Suspected local anesthetic resistance after intrathecal, perineural, intraarticular and subcutaneous injections: a case report.

Background: Local anesthetic (LA) resistance is an exceedingly rare phenomenon. Incidence is unknown given the rarity of disease. Often, inadequate response to LA can be attributed to many factors including suboptimal dosing, maldistribution, or poor procedural technique. However, in the absence of these technical factors, true LA resistance can be attributed to mutations in the voltage gated sodium channel and is strongly associated with hypermobility conditions such as Ehlers Danlos and muscular dystrophies such as Emery-Dreifuss. There have also been reports describing LA resistance after scorpion bites, although the underlying mechanism for this type of resistance is unknown. We aim to present a case of suspected LA resistance in the setting of multiple failed LA delivery.

Case description: In this case report, we describe a patient with suspected LA resistance after failed intrathecal, perineural, intraarticular and subcutaneous delivery of LA. Our patient was unresponsive to three different LAs at varying doses.

Conclusions: Patients with failure to achieve adequate anesthesia with more than one route of LA administration should be evaluated for LA resistance. A thorough medical history and physical examination, along with a focus on identifying prior LA failure such as with dental procedures, and physical examination findings suggestive of connective tissue disorders may help establish the diagnosis with confirmatory genetic testing.