Sedation of difficult-to-sedate children undergoing MR imaging: value of thioridazine as an adjunct to chloral hydrate.

OBJECTIVE: The purpose of this prospective study was to evaluate the safety and efficacy of thioridazine as an adjunct to chloral hydrate sedation when children undergoing MR imaging are difficult to sedate. SUBJECTS AND METHODS: All 87 children in the study either could not be sedated with chloral hydrate alone or were mentally retarded. Thioridazine (2-4 mg/kg) was administered orally 2 hr before and chloral hydrate (50-100 mg/kg) was administered orally 30 min before the 104 MR examinations. All children were monitored by continuous pulse oximetry. All images were individually evaluated by pediatric radiologists and were graded acceptable if they contained only minimal motion artifact or no motion artifact. Studies were considered successful only when 95% or more of the images were acceptable. RESULTS: MR imaging was successful in 93 (89%) of 104 examinations. The success rate for children entered into the study because of prior failure of chloral hydrate sedation was not significantly different from the success rate for children with mental retardation. A tendency for increasing failure rate with age was not significant. No serious complications occurred during the study. The most common adverse reaction, transient reduced oxygen saturation, was seen in five children. Other adverse effects encountered were vomiting in four children, hyperactivity in two children, transient tachycardia in one child, and prolonged sedation in one child. No child required hospitalization because of an adverse reaction to sedation. CONCLUSION: The study indicates that thioridazine is a safe and effective adjunct to chloral hydrate when a child undergoing MR imaging is difficult to sedate.