Reference electrode sites for potential difference measurements in the gastrointestinal tract.

Simpler alternatives to the use of an intravenous reference electrode for potential difference measurement in the gastrointestinal tract were considered. Lancet puncture of the forearm skin, and intradermal injection of 0.1 ml 154 mmol/l NaCl into the forearm were shown to effectively abolish the skin-blood potential difference, thereby rendering such sites suitable for reference electrode placement. Another acceptable method was to use an intravenous "butterfly" cannula filled with heparinized saline. The tip of the electrolyte bridge was inserted into the distal end of the cannula, thereby making indirect contact with the bloodstream. It is suggested that the use of any one of these three methods of reference electrode placement would facilitate the measurement of esophageal or gastrointestinal potential difference during a routine endoscopy without significantly altering the accuracy of the measurements.