Saphenous nerve anaesthesia - A nerve stimulator technique

Purpose: This two part study was undertaken to assess both the feasibility of identifying the saphenous nerve with a nerve stimulator and to assess the efficacy of saphenous nerve anaesthesia with electrical isolation of the nerve. Methods: (Part I): in Part I we studied 25 volunteers. Each had saphenous nerve blocks performed using a nerve stimulator (NS) and loss of resistance (LOR) technique. We recorded 10 cm linear visual analogue pain scores on completion of the blocks, time to completion 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 patients having surgery below the knee. Results: (Part I): The LOR technique successfully produced saphenous nerve anaesthesia in 18/25 (72%) volunteers 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 technique 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. Conclusions: (Part I): The first part of the study established the feasibility of electrical identification of the saphenous nerve and demonstrated that the NS technique could be utilized to provide superior anaesthesia of the saphenous nerve when compared with a previously validated LOR technique. (Part II): The clinical utility of the NS technique of saphenous nerve block was successfully demonstrated.