A recent publication in the New England Journal of Medicine highlighted the accumulating evidence for neurotoxic effects of anesthetics in animal models and a collection of epidemiologic studies in humans. Recent studies of anesthesia in fetal and neonatal primates are yielding more evidence of neurotoxicity associated with many common anesthesia and sedation techniques (e.g. propofol, etomidate, sevoflurane, desflurane and isoflurane). On the other hand, the data suggests that some alternative sedative agents, such as Dexmedetomidine, may not have the same neurotoxic effect.~Children routinely undergo sedation for MRI scanning with large doses of propofol and other sedatives. Many of these scans occur at young ages when these children may be at risk of neurological injury from sedative exposure. In addition, these scans do not involve any stimulation - which could be protective against neurodegeneration.~The investigators propose a pilot study to determine if a standard bolus dose and infusion of dexmedetomidine can significantly decrease the dose of propofol (infusion) required for accomplishing an MRI. Based on previous work with the combination of propofol with dexmedetomidine for other procedures, the investigators propose a standard dose of dexmedetomidine (1 mcg/kg bolus followed by an infusion at 0.5 mcg/kg/hour). The investigators will augment this sedation with propofol 2-3mg/kg titrated bolus followed by 100mcg/kg/min infusion which can also be titrated up or down to a maximum of 300mcg/kg/min to keep the blood pressure and heart rate within 30% of baseline levels.) This arm of the study was completed in January 2018 and results were posted on clinicaltrials.gov thereafter.~The investigators are now adding a second arm to this study (amendment submitted to the FDA August 2021) to examine the effectiveness of dexmedetomidine (single) bolus dose (with no infusion) followed by propofol infusion to accomplish MRI. Recruitment for this arm is currently open (started October 2021) and therefore no data is available to be reported on this arm of the study.~The investigators hypothesize that the use of low dose propofol with dexmedetomidine will be effective undergoing MRI while sparing exposure to the high dose of the sedative.
This is a pilot study to determine if a standard bolus dose and infusion of dexmedetomidine can significantly decrease the dose of propofol (infusion) required for accomplishing an MRI. The investigators are adding a second arm to this study to examine the effectiveness of dexmedetomidine (single) bolus dose (with no infusion) followed by propofol infusion to accomplish MRI.