Anantasit 2017.

Study characteristics
Methods	RCT
Participants	Number: 84 radial arteries Number per intervention Ultrasound: 43 radial arteries Palpation: 41 radial arteries Inclusion criteria Critically ill condition Age 1 month–15 years Need for invasive monitoring and frequent blood sampling Exclusion criteria Absence of an amplitude of radial pulsation  Skin erosions near the insertion site Former cannulation Surgery/setting: paediatric ICU Baseline characteristics Ultrasound Mean age: 20 months Mean weight: 9 kg Sex ratio (male:female): 25:16 Palpation Mean age: 32 months Mean weight: 11 kg Sex ratio (male:female): 31:12
Interventions	Randomisation: stratified block randomisation (blocks of 4, stratified by age < 1 year and > 1 year) Intervention: ultrasound‐guided artery cannulation (short‐axis view). Artery was lined up with centre of transducer, needle inserted at centre of transducer in real‐time. Single‐ or double wall technique chosen depending on operator preference (Seldinger technique employed in both cases). Control: palpation Co‐intervention: standard 22‐ to 24‐gauge Jelco intravenous catheter (Smiths Medical International, Ashford, England) percutaneously punctured the radial artery Experience of operator: attended course in ultrasound‐guided vascular access course; experience of > 10 cases in ultrasound‐guided or traditional palpation technique.
Outcomes	Primary endpoints First‐attempt success rate Total success rate (within 3 attempts; attempts quantified as number of needle tips completely withdrawn from the skin Secondary endpoints Time to successful cannulation (from initial needle penetration through skin to removal of needle and flash of arterial blood) Incidence of complications (hand ischaemia, haemorrhage, thrombosis, hematoma)
Notes	No information was provided regarding funding and conflicts of interest.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	RCT with stratified randomisation (children < 1 year and > 1 year). Method of randomisation and stratification not explained.
Allocation concealment (selection bias)	Unclear risk	Method of randomisation and stratification not explained.
Blinding of participants and personnel (performance bias) All outcomes	High risk	The anaesthesiologist was aware of the allocated intervention before performing arterial catheterisation.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Objective outcomes not affected by lack of blinding.
Incomplete outcome data (attrition bias) All outcomes	Low risk	No missing data.
Selective reporting (reporting bias)	Low risk	All outcomes were addressed.
Other bias	Unclear risk	Quote: "The operators included 7 fellows. The experience of each fellow may have affected the success rate of radial artery cannulation; however, we used a multiple logistic regression analysis, which included the operator to reduce operator bias."