Pappas 2006.

Study characteristics
Methods	Randomised, open‐label trial
Participants	Setting: operating room Number of participants: 18 (USG 12, LM 6) Age, mean (SD) years: not specified Difficulty: at least 2 failed attempts with LM Sites of peripheral veins: upper extremity (forearm)
Interventions	Technique LM vs USG: Machine: Site‐Rite3 Ultrasound Unit (Bard Access Systems) with a 9.0 MHz probe Axis: not specified Guidance: dynamic Operator Profession: anaesthesia provider Number of operators: 3 Experience of USG before the study: yes Length of experience with USG before the study: not specified A training programme of USG for the study: not specified Number of clinical cases with USG required or experienced before the study intervention started: 5 Needle Length: not specified Gauge: 18 or 20
Outcomes	Procedure time for overall cannulation, number of attempts, pain Definition of successful cannulation: blood return from a catheter Definition of start and end of time measurement: Start: USG, a transducer was placed and a target vein was identified LM, an anesthesia provider began detecting potential veins End: successful intravenous cannulation
Funding	None
Declarations of interest	Not specified
Notes	Although original sample size was 46, they actually randomised only 22 participants, and did not mention the reason. Of the 22 participants, 2 were excluded due to broken randomisation and another 2 were excluded due to unsuccessful cannulation. We attempted to contact the authors to obtain additional information but were unable to reach them.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Packets, including consent and data collection tool with operational definitions, were shuffled and then numbered consecutively
Allocation concealment (selection bias)	Unclear risk	No description of allocation concealment
Blinding (performance bias and detection bias) Pain	High risk	Blinding of participants and operators is impossible due to the nature of the intervention. Operators assessed the outcome themselves
Blinding (performance bias and detection bias) Procedure time for overall cannulation	High risk	Blinding of participants and operators is impossible due to the nature of the intervention. Operators assessed the outcome themselves
Blinding (performance bias and detection bias) Number of attempts	High risk	Blinding of participants and operators is impossible due to the nature of the intervention. Operators assessed the outcome themselves
Incomplete outcome data (attrition bias) Pain	High risk	22 participants were initially randomised, but two participants were excluded due to broken randomisation, and another two participants were excluded from analysis due to unsuccessful cannulation
Incomplete outcome data (attrition bias) Procedure time for overall cannulation	High risk	22 participants were initially randomised, but two participants were excluded due to broken randomisation, and another two participants were excluded from analysis due to unsuccessful cannulation
Incomplete outcome data (attrition bias) Number of attempts	High risk	22 participants were initially randomised, but two participants were excluded due to broken randomisation, and another two participants were excluded from analysis due to unsuccessful cannulation
Selective reporting (reporting bias)	Unclear risk	No study register or protocol was available
Other bias	Low risk	No concerns about other sources of bias
Overall risk Pain	High risk	At least one domain was at high risk
Overall risk Procedure time for overall cannulation	High risk	At least one domain was at high risk
Overall risk Number of attempts	High risk	At least one domain was at high risk