Table 1.

Summary of the baseline characteristics of included trials.

Study	Country	Dosing Information	Control	Begin Time	Following Time	Type of Surgery	Age (years)	Male (%)	Incidence (%)	N
Avidan 2017 [16]	USA	0.5 or 1.0 mg/kg ketamine by injection as single dose.	placebo	before surgery	3d	major surgery	70	62.2	19.6	672
Clemmesen 2017 [17]	Denmark	125 mg methylprednisolone by injection for once.	saline	before surgery	3d	hip	80	35.9	24.8	117
de Jonghe 2014 [18]	Netherlands	3 mg melatonin taken orally for 5 days.	placebo	before surgery	8d	hip	84	29.9	27.5	378
Deiner 2017 [19]	USA	0.5 μg/kg/h dexme by infusion continued until 2 hours into recovery.	saline	before surgery	30d	cardiac	74	48.7	15.4	390
Dieleman 2012 [20]	Netherlands	1 mg/kg dexamethasone by injection for once.	placebo	during surgery	30d	cardiac	66	72.5	10.4	4482
Dighe 2014 [21]	Canada	200 mg gabapentin taken orally tid for 4 days.	placebo	after surgery	NA	knee	63	49.7	10.6	161
Djaiani 2016 [22]	Canada	a bolus of 0.4 μg/kg dexme followed by 0.2-0.7 μg/kg/h infusion for maximum 24 h.	propofol	after surgery	5d	cardiac	73	75.4	24.6	183
Farlinger 2018 [23]	Canada	150 mg pregabalin preoperatively and 75 mg bid postoperatively for 7 days.	placebo	before surgery	NA	hip	60	50.9	0.6	163
Fukata 2014 [24]	Japan	2.5 mg haloperidol for 3 days.	blank	after surgery	7d	abdominal, orthopedic	80	52.9	37.2	121
Gamberini 2009 [25]	Switzerland	1.5 mg oral rivastigmine tid for 7 days.	placebo	before surgery	6d	cardiac	74	68.1	31	113
Hudetz 2009 [26]	USA	0.5 mg/kg ketamine intravenous bolus for once.	saline	before surgery	5d	cardiac	64	NA	17.2	58
Kalisvaart 2005 [27]	Netherlands	0.5 mg haloperidol tid until 3 days after surgery	saline	before surgery	14d	hip	79	20.2	15.8	430
Kaneko 1999 [28]	Japan	5 mg haloperidol intravenous for 5 days	saline	after surgery	5d	gastrointestinal	73	64.1	21.8	78
Larsen 2010 [29]	USA	5 mg of orally-disintegrating olanzapine or placebo just before and after surgery.	placebo	before surgery	8d	joint	74	45.8	27.5	400
Lee 2018 [30]	Korea	1 μg/kg bolus dexme followed by 0.2-0.7 μg/kg/h infusion during surgery.	saline	before surgery	5d	laparoscopic	73	44.3	17.9	318
Leung 2017 [31]	USA	900 mg gabapentin administered preoperatively and for the first 3 postoperative days.	placebo	before surgery	3d	orthopedic	73	49.6	22.4	697
Li.X 2017 [32]	China	0.6 μg/kg dexme for 10 minutes followed by 0.4 μg/kg/h during surgery.	placebo	before surgery	5d	cardiac	67	68.6	6.3	287
Li.YN 2017 [33]	China	7.5 μg/kg/h nimodipine was injected continually 30minutes before anesthesia induction.	saline	before surgery	7d	spine	70	40	11.7	60
Liu. YZ 2016 [34]	China	0.2-0.4 μg/kg/h dexme during surgery	saline	before surgery	7d	joint	73	48.7	29.4	197
Maldonado 2009 [35]	USA	received one of three postoperative sedation regimens: dexme, propofol and midazolam.	propofol, midazolam	after surgery	3d	cardiac	58	63.8	34.4	90
Mardani 2013 [36]	Iran	8 mg of intravenous dexamethasone before surgery and followed by 8 mg q8h for 3 days.	placebo	before surgery	3d	cardiac	62	NA	18.3	93
Mei 2018 [37]	China	a bolus of dexme at 0.8-1.0 μg/kg followed by 0.1-0.5 μg/kg/h infusion or propofol.	propofol	before surgery	7d	hip	75	45.6	11.8	296
Mohammadi 2016 [38]	Iran	4 mg cyproheptadine tid for 7 days.	placebo	after surgery	7d	non-cardiac	60	65	25	40
Papadopoulos 2014 [39]	Greece	8 mg intravenous ondansetron daily for 5 days.	placebo	after surgery	5d	femoral, hip	72	44.3	44.3	106
Park 2014 [40]	Korea	loading dose of 0.5 μg/kg dexme followed by 0.2-0.8 μg/kg/h or remifentanil 1-2.5 mg/h during ICU.	remifentanil	after surgery	3d	cardiac	53	55.6	16.2	142
Prakanrattana 2007 [41]	Thailand	1 mg risperidone sublingually when regained consciousness	placebo	after surgery	3d	cardiac	61	58.7	21.4	126
Priye 2015 [42]	India	0.4 μg/kg/h dexme for 12 hours.	saline	after surgery	ICU	cardiac	43	51.6	9.4	64
Robinson 2014 [43]	USA	1g tryptophan enterally tid for 3 days.	placebo	after surgery	ICU	mixed	69	98	38.5	301
Royse 2017 [44]	Australia	250 mg methylprednisolone at induction and 250 mg methylprednisolone before surgery.	placebo	during surgery	3d	cardiac	74	64.1	9.2	298
Sampson 2007 [45]	UK	5 mg donepezil after surgery and continuing for a further 3 days.	placebo	after surgery	4d	hip	69	51.5	21.2	33
Shehabi 2009 [46]	Australia	received dexme 0.1–0.7g/kg/h or morphine 10-70g/kg/h to maintain target sedation & analgesia.	morphine	after surgery	5d	cardiac	71	75.3	11.7	299
Sheikh 2018 [47]	India	1 μg/kg dexme bolus followed by infusion 0.2–0.6 μg/kg/h or 0.25–1 mg/kg/h propofol	propofol	before surgery	ICU	cardiac	35	NA	13.3	60
Su 2016 [48]	China	dexme 0.1 μg/kg/h from ICU admission on the day of surgery until 08:00 h on postoperative day 1.	saline	after surgery	7d	non-cardiac	74	60.4	15.9	700
Sugano 2017 [49]	Japan	2.5g TJ-54 tid for 7 days prior to surgery and 4 days after surgery, except for the operation day.	blank	before surgery	NA	gastrointestinal, lung	77	64.5	8.1	186
Wang 2012 [50]	China	0.5 mg haloperidol intravenous bolus followed by infusion at a rate of 0.1 mg/h for 12 hours.	saline	after surgery	7d	non-cardiac	74	41.1	19.3	457
Whitlock 2015 [51]	Canada	250 mg methylprednisolone at anaesthetic induction and 250 mg at initiation of cardiopulmonary bypass.	placebo	during surgery	3d	cardiac	67	60.4	7.8	7507
Xin 2017 [52]	China	4ml/kg 7.5% hypertonic saline was given before surgery.	saline	before surgery	3d	hip	76	51.7	25	120
Yang 2015 [53]	China	0.5 mg/kg dexme was given for 1 hour.	saline	before surgery	5d	free flap	50	53.2	8.9	79

Note: dexme: dexmedetomidine; N: the number of participants; NA: not available.