Abstract: Objective To investigate the impact of dexmedetomidine (DEX) on serum neuron-specific enolase (NSE), oxidative stress, inflammatory response and postoperative cognitive function after lower limb tourniquet surgery in elderly patients with diabetes. Methods A total of 96 elderly patients with type 2 diabetes mellitus who underwent lower extremity surgery under selective general anesthesia tourniquet were randomly divided into DEX group and control group by using a random number table method, 48 cases in each group. After induction of general anesthesia, the DEX group was pumped with 0.5 μg/kg DEX within 15 min, followed by an infusion of 0.5 μg/(kg·h) until 30 min before the end of the operation. The control group was pumped with the same volume of normal saline. The serum levels of malonaldehyde (MDA), NSE，tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) were detected by thiobarbituric acid and enzyme-linked immunosorbent assay (ELISA) before using the tourniquet, 30 min, 24 h and 72 h after releasing the tourniquet. The mini-mental state examination (MMSE) was used to evaluate cognitive function 1 d before operation, 1 d and 3 d after operation. The awake time, extubation time and adverse reactions were recorded in the two groups. Results Compared with before using the tourniquet, the level of NSE increased from 24 h after  releasing the tourniquet in both groups, while the levels of MDA, TNF-α and IL-1β increased from 30 min after releasing the tourniquet (P＜0.05). Compared with the control group, the level of NSE decreased from 24 h after tourniquet release in the DEX group, while the levels of MDA, TNF-α and IL-1β decreased from 30 min after tourniquet release (P＜0.05). Compared with 1 day before surgery, MMSE scores were decreased at the 1 d and 3 d after surgery in both groups (P＜0.05). Compared with the control group, MMSE scores increased at the 1 d and 3 d after surgery in DEX group (P＜0.05). There were no significant differences in wake time, extubation time and incidence of adverse reactions between the two groups. Conclusion Dexmedetomidine can reduce serum NSE, reduce oxidative stress and inflammation response, and improve postoperative cognitive function on lower limb tourniquet surgery in elderly patients with diabetes.

Key words: diabetes mellitus, type 2, tourniquets, neuroprotection, aged, Dexmedetomidine, lower extremity surgery;postoperative cognitive dysfunction