To the Editor:
With great interest we have read the article written by Quan et al.1 recently published in Anesthesiology. In their article, they describe a method to improve the success rate of correct placement of radial artery cannulation in young children. They use acoustic shadowing ultrasound to guide cannulation versus conventional ultrasound use. They found a significantly improved success rate of radial artery puncture using acoustic shadowing ultrasound.
Arterial cannulation in young children can be challenging, and its success is influenced by patient characteristics and operator experience. We explored its use in our own practice. Doing so, we came across the following issues. First, we experienced that the described gain in puncture time was outweighed by the extra preparation time.
To extract the metal-containing strand out of a surgical gauze and fixate it on the ultrasound probe exceeds the 16 s of time won during correct placement. Second, extracting the metal-containing strand from a surgical gauze in the operation theatre could lead to confusion during surgical gauze counting, compromising patient safety.
Third, with use of the acoustic shadowing, the first attempt success rate was 90%. The control group, however, had a first pass success of only 60%, which is low compared with recent published literature, 68 to 83%.2–4
Fourth, the authors used a short-axis, out-of-plane approach, while recent literature suggests that an in-plane approach has additional benefits with a lower incidence of posterior wall puncture.5 In our opinion, a combined short- and long-axis approach should be used for optimal success.
Finally, we have concerns about figure 3, which demonstrates the process of radial artery puncture in humans. However, we noticed discrepancies in distances between the figure and the reported patient data. The average depth of the radial artery in the article was 2 mm. This leads to a distance between the acoustic shadowing to be around 0.6 mm. This equals the diameter of the suggested radial artery in figure 3. In the final frame, the arterial canula is correctly positioned in the artery. However, the diameter of a 24-gauge catheter is also 0.6 mm. The general appearance suggests a tissue phantom, not representing reality.
In conclusion, we suggest using a long-axis approach when possible. If extra guidance is needed and a short-axis approach is used, existing and commercially available ultrasound with centerline functionality could be easier and more reliable to use in daily practice.
The authors declare no competing interests.