- 1780: Galvani1 was the first to describe the effect of electrical neuromuscular stimulation
- 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 stimulators7,8
The use of nerve stimulation became commonplace in clinical practice only in the mid- to late 1990s. Research on the needle–nerve relationship and the effect of stimulus duration ensued.9–11 More recently, the principles of electrical nerve stimulation were applied to surface mapping of peripheral nerves using percutaneous electrode guidance (PEG)12–15 for confirmation and epidural catheter placement16–18 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 modern regional anesthesia.
Nerve stimulation is a commonly used method for localizing nerves before the injection of local anesthetic. Electrical nerve stimulation in regional anesthesia is a method of using a low-intensity (up to 5 mA) and short-duration (0.05–1 ms) electrical stimulus (at 1–2 Hz repetition rate) to obtain a defined response (muscle twitch or sensation) to locate a peripheral nerve or nerve plexus with an (insulated) needle. The goal is to inject a certain amount of local anesthetic in close proximity to the nerve to block nerve conduction and provide a sensory and motor block for surgery and/or, eventually, analgesia for pain management. The use of nerve stimulation can also help to avoid an intraneural intrafascicular injection and, consequently, nerve injury.
Electrical nerve stimulation can be used for a single-injection technique, as well as for guidance during the insertion of continuous nerve block catheters. More recently, ultrasound (US) guidance and, in particular, the so-called dual guidance technique in which both techniques (peripheral nerve stimulation [PNS] and US) are combined, has become a common practice in many institutions.
In principle, almost all plexuses or other larger peripheral nerves can be located using PNS.20 The goal of nerve stimulation is to place the tip of the needle (more specifically, its orifice for injection) in close proximity to the target nerve to inject the local anesthetic in the vicinity of the nerve. The motor response (twitch) to PNS is objective and reliable and independent from the patient's (subjective) response. Nerve stimulation is often helpful to confirm that the structure imaged with ultrasound (US) is ...