In vivo measurements of leakage current during transurethral resection

To estimate the magnitude of leakage current during transurethral resection 3 tape electrodes were applied to the penis and connected to earth through 50 kohm resistances (in order to minimize the current drawn from the neutral plate). A total of maximally 4 mAmp was measured through these electrodes. The measurements were independent of the concentration of hemoglobin in the irrigation fluid, the lubricant applied or whether a Teflon coated shaft was used. The maximum current of 4 mAmp has to pass an area as small as 0.1 mm2 for 0.2 sec in order to produce a second degree burn in the urethra. It is thus concluded that from an electrical point of view transurethral resection is a safe procedure not liable to give rise to any urethral burns. Using an isolated Teflon coated shaft has thus no practical value in reducing the leakage current.