Table 1

Characteristics of eligible trials

Study	Setting	Participants	Exclusions	Method	Outcomes measured	Outcome (US vs ST)	Operator experience	Randomisation method	Jadad score
25	ICU in France	Adult patients with DA defined as absence of visible/palpable veins in arms after tourniquet placement	Not stated	RT, SO performed by nurse in transverse plane versus ST. Crossover to alternative group after two failed attempts	Successful PIV cannulation before and after crossover, procedure time	21/30 (70%) vs 11/30 (37%) Time in mins: 6.6 vs 7.25	Nurse—number participating in study not reported, level of training with Ultrasound not reported	Not reported	1
21	ED tertiary care, teaching hospital in USA.	Patients with two failed blind PIV attempts or reported history of DA	Not stated	SO performed by ENs vs ST	Number of attempts, procedure time, patient satisfaction, patient pain perception	No. of punctures: 1.9 vs 2.3 Time in minutes: 23.7 vs 8.1. Patient satisfaction: 93.3% vs 77.8%	Number not reported. EN received 2 h tutorial from diagnostic medical sonography-certified EP	Not reported	1
26	ED at urban tertiary care teaching hospital in USA.	Patients >18 years with >DA in arm veins (brachial, forearm, cephalic, and basilic) and EJV DA≥2 peripheral attempts Ultrasound guidance versus ST	Unstable patients/patients requiring emergency intravenous line	EPs instructed to use their most effective method including SO/DO, transverse/longitudinal versus ST	Number of attempts, procedure time, patient satisfaction	2.07 vs 2.37 (mean no) 2 vs 2 (median) Time in minutes: 26 vs 29 Patient satisfaction Likert scale: 8 vs 7	Twenty EC, 12 credentialed in Ultrasound. Remainder received introductory course 1-year prior plus 1 h training program on model. All received 6-month period to practice technique before trial	Computer-generated randomisation.	3
3	Level 1 Paediatric trauma centre in USA	Patients <10 years with DA DA=2 peripheral attempts or history of difficult access	Critical illness, no guardians to provide consent, primary language other than English or Spanish	RT, DO (physician used Ultrasound, nurse placed line). Transverse axis inserted at 30° angle versus ST ± fiberoptic transillumination by nurse	Overall success rates, number of attempts, procedure times	20/25 (80%) vs 16/25 (64%) No. of attempts: 1 vs 3 (median) Total time in min 6.3 vs 14.1	Five Paediatric EC and fellows with limited experience received 90 min tutorial. Twenty-nine paediatric EN, 16 who performed Ultrasound-guided attempts with 15 min tutorial and practice on live patients	Block randomisation according to computer-generated programme	2
24	ED at urban level 1 trauma centre in USA.	Patients <7 years with 1 failed intravenous attempt Ultrasound guidance	Unstable patients	Indirect method, DO vs ST Vein localised by physician with Ultrasound, marked and intravenous placed by nurse. Crossover for ST group to Ultrasound after 1 failed attempt	Venopuncture and PIV cannulation success rate at 1st attempt Perceived ease of puncture by nurses	IVC: 8/23 (35%) vs 6/21 (29%) EOP: 4/18 (22%) vs 0	Six board certified EP with 1 h tutorial and experience visualising veins in 1 adult and 1 child. Paediatric EN given overview of technique.	Computer generated randomisation	2
23	2007, USA	Patients >18 years Past history of DA or DA determined by anaesthetist	Not stated	RT SO performed by nurse anaesthetist versus ST	Successful rate on 1st attempt, number of attempts, procedure time	74% vs 81% in Ultrasound vs ST 1.4 vs 1.3. Time in mins: 5.06 vs 2.87	Two certified registered nurse anaesthetists with >3 years' experience		1
22	2006, USA	Patients >18 years Two unsuccessful attempts by ST	Steroid or anticoagulant therapy	RT, SO performed by anaesthetist versus ST at antecubital fossa	No. of attempts, procedure time, patient pain perception	1.7 vs 3.2 in Time in mins: 13.9 vs 11.3	Trained anaesthetists with >5 previous successful Ultrasound intravenous attempts	Random number	3

DA, difficult access; DO, dual operator; EC, emergency consultant.; ED, emergency department; EN, emergency nurse; EOP, ease of puncture; EP, emergency physician; PIV, peripheral intravenous; RT, real time; SO, single operator; ST, standard technique; Ultrasound, ultrasound.