BACKGROUND: Previous studies have shown that 3.6 (2.8-4.0) mg/kg of intravenous thiamylal is effective and safe for pediatric sedation during magnetic resonance imaging (MRI) scans, although its success rate (96.6%) is slightly lower than that via propofol (99%). This retrospective study aimed to evaluate whether a higher induction dose of thiamylal can reduce MRI scan interruptions without increasing the incidence of adverse events. METHODS: This study included patients aged <
18 years who underwent MRI under thiamylal sedation between January 2021 and December 2022. Intravenous atropine (0.01 mg/kg) and midazolam (0.08 mg/kg) were administered as premedications. An induction intravenous dose of 2-5 mg/kg thiamylal was administered, with additional doses administered as needed. The induction dose was defined as the total amount of thiamylal administered before the scan. Once adequate sedation was achieved, MRI was performed. Any additional doses of thiamylal required because of scan interruption were recorded as rescue doses. Patients who received an induction thiamylal dose of <
3.6 mg/kg were categorized into the lower induction dose group. The primary endpoint was the rate of MRI interruptions. Secondary endpoints included adverse events related to sedation, total thiamylal dose, and total MRI scanning time. RESULTS: A total of 566 patients, with a median age of 56.4 months (range: 24.0-79.2 months) and median weight of 16.0 kg (range: 10.3-21.0 kg), were included in the analysis. The median induction and total dose of thiamylal per body weight were 4.7 (3.8-5.8) mg/kg and 6.0 (4.6-8.1) mg/kg, respectively. No respiratory or other adverse events were recorded. For 30- to 60-min MRI scans, the higher induction dose group had a lower scan interruption rate, and a lower total thiamylal dose was required than that for the lower induction dose group. CONCLUSION: A higher induction dose of thiamylal (5.4 ± 1.6 mg/kg) is safe and is associated with a reduced scan interruption rate for 30- to 60-min MRI scans, as well as a lower total thiamylal dose requirement. However, thiamylal is not an ideal sedative agent for MRI scans longer than 1 h.