Skulec 2019.

Study characteristics
Methods	Randomised, open‐label trial
Participants	Setting: prehospital Number of participants: 300 (dynamic USG 100, static USG 100, LM 100) Age, mean (SD) years: dynamic USG 66.6 (17.4), static USG 65.3 (21.2), LM 64.5 (18.8) Difficulty: not restricted (all participants irrespective of difficulty) Sites of peripheral veins: upper extremity
Interventions	Technique LM vs Dynamic USG vs Static USG Machine: Vscan dual probe (General Electric) Axis: short Operator Profession: paramedic, emergency physician Number of operators: 7 (5 paramedics, 2 emergency physicians) Experience of USG before the study: paramedics no; emergency physicians yes Length of experience with USG before the study: paramedics none, emergency physicians not specified A training programme of USG for the study: paramedics yes; emergency physicians no Number of clinical cases with USG required or experienced before the study intervention started:  paramedics: static 5, dynamic 5 emergency physicians: static > 200, dynamic > 200 Needle Length: 32 or 45 mm Gauge: 20 or more
Outcomes	First‐pass success of cannulation, overall success of cannulation, procedure time for first‐pass cannulation, procedure time for overall cannulation, number of attempts, complications Definition of successful cannulation: blood return from a catheter, smooth normal saline flush, and no signs of extravasation Definition of start and end of time measurement Start: all equipment was prepared, including the ultrasound device being turned on End: successful cannulation or termination of the cannulation attempts
Funding	None
Declarations of interest	The author received a temporary loan of ultrasound machines from GE Medical Systems Ceska republika for study purposes, but no financial support
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	The randomisation scheme was created by computer (this was not stated in the article, but obtained through communication with an author (RS))
Allocation concealment (selection bias)	Low risk	Each random allocation was conducted by a person independent of the study, and used opaque, sealed envelopes (this was not stated in the article, but obtained through communication with an author (RS))
Blinding (performance bias and detection bias) First‐pass success of cannulation	Low risk	Although blinding of participants and operators is impossible due to the nature of the intervention, a third‐person assessed the outcome (this was not stated in the article, but obtained through communication with an author (RS))
Blinding (performance bias and detection bias) Overall‐success of cannulation	High risk	Blinding of participants and operators is impossible due to the nature of the intervention. Operators assessed the outcome themselves (this was not stated in the article, but obtained through communication with an author (RS))
Blinding (performance bias and detection bias) Procedure time for first‐pass cannulation	Low risk	Although blinding of participants and operators is impossible due to the nature of the intervention, a third‐person assessed the outcome (this was not stated in the article, but obtained through communication with an author (RS))
Blinding (performance bias and detection bias) Procedure time for overall cannulation	Low risk	Although blinding of participants and operators is impossible due to the nature of the intervention, a third‐person assessed the outcome (this was not stated in the article, but obtained through communication with an author (RS))
Blinding (performance bias and detection bias) Number of attempts	Low risk	Although blinding of participants and operators is impossible due to the nature of the intervention, a third‐person assessed the outcome (this was not stated in the article, but obtained through communication with an author (RS))
Blinding (performance bias and detection bias) Overall complications	High risk	Blinding of participants and operators is impossible due to the nature of the intervention. Operators assessed the outcome themselves (this was not stated in the article, but obtained through the communication with an author (RS))
Incomplete outcome data (attrition bias) First‐pass success of cannulation	Low risk	The outcome was available for all participants
Incomplete outcome data (attrition bias) Overall success of cannulation	Low risk	The outcome was available for all participants
Incomplete outcome data (attrition bias) Procedure time for first‐pass cannulation	High risk	The outcome was evaluated only for participants with successful cannulation
Incomplete outcome data (attrition bias) Procedure time for overall cannulation	Low risk	The outcome was available for all participants
Incomplete outcome data (attrition bias) Number of attempts	Low risk	The outcome was available for all participants
Incomplete outcome data (attrition bias) Overall complications	Low risk	The outcome was available for all participants
Selective reporting (reporting bias)	Low risk	The outcomes reported in the article were consistent with the trial registry (NCT03709394)
Other bias	Low risk	No concerns about other sources of bias
Overall risk First‐pass success of cannulation	Low risk	All domains were at low risk
Overall risk Overall success of cannulation	High risk	At least one domain was at high risk
Overall risk Procedure time for first‐pass cannulation	High risk	At least one domain was at high risk
Overall risk Procedure time for overall cannulation	Low risk	All domains were at low risk
Overall risk Number of attempts	Low risk	All domains were at low risk
Overall risk Overall complications	High risk	At least one domain was at high risk