Keep It Simple

I n clinical medicine and ethics, equipoise can be considered a true state of uncertainty regarding the benefits and harms of the intervention versus the control. A great litmus test for a researcher in assessing equipoise occurs when a patient asks, ‘‘Doc, which treatment would you pick?’’ If the researcher is uncomfortable saying, ‘‘I’d take either one,’’ then there is no equipoise. Common wisdom would then suggest that the more sophisticated technique would be superior. In this issue of Regional Anesthesia and Pain Medicine, Bernucci et al take on the stimulating question of where to inject local anesthetic to generate a clinically effective axillary plexus block. They compared the clinical characteristics associated with performing a single-injection perivascular block versus a triple-injection perineural block. In both approaches, seperate musculocutaenous nerve blocks were performed. At first glance, it may seem as though this study distinctly lacked any hint of equipoise. How could a simple perivascular block compete with a comprehensive and meticulous approach in which each specific nerve was imaged, targeted, and subsequently received an aliquot of local anesthetic? As patients, we instinctively want the more sophisticated, and presumably more successful, comprehensive multineural approach. After all, the often argued advantage of ultrasound is the ability to actually image the individual nerves! On deeper analysis, however, we realize that our community has not yet determined the best deposition locations and techniques for the wide range of procedures offered by most regional anesthesia services. Perhaps it is time to assess whether a simple, and arguably rudimentary, approach offers a reasonable alternative to the elegant technique of individual neural identification and blockade. In their randomized and controlled trial, Bernucci et al clearly and reasonably defined metrics that included performance time, onset time, block success, needle passes, arterial puncture, and procedural pain. Their findings are both provocative and clinically relevant. There were no differences between the simple perivascular approach and the complex perineural approach with respect to success rate (92%Y96%), total anesthesia-related time (performance time plus onset time), and block-related pain scores. The simple perivascular approach required fewer needle passes (3.5 [1.0] versus 8.2 [2.2]) and shorter performance times (8.2 [2.3] versus 15.7 [3.2] minutes), generated fewer vascular punctures (0 versus 24%), and reduced the incidence of paresthesia (8% versus 52%). As it turned out, the potential benefit of the shorter onset time of the perineural approach was lost by the concomitantly longer procedure time. With respect to ultrasound-guided regional anesthesia, this theme of the simpler approach being either superior or equivalent to a presumed more comprehensive approach is emerging. Tran et al demonstrated that there was no distinct clinical benefit to a quadruple injection compared with a double injection when performing axillary plexus blocks. Chan et al confirmed that the addition of neurostimulation to ultrasound only prolonged the procedure time and did not improve the quality of the block. This same finding of prolongation of performance times without tactical benefit of neurostimulation added to ultrasound has also been demonstrated for single-injection femoral nerve blocks. In addition, Spence et al demonstrated that a conservative perisheath brachial plexus block was equivalent to a more aggressive intrasheath. However, if regional anesthesia scientific inquiry has taught us nothing else, it has taught us the lessons of block specificity. That is, what applies to one approach or technique may not necessarily apply to another. Although results from the study of Bernucci et al call into question the value of (more complex) multiple injections for ultrasound-guided axillary block, the literature is equally clear regarding the value of multiple injections when using a peripheral nerve stimulator or paresthesia-seeking technique for the very same axillary approach to the brachial plexus. And one need look no further than recent pages of this Journal to find preliminary evidence to support the value of circumferential deposit of local anesthetic around the popliteal sciatic nerve, as opposed to the simpler single-injection technique. Because it is the local anesthetic that ultimately achieves the intended clinical effect, it should behoove clinicians to define the best deposition site. ‘‘Best’’ should be defined by several metrics, including clinical success, simplicity of performance, safety profile, and patient tolerance. Assuming EDITORIAL