The Use of the Nerve Stimulator With Standard Unsheathed Needles in Nerve Blockade

HE practice of regional anesthesia deT pends upon accurate, placement of local anesthetic solution in close proximity to nerve trunks. Normally, in most peripheral somatic nerve blocks, this depends upon paresthesia elicited by the physician and reported by the patient and upon the experience and knowledge of the physician performing the block. Success rate in performing the block may be poor, because of inappropriate responses from the patients. They may be apprehensive, heavily sedated or disoriented, or at the extremes of age. Paresthesia is a subjective feeling and may be misinterpreted by even an alert and cooperative patient, especially if difficulty is being experienced finding the exact location of the nerve. Preblockade localization of needle points can be done by x-ray examination, but this is much too cumbersome and impractical for most clinical applications. It is costly and often unavailable when required. The use of nerve stimulation for nerve localization during regional blockade is simple and has been described by others previously. However, these reports have always made use of special needles which were covered with insulation or shielding; for example, von Perthes,l in 1912, described the use of an induction apparatus. This was the source of faradic current which was then transmitted down a pure nickle needle previously coated with lacquer down to the tip to provide insulation. Many authors, including Greenblatt and Denson,2 Magora and associates,3 Wright,4 and Koons,5 have made use of similar technics. ChapmanG recently described the use of a nerve stimulator, but he also used coated needles (in this case, intravenous cannulas covered with Teflon or flurene-N coated needles). The use of these needles can alter the feel of the tissues, making accurate anatomic location more difficult than with standard needles. The coating occasionally tears off or curves