
Peripheral nerve stimulators are electrical medical devices used to localize the nerve prior to the injection of anesthetic drug while performing regional anesthesia. It consists of two electrodes, (positive and negative electrode), disposable nerve-stimulator needles of different sizes and lengths, and catheter for continuous nerve block. The negative electrode is connected to the nerve-stimulator needle, while the positive electrode is attached to the skin electrode placed near the site of the nerve to be blocked. Peripheral nerve stimulators are used to access the degree of neuromuscular block in patients. The success of this type of regional anesthesia depends upon the precise location of the nerve. These devices generate small amounts of current, which results in muscular twitching, paresthesia, or combination of the both depending upon the nerve morphology. Electric pulse generated by these devices through a needle stimulates muscular twitching at very close proximity to nerve without touching it. This facilitates a high degree of accuracy for local anesthetic drug deposition surrounding the nerve. Characteristics of peripheral nerve stimulators include monophasic and rectangular shape, i.e. square wave stimulus, 0.2-0.3 msec duration, battery powered, digital display of delivered current, audible signal on delivery of stimulus, and multiple patterns of stimulation such as single twitch, train of four, double burst, and post tetanic count.