Premedication With Intranasal Dexmedetomidine Decreases Barbiturate Requirement in Pediatric Patients Sedated for Magnetic Resonance Imaging

A Retrospective Study

Panu Uusalo; Mirjam Lehtinen; Eliisa Löyttyniemi; Tuula Manner; Mika Scheinin; Teijo I. Saari


BMC Anesthesiol. 2019;19(22) 

In This Article


To our knowledge, this is the first study to investigate the impact of premedication with IN dexmedetomidine on barbiturate requirements for procedural MRI sedation of pediatric patients. We compared two different pediatric MRI sedation protocols, employing retrospective analysis of hospital records. Our hypothesis was that the requirement of intravenous thiopental would decrease when IN dexmedetomidine is used as premedication. Our results indicate that significantly less thiopental is needed for pediatric procedural MRI sedation when IN dexmedetomidine is used as premedication.

We hypothesized that use of dexmedetomidine as premedication could reduce the risk of respiratory depression caused by thiopental, which was seen as reduced need for supplemental oxygen. Despite 33% of patients in THIO-group and only 2% of patients in DEX-group received supplemental oxygen, lower peripheral oxygen saturations were measured in THIO-group. It seems that patients receiving dexmedetomidine as premedication do not mostly need supplemental oxygen, which may protect patients from hypercapnia and respiratory depression that oxygen administration may cause.

It is well known that dexmedetomidine decreases heart rate due its sympatholytic effects.[8,10–12] In our study two patients in DEX-group received atropine for bradycardia, which, however, only emerged first after thiopental administration. It has been suggested in the literature that liberal correction of bradycardia induced by alpha-2-agonists may cause hypertensive crisis among pediatric patients.[27,28] However patients sedated with dexmedetomidine and furthermore receiving other sedatives must be carefully monitored for adverse events such as bradycardia. Blood pressure was not measured routinely in the patients included in our study, and was thus not included in the analysis. However, the effect of dexmedetomidine on mean arterial blood pressure levels of pediatric patients has been widely studied and it has been shown that intranasal dosages of 3 μg/kg do not cause clinically significant hypotension or hypoperfusion.[13] Instead, hypertension may result, especially when higher dosages of dexmedetomidine are used in pediatric patients sedated for MRI. Still, a previous study with over 3500 pediatric patients showed that the incidence of hypertension is low.[29]

The duration of MRI was shorter in DEX group compared to THIO-group. Head MRI was the most common MRI type (n = 52 and n = 59) in DEX and THIO group, respectively. The mean time of head MRI was shorter in DEX group (42 vs 47 min). Despite all imaging were performed with same Siemens 1.5 T MRI scanner, there has been an software update of the scanner in year 2017, which may have reduced the length of head MRI. Indications for MRI scan varied in our patient group which partly explain the variability in the time of MRI. Furthermore in some occasions the sedation was not sufficient and some scans were repeated after additional doses of thiopental were administered to complete the MRI. Thus we cannot draw any conclusions that use of dexmedetomidine as premedication would reduce the length of MRI. There was no statistically significant difference in time to discharge between two groups. For safety and ethical reasons all patients were observed at least 2 h after the end of MRI, despite all patients were alert soon after the end of MRI.

Sedation with dexmedetomidine resembles physiological sleep and maintains the patients arousable. This may be challenging in procedures where the patients are expected to remain immobile. On the other hand, patients should be arousable soon after MRI to be discharged from the imaging unit. Almost all (98 of 100) of our DEX patients received thiopental due to emergence during transfer to the MRI room. To minimize the need of additional sedation at this time point, it would be worthwhile to wait until the patients again calm down on the MRI bed. After our clinic started to employ IN dexmedetomidine as a routine premedication for pediatric patients undergoing MRI, the need for thiopental appears to have markedly decreased. Considering the respiratory depression, nausea and other adverse effects that barbiturates may cause, the reduced consumption of thiopental is probably favorable and may reduce the risk of adverse events in sedation of pediatric patients for MRI. However, the use of IN dexmedetomidine as premedication appears not to totally remove the further need for gamma aminobutyric acid agonists.

To our knowledge there are two reports on the impact of dexmedetomidine premedication on the propofol consumption in pediatric patients undergoing MRI. In a retrospective study of Boriosi et al. (2017) 256 ASA-class 1–2 pediatric patients were sedated for MRI with propofol and two third of them received 1–2 μg/kg of intravenous dexmedetomidine before MRI. Both groups received oral midazolam (0.3–0.5 mg/kg) as premedication. There was reduced propofol consumption (P < 0.001) and less adverse events (P = 0.008) in dexmedetomidine group. 12% of patients needed interventions on airway and 4% of patients had upper airway obstruction in dexmedetomidine group.[20] In the study of Gyanesh et al. (2014), the use of IN dexmedetomidine (1 μg/kg) as premedication (n = 52) reduced propofol dose (P < 0.001), duration of awakening (P < 0.001) and duration of discharge (P < 0.001) compared to the use of IN saline as premedication (n = 46) in children aged 1 to 10 years undergoing MRI. All patients were breathing spontaneously and no artificial airway was needed.[21]

Use of IN dexmedetomidine in combination with midazolam has also been shown to be effective way to maintain patient satisfaction, adequate respiration and stable hemodynamics in MRI sedation of pediatric patients.[30] In the era of multimodal anesthesia it appears that the use of two sedative agents can provide a safer way for sedating pediatric patients undergoing MRI with respect to adequate respiration and hemodynamic control.[1]

Thiopental has been used in our unit successfully for decades in sedation of pediatric patients undergoing MRI. Children, on the average, eliminate thiopental more rapidly than adults, but the elimination half-life of thiopental is still quite long, from 6 to 12 h.[31,32] Artificial airway and mechanical ventilation have been warranted only in rare cases (e.g. aspiration risk or suspected impaired consciousness) and dosing of 10–15 mg/kg/h of intravenous thiopental has allowed the patients to maintain spontaneous, unassisted respiration and rapid recovery after the MRI. However, supplemental oxygen has been administered frequently to the patients.

Our study has obvious limitations. A relatively new sedation protocol was used when the patients in the DEX group were treated. This might have influenced the outcome as the personnel sedating children for MRI were still collecting experience on the use of IN dexmedetomidine. On the other hand, the same few pediatric anesthesiologists were in charge of all of the patients. Another limitation is the retrospective design of this study, which could have affected the results, even when consecutive patients were collected in order to avoid any selection bias.