Abstract: Objective: To evaluate the effects of dexmedetomidine on preoperative sleep in elderly patients undergoing hip replacement,and to observe its effects on preoperative anxiety and intraoperative circulatory stability. Methods: A total of 102 patients who underwent hip replacement under ultrasound guided superior iliac fascia space block combined with subarachnoid block were randomly divided into two groups,with 51 patients in each group,which were dexmedetomidine group (group D) and 0.9% sodium chloride solution group (group C).The patients in the two groups were infused with dexmedetomidine or 0.9% sodium chloride solution 0.5 μg /kg by micropump the night before operation,and the incidence of adverse reactions in the two groups during the intervention period was recorded and compared.The scores of Leeds sleep evaluation questionnaire(LSEQ) and Hamilton anxiety scale were evaluated after intervention in the two groups.The visual analogue scores(VAS) of patients before (T₀),after (T₁),24 h (T₂),48 h (T₃) after operation were recorded.The mean arterial pressure,heart rate,number of vasoactive drugs used,and blood loss after anesthesia were recorded by comparing the two groups of patients,and the adverse events and outcomes after operation were compared. Results: There was no significant difference in the incidence of adverse reactions between the two groups after intervention (P>0.05).After intervention,the LSEQ score of group D was significantly higher than that of group C in the morning of operation (P<0.05),and the incidence of anxiety in group D was lower than that in group C (P<0.05).Compared with group C,group D had more stable hemodynamics during operation,lower mean arterial pressure and heart rate after anesthesia,and less use of vasoactive drugs (P<0.05).At T₀ and T₁,there was no significant difference in VAS scores between the two groups (P>0.05).At T₂ and T₃,the VAS score in both groups was significantly lower than that at T₀ and T₁ before operation (P<0.01),and the VAS score in group D was lower than that in group C (P<0.05).Compared with group C,patients in group D had less pressing times of analgesia pump and accumulated consumption of analgesia pump drugs for postoperative patient-controlled intravenous analgesia (P<0.05),and the incidence of postoperative nausea,vomiting and delirium and hospital stay were lower than those in group C (P<0.05). Conclusions: Intravenous infusion of low dose dexmedetomidine one day before operation can significantly improve the preoperative sleep and anxiety of elderly patients with hip fracture,maintain the stability of intraoperative circulation,reduce the occurrence of postoperative complications,and be beneficial to the rapid surgical rehabilitation of elderly patients.