Safe performance of peripheral regional anaesthesia: the significance of ultrasound guidance

Ultrasound guidance has raised regional anaesthesia from an art relying on chiefly morphometric data to a science governed by reproducible and predictable methods. Besides the large number of scientific publications in the field of ultrasound and regional anaesthesia, there are still open questions regarding safety issues. In this issue of Anaesthesia, Sermeus et al. [1] present their findings from an investigation into the incidence of nerve puncture and intraneural injection based on various needleto-nerve approaches. This study provides new findings about safety in ultrasound-guided regional anaesthesia. Whether ultrasound guidance increases safety in regional anaesthesia is of particular interest for those practitioners using such techniques in their daily clinical practice and is the subject of this editorial. We all know that initial hypes about exciting innovations have a way of rapidly giving way to greater realism. Many physicians have raised specific questions about ultrasound-guided regional anaesthesia, and indeed there are two major questions that remain to be answered: does ultrasound truly provide better success, and does it truly provide better safety, than conventional methods of nerve identification can nowadays offer? On the face of it, it would seem obvious that ultrasound guidance performs better than any techniques relying on nerve localisation, like nerve stimulation or strictly landmarkor paraesthesia-based techniques. After all, a multitude of comparative studies, systematic reviews, and meta-analyses have demonstrated faster onset times, longer block durations, better predictability of block success, and reduced needs for supplemental analgesia [2–5]. Nevertheless, a study offering ultimate proof to settle this issue of superiority once and for all has yet to be published. Assuming that the appropriate measure of superiority of a nerve block is improved success and better safety, the question arises what kind of study design would be appropriate to verify such superiority? Success would be the sum of various parameters like sensory and motor onset time, duration of sensory and motor blockade, or number of failed blocks. In fact, there is no shortage of available studies on all these aspects of successful blockade, but the chances are slim that a definitive study providing ultimate proof of one specific technique being superior to the others is ever going to be published. What makes this outlook seem unrealistic is that, in the meantime, every institution favours one specific technique (mainly ultrasound or nerve stimulation, maybe paraesthesiabased identification of nerves in some cases), which implies that no single institution can possibly offer the same level of expertise for two different techniques. Thus, any multi-centre study design would involve an inter-institutional bias precluding a valid comparison of methods, and would likely end up showcasing competing philosophies rather than straightforward science. As to the safety offered by specific methods of peripheral nerve blockade, the cadaveric study by Sermeus et al. compared a tangential with a direct needle-to-nerve approach [1]. The gist of their data is that the tangential approach involved fewer ‘intraneuronal’ injections than the direct approach (12% vs. 58%; p < 0.001). The authors also used additional injections with ink for histological analysis to see whether these intraneuronal injections were actually intrafascicular injections. The fact that they This editorial accompanies an article by Sermeus et al., Anaesthesia 2017; 72: 461– 9.