Ultrasound-Guided Ulnar Versus Radial Artery Cannulation in Children

Children older than one year, of ASA physical status I to III, requiring invasive arterial pressure monitoring for elective surgery or in the intensive care unit, were randomly assigned in a 1:1 ratio to cannulation of the radial artery (group R) or the ulnar artery (group U). The allocation sequence was computer-generated and applied by an investigator not involved in the puncture, after sedation had been established. Patients and their legal guardians remained unaware of the allocated site; operators could not be blinded. The allocated artery was screened sonographically before puncture to exclude thrombosis or anatomical variants, and its diameter and depth were measured. The wrist was placed in 45 degrees of dorsiflexion. The artery was punctured on the anterior aspect of the wrist through a short-axis out-of-plane approach, using a 25-gauge 4 cm catheter and a 6-13 MHz linear probe, by anesthesia residents in their seventh semester of training or beyond under direct senior supervision. An attempt was considered failed when a large hematoma or arterial spasm occurred; cannulation was then reattempted at the same arterial site on the contralateral limb, and the supervising senior physician took over in case of persistent failure.

• Radial artery cannulation (Procedure): The radial artery is identified sonographically at the anterior aspect of the wrist and confirmed with Doppler, with the wrist in 45 degrees of dorsiflexion. It is punctured through a short-axis out-of-plane approach using a 25-gauge 4 cm catheter and a Sonosite M-Turbo system with a 6-13 MHz linear probe.
• Ulnar artery cannulation (Procedure): Identical procedure applied to the ulnar artery.

Primary outcomes

• Successful arterial cannulation at the first attempt [During the cannulation procedure, up to 15 minutes from skin puncture]: Proportion of patients in whom an arterial pressure waveform was obtained on the monitor at the first puncture attempt

Secondary outcomes

• Artery localization time [During the cannulation procedure, up to 15 minutes]
• Catheter insertion time [During the cannulation procedure, up to 15 minutes]
• Total procedure time [During the cannulation procedure, up to 15 minutes]
• Number of puncture attempts [During the cannulation procedure, up to 15 minutes]
• Need for a second operator [During the cannulation procedure, up to 15 minutes]
• Incidence of local complications [From the cannulation procedure until catheter removal, up to 7 days]

Sex: All, ages: 1 Year to 18 Years

Inclusion Criteria:

* Age older than one year - American Society of Anesthesiologists physical status I to III - Need for invasive arterial pressure monitoring during elective surgery or in the intensive care unit - Written informed consent from the legal guardian

Exclusion Criteria:

* Refusal or unavailability of the legal guardian at the time of the pre-anesthetic assessment - Arterial catheterization at the same site within the preceding month - Contraindication to arterial catheterization: inflammatory, ischemic or infectious lesions of both upper limbs, dialysis fistula - Abnormal Allen test - Hemostatic disorder - Treatment with catecholamines above 0.1 microgram per kilogram per minute - Wrist arterial malformation identified at sonographic screening