Massage application to increase spread of local anesthesia in sciatic nerve blocks: a cadaveric study

Introduction: Sciatic nerve blockades are essential for treatment of a variety of lower limb pathologies. Due to the complexity and variation of anatomical landmarks, ultrasound (US) is used to guide injection of local anesthesia. In patients with thicker thigh girth (i.e., obese patients) excess tissue can distort US penetration, diminishing efficacy of the nerve block and/or post-operative pain. Dye tracing techniques have been used to test the effectiveness of nerve blocks, but there is little research on using massage to increase anesthetic spread. Therefore, this study will assess whether local massage can spread anesthetic proximal to the injection site. Methods: Fresh cadaveric legs were injected with 15cc's of 25:75 mixture of methylene blue dye and 0.5% bupivacaine. The specimens were divided into control (non-massage) and experimental (massage) groups. Nerve blockades with dye were performed by an anesthetist using US guidance at the popliteal fossa traveling proximally until the formation of the sciatic nerve, where the location was tagged. Immediately following, experimental specimens received repeated, proximally directed massages with the US transducer head. Specimens from both groups were dissected to expose the sciatic nerve. Measurements of the distance traveled from marked site of injection to proximal end of dyed area were measured and compared using statistical analysis. Results: Researchers expect significant difference in distance of injected materials proximal to injection site in the massage group compared to the experimental group. Conclusion: Post-injection massage can be used in clinical settings to increase efficacy of higher risk local anesthetic injections.