The purpose of this study is to compare the efficacy of ultrasound- guided with the traditional palpation radial artery cannulation in critically ill children.

Arterial catheterization is often performed in critically ill patients for continuous hemodynamic monitoring and blood sampling. However, insertion of radial artery catheter with traditional palpation may be technically challenging, particularly in pediatric patients. There are few published studies on the use of ultrasound guidance for radial-artery catheter placement and mostly they were elective surgery children which received inhalation or deep sedative medication. Recently no setting published in pediatric intensive care unit.

Inclusion Criteria:

• Pediatric patients who required radial artery cannulation for hemodynamic monitoring or frequent blood samples in intensive care unit

Exclusion Criteria:

• Wound at area of cannulation
• Can not palpate or weak radial artery pulse