SAPHENOUS NERVE ANESTHESIA - A NERVE STIMULATOR TECHNIQUE

Purpose: This two part study was undertaken to assess both the feasibi lity of identifying the saphenous nerve with a nerve stimulator and to assess the efficacy of saphenous nerve anaesthesia with electrical is olation of the nerve. Methods: (Part I): in Part I we studied 25 volun teers. Each had saphenous nerve blocks performed using a nerve stimula tor (NS) and loss of resistance (LOR) technique. We recorded 10 cm lin ear visual analogue pain scores on completion of the blocks, time to c ompletion of the blocks, onset rime, and success of the blocks. (Part II): Clinical utility of the NS technique of saphenous nerve block was investigated. We evaluated the NS technique in 21 consecutive patient s having surgery below the knee. Results: (Part I): The LOR technique successfully produced saphenous nerve anaesthesia in 18/25 (72%) volun teers and the NS technique was successful in all volunteers (25/25 - P < 0.05). The nerve stimulator approach required more rime to complete (NS 13 +/- 7 min vs LOR 8 +/- 2 min; P < 0.05). Visual analogue pain scores differed (P < 0.05) with a median of 1.0 cm for the LOR techniq ue and a median of 2 cm for the NS technique. (Parr II): The saphenous nerve block was successful in 20/21 (95%) of the patients. Conclusion s: (Part I): The first part of the study established the feasibility o f electrical identification of the saphenous nerve and demonstrated th at the NS technique could be utilized to provide superior anaesthesia of the saphenous nerve when compared with a previously validated LOR t echnique. (Part II): The clinical utility of the NS technique of saphe nous nerve block was successfully demonstrated.