[Interscalene block and shoulder surgery. Literature review and new method of infiltration]

Nowadays, interscalene block is the gold standard for intra- and post-operative analgesia for shoulder surgery. It consists of distributing a sufficient volume of local anesthetics, within the interscalenic space which contains the C5 to C7 nerve roots. Due to its proximity to the area where the anesthetic is injected, the phrenic nerve can be transiently blocked causing a kind of paralysis of an hemidiaphragm. First, the use of ultrasound has reduced the incidence of diaphragmatic hemiparesis especially when the injection is performed at the C7 level rather than the C5 or C6 level. Then, decreasing the doses of local anesthetics has reduced the diffusion to the non-targeted structures, such as the phrenic nerve, causing less diaphragmatic hemiparesis. Finally, Palhais and Lee et al discovered that injecting LA at distance from the nerves roots can be useful in reducing this side effect. Based on their work, we decided to inject the local anesthetic into the muscle fascia. Our experience with this injection into the muscle itself seems to confirm the results described in the literature with less diaphragmatic hemiparesis. Further studies are needed to support our hypothesis and will be the subject of future researches in our institution.