Background Information: Dexmedetomidine is an α-adrenoceptor agonist, and its chemical name is (+)-4-(S)-[1-(2,3-dimethylphenyl ) ethyl]-1H-imidazole hydrochloride. Its structure and pharmacological activity are similar to clonidine. Dexmedetomidine was developed by the Orion Pharma (Finland) Corporation and Abott (USA), and introduced to China in 2009 (trade name: Ai Beining). Preclinical studies have shown that, like clonidine, dexmedetomidine is an agonist of α2-adrenergic receptors, and exhibits effectiveness about 10 times more than clonidine. Originally developed as an antihypertensive drug, dexmedetomidine functions in lowering blood pressure and HR, and is found to have a powerful anesthetic effect. Up to now, dexmedetomidine has been widely used in general anesthesia, monitored anesthesia care (MAC), ICU sedation. Dexmedetomidine is a sedative, hypnotic, analgesic, anti-sympathetic medication, and uniquely characterized as "cooperative sedation" and "no respiratory depression".