Min 2019.

Study characteristics
Methods	RCT
Participants	Number: 74 radial arteries Number per intervention Ultrasound: 37 radial arteries Palpation: 37 radial arteries Inclusion criteria Age < 12 months Scheduled cardiac surgery Exclusion criteria: Signs of skin infection or a recent wound at or near the puncture site Diagnosed abnormal peripheral circulation of the hand Diagnosed vascular abnormality or radial arterial variation Problem at the radial or ulnar artery sites Haemodynamic instability  Surgery/setting: cardiac surgeries for congenital heart disease Baseline characteristics Ultrasound Mean age: 1.7 (SD 2.7) months Mean weight: 4.8 (SD 1.9) kg Sex ratio (male:female): 18:19 Palpation Mean age: 3.5 (SD 3.5) months Mean weight: 5.7 (SD 2.1) kg Sex ratio (male:female): 24:13
Interventions	Randomisation: participants were assigned randomly to either a palpation‐guided group or an ultrasound‐guided group using computer‐generated numbers found in sealed envelopes. Intervention: a linear ultrasound transducer in the short‐axis view was used in the US group. The least depth‐of‐field setting was 1.5 cm, and a 24‐gauge angiocatheter was inserted. The needle was advanced until a bright white dot of the needle tip was observed. The needle was then advanced, targeting the radial artery using an anterior or posterior puncture technique. Control: palpation of the radial arterial pulse Co‐intervention: general anaesthesia with inhaled sevoflurane, intravenous midazolam (0.15 to 0.3 mg/kg) and rocuronium (0.6 to 0.9 mg/kg) Experience of operator: all ultrasound recordings and arterial catheterisations were performed by one of two anaesthesiologists (> 2 years of experience in paediatric cardiac anaesthesia and > 50 cases of ultrasound‐guided radial arterial catheterisation in paediatric patients).
Outcomes	Primary endpoints  First‐pass success  Success within 10 minutes Total number of attempts Total procedural time for successful catheterisation  Secondary endpoints Complications during the procedures (e.g. haematoma formation, arterial spasm or ischaemic signs)
Notes	Supported by institutional resources. Study authors disclosed no potential conflicts of interest.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "Patients were assigned randomly to either a palpation‐guided group or an ultrasound‐guided group using computer‐generated numbers found in sealed envelopes."
Allocation concealment (selection bias)	Low risk	Quote: "The sealed envelope was opened by a physician just after induction of general anaesthesia."
Blinding of participants and personnel (performance bias) All outcomes	High risk	All participants underwent induction of general anaesthesia prior to arterial catheterisation (low risk of bias). The anaesthesiologist was aware of the allocated intervention before performing arterial catheterisation (high risk of bias).
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Successful arterial cannulation is the endpoint of the procedure for both techniques (unequivocal endpoint).
Incomplete outcome data (attrition bias) All outcomes	Low risk	No missing data.
Selective reporting (reporting bias)	Low risk	An investigator recorded all procedures on video for analysis.
Other bias	Unclear risk	Participant age and height were significantly different between the 2 groups. The investigators set a time limit of 10 minutes.