Study of QL Analgesic Response and Extent (SQUARE)

Regional anesthesia techniques are widely employed to achieve sensory blockade of the abdominal wall. Among these, the epidural remains the most well-established approach, offering bilateral spread. However, its association with neuraxial complications has led to a decline in its clinical use. In contrast, fascial plane blocks, avoid neuraxial-related risks. The advent of ultrasound-guided blocks has sparked growing interest in novel fascial plane blocks, that can deliver multi-dermatomal with a lower rate of complications.

Three Quadratus Lumborum (QL) blocks are an example of these fascial plane blocks, commonly performed for abdominal and pelvic surgery. Despite their widespread clinical use, no prior studies have directly compared the three techniques in terms of their cutaneous distribution. Additionally, case reports note that lower extremity weakness can sometimes temporarily occur as a result of accidental spread to the lumbar plexus. Thus, this randomized, double-blinded trial aims to investigate the cutaneous distribution of these three blocks in healthy adult volunteers. Lastly, this study will assess the incidence and severity of lower extremity weakness that may occur with each technique. In addition, this study also seeks to investigate the pharmacokinetics (PK) of lidocaine in each technique. The rationale for this lies in the anatomical differences between the blocks. Theoretically, there may be a difference in the anatomical target for these blocks, but the investigators hypothesize that there is no difference in the local anesthetic absorption. Therefore, as the investigators expect similar systemic absorption, the chances of local anesthetic systemic toxicity (LAST) should be equally low, and all blocks should be similarly safe.