Dispersion Following ESP Versus ITP Blocks Using Lidocaine Study

Regional anesthesia techniques (or nerve blocks) are used to provide sensory blockade over the chest wall. The most established technique is thoracic epidural. This provides bilateral spread but is also associated with neuraxial complications, which has led to a decrease in clinical usage. Alternative peripheral nerve block techniques, such as intercostal nerve blocks, eliminate the neuraxial complications but, in turn, require numerous injections to provide unilateral coverage. The introduction of ultrasound-guided (USG) nerve blocks has generated clinical interest in the development of novel paraspinal (non-epidural) nerve block techniques, which will provide multiple dermatomal coverage with a single injection. Two such techniques are the Erector Spinae Plane (ESP) block and the Intertransverse Process (ITP) block. The Intertransverse Process (ITP) block targets a slightly deeper plane than the Erector Spinae Plane (ESP) block and was specifically designed to address the ESP block's variable anesthetic spread. Despite its potential for more localized and precise dermatomal coverage, no prior studies have directly compared the two techniques in terms of their cutaneous distribution. Thus, this randomized, double-blinded trial aims to compare the cutaneous distribution of both these blocks in healthy adult volunteers. To compare the dermatomal sensory block distribution, the investigators will use detailed mapping with pinprick, cold, and heat stimuli. In addition to assessing the distribution and coverage of the ESP and ITP blocks, 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 two blocks. Theoretically, there may be a difference in the anatomical target for both blocks, but the investigators hypothesize that there is no difference in the local anesthetic absorption. Therefore, the investigators expect similar systemic absorption, the chances of