The Effect of Age on the Median Effective Dose (ED50) of Intranasal Dexmedetomidine for Rescue Sedation Following Failed Sedation With Oral Chloral Hydrate During Magnetic Resonance Imaging

Increasing evidences suggest that dexmedetomidine Pharmacokinetic are different in children. We performed a up-down sequential allocation study to determine the ED50 for rescue sedation following sedation failures in children and to investigate age-related differences in the rescue sedation with dexmedetomidine.

About 150 children who were not adequately sedated ( no evidence of adequate sedation within 30 min after administration of Initial dose of chloral hydrate) were stratified into four age groups as follows: 1-6 month, 7 -12 month, 13 -24 month, and 25-36 month. The intranasal dexmedetomidine dose was determined by the success or failure of rescue sedation achieved by the previous patients, according to Dixon's up-down sequential allocation method. Successful sedation was defined as a MOAA/S(modified Observer Assessment of Alertness and Sedation) of between 0 and 3. The EC50 were estimated from the up-and-down sequences using the method of Dixon and Massey and logistic regression. Patients' sedation status, sedation induction time, time to Wake up, blood pressure, heart rate, and oxygen saturation were recorded.

Inclusion Criteria:

• 150 children of ASA physical status I or II, aged between 1 and 36 months, failed chloral hydrate sedation during MRI scanning,

Exclusion Criteria:

• known allergy or hypersensitive reaction to drugs of this study, Weight greater than 20 kg or less than 4.5 kg, organ dysfunction, pneumonia, acute upper respiratory airway inflammation, preterm, cardiac arrhythmia and congenital heart disease.