Table 1. Characteristics of included studies.

Reference	Age, years	Patient number (magnesium/ control)	Surgery	Local anesthetics used for caudal anesthesia	Amount of local anesthetics	Scoring tool for pain	Definition of the end of analgesic duration
Birbicer 2007 [18]	2–10	23/37	Inguinal hernia repair, orchidopexy, circumcision	0.25% ropivacaine	0.5 mL/kg	POPS, CHEOPS	Not defined
Elshal 2009 [19]	4–10	20/20	Hypospadias surgery	0.25% ropivacaine	0.5 mL/kg (1 mL/kg in Discussion)	OPS	First dose of analgesia administered (OPS ≥4)
Kim 2014 [20]	2–6	39/38	Inguinal hernia repair	0.15% ropivacaine	1 mL/kg	PPPM	First oral acetaminophen administration after surgery (when PPPM was ≥6)
Yousef 2014 [21]	1–6	35/35	Inguinal hernia repair	0.15% ropivacaine	1.5 mL/kg	CHEOPS, FLACC	Time when FLACC and CHEOP was ≥4
Sridhar 2017 [16]	3–12	32/32	Infraumbilical surgery	0.2% ropivacaine	0.5 mL/kg	MOPS	The time from caudal block to acetaminophen administration (MOPS >4)
Askar 2017 [17]	1–6	30/30	Inguinal orchidopexy, distal hypospadias surgery, inguinal hernia repair	0.25% bupivacaine	1 mL/kg	FLACC	The time from caudal block to the first analgesic administration (FLACC > 7)

POPS, Paediatric Objective Pain Score; CHEOPS, Children’s Hospital of Eastern Ontario Pain Scale; OPS, Objective Pain Scale; PPPM, Parent’s Postoperative Pain Measurement; FLACC, Faces Legs Activity Cry Consolability tool; MOPS, Modified Objective Pain Score