Laursen 2015.

Study characteristics
Methods	[Abstract of event] Single‐centre prospective randomised controlled 2‐arm study, with blinding not reported Denmark Duration: not reported
Participants	238 participants randomised (experimental = 115, comparator = 109) 224 analysed mean age (years, range): not reported gender (male/female): not reported severity of condition (experimental/comparator): not reported comorbidities (experimental/comparator not reported): not reported body weight (kg): not reported height (cm): not reported artery of interest: radial diameter (mm), mean ± SD: not reported catheterisation purpose (experimental/comparator): all for diagnosis (blood test) Inclusion criteria arterial puncture for blood gas analysis ordered by attending physician participant admitted or treated in the acute emergency department Exclusion criteria permanent mental disability younger than 18 years declining to participate arterial puncture for blood gas analysis contraindicated
Interventions	Experimental: ultrasound‐guided RA puncture (real‐time, artery short axis, DNTP) Comparator: RA puncture via palpation and landmarks Level of experience of person carrying out the procedure: not reported Concomitant medications: not reported Excluded medications: not reported
Outcomes	Primary (specified) proportion of patients for whom arterial puncture for blood gas analysis was successful in the first attempt Primary (collected) first‐attempt success rate Secondary (specified) median time used for the procedure number of attempts to successful arterial puncture for blood gas analysis patient cooperation. The degree of patient cooperation was assessed on a scale from 1 to 5, where 1 is very poor patient cooperation and 5 is perfect patient cooperation patient pain (VAS) Secondary (collected) median time used for the procedure number of attempts to successful arterial puncture for blood gas analysis patient cooperation. The degree of patient cooperation was assessed on a scale from 1 to 5, where 1 is very poor patient cooperation and 5 is perfect patient cooperation patient pain (VAS) adverse events Time points reported: up to 1 hour after puncture
Notes	Funding: quote: "the publication charges for this supplement were funded by TrygFonden" Conflicts of interest: not reported Protocol (NCT01660724) 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	Trial authors reported data for 224 of 238 randomised participants. Trial authors did not report data for 14 of 238 (5.8%) participants
Selective reporting (reporting bias)	High risk	Trial authors apparently collected all planned outcomes but reported numerical data for only 2 of them, which showed a difference between intervention groups (first‐attempt success rate and median time used for the procedure)
Other bias	Low risk	We do not suspect any other bias related to this study