Consciousness Disorders
Conditions
Brief summary
In this study, the investigators explore anesthesia as a tool for providing further insight into the level of consciousness of individuals with a clinical diagnosis of unresponsive wakefulness syndrome (UWS), but who possess some neurophysiological signatures of conscious awareness. This group, who could potentially be conscious, will herein be referred to as the target population. Our goal is to assess whether or not neurological patterns of consciousness in the target population respond to anesthesia in a similar manner to neurologically compromised individuals with known consciousness (e.g. those in minimally conscious state (MCS). In healthy controls, propofol-induced unconsciousness results in an elimination of the mismatch negativity event-related brain potential (ERP) and a diminished directed connectivity. The investigators hypothesize that at doses well below those required for surgery, anesthesia will have similar effects on these neural patterns in neurologically compromised patients with the potential for conscious awareness, but will not affect these patterns in those who lack consciousness.
Interventions
DEVICEEEG recording
EEG recording with anesthetic (DIPRIVAN)
DRUGAnesthetics, Intravenous
The participant will receive an intravenous infusion of propofol (DIPRIVAN Injectable Emulsion USP 1%, AstraZeneca).
Sponsors
McGill University
McMaster University
University of Michigan
Study design
Allocation
NON_RANDOMIZED
Intervention model
PARALLEL
Primary purpose
BASIC_SCIENCE
Masking
NONE
Eligibility
Sex/Gender
ALL
Age
18 Years to 50 Years
Healthy volunteers
No
Inclusion criteria
* Patients admitted to the intensive care unit at Hamilton General Hospital who: * Clinical status consistent with UWS (no responsiveness to commands) * Clinical status consistent with MCS (minimal response to at least one command) * Presence of an endotracheal tube (ETT) or a tracheostomy tube * Between 18 and 50 years of age
Exclusion criteria
* • Elevated intracranial pressure (ICP) * Hepatic or renal failure * Hemodynamic instability * Active vasopressor therapy * Previous open-head injury * Previous intracranial pathology requiring neurosurgical interventions in the past 72 hours * Anticipated ICU stay \< 24 hours * Documented allergy to propofol * Pregnancy * BMI \> 35 kg/m2 * Anyone who is deemed medically unsuitable for this study by the attending intensivist * Patients who are already in a medically-induced coma for intracranial hypertension or status epilepticus
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Asymmetry in feedback vs. feedforward network connectivity | 3 hours | EEG networks will be monitored pre, during and post anesthesia. Directed connectivity will be calculated using phase lag index (PLI) and symbolic transfer entropy (STE) between all combinations of EEG sensors. Average values of feedback connectivity (e.g. from the frontal regions to parietal and occipital regions) will be compared to average values of feedforward connectivity (e.g. from parietal and occipital regions to frontal regions). Positive asymmetry will be correlated to the presence of conscious awareness and negative asymmetry will be correlated to the absence of conscious awareness. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Presence of P300 and N400 event-related potentials | 3 hours | EEG signals will be processed to extract the event-related EEG reactions to the auditory stimulation paradigm. Signals will be average 300 ms post-stimuli and 400 ms post-stimuli to assess the presence of the P300 and N400 event-related potentials. Presence of these event-related potentials will be correlated to the presence of conscious awareness and absence of these event-related potentials will be correlated to the absence of conscious awareness. |
Outcome results
None listed