When performing deep sedation in children undergoing magnetic resonance imaging (MRI) studies, anesthesiologists often are on the lookout for a drug that will not inhibit airway patency. A trial by a group of Buffalo researchers has concluded that dexmedetomidine may be one such alternative, as it causes no more airway collapses than propofol in these patients.
Fonte: Anesthesiology News
“The story begins in 2008, when we performed a review of 20 children undergoing MRI,” said Rafeek Hegazy, MD, a fellow in pediatric anesthesiology at the Women & Children’s Hospital of Buffalo, N.Y. “We found a trend toward less upper airway collapsibility with dexmedetomidine.
“These data were supported by a study from Cincinnati [J Clin Anesth 2013;25:529-541], which found significantly less airway collapse in dexmedetomidine patients who have obstructive sleep apnea [OSA],” he continued. “The weakness in that study was that most OSA patients obstruct, even without medication. So we wanted to do our study in children who weren’t suffering from it.”
Dr. Hegazy and his colleagues enrolled 31 children (mean age, 4.9 years; range, 3-7 years) into the trial. Each child underwent MRI of the head under anesthesia; none required intubation, none had cardiac history, and none were being treated for attention-deficit/hyperactivity disorder. After baseline MRIs were obtained and anesthesia was induced with sevoflurane, one group of participants was randomized to receive a bolus of 1 mcg/kg dexmedetomidine, followed by an infusion of 1 mcg/kg per hour dexmedetomidine for 10 minutes, and a 1 mg/kg dose of midazolam. “This regimen came from another study we performed where we found this was the best dexmedetomidine protocol for deep sedation,” Dr. Hegazy explained. “Because if you don’t give the Versed [midazolam], most patients will wake up in the middle of the procedure.” The other group received a propofol load of 300 mcg/kg per minute over 10 minutes, followed by a 250 mcg/kg per minute infusion.
MRI scans were started immediately after drug administration, and included a sagittal scout film, an axial spoiled gradient (SPGR), and two cine sequences. These images were then repeated 20 minutes later, during the infusion of the study drug, for comparison. “So the first scans examined sevoflurane’s effect on the airway. Twenty minutes later, the effect of the study drug was examined.”
As Dr. Hegazy reported at the 2014 annual meeting of the International Anesthesia Research Society (abstract S-259), no meaningful differences were found between groups with respect to airway collapsibility. “The only difference was in SPGR, where we found a statistically significant difference between the dexmedetomidine and propofol groups at 20 minutes. But this difference was not clinically significant.
“The only difference was that the PACU [postanesthesia care unit] time was prolonged with dexmedetomidine,” Dr. Hegazy said. “Interestingly, however, the time from scan to discharge was almost the same between groups.” Heart rate and blood pres sure were decreased in dexmedetomidine patients; end-tidal CO2 was comparable.
Dr. Hegazy recognized that individual results may vary given differences in drug administration, but maintained that dexmedetomidine would provide results comparable to that of propofol. “Although there is some radiologic evidence that there is less airway collapsibility with dexmedetomidine, clinically it’s not different,” he told Anesthesiology News. “Some institutions use higher doses of propofol and dexmedetomidine and have evidence of clinical airway obstruction. But if you follow this, it should work perfectly.
“I think dexmedetomidine is going to be a very good option, especially for obstructive sleep apnea or difficult intubation patients,” he said. “I use dexmedetomidine for most of these cases now.”
Caleb H. Ing, MD, assistant professor of anesthesiology at Columbia University Medical Center, New York City, found the lack of clinical difference between the two drugs somewhat surprising. “Based on prior studies, propofol has been associated with airway obstruction [Anesthesiology 2006;105:45-50], whereas even at high doses dexmedetomidine was not found to be associated with obstruction [Paediatr Anesth 2010;20:506-515].
“I agree with the authors that dexmedetomidine could be a viable option for sedation during MRI,” he added. “In longer MRI scans, however, using dexmedetomidine as a sole agent may not be adequate to prevent movement in all children.”
—Michael Vlessides
