OBJECTIVE: To explore the effects of low-dose midazolam on postoperative delirium in elderly patients after lower abdominal short surgery. METHODS: Totally 120 elderly patients with lower abdominal short surgery admitted into Hubei Provincial Hospital of Traditional Chinese Medicine from Oct. 2015 to Oct. 2018 were extracted to be randomly divided into the low-dose group

the high-dose group and the control group

with 40 cases in each group.All patients were given general anesthesia

the low-dose group was given 0. 02 mg/kg midazolam

the high-dose group was treated with 0. 1 mg/kg midazolam

and the control group received 0. 9% normal saline. The vital signs [mean arterial pressure（ MAP）

heart rate（ HR）

and pulse oximetry（ SpO2） ]were observed among three groups before anesthesia induction（ T0）

5 min after administration（ T1）

at the beginning of the surgery when the skin was cut（ T2）

at 5 min of surgery（ T3）

at 10 min of surgery（ T4）

at 30 min of surgery（ T5） and at the end of surgery（ T6）. The doses of intraoperative propofol and fentanyl were observed. The delirium status was evaluated by confusion assessment method-chinese reversion（ CAM-CR） among three groups before surgery and 1 to 72 h after surgery. The serum cortisol（ Cor） level of three groups was analyzed before surgery and 1 d after surgery. RESULTS: From T0 to T6

there were statistically significant differences in the time-point effects and interaction effects of time-points and between-groups of MAP and the time-point effects of HR among three groups（ P<0. 05）

and there were no significant differences in the between-group effects

time-point effects and interaction effects of time-points and between-groups of SpO2 among three groups（ P > 0. 05）. There were statistically significant differences in the doses of propofol and fentanyl among three groups（ P < 0. 05）

and the doses in the low-dose group and the high-dose group were significantly lower than those in the control group

and the doses in the low-dose group were significantly lower than those in the high-dose group

with statistically significant differences（ P<0. 05）. At 1 to 72 h after surgery

the CAMCR score in three groups was increased firstly and then decreased

and there was significant difference at 1 to 24 h after surgery among three groups and at different time points within the groups（ P < 0. 05）. On the 1 st day after surgery

the serum Cor level of three groups increased significantly

with statistically significant difference（ P<0. 05）

and there was statistically significant difference among three groups（ P<0. 05）. The serum Cor level in the low-dose group and the high-dose group was significantly lower than that in the control group

and the serum Cor level in the low-dose group was significantly lower than that in the high-dose group

with statistically significant differences（ P <0. 05）. CONCLUSIONS: Low-dose midazolam has better sedation effects in elderly patients with lower abdominal short surgery

which can facilitate the stability of intraoperative circulation in elderly patients

reduce the doses of intraoperative anesthetics

and reduce occurrence of postoperative delirium.