Table 1.

Characteristics of all included studies.

Studies	Age (yr) (Dex/Oth)	Sex (male/ female)	No. (Dex/Oth)	Surgery	Research center	Delirium assessment	Medicine administration
Jun Hu 2020[25]	69.6/69.1	None	77/75	Noncardiac surgery (Open transthoracic oesophagectomy)	Single-center	CAM	Dex: A loading dose of dexmedetomidine, 0.4 μg/kg, bolus was administered over 15 min immediately prior to induction of anaesthesia, followed by a maintenance dexmedetomidine infusion of 0.1 μg/kg/h until 1 h before the anticipated end of surgery.
Shokri 2020[26]	63.8/64.4	Dex: 77/67Clo: 62/80	144/142	CABG	Single-center	CAM-ICU	Dex: 0.7–1.2 μg/kg/h after arriving on ICU, if the RASS score ranged from +1 to +4, the infusion rate of dexmedetomidine was increased up to the maximum dose of 1–1.4 μg/kg/h. Clo: 0.5 μg/kg intravenous infusion over a period of 10–15 min, followed by a continuous intravenous infusion of 1–2 μg/kg/h until extubation.
Li 2020[27]	69.0/69.0	Dex: 126/183Con: 120/190	309/310	Noncardiac surgery	Single-center	CAM/CAM-ICU	Dex: 0.6 μg/kg loading dose before induction, followed by 0.5 μg/kg/h until 1h before the end of surgery.
Shi 2019[20]	74.7/74.2	Dex: 63/21Con: 56/24	84/80	Cardiac surgery	Multi-center	CAM	Dex: 0.4–0.6 μg/kg/h until the end of surgery.
Sun 2019[19]	68.0/69.0	Dex: 161/120Con: 154/122	281/276	Noncardiac Surgery (spine, orthopedic, urologic, thoracic, general surgery)	Single-center	CAM/CAM-ICU	Dex: 0.1 μg/kg/h immediately after surgery, the total duration <48 h.
Azeem 2018[28]	65.3/66.7	Dex: 17/13Con: 15/15	30/30	Cardiac surgery	Single-center	CAM-ICU	Dex: loading dose of 1 μg/kg dexmedetomidine infused over 10 min immediately postoperative, followed by continuous infusion of 0.2–0.7 μg/kg/h, maintained <24 h after extubation. Com: Morphine in a dose of 10–50 μg/kg/h as an analgesic with midazolam in a dose of 0.05 mg/kg up to 0.2 mg/kg repeated as needed, and stopped before extubation.
Lee 2018[29]	72.2/73.8	Dex1: 44/51NS: 47/62	95/109	Noncardiac surgery (Laparoscopic or robotic-assisted radical cystectomy/ partial or total nephrectomy/colorectal)	Single-center	CAM	Dex1: 1 μg/kg bolus followed by 0.2–0.7 μg/kg/h infusion from induction of anesthesia to the end of surgery; NS: received an equivalent volume of saline 15 min before the end of surgery.
Li 2017[30]	66.4/67.5	Dex: 95/47Con: 102/41	142/143	Cardiac surgery	Two-center	CAM/CAM-ICU	Dex: 0.6 μg/kg loading dose once the intravenous access was established, followed by 0.4 μg/kg/h until the end of surgery, then received 0.1 μg/kg/h until the end of MV.
Deiner 2017[31]	74.0/74.0	Dex: 92/97Con: 98/103	189/201	Noncardiac Surgery (spine, orthopedic, urologic, thoracic, general surgery)	Multi-center	CAM/CAM-ICU	Dex: 0.5 μg/kg/h on entering the operating room and was continued until 2 h into recovery.
Su 2016[32]	>65	Non	350/350	Noncardiac Surgery (abdominal, thoracic, Spinal, Superficial and transurethral)	Two-center	CAM-ICU	Dex: 0.1 μg/kg/h within 1 h after ICU admission until 08:00 in the morning on the first day after surgery.
Liu 2016[33]	71.2/72.8	Dex: 26/34Con: 29/29	60/58	Noncardiac surgery (hip, knee, or shoulder joint replacement)	Single-center	CAM	Dex: 0.2 - 0.4 μg/kg/h throughout the surgery and be stopped 20 min before the end of surgery.
Djaiani 2016[34]	72.7/72.4	Dex: 68/23Pro: 70/22	91/92	Cardiac surgery	Single-center	CAM/CAM-ICU	Dex: 0.4 μg/kg bolus followed by 0.2–0.7 μg/kg/h infusion until arrive in ICU for 24 h, or not discontinued before extubation; Pro: received propofol infusion 25 to 50 μg/kg/min until extubation.
Guo 2015[35]	71.9/70.7	Dex: 41/37Con: 39/39	78/78	Oral cancer	Single-center	CAM-ICU	Dex: 0.2 μg/kg/h after arrive on ICU for 12 h.
Shehabi 2009[36]	71.5/71.0	Dex: 114/38Mor: 111/36	152/147	Cardiac surgery	Two-center	CAM-ICU	Dex: 0.1–0.7 μg/kg/h after arriving on ICU until removal of chest drain, when ready to discharge from ICU, or for up to 48 h of MV; Mor: 10–70 μg/kg/h same as Dexmedetomidine group.