Table 1.

Characteristics of included studies. PCA, patient-controlled analgesia; POD, postoperative day.

First author, year of publication, reference	Type of surgery	Number of (intervention vs control)	Intervention	Comparator	Postoperative analgesic regimen	Sham procedure	Subgroup	Urinary catheter
Abd El-Rahman, 201827	Major abdominal cancer surgery	30 vs 30	300 μg morphine, 10 mg bupivacaine, 0.1 mg kg−1 ketamine	10 mg bupivacaine, 0.1 mg kg−1 ketamine	PCA morphine	Intrathecal medication	A	Unspecified
Abdel-Ghaffar, 201628	Major abdominal cancer surgery	30 vs 30	500 μg morphine, 10 mg bupivacaine	10 mg bupivacaine	PCA morphine	Intrathecal medication	A	Urinary catheter removed on POD1
Andreoni, 200229	Percutaneous nephrolithotomy	9 vs 11	0.3–0.5 μg kg−1 morphine	Local infiltration with ropivacaine	Unspecified	None	B	Nephrostomy catheter, no urinary catheter
Andrieu, 200930	Retropubic radical prostatectomy	17 vs 16	4 μg kg−1 morphine, maximum of 300 μg	No additional medication	Paracetamol, PCA morphine	None	B, D	Unspecified
Bae, 201731	Robotic-assisted laparoscopic prostatectomy	15 vs 15	300 μg morphine	No additional medication	PCA morphine, pethidine rescue dose	None	B, C	Urinary catheter for 1 week
Beaussier, 200632	Colonic surgery	26 vs 26	300 μg morphine	No additional medication	Paracetamol, PCA morphine	S.C. saline	B	Unspecified
Beltrutti, 200233	Hysterectomy	15 vs 14	4.3 μg kg−1 morphine	1.3 μg kg−1 buprenorphine i.v.	I.V. buprenorphine	Intrathecal saline	B, D	No postoperative urinary catheter in a part of the patients
Blay, 200634	Abdominal aortic surgery	15 vs 15	200 μg morphine	No additional medication	Paracetamol, nefopam, morphine rescue dose	S.C. saline	B, D	Urinary catheter of unknown duration
Boonmak, 200735	Kidney surgery	40 vs 40	300 μg morphine	No additional medication	PCA morphine	None	B, D	Unspecified
Brown, 200436	Radical prostatectomy	49 vs 50	200 μg morphine, 15 mg bupivacaine, 75 μg clonidine	15 mg bupivacaine, 75 μg clonidine	Paracetamol, ketorolac, PCA morphine	SC saline	A, D	Unspecified
Child, 198537	Colonic surgery	8 vs 8	50 μg kg−1 diamorphine	3–5 μg kg−1 fentanyl i.v.	Unspecified	None	B, D	Unspecified
Colibaseanu, 201938	Colorectal surgery	98 vs 102	100 μg morphine	Bilateral TAP-block with liposomal bupivacaine	Multimodal analgesia, unspecified	None	B, E	Unspecified
Day, 201539	Colorectal surgery	60 vs 60	250 μg diamorphine, 12.5 mg bupivacaine	10 mg morphine i.v. and PCA morphine	Tramadol and morphine p.o. as needed, diclofenac, paracetamol	None	A, C	Urinary catheter removed on POD1
Devys, 200340	Mixed abdominal surgery	30 vs 30	300–400 μg morphine	No additional medication	PCA morphine	None	B	Unspecified
Dichtwald, 201741	Hepatopancreatic surgery	23 vs 26	4 μg kg−1 morphine	I.V. loading dose of 0.15 μg kg−1 morphine	PCA morphine, paracetamol, and dypirone rescue doses	None	B, D	Urinary catheter of unknown duration
Downing, 198542	Cholecystectomy	10 vs 10	800 μg morphine	I.V. titration of papaveretum during surgery	I.V. papaveretum rescue dose	None	B, D	Unspecified
Drasner, 198843	Major gynaecological surgery	10 vs 10	750 μg morphine	I.M. 750 μg morphine	Unspecified	None	B, D	Unspecified
El-Sherif, 201644	Laparoscopic bariatric surgery	50 vs 50	300 μg morphine, 6 mg bupivacaine	Intrathecal 6 mg bupivacaine and saline	Paracetamol, ketorolac, PCA morphine, wound infiltration with ropivacaine	Intrathecal medication	A, C	Removal of urinary catheter after surgery
Fléron, 200345	Abdominal aortic surgery	102 vs 115	8 μg kg−1 morphine, 1 μg kg−1 sufentanil	Continuous i.v. sufentanil	Paracetamol, PCA morphine	None	D	Urinary catheter of unspecified duration
Hein, 201246	Abdominal hysterectomy	102 vs 34	Mean 200 μg morphine, 12 mg bupivacaine	Intrathecal 12 mg bupivacaine	Paracetamol, PCA morphine	Intrathecal medication	A, D	Unspecified
Houweling, 199347	Abdominal aortic surgery	18 vs 18	50 μg kg−1 morphine	Intrathecal 150 μg sufentanil	500 μg morphine intrathecal	Intrathecal medication	B, D	Urinary catheter of unspecified duration
Kang, 201948	Laparoscopic partial hepatectomy	27 vs 27	400 μg morphine	Bilateral ESP-block with ropivacaine	Paracetamol, ibuprofen, PCA fentanyl, i.v. meperidine	None	B, C, E	Urinary catheter of unspecified duration
Kara, 201249	Major gynaecological surgery	30 vs 30	300 μg morphine	No additional medication	PCA morphine	S.C. needle introduction	B	Unspecified
Karaman, 200650	Abdominal hysterectomy	12 vs 12	5 μg kg−1 morphine	No additional medication	Diclofenac, PCA morphine	None	B, D	Unspecified
Kim, 201651	Kidney surgery	22 vs 23	300 μg morphine	No additional medication	PCA morphine, pethidine rescue dose	None	B, D	Unspecified
Ko, 200952	Liver transplantation donors	20 vs 20	400 μg morphine	No additional medication	PCA fentanyl	None	B, D	Urinary catheter of unspecified duration
Kong, 200253	Laparoscopic colorectal surgery	18 vs 17	200 μg morphine, 15 mg bupivacaine	15 mg bupivacaine	PCA morphine	Intrathecal medication	A, C	Unspecified
Koning, 20183	Laparoscopic colonic surgery	27 vs 29	300 μg morphine, 12.5 mg bupivacaine	I.V. 0.1 mg kg−1 piritramide	Paracetamol, diclofenac, PCA piritramide	SC lidocaine	A, C	Urinary catheter removed on POD1
Koning, 201954	Robot-assisted radical prostatectomy	76 vs 79	300 μg morphine, 12.5 mg bupivacaine	I.V. 0.1 mg kg−1 morphine	Paracetamol, diclofenac, PCA morphine	SC lidocaine	A, C	Urinary catheter for one week
Levy, 20115	Laparoscopic colorectal surgery	31 vs 30	250 μg diamorphine, 12.5 mg bupivacaine	I.V. 10 mg morphine	Paracetamol, diclofenac, tramadol, or morphine	None	A, C	Urinary catheter removed on POD1
Licina, 199155	Mixed abdominal surgery	12 vs 12	15 μg kg−1 morphine	No additional medication	Unspecified	SC saline	B, D	Unspecified
Marion, 201056	Abdominal hysterectomy	35 vs 32	200 μg morphine, 10 μg fentanyl, 12.5 mg bupivacaine	Intrathecal 10 μg fentanyl, 12.5 mg bupivacaine	Paracetamol, diclofenac, and PCA ketobemidone	Intrathecal medication	A, D	Unspecified
Motamed, 200057	Laparoscopic cholecystectomy	17 vs 17	100 μg morphine, 5 mg bupivacaine	No additional medication	PCA morphine, paracetamol, and ketoprofen rescue doses	SC saline	A, C	No catheterisation
Nuri Deniz, 201358	Retropubic radical prostatectomy	28 vs 28	200 μg morphine	No additional medication	PCA tramadol, paracetamol, and diclofenac rescue doses	None	B, D	Unspecified
Ray, 201759	Major abdominal surgery	46 vs 46	750 μg morphine, 10 mg bupivacaine	I.V. 0.2 mg kg−1 morphine, s.c. 0.1 mg kg−1 morphine	Paracetamol, SC morphine	Intrathecal saline	A	Urinary catheter of unspecified duration
Roy, 200660	Partial hepatic resections	10 vs 10	500 μg morphine, 15 μg fentanyl	No additional medication	PCA morphine	S.C. needle introduction	D	Unspecified
Sarma, 199361	Abdominal hysterectomy	60 vs 20	Mean 300 μg morphine	No additional medication	Pethidine rescue dose	Intrathecal saline	B, D	Urinary catheter removed on POD1
Selvam, 201862	Laparoscopic hysterectomy	16 vs 15	200 μg morphine, 5 mg bupivacaine	Intrathecal 5 mg bupivacaine	Paracetamol, PCA fentanyl	Intrathecal medication	A, C	Unspecified
Togal, 200463	Abdominal hysterectomy	25 vs 25	100 μg morphine	No additional medication	PCA morphine	Intrathecal saline	B, D	Urinary catheter removed on POD1
Wongyingsinn, 201264	Laparoscopic colonic resection	24 vs 25	200 μg morphine, 10 mg bupivacaine	PCA morphine	Paracetamol, naproxen, oxycodone	None	A, C	Urinary catheter removed on POD1

‘No additional medication’ under Comparator means that no additional medication to the postoperative analgesic regimen was administered.

A, addition of bupivacaine to intrathecal hydrophilic opioids; B, only intrathecal hydrophilic opioids; C, laparoscopic procedures; D, open procedures; E, regional anaesthesia.