Cytokines such as such as TNF-a, IL-1, IL-6 correlate with the severity of pancreatitis.Neuroendocrine pathways, such as the sympathetic nervous system or parasympathetic nervous system, in turn, have some impact on the immune systems, through a-2 adrenoreceptor stimulation or the cholinergic anti-inflammatory pathway. The investigators aim to use Dexmedetomidine Hydrochloride to decrease the activity of sympathetic nervous system, thus relieve inflammation response.