Assessing Covert Consciousness During Dexmedetomidine and Ketamine Sedation: An fMRI Study
University of Michigan
Summary
This research is studying whether mental functions take place during different levels of anesthesia, using a commonly used drug (either dexmedetomidine \[with propofol in some participants\] or ketamine), which shows areas in the brain involved in thinking at different depths of anesthesia. As a result of this study, the researchers expect to gain a deeper understanding of mental function during different levels of anesthesia.
Description
Dexmedetomidine is an FDA-approved sedative agent and is used off-label in this study for controlled experimental modulation of consciousness under direct anesthesiology supervision. Ketamine is a FDA-approved anesthetic and analgesic agent and is used off-label in this study for controlled experimental modulation of consciousness under direct anesthesiology supervision. Using fMRI and established cognitive paradigms, the proposed study will directly examine residual conscious processing under dexmedetomidine and ketamine and compare these findings with our existing propofol dataset from NCT0…
Eligibility
- Age range
- 18–40 years
- Sex
- All
- Healthy volunteers
- Yes
Inclusion Criteria: * Healthy study subjects with American Society of Anesthesiologists (ASA)-1 status * Right-handed * Body mass index (BMI) less than 30 * Participants will have the experience of playing tennis (or other racquet sport) at least 30 times in their lifetime * English speaking Exclusion Criteria: * Medical contraindication to MRI scanning; are unable to undergo MRI scanning because of possible pregnancy or currently breastfeeding * BMI greater than or equal to 30 * Metallic substances in the body * claustrophobia, anxiety, or cardiopulmonary disease; or have an intracranial s…
Interventions
- DrugDexmedetomidine (+propofol as indicated)
Dexmedetomidine dosing will follow FDA-labeled parameters for procedural sedation, with a loading dose of 1 mcg/kg administered intravenously over 10 minutes, followed by maintenance infusion within the range of 0.2 to 1.0 mcg/kg/hr, titrated to clinical effect under anesthesiologist supervision. Sedation depth will be assessed behaviorally using standardized squeeze-response testing to determine lost responsiveness (LOR). If LOR is not achieved within labeled dexmedetomidine dosing limits, low-dose propofol will be conditionally added using a target-controlled infusion at an effect-site concentration of 0.5-1.5 μg/ml, which is below typical induction levels and intended to provide supplemental sedation while preserving spontaneous ventilation. Once LOR is achieved, sedation will be maintained within the approved dexmedetomidine range, with adjunct propofol continued only as clinically indicated.
- DrugKetamine
participants will first receive a subanesthetic ketamine infusion of 0.5 mg/kg administered intravenously over 40 minutes. After that, 1.5 mg/kg ketamine will be administered slowly as a bolus over 60 seconds. Based on prior experience with this paradigm, most subjects who lose responsiveness do so for approximately 10 minutes following the bolus dose. For a 70 kg healthy subject, the total ketamine dose in this paradigm is approximately 140 mg. This dosing remains within the range of standard anesthetic induction dosing, which is typically 1.5 to 2 mg/kg in clinical practice.
Location
- University of MichiganAnn Arbor, Michigan