None listed
Conditions
Brief summary
This study will be a single-site, randomized, controlled, blinded study at the Royal Prince Alfred Hospital to examine changes in High definition-electroencephalogram (HD-EEG) correlates of cognition and consciousness during waking and sedation. Our study will address the neural correlates of consciousness and modulate these neural correlates through low frequency Transcranial alternating current stimulation (tACS).
Interventions
Transcranial alternating current stimulation (TACS) will occur using an Soterix MxN 33 channel transcranial alternating current stimulation device that is designed for non-invasive stimulation of brain function which has a long history of safety. Notably the stimulation currents are significantly lower than current stimulation techniques used in the operating theatre (e.g. 50mA is typically used for somatosensory evoked potentials and tetanic stimulation with up to 200mA used to drive motor evok
Transcranial alternating current stimulation (TACS) will occur using an Soterix MxN 33 channel transcranial alternating current stimulation device that is designed for non-invasive stimulation of brain function which has a long history of safety. Notably the stimulation currents are significantly lower than current stimulation techniques used in the operating theatre (e.g. 50mA is typically used for somatosensory evoked potentials and tetanic stimulation with up to 200mA used to drive motor evoked potentials). TACS (or sham dependent on randomisation) will be performed 5 minutes prior to the wakeup protocol stage 3 (see protocol section 6.1.3- attached at bottom of this form) being performed. The total amperes will not exceed 2 mA, and each stimulation period will be brief across different periods throughout the experience. Stimulation will be performed using five electrodes, four centred around Cz/Fz and one placed around Pz/Oz. These are located at the back and central area of the head. The placement of the electrodes makes a focal ‘closed’ circuit for stimulation around the given area.. Stimulation will be targeted to electrodes Oz/Cz/Fz using a five electrode montage that has previously been shown to modulate default mode network activity and connectivity and we have shown these regions are important for consciousness under dexmedetomidine sedation. Stimulation will occur for 5 minutes at a time with a total of 1:15 stimulation time). The intervention will be administered by the Anaesthetic consultant and Dr Jordan Wehrman (post doctorate associate researcher). The intervention is monitored via computer linked to the tACS machine and checked throughout the study by Dr. Wehrman, Dr. Wehrman is unblinded in the study and in charge of administering the intervention. The study will occur in 4 stages. Stage 1- resting state EEG data with 10X blocks of data collection for periods of 5-7 minutes. Participants will be randomised live to resting (no stimualtion - patient rests with eyes closed) or auditory stimulation (a series of sounds played on speaker to patient). There will be a total of 3 auditory, 7 resting stages. This will take around 1-1.5 hours and the following stage commences immediately after. Stage 2- Sedation -Professor Robert Sanders or an anaesthetic fellow will administer the dexmedetomidine via intravenous cannula. Dexmedetomidine will be titrated at a starting of 0.5 mcg/kg/hr until the patient falls asleep. The sedation, monitoring and safety interventions such as fluid administration and oxygen therapy will be managed by the two anaesthetic doctors present. There will be a series of 10 wake ups during this stage. Prior to each stage live randomisation to resting or auditory stimulation will occur. The resting stage is just relaxing with eyes closed. The auditory stimulation involves playing a series of sounds via a small speaker to the patient. This will take around 1-1.5 hours and the following stage commences immediately after. Stage 3- TACs/Sham - Live randomisation to TACS or sham will occur prior to each block of data. There will be 30 wake ups in total in a random order following the stimulation period of 5 minutes before each wake up. This will take around 3 hours and the next stage will commence immediately. Stage 4- Live randomisation to 15 minutes of TACs or sham and then after 3 minutes the participant will be allowed to naturally wake up. This will take around 1 hour and the patient will be recovered following this stage. The total project time is 8 hours with approximately 5 hours sedated.
Sponsors
Sydney Local Health District
Study design
Allocation
Randomised controlled trial
Intervention model
Crossover
Primary purpose
Treatment
Masking
Blinded (masking used) (Subject, Investigator, Outcomes Assessor)
Eligibility
Sex/Gender
All
Age
18 Years to 40 Years
Healthy volunteers
Yes
Inclusion criteria
• Adults, ages greater than or equal to 18 and 40 years old • In good health, determined by the PI on the basis of medical history and a standard assessment for anaesthesia to be documented as part of the study record • English Language Proficiency (suitable to provide informed consent and participate in research activities).
Exclusion criteria
• Adults <18 years old or >40 years old • Pregnancy confirmed on pregnancy test on day of sedation • Use of recreational drugs • Use of sedatives/sleeping medication within 24 hours prior to sedation visit • Prescription for opioids (chronic or PRN) or other medications that cause sedation • Contraindication to anaesthesia or allergy to study drug • Difficult anaesthesia: American Society of Anesthesiologists Physical Status greater than 1, per the discretion of the PI. Examples of ASA>1 status includes, but are not limited to: o Any systemic disease present, such as diabetes, cardiac, pulmonary, or other acute or chronic disorder, or history of smoking o Narrow angle glaucoma o Abnormal airway examination o Any abnormality on physical examination that could increase anaesthetic risk o Snoring or sleep disorders including apnea o Antecedent pulmonary aspiration risk (e.g., history GI reflux, heartburn, hiatal hernia) o Adverse reaction or allergy with anaesthesia or other sedatives o Chronic medication use o History of difficult anaesthesia, laryngoscopy or intubation o Family history of difficulty with anaesthesia or sedation o History of vertigo, nausea or vomiting after anaesthesia • BMI > 35 • Contraindication to HD-EEG for relative parts of the procedures. • Exclusion from Dexmedetomidine: o Resting heart Rate<50 bpm o Known dexmedetomidine allergy • People working in anaesthesia (such as anaesthetic registrars) • People who are occupationally exposed to the study drugs. Additional exclusion criteria on the day of sedation: • Anything to eat or drink for the preceding 6 hours (excluding clear fluids) • Anything to drink for the preceding 2 hours • Any use of over-the-counter or recreational drugs (including alcohol or tobacco) within the preceding 24 hours • Any use of opioid, sedative or sleep agents within the preceding 24 hours • Recent change in health, including cough, cold, or fever • Exposure to anaesthesia or sedation in the last 6 days
Outcome results
None listed