The increase in internal diameter (ID) and cross-sectional area (CSA) may facilitate better arterial catheterization. Since an increase in body temperature can cause peripheral vasodilation, we aimed to determine if local warming of the radial artery (RA) catheterization site could improve the success rate of catheterization in pediatric patients.

This randomized, controlled study enrolls 126 pediatric patients aged ≤ 2 years who were scheduled for heart surgery. They are randomized into non-warming (C) and warming (W) groups. After induction, the baseline artery ultrasonography images are collected. In the warming group (W), local warming is applied on the catheterization site. Before catheterization, the artery ultrasonography images are collected. The primary outcome is the first-attempt success rate. The secondary outcomes included the ID and CSA of the artery and overall complications.

Inclusion Criteria:

• aged ≤ 2 years
• cardiac surgery with peripheral artery catheterization

Exclusion Criteria:

• unstable vital signs
• pre-existing arterial catheter (exception of umbilical artery catheterization)