Propofol-Only Versus Dexmedetomidine-Propofol in Children Undergoing Magnetic Resonance Imaging

A Randomized, Dose-Ranging Trial of Propofol-Only and Dexmedetomidine-Propofol in Children Undergoing Magnetic Resonance Imaging

The most common imaging procedure requiring sedation/anesthesia for the pediatric population is magnetic resonance imaging (MRI). However, the optimal anesthetic/sedation plan has not been determined for these procedures. Historically, common medications have included the use of pentobarbital and propofol, but in 2015, publication in the New England Journal of Medicine highlighted the accumulating evidence for the possible neurotoxic effects of these types of anesthetics in animal models and a collection of epidemiologic studies in humans. Although these initial possibilities have since been proven as less of a concern, in the interim, data has shown that alternative sedative agents, such as dexmedetomidine, may not have the same neurotoxic effect and could possibly even provide neuroprotection. Dexmedetomidine also possesses other beneficial traits such as reducing risks of pulmonary atelectasis or upper airway collapse, typically found with the administration of propofol.

A concern raised by previous studies has been the possibility that the addition of dexmedetomidine could increase recovery times, leading to disruptions in workflow. Although it has been shown that large doses of dexmedetomidine exposure may lead to longer PACU stays, it is uncertain whether a small dose of dexmedetomidine would have such a significant impact. Based on the investigators' pilot trial6, the investigators found that a bolus of 1 mcg/kg dose of dexmedetomidine with a bolus of titrated propofol of 2-3 mg/kg and an infusion of propofol of 100 mcg/kg/min provided adequate sedation for successful scans, reduced propofol (infusion) exposure by 60%, and did not significantly increase recovery times.

Finally, there is a paucity in literature for studies examining a range of doses subsequently; often, a control group is compared to a single, self-selected dose of choice. Here, the investigators hope to provide a range of doses to minimize selection bias in our study design and determine the dose that would provide the optimal sedation for these scans and minimize excess anesthetic exposure.

Inclusion Criteria:

• Patients presenting as outpatients, scheduled to receive an anesthetic for MRI of brain, body (spine, chest, abdomen, and/or pelvis) and/or extremity (arm and/or leg).
• Patients must be a candidate for the sedation technique described in this study with a natural airway. This decision will be made by a staff member of the Department of Anesthesiology.
• Between 1 and 12 years of age.
• ASA status I, II, or III

Exclusion Criteria:

• Inpatient at BCH
• Diagnosis of a difficult airway, severe obstructive sleep apnea that is not compatible with spontaneous ventilation in a supine position, or requires an oral airway.
• Congenital heart disease or history of dysrhythmia.
• Taking digoxin or beta-blocker
• Anxiolytic medication is ordered before the MRI (e.g., midazolam or ketamine).
• History or a family (parent or sibling) history of malignant hyperthermia.
• Allergy to or has a contraindication to propofol, lidocaine, or dexmedetomidine.
• Tracheostomy or other mechanical airway device present
• Received within the past 12 hours an oral or intravenous alpha-adrenergic, beta-adrenergic agonist, or antagonist drugs (e.g., clonidine, propranolol, albuterol).
• Patient is not scheduled to receive anesthesia-sedation care or is noted to "try-without anesthesia" for the MRI
• Patient has significant developmental or psychological delays
• Patient scheduled for scan of duration <30 minutes or >90 minutes