Dual Guidance in Regional Anesthesia – Influence of Needle Electrode Configuration on Stimulation Success at Sciatic Nerve; A Randomized, Controlled Pilot Trial

ABSTRACT Introduction In contrast to ultrasound technology (US), peripheral nerve stimulation (PNS) for regional anesthesia was little improved in recent years. When using the combination of both techniques, PNS can give additional information for nerve localization to improve safety and success of regional anesthesia. There are influencing factors on the success rate of stimulation in PNS remaining uninvestigated in a clinical setting to date. This randomized controlled pilot trial evaluates the impact of shape and size of stimulation needles electrodes under dual guidance conditions. Methods In a randomized controlled clinical trial 35 participants undergoing lower limb surgery received a preoperative proximal sciatic nerve block in dual guidance technique. Use of facet needles with point shaped electrodes (N=19, facet group) were compared with tuohy needles with large electroconductive tips (N=16, touhy group). Stimulation success at minimal distance between needle tip and nerve was recorded. Block success and complications of regional anesthesia were assessed. Results In 87% of successful stimulation (20 of 23) an ultrasound-proven contact of needle tip and sciatic nerve was necessary to elicit a motor response. More successful stimulations could performed using facet needles (84%, 16/19) compared to tuohy needles (44%, 7/16, p=0.03). If stimulation was successful the number of successful sensory blockades was increased (78%, 18/23, p=0.02). No serious complications of regional anesthesia were recorded. Discussion This pilot trial suggests that stimulation needles with small electrodes may be more reliable in indicating a contact of needle and nerve, which may improve safety and success of proximal sciatic nerve blocks.