Dexmedetomidine (trade name Precedex) is an alpha-2 receptor agonist, similar to clonidine. Whereas clonidine provides a robust decrease in blood pressure with mild sedation, dexmedetomidine provides robust sedation with a mild decrease in blood pressure. It does not depress airway reflexes or respiration. It has a variety of potential uses in the emergency department, including procedural sedation, the facilitation of awake intubation or noninvasive ventilation, and the treatment of alcohol withdrawal. For these indications, however, we have agents that are at least as good, familiar, and a hell of a lot cheaper.
Sedation for painless procedures in children is the scenario that may push dexmedetomidine into the emergency physician’s toolkit. Kids who require sedation for CT or MR imaging would ideally be managed without placing an IV (nix etomidate), using an agent that does not cause significant cardiorespiratory depression (nix barbiturates), is otherwise safe (nix chloral hydrate, which is also unpredictable, untitratable, and lasts forever), and reliably causes kids to be still (nix ketamine).
This case series reports on 65 consecutive children sedated for CT or MRI with intramuscular dexmedetomidine, administered either once or twice at a dose of 1-4 mcg/kg, the exact dose left to provider discretion, to achieve a target Ramsay score of 4 (asleep but briskly responsive to a light stimulus). 4 patients out of 65 required a second IM dose to achieve a Ramsay score of 4. Once Ramsay 4 was achieved, no other agents were given for the duration of the procedure. The mean dose was about 2.5 mcg/kg.
All 65 children successfully completed the study. Though 9 out of 65 patients developed transient hypotension, there were no adverse events that required intervention. 65 patients is not enough to conclusively demonstrate safety, but 100% efficacy is hard to beat, and I suspect the safety profile will stand up in larger series.
Average time to sedation was 13 minutes. The average time from the end of the study to recovery was 22 minutes in the MRI group and 17 minutes in the CT group, with wide confidence intervals, i.e. there was no difference in recovery times. Since MRI is significantly longer than CT, and no sedatives were administered after the initial dose, how can this be?
Dexmedetomidine causes a different type of sedation than what we’re used to. It’s not a CNS depressant in the typical sense, it’s a powerful sympatholytic. Patients sedated with with dexmedetomidine will wake up with minimal stimulation, but when that stimulation is removed, they gently drift off to sleep. This is not a useful feature when trying to facilitate awake intubation, but it’s perfect for getting a 3 year old through the CT scanner.
Mason KP, Lubisch NB, Robinson F, Roskos R. Intramuscular dexmedetomidine sedation for pediatric MRI and CT. American Journal of Roentgenology 2011 Sep;197(3):720-5.