Aims: to evaluate the success rate of radial artery cannulation in patients undergoing cardiac catheterization, using different methods such as palpation, hyperemia or ultrasound-guided puncture, together or each method separately. Specifically, the success rate at the first attempt, the number of attempts with each technique and the time spent will be assessed.

The hypothesis is that there are different success rates for each puncture technique when cannulating radial artery for cardiac catheterization.

Methods: randomized clinical trial with four parallel groups, with operator blinding. Those patients who will have the radial artery cannulated for an interventional cardiology procedure will be selected.

Once the participant agrees to be included in the study and signs the informed consent, they are randomized to one of four groups: ultrasound and hyperemia puncture, only ultrasound puncture, only hyperemia puncture, palpation puncture (control group). Subsequently, an ultrasound assessment of the participant's radial artery (diameter, depth and systolic peak velocity) will be performed. Once in the intervention room, the puncture will be performed according to the corresponding method. The puncturing operator in charge will not perform the randomization or the ultrasound assessment to avoid bias.

Variables will be collected in an ad hoc questionnaire designed to respond all study aims. Regarding the sample size, accepting an alpha risk of 0.05 and a beta risk of 0.2 in a bilateral contrast, 92 subjects per group are required to detect significant differences. Therefore, the total sample size would be made up of 368 participants, estimating losses of 5%.

For variables description and hypotheses contrast, the statistical program SPSS version 22.0 for Windows will be used, working with a significance level of 5%.

Background: ultrasound-guided puncture seems to facilitate cannulation of the radial artery in patients who undergoing cardiac catheterization. The efficacy of reactive hyperemia has also been seen, however, the combination of different methods in radial artery puncture has not been evaluated.

Aims: to evaluate the success rate of radial artery cannulation in patients undergoing cardiac catheterization, using different methods such as palpation, hyperemia or ultrasound-guided puncture, together or each method separately. Specifically, success rate at the first attempt, attempts numbers with each technique and time spent will be assessed. Possible complications and perceived pain by the participant in each technique will be evaluated.

The hypothesis is that there are different success rates for each puncture technique when cannulating radial artery for cardiac catheterization.

Methods: randomized clinical trial with four parallel groups, with operator blinding.

Participation in the clinical trial does not imply an increased risk for the patient since both ultrasound and hyperemia are harmless and non-invasive methods.

Once the participant agrees to be included in the study and signs the informed consent, they are randomized to one of four groups: ultrasound and hyperemia puncture (for hyperemia, a blood pressure cuff is inflated 50mmHg above systolic until a maximum of 200mmHg for 5 minutes before puncture, it is known that maximum hyperemia is achieved 60 to 180 seconds after deflation), ultrasound puncture only, hyperemia puncture only, palpation puncture (control group).

Similarly, before the puncture, an ultrasound assessment of the participant's radial artery (diameter, depth and systolic peak velocity) will be performed. Once in the intervention room, the puncture will be performed according to the corresponding method. The puncturing operator will not perform the randomization or the ultrasound assessment to avoid bias.

Participation in the study ends once the radial artery has been cannulated with the guide according to the Seldinger technique.

The randomization sequence was generated by the center's Biostatistics and Epidemiology Unit. The four possible puncture methods were stratified by operator.

All operators have performed hundreds of radial punctures by palpation and more than 20 ultrasound-guided punctures, as established by the study of the learning curve carried out by Jayanti S et al, before starting participants recruitment.

All the variables will be collected in an ad hoc questionnaire designed to respond all study objectives.

Regarding the sample size, accepting an alpha risk of 0.05 and a beta risk of 0.2 in a bilateral contrast, 92 subjects per group are required to detect a statistically significant difference, which for the control group (traditional puncture) is expected to be 0.44 the percentage of success at the first puncture attempt, and for the rest is at least 0.65. Therefore, the total sample size would be made up of 368 participants, estimating a follow-up loss of 5%.

Regarding the statistical analysis, the quantitative variables will be described with the mean and the standard deviation if they follow a normal distribution, or with the median and the interquartile range if they do not follow a normal distribution. The normality will be contrasted using the Kolmogorov-Smirnov test. The qualitative variables will be described through the distribution of frequencies and percentages.

For the comparisons of the quantitative variables following a normal distribution, the one factor analysis of variance (ANOVA) will be used for the global comparison, and the Student's t-test in the comparisons by pairs. For variables do not following a normal distribution, the Kruskal Wallis test will be used in the global comparison, and Dunn's test in pairwise comparisons. For comparisons of qualitative variables, the Chi-square test will be used, or Fisher's exact test in those situations in which the criteria for using the Chi-square are not met. In pairwise comparisons, the Bonferroni correction will be applied for multiple comparisons.

In all hypothesis contrasts, a significance level of 5% will be used. The statistical program SPSS version 22.0 for Windows will be used.

Inclusion Criteria:

• over 18 years of age
• understand, accept and sign the informed consent
• participants undergoing radial artery cannulation for a diagnostic, therapeutic, or structural interventional cardiology procedure
• patent radial artery in the previous ultrasound evaluation

Exclusion Criteria:

• systolic blood pressure greater than 150mmHg
• diagnosis of acute myocardial infarction (with or without ST-segment elevation)
• previous surgeries that have affected the arterial system of the upper limbs (arteriovenous fistula, radial artery for bypass surgery, etc.)
• language barrier that hinders a clear study understanding for potential participant

After completing the recruitment, the data collected will be analyzed for publication