Kiberenge 2018.

Study characteristics
Methods	Single‐centre prospective randomised controlled 2‐arm parallel‐assignment single‐blinded (outcomes assessor) study USA Duration: May 2015 to December 2015
Participants	260 participants randomised (experimental = 132, comparator = 128) 73 participants analysed mean age (years) ± SD: 58 ± 15 experimental, 61 ± 16 comparator gender (male/female): 74/58 experimental, 66/62 comparator severity of condition (experimental/comparator): all participants undergoing non‐emergent operation comorbidities (experimental/comparator): peripheral vascular disease 26/15 BMI (kg/m²) ± SD: 30 ± 8 experimental, 31 ± 7 comparator artery of interest: radial diameter (mm), mean ± SD: 2.8 ± 0.7 experimental, 2.9 ± 0.7 comparator catheterisation purpose (experimental/comparator): all for diagnosis (pressure monitoring) Inclusion criteria needing radial arterial cannulation intraoperatively Exclusion criteria refusal to consent minor incarcerated individual radial cannulation within past month negative modified Allen's test shock non‐English‐speaking pregnant requiring radial forearm flap harvest
Interventions	Experimental: ultrasound‐guided RA puncture (real‐time, artery short axis, needle out‐of‐plane, DNTP) Comparator: RA puncture via palpation and landmarks Level of experience of person carrying out the procedure: quote: "arterial cannulation was performed by anaesthesia residents or faculty members" and "the operators (anesthesia residents, fellows, and faculty) placing the arterial catheters were required to have placed at least 10 radial arterial catheters using each technique prior to participation in the study" Outcome data were reported separately by experienced and inexperienced operators Concomitant medications: quote: "arterial cannulation was performed either before or after induction of general anesthesia based on the preference of the faculty anesthesiologist" Excluded medications: not reported
Outcomes	Primary (specified) first‐pass success [Time Frame: 5 minutes]. Placement of arterial cannula in 5 minutes after touching the wrist Primary (collected) first‐pass success of radial arterial line placement (yes/no) Secondary (specified) overall success [Time Frame: 5 minutes]. Successful arterial cannulation after any number of passes as long as it is within 5 minutes Secondary (collected) overall success rate number of catheters used number of skin perforations time to achieve successful cannulation (seconds) systolic blood pressure before and after radial artery puncture diastolic blood pressure before and after radial artery puncture heart rate before and after puncture Time points reported: up to 5 minutes
Notes	Funding: University of Iowa Hospitals and Clinics Conflicts of interest: quote: "the authors declare no conflicts of interest" Protocol (NCT02557828) available
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "the assignments were computer generated, with randomly selected block sizes using nQuery Advisor 7.0 (Statistical Solutions Ltd, Cork, Ireland) and then placed in sealed envelopes"
Allocation concealment (selection bias)	Low risk	Quote: "the technique to be used for cannulation was determined when the research team member opened an opaque randomization envelope containing a piece of paper with either ultrasound or palpation printed on it"
Blinding of participants and personnel (performance bias) All outcomes	High risk	No blinding for participants or personnel
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Protocol states that this was an 'outcomes assessor' blinding study
Incomplete outcome data (attrition bias) All outcomes	Low risk	There were no losses
Selective reporting (reporting bias)	Low risk	All prespecified outcomes were reported. Protocol violations were reported and were treated in an ITT analysis Quote: "there were 3 protocol violations: one was due to the use of a different catheter, one operator refused to use the palpation technique after randomization, and another used a wire to guide the catheter into the vessel lumen while using the dynamic needle tip positioning technique. These 3 patients were treated as failed attempts in the intention to treat analysis"
Other bias	Low risk	We do not suspect any other bias related to this study