Table 1

Main characteristics of randomised controlled trials in this meta-analysis of ultrasound-guided lumbar puncture and epidural catheterisation

Study	Year	Country	Patients (n)	Population	Setting	Procedure	Equipment	Operator experience
Grau²⁵	2001	Germany	36/36	Parturients with presumed difficult puncture	LD	EC	NA	Not reported
Grau²⁶	2002	Germany	150/150	Parturients scheduled for caesarean section or vaginal dilivery	LD	EC	Sonoace 6000, 5.0 MHz curved array probe (Kretz, Marl, Germany)	Not reported
Grau²⁷	2004	Germany	20/10	Obstetric patients scheduled for caesarean section	LD	CSE	Logiq 400, 7.5 MHz linear array probe	Not reported
Pisupati³⁴	2004	USA	14/19	Adults	ED	LP	Not reported	Not reported
Nomura²⁸	2007	USA	24/22	Adults	ED	LP	SonoSite (Bothell, WA, USA), 5–10 MHz linear probe	Postgraduate year 2 residents who had fulfilled the ED
Lee²⁹	2008	Korea	29/32	Adults	ED	LP	Sonosite MicroMaxx, 2–5 MHz curved probe	Not reported
Cho³⁰	2009	Korea	30/30	Adults >60 years old	ED	LP	Sonosite MicroMaxx, 2–5 MHz curved probe	Not reported
Vallejo³¹	2010	Canada	189/181	Laboring parturients	LD	EC	The Sonosite MicroMaxx ultrasound system (Sonosite), 2–5 MHz curved probe	Residents had no more than five epidural placement attempts
Chin³²	2011	Canada	60/60	Adults with difficult surface anatomic landmark	OR	LP	NA	Anesthetists with more than 5 years of clinical experience in regional anaesthesia or consultant
Mofid³³	2011	Iran	40/40	Adults	ED	LP	NA	Not reported
Kawaguchi³⁵	2011	Japan	12/12	Adults scheduled scheduled to undergo total replacement of a hip joint	OR	EC	Logiq Book XP with 3 C-RS 2–5 MHz convex probe	Not reported
Wang⁴¹	2012	China	30/30	Obese parturients scheduled for caesarean section	LD	CSE	Turbo with a 5–10 MHz, convex probe, Sonosite	Anaesthetist with more than 10 years of experience in obstetric anaesthesia
Abdelhamid³⁶	2013	Egypt	45/45	Adults	A block room	LP	Sonosite S-Nerve (Sonosite) ultrasound machine, a low-frequency (2–5 MHz)	Not reported
Sahin³⁷	2013	Germany	50/50	Parturients scheduled for caesarean section	LD	LP	A Esaote Mylab 30 (Florence, Italy, convex transducer of 2–5 MHz)	Operator who with extensive experience
Nassar⁴⁴	2014	Egypt	55/55	Parturients scheduled for vaginal dilivery	LD	CSE	2–5 MHz, Sonosite MicroMaxx Ultrasound System English, USA	Operator with more than 10 years of experience
Ansari¹²	2014	United Arab Emirates	75/75	Obstetric patients scheduled for caesarean section	LD	LP	(GE, Solingen, Germany), 4CRS 2–5.5 MHz broadband multifrequency probe	Anesthetists with experience in ultra sound-guided neuraxial block (each had performed between 200 and 300 ultrasound-guided neuraxial blocks)
Peterson¹⁴	2014	USA	50/50	Adults	ED	LP	Aloka SSD 1400 US machin(Aloka, Wallingfod, CT), 3.5 MHz convex array or a 7.5 MHz linear array probe	Operators performed at least 10 previous successful LPs by their own report
Lim⁴⁵	2014	Singapore	85/85	Adults	OR	LP	Turbo ultrasound machine (SonoSite, Fujifilm, Bothell, WA, USA), low frequency (2–5 MHz) curvilinear probe	Anaesthetists experienced in ultrasound-assisted neuraxial block
Mrcpi⁴⁶	2015	Ireland	50/50	Adults scheduled for elective total joint replacements	OR	LP	Ultrasound unit (SonixTablet, Peabody, MA) with a curved 2–5 MHz probe	Anaesthesiologists had performed >75 neuraxial ultrasound scans before the study
Creaney¹¹	2016	Ireland	10/10	Obstetric patients scheduled for caesarean section	LD	LP	Sonosite NanoMaxx C60, 2–5 MHz	Anaesthetists had completed 10 LPs with ultrasound guidance
Lahham¹³	2016	USA	71/87	Adults	ED	LP	Sonosite Fujifilm, 10–5 MHz linear array probe	Resident physician
Perna⁴⁷	2017	Italy	30/28	Obstetric patients scheduled for vaginal or caesarean dilivery	LD	EC	Sonosite NanoMaxx, 5-2 MHz C60n Convex probe	Anaesthetist with experience of more than 150 epidural procedures yearly
Elsharkawy⁴³	2017	USA	14/18	Adults with predicted difficult anatomy	OR	LP	GE Venue 40 (GE Healthcare, Waukesha, WI, USA) or Sonosite S-Nerve, low frequency (2–5 MHz) transducer	Anaesthesiologists experienced with previously performed at least 10 ultrasound-guided spinal anesthet ics prior to study initiation
Auyong³⁸	2017	USA	33/37	Adults undergoing any thoracicor upper abdominal surgery	OR	EC	Not reported	Not reported
Abraham³⁹	2018	Canada	20/20	Adults	Outpatient neuromuscular clinic.	LP	General Electric LOGIQ S7 Expert, Toronto, Canada, 5 MHz (ML2-5)	Not reported
Li⁴²	2018	China	40/40	Obese parturients scheduled for caesarean section	LD	LP	M-Turbo ultrasound machine (GE, Solingen, Germany), a low-frequency (2–5 MHz) curvilinear probe.	Three anaesthesiologists with 3 years of clinical expe rience in spinal anaesthesia
Ghisi¹⁶	2019	Italy	47/52	Adults scheduled for lower limb surgery	OR	LP	Accuro, Rivanna Medical, Praesidia Medical Devices, via dei Lapidari 19, Bologna, Italy	Anaesthesiologists skilled in both tech niques with a 25 or 27 G needle
Rizk¹⁷	2019	USA	120/60	Adults scheduled for elective surgery	OR	LP	The Sonosite with a low frequency (2–5 MHz) curvilinear probe	Anaesthesiologist trained and experienced in ultrasound-assisted neuraxial block.

CSE, combined spinal-epidural anaesthesia; ED, emergency department; EC, epidural catheterisation; LD, labour and delivery suite; LP, lumbar puncture; NA; OR, operating room.