Double-Edge, Single-Edge, and Intermediate-Edge Ultrasound Sign and Correlation With Fascial Plane Block Efficacy: An Experimental Study.

Introduction Ultrasound-guided fascial plane blocks are nowadays the gold standard technique for regional anesthesia and postoperative analgesia. Despite their high success rate, cases of partial or total failure of this method have been reported. This experimental study aims to address the corresponding ultrasound signs and their association with fascial plane block efficacy. Methods After capturing the appropriate sonographic image that included muscle layers and their fasciae, an 18-gauge epidural needle penetrated the cadaveric porcine tissue and was forwarded until the tip of the needle reached the target fascial plane. The infusion of methylthioninium chloride or methylene blue dye was performed, causing tissue hydro dissection. The documentation of the generated ultrasound images was followed by surgical exposure of the tip of the needle. Results The distribution of the dye into the plane of interest (double-edge sign) was equivalent to block success, whereas the single-edge sign (accumulation of the dye between fascia and epimysium) indicated total block failure. The intermediate-edge sign, a combination of the previous ultrasound signs, is related to partial failure of block performance. Conclusion The identification of the three novel sonographic signs is an accurate predictive factor of peripheral nerve block efficacy. The respective data are expected to aid the rapid improvement of interfascial plane block accuracy and techniques, leading to their more effective execution and simultaneously eliminating the failure rates. Thereby, the amelioration of intra and postoperative analgesia will be accomplished, expediting the patient's hospital discharge and reducing or even avoiding opioid consumption.