Pudendal Nerve Block by Adaptively Stepwise Increasing the Intensity of High-Frequency (10 kHz) Biphasic Stimulation.

OBJECTIVE: The purpose of this study is to determine whether adaptively stepwise increasing the intensity of a high-frequency (10 kHz) biphasic stimulation (HFBS) can produce nerve conduction block without generating a large initial response.

MATERIALS AND METHODS: In anesthetized cats, three cuff electrodes were implanted on the left pudendal nerve for stimulation or block. The urethral pressure increase induced by pudendal nerve stimulation was used to measure the pudendal nerve block induced by HFBS.

RESULTS: HFBS applied suddenly with a large step increase in intensity induced a large (86 ± 16 cmH2 O) urethral pressure increase before it blocked pudendal nerve conduction. However, HFBS applied by adaptively stepwise increasing the intensity every 10 to 60 seconds over a long period (33-301 minutes; average 108 ± 35 minutes) with many small intensity increases (0.005-0.1 mA) induced no response or low-amplitude high-frequency urethral pressure changes before it blocked pudendal nerve conduction. The minimal HFBS intensities required by the two different methods to block pudendal nerve conduction are similar.

CONCLUSION: This study is important for better understanding the possible mechanisms underlying the HFBS-induced nerve block and provides the possibility of developing a new nerve block method for clinical applications in which an initial large response is a concern.