The main findings of the trial are that the lateral short axis in the plane technique is non-inferior to the conventional one regarding the first cannulation attempt success rate, time of the procedure, and complication rate. Another important finding of the trial is that the novel technique is associated with a significantly larger diameter of the IJV and that the insert side is significantly further from the thyroid cartilage and jugulum.

We discovered that the novel technique was statistically significantly faster compared to the conventional technique. However, the difference was only 15 s. The mean duration of the procedure time in our trial was nearly six minutes. In other trials, the reported procedure duration time is about 3 min [11, 12]. However, in these trials, the time is measured from the insertion of the guiding needle till catheter insertion. In our trial, we measured the time until the sterile covering of the catheter to compare the time that is needed for the catheter to be prepared for use. We can conclude that 15 s is a short time compared to the total procedure duration time and therefore there is no clinical relevance in the difference in duration procedure time between the novel technique and conventional one.

We explain the larger diameter of the IJV in the novel technique by the fact that the cannulation site in the novel technique is closer to the heart and therefore the vessel has a bigger diameter. The second reason for this finding could be that the vessel is never a perfect circle even when displayed on a short axis and we measured the diameter in the direction of the needle trajectory. The larger diameter of the IJV was linked also to oblique axis visualization compared to conventional short axis visualization in published trials [3, 4, 13]. Therefore, we can predict that the novel technique described in our trial could be associated with a lower incidence of posterior vessel wall puncture (PVWP) same as the oblique technique compared to the conventional technique [13].

In the last decade, there have been several publications regarding alternative techniques for IJV cannulation to lower the complication rate by using in-plane needle visualization and moving the exit site to the supraclavicular region to reduce infectious complications [2, 6, 9, 13]. In our trial, we described a novel cannulation technique. Our findings concord with other trials that described and investigated oblique axis IJV catheterization which is another technique using in-plane needle visualization. Same as Wilson [13] we did not find significantly more complications in the novel technique compared to the conventional technique. We admit that opposite to Wilson we did not measure the PVWP rate which is one of the most common complications of IJV cannulation [3]. However, in our trial, we measured the incidence of post-cannulation thrombosis that is linked to PVWP [13]. The incidence did not differ between the novel technique and the conventional technique.

Our results regarding complication rate correspond to results presented by Song [10] who described a similar cannulation technique for the insertion of large bore catheters in his trial.

We admit several limitations of the study. All the cannulations were done by operators who are experienced in the conventional technique, oblique technique, and novel technique. Therefore, the trial results cannot be generalized to operators without experience with the cannulation techniques. Because the trial is monocentric the cannulation time and complication rate may be center-specific which is another limitation of the generalisability of the findings. We also did not include paediatric patients. Lastly, we did not measure the infectious complication rate. The reason for not measuring is that the trial is focused on the procedure of the catheter insertion. Infectious complications are largely related to nursing care and proximity to the oropharyngeal secretion. We can assume that the infectious complication rate using a novel technique may be lower as the exit site is moved from the neck (red zone) to the supraclavicular region (yellow zone). This change of exit site is associated with lower infectious complications, as showed by Brescia [1].

In our study, we did not specifically examine the difference in learning curves between the novel and conventional techniques. Currently, there is a lack of relevant data available to determine whether the novel technique offers a faster learning curve. However, it is common practice for physicians undergoing anaesthesia training to initially be trained in regional anaesthesia with in-plane needle visualization. This suggests that there is a possibility that the novel technique may have a faster learning curve than the conventional method. Further research is needed to thoroughly investigate this hypothesis.

We can conclude that the novel technique that we described is not inferior to the conventional technique. We also came to very similar findings as authors describing the oblique axis cannulation technique. Therefore, the novel technique can be another valuable alternative way for IJV cannulation with lower PVWP incidence compared to the conventional technique.