third aim is to evaluate the effects of targeted deep brain stimulation on anesthesia induced loss and recovery of consciousness. This study focuses on experimentally studying these related brain circuits by taking advantage of pathological differences in movement disorder patient populations undergoing deep brain stimulation (DBS) surgery. DBS is a neurosurgical procedure that is used as treatment for movement disorders, such as Parkinson's disease and essential tremor, and provides a mechanism to acquire brain activity recordings in subcortical structures. This study will provide important insight by using human data to shed light on the generalizability of the current model of consciousness. The subject's surgery for DBS will be prolonged by up to 40 minutes in order to record the participant's brain activity and their responses to verbal and auditory stimuli.
- Conditions
- Loss of Consciousness, Parkinson Disease, Essential Tremor, Anesthesia
- Being tested
- Propofol
- Keywords
- general anesthesia, deep brain stimulation, basal ganglia, thalamus, sensorimotor cortex
- Medical subject headings
- Unconsciousness, Parkinson Disease, Essential Tremor
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
PropofolDrug
Target effect-site concentration of propofol will be started at 1.4 μg/mL and will be increased by 0.3 μg/mL with reassessment until endpoints are achieved.
| Study group | Role | What they receive |
|---|---|---|
| Parkinson's Disease patients with DBS, no stimulation | This cohort will serve as as the observed group, displaying basal ganglia pathology.
A syringe pump controlled by Stanpump implementing the Eleveld Pharmacokinetics-Pharmacodynamics (PK-PD) model for propofol will be used as a targeted controlled infusion (TCI) system to achieve plasma target propofol concentrations. Target effect-site concentration of propofol will be started at 1.4 μg/mL and will be increased by 0.3 μg/mL with reassessment until endpoints are achieved.
Experiments will be completed with DBS off. Receives: Drug: Propofol | |
| Essential Tremor patients with DBS | This cohort will serve as a control group (no basal ganglia pathology). A syringe pump controlled by Stanpump implementing the Eleveld Pharmacokinetics-Pharmacodynamics (PK-PD) model for propofol will be used as a TCI system to achieve plasma target propofol concentrations. Target effect-site concentration of propofol will be started at 1.4 μg/mL and will be increased by 0.3 μg/mL with reassessment until endpoints are achieved.
Experiments will be completed with DBS off. Receives: Drug: Propofol | |
| Parkinson's Disease patients with DBS, Gpi stimulation | This cohort will serve as as the observed group, displaying basal ganglia pathology.
A syringe pump controlled by Stanpump implementing the Eleveld Pharmacokinetics-Pharmacodynamics (PK-PD) model for propofol will be used as a targeted controlled infusion (TCI) system to achieve plasma target propofol concentrations. Target effect-site concentration of propofol will be started at 1.4 μg/mL and will be increased by 0.3 μg/mL with reassessment until endpoints are achieved.
Participants will be stimulated at the Gpi via DBS leads during propofol induced loss of consciousness. Receives: Drug: Propofol | |
| Parkinson's Disease patients with DBS, Gpe stimulation | This cohort will serve as as the observed group, displaying basal ganglia pathology.
A syringe pump controlled by Stanpump implementing the Eleveld Pharmacokinetics-Pharmacodynamics (PK-PD) model for propofol will be used as a targeted controlled infusion (TCI) system to achieve plasma target propofol concentrations. Target effect-site concentration of propofol will be started at 1.4 μg/mL and will be increased by 0.3 μg/mL with reassessment until endpoints are achieved.
Participants will be stimulated at the Gpe via DBS leads during propofol induced loss of consciousness. Receives: Drug: Propofol | |
| Parkinson's Disease patients undergoing DBS surgery, Gpe stimulation | A syringe pump controlled by Stanpump implementing the Eleveld Pharmacokinetics-Pharmacodynamics (PK-PD) model for propofol will be used as a targeted controlled infusion (TCI) system to achieve plasma target propofol concentrations. Target effect-site concentration of propofol will be started at 1.4 μg/mL and will be increased by 0.3 μg/mL with reassessment until endpoints are achieved.
Participants will be stimulated at the Gpe via DBS leads, and cortical activity will be recorded via ECoG during propofol induced loss of consciousness. Receives: Drug: Propofol | |
| Parkinson's Disease patients undergoing DBS surgery, Gpi stimulation | A syringe pump controlled by Stanpump implementing the Eleveld Pharmacokinetics-Pharmacodynamics (PK-PD) model for propofol will be used as a targeted controlled infusion (TCI) system to achieve plasma target propofol concentrations. Target effect-site concentration of propofol will be started at 1.4 μg/mL and will be increased by 0.3 μg/mL with reassessment until endpoints are achieved.
Participants will be stimulated at the Gpi via DBS leads, and cortical activity will be recorded via ECoG during propofol induced loss of consciousness. Receives: Drug: Propofol | |
| Parkinson's Disease patients undergoing DBS surgery, no stimulation | A syringe pump controlled by Stanpump implementing the Eleveld Pharmacokinetics-Pharmacodynamics (PK-PD) model for propofol will be used as a targeted controlled infusion (TCI) system to achieve plasma target propofol concentrations. Target effect-site concentration of propofol will be started at 1.4 μg/mL and will be increased by 0.3 μg/mL with reassessment until endpoints are achieved.
Participants will not receive any stimulation via DBS leads, and cortical activity will be recorded via ECoG during propofol induced loss of consciousness. Receives: Drug: Propofol |
What is being measured
The primary outcome is the main question the study is designed to answer.
Propofol Dose Response Curve
Average targeted serum dose of propofol at which 50% of patients had loss of behavioral responses
Measured: Baseline visit
Behavioral Assessment of Propofol Induced Loss / Recovery of Consciousness and Responsiveness
Number of participants with loss of at least 50% of behavioral responses at a targeted serum concentration of 1.5 ug/mL using the following three behavioral responses will be evaluated: (1) loss/recovery of spontaneous movement (i.e., loss and recovery of responsiveness) (2) loss/recovery of movement in response to stimuli (separately to clicks [non-salient] and verbal stimuli [salient]), and (3) loss/recovery of movement to command (verbal command with patient name with instruction to open their eyes, as proxy of loss/recovery of consciousness).
Measured: baseline
Electrocorticogram (ECoG) and Pallidal Local Field Potential (LFP) Recordings
Oscillatory frequency at which maximal power changes occur with inducing loss of consciousness, as measured using ECoG and Globus Pallidus internus / Globus Pallidus externus (GPi/GPe) LFP recordings during DBS implantation surgery with target-controlled infusion of propofol. This is not an average frequency but a single peak value based on population spectra at which maximal changes are noted. The number reported is not an average of peaks across patients, but the peak identified after integrating data across the population studied. There is no corresponding measure of dispersion or prevision based on the way the value is identified. Rather, it is a single peak value.
Measured: Baseline
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted6 Aug 2020
- Study start15 Oct 2020
- Primary completion14 Nov 2024
- Study completion31 Dec 2025
Why it stopped: Conclusion of funding
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Posted resultsParticipant flow, outcome measures and adverse events reported by the sponsor.
- Other trials for Loss of ConsciousnessStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Observational
- Observational model
- Case-control
- Time perspective
- Prospective
- Enrolment
- 57 participants (actual)
Sponsor and investigators
- Lead sponsor
- University of Texas Southwestern Medical Center
- Sponsor type
- University, hospital or other
- Collaborators
- University of California, Los Angeles
- Responsible party
- Principal investigator, Nader Pouratian, University of Texas Southwestern Medical Center
- Investigators
- Nader Pouratian, MD, PhD, Principal investigator, University of Texas Southwestern Medical Center
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT04502550
- Sponsor's protocol ID
- STU-2021-0396
- Status last verified
- Jun 2026
- First submitted
- 30 Jul 2020
- Last updated
- 8 Jun 2026
- Results posted
- Yes, on ClinicalTrials.gov
- Data monitoring committee
- Yes
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 8 Jun 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Subcortical-cortical Network Dynamics of Anesthesia and Consciousness
- ClinicalTrials.gov ID
- NCT04502550
- Acronym / sponsor ID
- STU-2021-0396
- Conditions
- Loss of Consciousness, Parkinson Disease, Essential Tremor, Anesthesia
- Keywords
- general anesthesia, deep brain stimulation, basal ganglia, thalamus, sensorimotor cortex
- Study type
- Observational
- Recruitment status
- TerminatedReason stopped: Conclusion of funding
- Enrolment
- 57 participants (actual)
- Lead sponsor
- University of Texas Southwestern Medical CenterUniversity, hospital or other
- Collaborators
- University of California, Los Angeles
- Study start
- 15 Oct 2020 (actual)
- Primary completion
- 14 Nov 2024 (actual)
- Study completion
- 31 Dec 2025 (actual)
- First posted
- 6 Aug 2020 (actual)
- Results
- Posted 8 Jun 2026
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
General anesthesia (GA) is a medically induced state of unresponsiveness and unconsciousness, which millions of people experience every year. Despite its ubiquity, a clear and consistent picture of the brain circuits mediating consciousness and responsiveness has not emerged. Studies to date are limited by lack of direct recordings in human brain during medically induced anesthesia. Our overall hypothesis is that the current model of consciousness, originally proposed to model disorders and recovery of consciousness after brain injury, can be generalized to understand mechanisms of consciousness more broadly. This will be studied through three specific aims. The first is to evaluate the difference in anesthesia sensitivity in patients with and without underlying basal ganglia pathology. Second is to correlate changes in brain circuitry with induction and emergence from anesthesia. The third aim is to evaluate the effects of targeted deep brain stimulation on anesthesia induced loss and recovery of consciousness. This study focuses on experimentally studying these related brain circuits by taking advantage of pathological differences in movement disorder patient populations undergoing deep brain stimulation (DBS) surgery. DBS is a neurosurgical procedure that is used as treatment for movement disorders, such as Parkinson's disease and essential tremor, and provides a mechanism to acquire brain activity recordings in subcortical structures. This study will provide important insight by using human data to shed light on the generalizability of the current model of consciousness. The subject's surgery for DBS will be prolonged by up to 40 minutes in order to record the participant's brain activity and their responses to verbal and auditory stimuli.
Study design
- Observational model
- Case-control
- Time perspective
- Prospective
- Number of arms
- 7
| Arm | Type | Receives |
|---|---|---|
| Parkinson's Disease patients with DBS, no stimulation | – | Drug: PropofolThis cohort will serve as as the observed group, displaying basal ganglia pathology. A syringe pump controlled by Stanpump implementing the Eleveld Pharmacokinetics-Pharmacodynamics (PK-PD) model for propofol will be used as a targeted controlled infusion (TCI) system to achieve plasma target propofol concentrations. Target effect-site concentration of propofol will be started at 1.4 μg/mL and will be increased by 0.3 μg/mL with reassessment until endpoints are achieved. Experiments will be completed with DBS off. |
| Essential Tremor patients with DBS | – | Drug: PropofolThis cohort will serve as a control group (no basal ganglia pathology). A syringe pump controlled by Stanpump implementing the Eleveld Pharmacokinetics-Pharmacodynamics (PK-PD) model for propofol will be used as a TCI system to achieve plasma target propofol concentrations. Target effect-site concentration of propofol will be started at 1.4 μg/mL and will be increased by 0.3 μg/mL with reassessment until endpoints are achieved. Experiments will be completed with DBS off. |
| Parkinson's Disease patients with DBS, Gpi stimulation | – | Drug: PropofolThis cohort will serve as as the observed group, displaying basal ganglia pathology. A syringe pump controlled by Stanpump implementing the Eleveld Pharmacokinetics-Pharmacodynamics (PK-PD) model for propofol will be used as a targeted controlled infusion (TCI) system to achieve plasma target propofol concentrations. Target effect-site concentration of propofol will be started at 1.4 μg/mL and will be increased by 0.3 μg/mL with reassessment until endpoints are achieved. Participants will be stimulated at the Gpi via DBS leads during propofol induced loss of consciousness. |
| Parkinson's Disease patients with DBS, Gpe stimulation | – | Drug: PropofolThis cohort will serve as as the observed group, displaying basal ganglia pathology. A syringe pump controlled by Stanpump implementing the Eleveld Pharmacokinetics-Pharmacodynamics (PK-PD) model for propofol will be used as a targeted controlled infusion (TCI) system to achieve plasma target propofol concentrations. Target effect-site concentration of propofol will be started at 1.4 μg/mL and will be increased by 0.3 μg/mL with reassessment until endpoints are achieved. Participants will be stimulated at the Gpe via DBS leads during propofol induced loss of consciousness. |
| Parkinson's Disease patients undergoing DBS surgery, Gpe stimulation | – | Drug: PropofolA syringe pump controlled by Stanpump implementing the Eleveld Pharmacokinetics-Pharmacodynamics (PK-PD) model for propofol will be used as a targeted controlled infusion (TCI) system to achieve plasma target propofol concentrations. Target effect-site concentration of propofol will be started at 1.4 μg/mL and will be increased by 0.3 μg/mL with reassessment until endpoints are achieved. Participants will be stimulated at the Gpe via DBS leads, and cortical activity will be recorded via ECoG during propofol induced loss of consciousness. |
| Parkinson's Disease patients undergoing DBS surgery, Gpi stimulation | – | Drug: PropofolA syringe pump controlled by Stanpump implementing the Eleveld Pharmacokinetics-Pharmacodynamics (PK-PD) model for propofol will be used as a targeted controlled infusion (TCI) system to achieve plasma target propofol concentrations. Target effect-site concentration of propofol will be started at 1.4 μg/mL and will be increased by 0.3 μg/mL with reassessment until endpoints are achieved. Participants will be stimulated at the Gpi via DBS leads, and cortical activity will be recorded via ECoG during propofol induced loss of consciousness. |
| Parkinson's Disease patients undergoing DBS surgery, no stimulation | – | Drug: PropofolA syringe pump controlled by Stanpump implementing the Eleveld Pharmacokinetics-Pharmacodynamics (PK-PD) model for propofol will be used as a targeted controlled infusion (TCI) system to achieve plasma target propofol concentrations. Target effect-site concentration of propofol will be started at 1.4 μg/mL and will be increased by 0.3 μg/mL with reassessment until endpoints are achieved. Participants will not receive any stimulation via DBS leads, and cortical activity will be recorded via ECoG during propofol induced loss of consciousness. |
Who may qualify
- Ages
- 18 years and older
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
- Study population
- Study participants are Parkinson's disease and essential tremor patients undergoing revision/replacement of an implantable pulse generator for DBS, or initial DBS implantation.
Key inclusion criteria (3 listed)
- Willingness and ability to cooperate during conscious operative procedure for up to 40 minutes
- Clinical diagnosis of Parkinson's disease or essential tremor
- Preoperative MRI without evidence of cortical or subdural adhesions or vascular abnormalities
Key exclusion criteria (3 listed)
- Patients with recent use (within one week) of anticoagulant or antiplatelet agent use
- Neurocognitive testing indicating amnestic cognitive deficits
- History of intolerance of propofol or medical indications to use an anesthetic other than propofol
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| PropofolTarget effect-site concentration of propofol will be started at 1.4 μg/mL and will be increased by 0.3 μg/mL with reassessment until endpoints are achieved. | Drug | Essential Tremor patients with DBS, Parkinson's Disease patients undergoing DBS surgery, Gpe stimulation, Parkinson's Disease patients undergoing DBS surgery, Gpi stimulation, Parkinson's Disease patients undergoing DBS surgery, no stimulation, Parkinson's Disease patients with DBS, Gpe stimulation, Parkinson's Disease patients with DBS, Gpi stimulation, Parkinson's Disease patients with DBS, no stimulation |
Primary outcome
Propofol Dose Response Curve
Time frame: Baseline visit
Average targeted serum dose of propofol at which 50% of patients had loss of behavioral responses
Behavioral Assessment of Propofol Induced Loss / Recovery of Consciousness and Responsiveness
Time frame: baseline
Number of participants with loss of at least 50% of behavioral responses at a targeted serum concentration of 1.5 ug/mL using the following three behavioral responses will be evaluated: (1) loss/recovery of spontaneous movement (i.e., loss and recovery of responsiveness) (2) loss/recovery of movement in response to stimuli (separately to clicks [non-salient] and verbal stimuli [salient]), and (3) loss/recovery of movement to command (verbal command with patient name with instruction to open their eyes, as proxy of loss/recovery of consciousness).
Electrocorticogram (ECoG) and Pallidal Local Field Potential (LFP) Recordings
Time frame: Baseline
Oscillatory frequency at which maximal power changes occur with inducing loss of consciousness, as measured using ECoG and Globus Pallidus internus / Globus Pallidus externus (GPi/GPe) LFP recordings during DBS implantation surgery with target-controlled infusion of propofol. This is not an average frequency but a single peak value based on population spectra at which maximal changes are noted. The number reported is not an average of peaks across patients, but the peak identified after integrating data across the population studied. There is no corresponding measure of dispersion or prevision based on the way the value is identified. Rather, it is a single peak value.
Results and safety
Loading the posted results from ClinicalTrials.gov…
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 8 Jun 2026.
- Posted resultsParticipant flow, baseline, all outcome measures and adverse events.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Nader Pouratian, MD, PhD principal investigator
University of Texas Southwestern Medical Center
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
An observational study of Loss of Consciousness and Parkinson Disease, run by University of Texas Southwestern Medical Center at 1 site in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 3 inclusion and 3 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: stopped early, as of the sponsor's last update on 8 Jun 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
Yes. Results are posted in the registry (first posted 8 Jun 2026). A summary is in the For doctors view, and the full results are on ClinicalTrials.gov.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Propofol Dose Response Curve (time frame: Baseline visit). The study lists 3 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 8 Jun 2026.