Table 1.

Characteristics of the studies included in the meta-analysis

First author	Published year	Country	Sample	Grouping	Dose of etomidate	Incidence of myoclonus				Jadad score
Total	Mild	Moderate	Severe
Zhao15	2008	China	50	Butorphanol 2 mg	0.3 mg/kg	2	2	0	0	2
			50	Normal saline		41	7	18	16
Ren16	2013	China	50	Butorphanol 15 µg/kg	0.3 mg/kg	8	4	3	1	3
			50	Normal saline		37	7	11	19
He4	2014	China	54	Butorphanol 15 µg/kg	0.3 mg/kg	7	3	3	1	7
			54	Normal saline		43	7	11	25
Zhang 14	2015	China	40	Butorphanol 15 µg/kg	0.3 mg/kg	5	4	1	0	3
			40	Normal saline		32	5	12	15
Zhang 12	2015	China	50	Butorphanol 15 µg/kg	0.3 mg/kg	7	5	2	0	7
			50	Normal saline		37	15	12	10
Yan13	2015	China	60	Butorphanol 20 µg/kg	0.3 mg/kg	3	2	1	0	2
			60	Normal saline		43	9	8	26