Nerve stimulators for nerve location--are they all the same? A study of stimulator performance

This study set out to examine the nerve stimulators available in one trust hospital. Six different models were identified (Braun Stimuplex, Braun Stimuplex DIG, Digistim 3, Digistim 3 Plus, Regional Master Corporation Nerve Finder, Bard 750 Digital) and the output characteristics were measured for each stimulator using a twin beam calibrated storage oscilloscope. Target current output values from 0.3 mA to 3 mA and load resistances from 560 omega to 10k omega were selected to model the normal ranges of operating current and skin electrode-needle impedance when performing regional anaesthesia. Only half of the stimulators tested were able to complete the test and deliver a target current to +/-20% accuracy. The variation in performance of nerve stimulators means that for a safe and successful nerve block it is important for the operator to be aware of the design and functional limitations of any stimulator being used in clinical practice.