Chapter 14: Electrical Nerve Stimulators and Localization of Peripheral Nerves

INTRODUCTION

Peripheral nerve stimulation (PNS), an important tool to aid administration of peripheral nerve blocks. Improvements in electrical nerve localization technology have led to a number of commercially available nerve stimulators that are superior and more advanced compared to older devices. With the introduction of ultrasound-guided nerve blocks, however, there has been confusion on the role of nerve stimulation in the setting of ultrasound-guided nerve blocks. This review focuses on the foundation of nerve stimulation with a short historical background, the latest developments in the technology, and the role of nerve stimulation with ultrasound-guided peripheral nerve blocks.

HISTORY

Quick Facts

• 1780: Luigi Galvani¹ was the first to describe the effect of electrical neuromuscular stimulation in a frog experiment.

• 1912: Perthes² developed and described an electrical nerve stimulator.

• 1955: Pearson³ introduced the concept of insulated needles for nerve location.

• 1962: Greenblatt and Denson⁴ introduced a portable solid-state nerve stimulator with variable current output and described its use for nerve location.

• 1973: Montgomery et al⁵ demonstrated that noninsulated needles require significantly higher current amplitudes than the insulated needles.

• 1984: Ford et al⁶ reported a lack of accuracy with noninsulated needles once the needle tip passed the target nerve.

• Ford et al suggested the use of nerve stimulators with a constant current source, based on the comparison of the electrical characteristics of peripheral nerve stimulators.^7,8

• In 2004, Hadzic & Vloka defined the electrical characteristics and suggested manufacturing standard for modern nerve stimulators.⁹

It took nearly 100 years from the concept of nerve stimulation to adoption of electrolocalization during peripheral nerve blockade in the 1990s. The more widespread introduction of nerve stimulation in the practice of peripheral nerve blockade led to research on the needle-nerve relationship and the effect of stimulus duration.^10,11 More recently, the principles of electrical nerve stimulation were applied to surface mapping of peripheral nerves using percutaneous electrode guidance^12,13,14,15 for confirmation and epidural catheter placement^16,17,18 and peripheral catheter placement.¹⁹ This chapter discusses the electrophysiology of nerve stimulation, electrical nerve stimulators, various modes of localization of peripheral nerves, and integration of the technology into the realm of ultrasound-guided regional anesthesia.

What Is Electrical Peripheral Nerve Stimulation?

Electrical nerve stimulation in regional anesthesia is a method of using a low-intensity (up to 5 mA) and short-duration (0.05 to 1 ms) electrical stimulus (at 1- to 2-Hz repetition rate) to obtain a defined response (muscle twitch or sensation) to locate a peripheral nerve or nerve plexus with an (insulated) needle before injecting local anesthetic in close proximity to the nerve to block nerve conduction for surgery or acute pain management. The use of nerve stimulation can recognize an intraneural or intrafascicular needle placement injection, prevent further ...