Assessing Covert Consciousness in Unresponsive Patients

Assessing the Potential for 'Covert Consciousness' in Unresponsive Patients

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.

Study Overview

• Status: Unknown
• Conditions: Consciousness Disorders
• Intervention / Treatment: Device: EEG recording; Drug: Anesthetics, Intravenous

• Study Type: Interventional
• Enrollment (Anticipated): 60
• Phase: Not Applicable

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 50 years (Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

Description

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

Study Plan

How is the study designed?

Design Details

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

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Placebo Comparator: Control 1 (negative control); Individuals with a diagnosis of UWS without neural markers of consciousness	Device: EEG recording; EEG recording with anesthetic (DIPRIVAN)
Active Comparator: Control 2 (positive control); Individuals with a diagnosis of MCS, who are behaviourally responsive and who present neural markers of consciousness	Device: EEG recording; EEG recording with anesthetic (DIPRIVAN)
Experimental: Target Population; Individuals with a clinical diagnosis of UWS, but who possess some neurophysiological signatures of conscious awareness	Device: EEG recording; EEG recording with anesthetic (DIPRIVAN); Drug: Anesthetics, Intravenous; The participant will receive an intravenous infusion of propofol (DIPRIVAN Injectable Emulsion USP 1%, AstraZeneca).

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Asymmetry in feedback vs. feedforward network connectivity	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.	3 hours

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Presence of P300 and N400 event-related potentials	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.	3 hours

Collaborators and Investigators

• Sponsor: University of Michigan
• Collaborators: McGill University; McMaster University

Study record dates

Study Major Dates

• Study Start: December 1, 2016
• Primary Completion (Anticipated): June 1, 2017

Study Registration Dates

• First Submitted: January 8, 2016
• First Submitted That Met QC Criteria: January 14, 2016
• First Posted (Estimate): January 20, 2016

Study Record Updates

• Last Update Posted (Estimate): October 27, 2016
• Last Update Submitted That Met QC Criteria: October 25, 2016
• Last Verified: October 1, 2016

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Mental Disorders; Nervous System Diseases; Neurologic Manifestations; Neurobehavioral Manifestations; Neurocognitive Disorders; Consciousness Disorders; Physiological Effects of Drugs; Central Nervous System Depressants; Anesthetics, General; Anesthetics; Anesthetics, Intravenous
• Other Study ID Numbers: 13-784