ABSTRACT
Nerve Stimulators The desirable qualities of a nerve stimulator include constant current output (despite varying resistances of the patient’s body, cables and connections, and ground lead), a digital display, variable linear output (the current changes in proportion to the movement of the dial), a short pulse width to deliver a precise current or charge to the nerve, and indicators of power or circuit failure. The optimal current with which to begin nerve localization without discomfort and the current associated with “successful” needle placement are unknown. A volunteer study reported that during femoral block, muscle contractions were painful with a stimulating current greater than 1.6 mA. In addition, after elicitation of a paresthesia, the minimal current needed to produce a motor response was less than 0.5 mA in 80% of cases, a suggestion that this may be a reasonable “final” current intensity to seek. However, this may vary between block techniques and in the presence of preexisting neurologic conditions.
