chloral hydrate 0.25 mg/kg oral solution diluted with oral syrup to 5 ml and 0.2 mL intranasal placebo (normal saline)

Group L received intranasal dexmedetomidine at 1mcg/kg and 5 ml oral syrup

Undiluted preservative-free dexmedetomidine (AiBeiNing; Jiang Su Heng Rui Medicine Co. Ltd, Jiangsu Province, China) was prepared in a concentration of 100mcg/ml and dripped into both nostrils using a 1 mL syringe with the child in the Supine position.

Group H received intranasal dexmedetomidine at 2mcg/kg and 5 ml oral syrup

Undiluted preservative-free dexmedetomidine (AiBeiNing; Jiang Su Heng Rui Medicine Co. Ltd, Jiangsu Province, China) was prepared in a concentration of 100mcg/ml and dripped into both nostrils using a 1 mL syringe with the child in the Supine position.

chloral hydrate 0.25 mg/kg oral solution diluted with oral syrup to 5 ml and 0.2 mL intranasal placebo (normal saline)

Sedation status was evaluated by a attending anesthesiologists every 5-10 min with a 6-point sedation scale, which was modified from the Observer Assessment of Alertness and Sedation Scale (MOAA/S; Table 1).

successful sedation was defined as an MOAA/S of between 0 and 3

Successful sedation was defined as an MOAA/S of between 0 and 2, and sedation induction time was defined as the time from rescue drug administration to the onset of satisfactory sedation

0 Does not respond to a noxious stimulus

1. Does not respond to mild prodding or shaking
2. Responds only after mild prodding or shaking
3. Responds only after name is called loudly orrepeatedly
4. Lethargic response to name spoken in normal tone
5. Appears asleep, but responds readily to namespoken in normal tone
6. Appears alert and awake, responds readily to namespoken in normal tone

changes in the non-invasive systolic blood pressure at the baseline, before and 15 , 30, 60, 75, 90 min after rescue drug administration