Evaluation of distal radial artery cross-sectional internal diameter in neonates and infants by ultrasound and adequate selection of an intra-arterial catheter size

Background: Radial artery catheterization in neonates, infants, and young children is a common and useful invasive procedure that brings technical placement challenges and potential complications due to the small diameter size of the radial artery in these patients. The aim of this study is to determine appropriate catheter sizes in infants up to 6 months of age. Materials and Methods: A total of fifty infants undergoing general anesthesia or hospitalized in the neonatal intensive care unit were included. Images of the radial artery diameter were obtained from the infant's wrist using Philips EPIQ Diagnostic Ultrasound System CVX Release 4.0. All images obtained were distal in the forearm, medial to the border of the styloid process of the radius, at the point of maximal impulse of the radial artery, and with the wrist at a 45-degree angle position. We recorded postmenstrual age, chronological age, gender, weight, location, comorbidities, medications, weight, and vital signs of each individual. Results: In this single cohort study of 50 children whose ages ranged from 0 to 6 months chronological age, their radial artery diameters were averaged proportionally to their weight and age. Use of a 22G catheter would result in 100% occlusion of the diameter of the artery in most study subjects. Use of a 24G catheter would result in a range of 75%–99% occlusion depending on weight, postmenstrual age, and chronological age of the infants. Conclusions: In view of these findings, we recommend using US to measure the diameter of the radial artery and choose the most appropriate catheter size before proceeding with US-guidance for radial artery cannulation in infants. This will prevent inappropriate sizing of the catheter and the thrombotic complications this can incur.