How Different Sedatives Affect Hip Fracture Patient's Postoperative Delirium

the hypothesis is that Dexmedetomidine seems to decrease incidence of post-operative delirium . one possible mechanism is that Dex have a minor influence on cognition, since it has no effect on GABA receptor，another is that Dex could induce a sleep similar to natural sleep, thereby decreasing sleep deprivation and circadian rhythm disorder in post-operative patients. In this study , investigators devise the two different sedatives(Dexmedetomidine and Propofol)\'influence on postoperative delirium in hip fracture elderly participants under spinal anesthesia