Transsartorial approach for saphenous nerve block

Blockade of conduction in the saphenous nerve is important in providing surgical anaesthesia in the lower leg. Unfortunately, previously described techniques have lacked clinical effectiveness in practice. We developed a transsartorial approach for conduction block of the saphenous nerve. We first confirmed its potential clinical utility in 12 cadaveric specimens by demonstrating that the saphenous nerve was consistently stained by injections of methylene blue. Subsequently, we compared the relative rates of successful saphenous nerve block and the extent of conduction block provided by three techniques: (1) transsartorial saphenous nerve block (TSSNB), (2) above knee femoral paracondylar field block (FPFB), and (3) below knee field block (BKFB) of the saphenous nerve in 20 ASA I volunteers. The transsartorial saphenous nerve block proved to be highly successful (80% success rate) and was superior to the other two approaches in providing cutaneous analgesia to pinprick in the saphenous nerve distribution (P < 0.05). The success rates of the BKFB and FPFB were 65% and 40% respectively. A successful block with the transsartorial approach provided complete anaesthesia of the medial malleolus in 94% of subjects whilst the BKFB and FPFB provided complete anaesthesia of the medial malleolus in less than 40% of the successful blocks. We recommend the transsartorial approach for more effective block of the saphenous nerve.     

Comparison of 4 techniques for internal saphenous nerve block

OBJECTIVE: To assess the efficacy of 4 techniques for internal saphenous nerve block with 10 mL of 1.5% mepivacaine. METHODS: Eighty ASA I-II patients scheduled for foot (hallux valgus) surgery with combined sciatic and saphenous nerve blocks were randomized to receive the saphenous nerve block by one of the following techniques: a paravenous approach (n = 20), a transsartorial approach (n = 20), a femoral nerve approach in the inguinal region using a nerve stimulator (n = 20), and by subcutaneous infiltration between the tibial tuberosity and the internal gastrocnemius muscle (n = 20). A pressure cuff was placed 10 cm below the knee of all patients. Success was assessed by pin prick inside the ankle 30 minutes after initiation of the block. Tolerance of the pressure cuff and discomfort during performance of the technique were also assessed. RESULTS: The 4 groups were similar as to distribution of males and females and mean weight, age, and height. Blocking the saphenous nerve by way of the femoral nerve in the inguinal region was the most effective approach (success in 95% of patients), significantly better than the other 3 techniques (P < 0.05). The paravenous approach was successful in 60% of cases, the transsartorial approach in 50%, and the subcutaneous infiltration technique in 45%. The pressure cuff was well tolerated by all patients (100%) in whom the femoral nerve approach was used. The cuff was tolerated by 70% in the paravenous approach group, by 65% in the transsartorial approach group, and by 60% in the subcutaneous infiltration group. Patients reported more discomfort during initiation of the blockade in the paravenous approach and subcutaneous infiltration groups than in the femoral nerve or transsartorial approach groups (P < 0.05). CONCLUSION: The femoral nerve approach in the inguinal region, with nerve stimulator, to block the internal saphenous nerve led to a larger number of successful blocks than did the paravenous or transsartorial approaches, or the technique of subcutaneous infiltration between the tibial tuberosity and internal gastrocnemius muscle.     

Efficacy of an ultrasound-guided subsartorial approach to saphenous nerve block: a case series

Purpose

The saphenous nerve, a branch of the femoral nerve, is a pure sensory nerve that supplies the anteromedial aspect of the lower leg from the knee to the foot. There is limited evidence of the effectiveness of ultrasound-guided techniques to block the saphenous nerve. We therefore undertook a retrospective case series to investigate the efficacy of an ultrasound-guided subsartorial approach to saphenous nerve block.

Methods

During a four-month period, all patients receiving a subsartorial saphenous nerve block for lower extremity surgery at our institution had their medical records reviewed. Patient demographics and data were recorded, including block characteristics, intraoperative anesthetic management, pre-block, post-block, and postoperative pain scores, as well as postoperative analgesic dosing. Preoperative block success was defined by minimal intraoperative analgesic administration and a pain score of 0 in the postanesthesia care unit not requiring analgesic supplementation. Postoperative block success was defined by reduction of pain score to 0 without need for additional analgesic dosing.

Results

Thirty-nine consecutive patients were identified as receiving an ultrasound-guided subsartorial saphenous nerve block. Overall, this ultrasound-guided technique was found to have a 77% success rate.

Conclusion

This case series shows that an ultrasound-guided subsartorial approach to saphenous nerve blockade is a moderately effective means to anesthetize the anteromedial lower extremity. The success rate is based on stringent criteria with an endpoint of postoperative analgesia. A randomized prospective study would provide a more definitive answer regarding the efficacy of this technique for surgical anesthesia.     

A new anterior approach to the sciatic nerve block

BACKGROUND: Although several anterior approaches to sciatic nerve block have been described, they are used infrequently. The authors describe a new anterior approach that allows access to the sciatic nerve with the patient in the supine position. METHOD: Sciatic nerve blocks were performed in 22 patients. A line was drawn between the inferior border of the anterosuperior iliac spine and the superior angle of the pubic symphysis tubercle. Next, a perpendicular line bisecting the initial line was drawn and extended 8 cm caudad. The needle was inserted perpendicularly to the skin, and the sciatic nerve was identified at a depth of 10.5 cm (9.5-13.5 cm; median and range) using a nerve stimulator and a 15-cm b-beveled insulated needle. After appropriate localization, either 30 ml mepivacaine, 1.5% (group 1 = knee arthroscopy; n = 16), or 15 ml mepivacaine, 1.5%, plus 15 ml ropivacaine, 0.75%, (group 2 = other procedures; n = 6) was injected. RESULTS: Appropriate landmarks were determined within 1.3 min (0.5-2.0 min). The sciatic nerve was identified in all patients within 2.5 min (1.2-5 min), starting from the beginning of the appropriate landmark determination to the stimulation of its common peroneal nerve component in 13 cases and its tibial nerve component in 9 cases. A complete sensory block in the distribution of both the common peroneal nerve component and the tibial nerve component was obtained within 15 min (5-30 min). A shorter onset was observed in patients who received mepivacaine alone compared with those who received a mixture of mepivacaine plus ropivacaine (10 min [5-25 min] vs. 20 min [10-30 min]; P < 0.05). Recovery time was 4.6 h (2.5-5.5 h) after mepivacaine administration. The addition of ropivacaine produced a block of a much longer duration 13.8 h (5.2-23.6 h); P < 0.05. No complications were observed. CONCLUSIONS: This approach represents an easy and reliable anterior technique for performing sciatic nerve blocks.     

A new approach to sciatic nerve block in the gluteal region

Two personal techniques of sciatic nerve block in the gluteal region were compared in a retrospective study. The study was carried out on 224 patients undergoing elective orthopaedic lower-limb surgery. The block was performed in 107 subjects with a modified Labat's technique, prolonging his line downwards to meet the surface projection of the sciatic nerve, according to Ellis and McLarry. In 117 patients the needle was inserted at the intersection of the hiatus-trochanteric line with a straight line joining the midpoint of the thigh with the posterior-superior iliac spine. The use of these landmarks improved paraesthesia elicitation and increased absolute success rate (66%). A dramatic drop in intra-operative supplemental analgesic and hypnotic needs was observed in these patients. Failure occurred in about 10% with both techniques, whilst side-effects were of minor importance. These results suggest that the new landmarks provide a more precise anatomo-clinical location of the sciatic nerve.