BACKGROUND	Relatively recent studies have shown that dexmedetomidine is able to decrease circulating plasma norepinephrine and epinephrine concentration in approximately 50 % , decreases brain blood flow by directly acting on post-synaptic alpha 2 receptors , decreases CSF pressure without ischemic suffering and effectively decrease brain metabolism and intracranial pressure and also , able to decrease injury caused by focal ischemia .\