The study protocol was approved by the Hospital District of South-West Finland (T252/2017).
Pediatric patients with normal growth (SD -1.5–1.5), aged between 1 month and 11 years, ASA (American Society of Anesthesiology) status I-II, scheduled for MRI and receiving either thiopental or dexmedetomidine and thiopental for procedural MRI sedation were included in this retrospective analysis. Patients receiving other sedatives than thiopental or dexmedetomidine for MRI and patients with previous exposure to dexmedetomidine within 14 days prior to the index episode, any clinically relevant concomitant drug therapy (e.g. CYP inducers, stimulants), or clinically significant abnormalities in medical examination, ECG or laboratory values were excluded. Eligible patients were identified and patient data were retrieved from the anesthesia reports and patient database of the hospital. One hundred consecutive patients who met the inclusion criteria and received thiopental sedation for MRI were identified between November 2014 and May 2015 (THIO group), and another 100 consecutive patients who had received premedication with IN dexmedetomidine before procedural MRI sedation between January and June 2017 were included in the DEX group. A 50% reduction in thiopental consumption was to be considered clinically significant.
MRI was performed using an 1.5 T MRI scanner (Siemens Avanto, Siemens, Erlangen, Germany) according to standard protocols.
The dose of IN dexmedetomidine (dexmedetomidine hydrochloride 100 μg/ml, Dexdor®, Orion Pharma, Finland) used in the DEX group (3 μg/kg) was based on previous reports[10,11] attesting to the safety of intravenous dexmedetomidine at doses up to 9 μg/kg given over 30 min. The individual dose was rounded to the nearest ten micrograms to facilitate dosing. IN dexmedetomidine was administered with an LMA MAD Nasal™ device (Teleflex MAD Nasal: Research Triangle Park, NC, USA) approximately 45 to 60 min prior to the planned MRI procedure. No other sedative medication was used. The patients of the THIO group received no sedative premedication. Their treatment was in other respects identical to that of the patients of the DEX group.
Before transfer to the MRI room, a venous cannula (B. Braun, Melsungen, Germany) was inserted in a suitable forearm vein. EMLA cream (lidocaine 2.5% and prilocaine 2.5%, AstraZeneca Inc., Södertälje, Sweden) was applied to some patients to facilitate the venous cannulation.
In the MRI room, the patients received intravenous thiopental (thiopental sodium 25 mg·ml−1, Pentocur®, Abcur, Helsingborg, Sweden) for sedation, as required. The decision to administer thiopental as well as the selection of the individual dose of thiopental was determined by the anesthetist in charge of the patient during the MRI procedure, and was based on the MOAA/S (Modified Observer's Assesment of Alertness/Sedation Scale). The aim of sedation was to keep the MOAA/S (Modified Observer's Assesment of Alertness/Sedation Scale) -level of the patients between 1 and 3.
Vital signs were monitored continuously with pulse oximetry (SpO2) and electrocardiography after dexmedetomidine administration in the DEX group, and from administration of thiopental until at least one hour after MRI in both groups.
The decision to deliver supplemental oxygen was based on SpO2 levels lower than 94%. Oxygen was delivered with the "blow by" method, which is commonly used in sedated spontaneously breathing children, with a flow of 4 to 6 l/min.
Time to Discharge
Patients fulfilled the discharge criteria when they were able to drink and eat. For safety and ethical reasons all patients were observed at least 2 h after the end of MRI. Time to discharge from the MRI unit was defined as the period of time between the end of the MRI procedure and the time of discharge. Clock times were obtained from the hospital's patient information system.
Patient data were collected from the hospital's patient information system and anesthesia reports, and possible adverse events (e.g. nausea and vomiting) related to the procedures were manually identified.
The sample size was based on previous experience in similar studies.[20,21] The primary outcome variable was the amount of thiopental administered to the patients (induction dose (mg/kg) and consumption of thiopental per hour (mg/kg/h). Secondary outcomes were the lowest HR values recorded during the MRI, lowest SpO2 values during the MRI, the need of supplemental oxygen during the MRI and adverse events. The Shapiro-Wilk test (P > 0.05) was used to assess normality assumptions. Student's t-test was used to compare the groups with normally distributed data, and Wilcoxon's rank sum test was used to test non-normally distributed data. Primary outcomes were tested using the Kruskal-Wallis test and continued with age group comparisons (corrected with the Steel-Dwass method). Nominal data were tested using chi-square analysis. P < 0.05 (two-tailed) was considered statistically significant. The results are expressed as mean values with standard deviations (SD), and as medians with interquartile ranges (IQR) when the normality assumption was not met. The analyses were performed with JMP Pro 13.0 and SAS® System programs, version 9.4 for Windows (SAS Institute Inc., Cary, NC, USA).
BMC Anesthesiol. 2019;19(22) © 2019 BioMed Central, Ltd.