Regional anesthesia and pain medicine
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Peripheral nerve stimulation has a long history in regional anesthesia. Despite the advent of ultrasound-guided peripheral nerve blockade, nerve stimulation remains a popular technique used alone or, now, in combination with ultrasound-guided techniques. In light of this evolving utility of nerve stimulation, this is an appropriate time to review the basic concepts and knowledge base of this historically important tool. ⋯ However, current magnitude is neither 100% sensitive nor specific. Independent of technical ability, both the biological environment and the equipment used impact the current-distance relationship. Thus, successful electrical nerve stimulation is dependent on an anesthesiologist with a solid foundation in anatomy and a thorough understanding of electrophysiology.
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Reg Anesth Pain Med · Jul 2012
Comparative StudyInjection inside the paraneural sheath of the sciatic nerve: direct comparison among ultrasound imaging, macroscopic anatomy, and histologic analysis.
There exists little anatomic knowledge regarding the structure and sonographic features of the sheath enveloping the sciatic nerve in the popliteal fossa. We investigated the spread of an injection inside the sheath to (1) determine whether the sheath is a structure distinct from the nerve or part of the epineurium and (2) to develop an ultrasound-guided injection technique. ⋯ There is a distinct tissue layer surrounding the popliteal sciatic nerve as a paraneural sheath that has distinct gross anatomic, histologic, and sonographic features. This sheath may have implications for regional anesthesia involving the popliteal sciatic nerve. We suggest that the ultrasound-guided injection technique described here could be used in future clinical studies investigating the importance of the paraneural sheath.
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Reg Anesth Pain Med · Jul 2012
Effect of adjuvant drugs on the action of local anesthetics in isolated rat sciatic nerves.
There is increasing clinical use of adjuvant drugs to prolong the duration of local anesthetic-induced block of peripheral nerves. However, the mechanistic understanding regarding drug interactions between these compounds in the periphery is quite limited. Accordingly, we undertook this study to determine whether selected adjuvant drugs are efficacious in blocking action potential propagation in peripheral nerves at concentrations used clinically and whether these drugs influence peripheral nerve block produced by local anesthetics. ⋯ These results suggest that the reported clinical efficacy of clonidine, buprenorphine, and dexamethasone influences the actions of local anesthetics via indirect mechanisms. Further identification of these indirect mechanisms may enable the development of novel approaches to achieve longer-duration, modality-specific peripheral nerve block.
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Reg Anesth Pain Med · Jul 2012
Sciatic nerve block fails in preventing the development of late stress-induced hyperalgesia when high-dose fentanyl is administered perioperatively in rats.
: Sciatic nerve block fails in preventing the development of late stress-induced hyperalgesia (SIH) when high-dose fentanyl is administered perioperatively in rats. ⋯ Perioperative use of long-lasting RA reduced both acute postoperative hyperalgesia and the development of long-term pain vulnerability. However, high doses of fentanyl for intraoperative analgesia induce central sensitization that cannot be reversed by using long-lasting RA.