One hundred consecutive patients were included in both study groups (DEX and THIO) (Additional file 1: Figure S1). These groups were subdivided into three clinically relevant age groups for statistical analysis, THIO1 and DEX1 (0–2 years), THIO2 and DEX2 (2–6 years) and THIO3 and DEX3 (6–11 years). Patient descriptors are shown in Table 1. The DEX patients had a mean (SD) age of 4.50 (2.56) years and a mean body-mass index (BMI) of 16.5 (2.2) kg/m2, and the THIO patients had a mean (SD) age of 4.06 (2.39) years and a mean BMI of 16.5 (1.8) kg/m2. The median (range) dose of dexmedetomidine was 50 (20–110) ug.
The MRI duration was somewhat shorter in the DEX group compared to the THIO group (medians 43 and 47 min, IQR 41–57 and 35–50 min; P < 0.001). There were no other statistically significant differences in the patient characteristics between the two groups. Diagnostic categories and MRI types are shown in a (Additional file 2: Table S1).
Significantly smaller induction and total doses of thiopental were needed for completion of MRI in all DEX age groups compared to the THIO age groups. The median (IQR) cumulative thiopental requirement during MRI was 4.4 (2.7–6.0) mg/kg/h compared to 12.4 (9.8–14.8) mg/kg/h in DEX and THIO groups, respectively (median difference 7.9 mg/kg/h, 95% CI: 6.8–8.8, P < 0.001). The median (IQR) induction doses of thiopental before MRI were 1.8 (1.2–2.3) mg/kg compared to 5.1 (4.6–6.2) mg/kg in the DEX and THIO groups, respectively (median difference 3.3 mg/kg/h, 95% CI: 3.1–3.6, P < 0.001). Differences in thiopental requirements were statistically significant between all three DEX and THIO age groups (P < 0.001) (Figure 1 and Table 2).
Induction doses and cumulative dosing of thiopental in three clinically relevant age groups. Difference between dexmedetomidine (DEX) and thiopental (TIO) groups was tested with Wilcoxon test for induction dose of thiopental (mg/kg) (a) and for cumulative dose of thiopental (mg/kg/h) (c). Difference in induction dose of thiopental (mg/kg) (b) and cumulative dose of thiopental (mg/kg/h) (d) between three clinically significant age groups of dexmedetomidine group (DEX1, DEX2 and DEX3) and thiopental group (THIO1, THIO2, THIO3) were tested using Kruskal-Wallis test and continued with pairwise comparisons which were corrected with Steel-Dwass method for all pairs
The median (IQR) of the lowest observed peripheral oxygen saturation reading was 97 (95–97) % in the DEX group compared to 96 (94–97) % in the THIO group (P < 0.001). This analysis did not take into account the use of supplemental oxygen, but the reported values are after possible oxygen administration. Thirty-three (33%) of the patients in the THIO group received supplemental "blow by" oxygen whereas only two (2%) the DEX patients received oxygen (P < 0.001). The median (IQR) time from the end of MRI to discharge was 140 (115–169) min in the DEX group compared with 150 (125–175) min in the THIO group (P = 0.15). The mean (SD) of the lowest measured HR was 78 (16) bpm in the DEX group compared to 92 (12) bpm in the THIO group (P = 0.0001) (Table 3).
Two patients (aged 4.7 and 7.8 years) in the DEX group received atropine for bradycardia (36 and 39/min respectively) after thiopental administration. Two patients in the DEX group and two patients in the THIO group reported mild nausea after MRI. No other adverse events were recorded.
BMC Anesthesiol. 2019;19(22) © 2019 BioMed Central, Ltd.