Literature Review

Comparison of propofol and dexmedetomidine techniques in children undergoing magnetic resonance imaging

Reviewed by Daniel Tsze, MD and Joseph Cravero, MD

Wu J, Mahmoud M, Schmitt M, Hossain M, Kurth D. Paediatr Anaesth. 2014;24:813-8.

Abstract
Propofol and dexmedetomiine (DEX) are commonly used sedatives for children undergoing MRI scans, including those that require more than one hour to complete.  This study compares propofol and DEX techniques in MRI scans of ≥ 75 minutes duration for differences in outcomes related to efficacy, safety, and parental satisfaction.   

This was a randomized trial in which patients were all induced in the same fashion using sevoflurane and nitrous oxide, and then randomized to receive either a loading dose and infusion of propofol (2 mg/kg, 200 mcg/kg/h, respectively) or DEX (2 mcg/kg, 2 mcg/kg/h).  Forty-nine and 46 patients were enrolled in the propofol and DEX cohorts, respectively.

The outcomes evaluated included:  timeliness/induction time; emergence time; frequency of MRI stoppage due to patient movement; number of patients who had a technique failure (i.e. inadequate sedation); number of critical events (arterial desaturation, airway obstruction, hypotension, and bradycardia which if untreated would have resulted in patient harm); PACU recovery duration; Pediatric Anesthesia Emergence Delirium (PAED) scale level; and parental satisfaction.

When compared to those who received DEX, patients in the propofol cohort were found to have: 1) an 8-minute shorter induction time; 2) half the time to emergence; 3) almost 40% less time in the PACU; 4) fewer MRI stoppages due to patient movement; 5) fewer technique failures; 6) fewer patients with emergence delirium (i.e. less patients with PAED scores of 10 or higher); and 7) higher parental satisfaction.  Overall, patients who received DEX spent nearly 40 minutes longer in the facility than those who received propofol.

Commentary

It should be noted that the results of any trial such as this are largely determined by the exact technique and doses of the drugs that were chosen in each cohort.  Different regimens for propofol and DEX could have changed some of the results however the overwhelming superiority of propofol would not likely have been changed.

There were no critical events in either group.  There were two brief episodes of oxygen desaturation in the group that received propofol, but both resolved by increasing the oxygen flow via nasal cannula and no other intervention.

The study results indicate propofol is preferable to DEX for children undergoing MRI scans lasting more than 75 minutes.  The advantage of propofol was present throughout several domains, with no factor identified in favour of DEX.  These findings are similar to those previously described in children receiving MRIs of shorter duration (i.e. ≤ 60 minutes) - which would support the generalizability of the benefits observed in this particular study.1 

In particular, the shorter overall duration of stay facilitated by using propofol has significant implications for MRI procedures in high-volume, busy institutions.  The decreased time for each patient could significantly increase the time available for additional cases and decrease total personnel expense.  Similarly, the lower incidence of MRI stoppages due to patient movement and technique failures would facilitate flow and improve the efficiency of completing procedures.

Although the study was not powered to statistically detect differences in adverse events between the propofol and DEX groups, the absence of critical events is supported by the low incidence of serious adverse events that has been described in other reports of propofol and DEX sedations.2-4 

Despite the evidence describing the multiple advantages of using propofol over DEX for MRI sedations in children, the latter technique may still be advantageous for some institutions. Specifically, sedation services that are restricted from using propofol may continue to successfully utilize DEX for MRI scans of various durations.

  1. Koroglu A et al. A comparison of the sedative, hemodynamic, and respiratory effects of dexmedetomidine and propofol in children undergoing magnetic resonance imaging.  Anesth Analg 2006;103:63-7.

  2. Mallory MD et al. Propofol vs. pentoparbital for sedation of children undergoing magnetic resonance imaging: results from the Pediatric Sedation Research Consortium. Pediatr Anesth 2009; 19:601-11.

  3. Mallory MD et al. Emergency physician-administered propofol sedation: A report on 25,433 sedations from the Pediatric Sedation Research Consortium. Ann Emerg Med 2011;57:462-8.

  4. Mason KP et al. Dexmedetomidine offers an option for safe and effective sedation for nuclear medicine imaging in children. Radiology 2013; 267:911-7.

  5. Mason KP et al. Review article: Dexmedetomidine in children: current knowledge and future applications. Anesth Analg 2011;113:1129-42.

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