The distal quarter of the forearm is the optimal insertion site for ultrasound-guided radial artery cannulation: A randomized controlled trial.

Background: Current guidelines recommend the use of ultrasound guidance for arterial cannulation. However, there are no recommendations on the best insertion site for radial artery cannulation in terms of catheter dwell time and incidence of complications.

Methods: In this randomized controlled study 94 patients were randomly assigned into three groups, corresponding to three different sites of insertion for radial artery cannulation: hand wrist: (Site/group 1,  = 29), distal quarter part of the forearm (Site/group 2,  = 30) and the midpoint of the forearm (Site/group 3,  = 35). Age, height, weight, and diagnosis of each patient were recorded prior to insertions which were performed by a single investigator experienced in ultrasound-guided vascular access.

Results: Radial artery diameters were similar (2.4 ± 0.4 vs 2.5 ± 0.3 vs 2.6 ± 0.4 mm), however skin to vessel distances were different between groups, and the depth of the radial artery increased progressively from distal to proximal sites. There was a significant difference between groups in terms of success rates at the first attempt. Only two cannulations were successful at first attempt, and overall, only 17 of 35 cannulations were successful at Site 1. Arterial cannula dislodgement rate was highest at Site 1(8/29, 26.7%), while the longest dwell time was at Site 2 with a median of 4 (IQR 3) days.

Conclusions: Considering the high removal rate at the wrist region and the high failure rate at the midpoint of the forearm, the distal quarter of the forearm can be identified as "the optimal insertion site' for ultrasound-guided radial artery cannulation.