A subcutaneous injection of saline for arteries whose depth was < 2 mm increased the success rate and decreased catheterization time. (A) Catheter positioned in the pooling saline solution. (B) Enhancement artifact of the anterior wall of the radial artery. (C) The artery is flattened by probe pressure on the skin and puncture pressure. (Image source: Anesthesia & Analgesia)

A subcutaneous injection of saline for arteries whose depth was < 2 mm increased the success rate and decreased catheterization time. (A) Catheter positioned in the pooling saline solution. (B) Enhancement artifact of the anterior wall of the radial artery. (C) The artery is flattened by probe pressure on the skin and puncture pressure. (Image source: Anesthesia & Analgesia)

Those who manage the anesthetic care of children who need an arterial line know that insertion can be difficult. The pulse is felt, yet pass after pass fails to cannulate the artery.  Ultrasound guidance is becoming more popular, particularly for difficult arterial cannulation.

Dr. Yoshinobu Nakayama, Department of Anesthesiology and Intensive Care, Kyoto Prefectural University of Medicine, Kyoto, Japan, and colleagues first determined factors that predicted ultrasound-guided percutaneous radial arterial catheterization in children and then used the strongest predictor of success as the basis of a randomized trial.  Their results are presented in this month’s Anesthesia & Analgesia in the article “A Novel Method for Ultrasound-Guided Radial Arterial Catheterization in Pediatric Patients.”

The authors used the Sonosite M-Turbo® ultrasound system. The arterial catheter was a 24 gaugeJelco® Plus catheter. The authors considered 102 patients in the initial assessment phase.  A subcutaneous arterial depth of 2-4 mm was found to be a significant independent predictor of success.  Based on these findings, the authors randomized 60 patients whose arterial depth was < 2 mm to receive either enough subcutaneous injection of a saline solution using a 27-gauge needle until the artery was located 2–4 mm below the skin surface or a placebo.   In the < 2 mm group, when depth of the artery increased to 2-4 mm below the skin surface by injecting saline, catheterization time and success rate improved.

This is an interesting report that proposes and tests a novel method of improving the success of radial arterial cannulation in infants. What’s especially nice is the two-phased approach in which the investigators analyzed observational data, found a possible predictor of success, and then devised an intervention to successfully test the hypothesis.  The investigators need to be commended for coming up with a novel idea to improve the performance of this age-old procedure.