Zaremski 2013.

Study characteristics
Methods	Single‐centre prospective randomised controlled 2‐arm parallel‐assignment study, with blinding not described Switzerland Duration: not described
Participants	202 participants randomised (experimental = 92, comparator = 91) 183 participants analysed, 19 excluded due to protocol violation mean age (years) ± SD: 69.33 ± 11.29 experimental, 66.66 ± 5.27 comparator gender (male/female): 55/37 experimental, 64/27 comparator severity of condition (experimental/comparator): elective procedure 63/61, emergency/urgent procedure 29/30 comorbidities (experimental/comparator): smoker 14/19, hypertension 72/69, dyslipidaemia 67/65, history of cardiovascular disease 54/53, chronic lung disease 15/8 BMI (kg/m²): 29.36 ± 5.79 experimental, 28.66 ± 4.89 comparator artery of interest: radial diameter (mm), mean ± SD: not reported. Catheter size 20 G catheterisation purpose (experimental/comparator): emergency or elective CA or PCI (not detailed) Inclusion criteria scheduled for emergency or elective cardiac catheterisation percutaneous coronary intervention via transradial access Exclusion criteria history of unsuccessful transradial access pathologic Allen's test cognitive impairment younger than 18 years of age
Interventions	Experimental: ultrasound‐guided RA puncture (real‐time; artery short axis, out‐of‐plane) Comparator: RA puncture by palpation and landmarks Level of experience of person carrying out the procedure: quote: "operator performing >200 transradial procedures per year" Concomitant medications: quote: "local anesthesia was administered with lidocaine 2% (Zhaohui Company, Shanghai, China) at the puncture site" Excluded medications: not reported
Outcomes	Primary (specified) total success rate cannulation duration Primary (collected) total success rate cannulation duration first‐attempt success rate Secondary (specified) rate of complications attributable to cannulation (vessel dissection and access‐site haematoma requiring medical attention) Secondary (collected) rate of complications attributable to cannulation (vessel dissection and access‐site haematoma requiring medical attention) Time points reported: up to 1 day and up to 2 days after the procedure
Notes	Funding: quote: "HU was supported by an unrestricted research grant by the University of Basel, Switzerland" Conflicts of interest: quote: "Dr. Quesada is a member of the Abbott Advisory Board; a consultant for the Medicines Company; and a consultant/speaker’s bureau member for Abbott, Boston Scientific, Cordis Corporation, St Jude Medical, WL Gore, NMT Medical, and Terumo; he also reports travel expenses from the above companies" Protocol not available
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not described
Allocation concealment (selection bias)	Unclear risk	Not described
Blinding of participants and personnel (performance bias) All outcomes	High risk	Not described, but due to the nature of the interventions, we assumed that blinding of personnel was not possible
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not described
Incomplete outcome data (attrition bias) All outcomes	High risk	There was a balanced but large amount of cross‐over interventions in both groups (12/92 experimental (6 switch to palpation and 6 switch to femoral) and 12/91 comparator (all switch to ultrasound)). Ten participants in experimental group and 9 in comparator group were switched to femoral access
Selective reporting (reporting bias)	Low risk	All planned outcomes were reported
Other bias	Low risk	We do not suspect any other bias related to this study