The ability of transversus abdominis plane (TAP) blocks to anesthetize the upper abdomen remains debatable. We aimed to describe the local anesthetic distribution following ultrasound-guided TAP blocks with repeated magnetic resonance imaging investigations and to relate this to the resulting dermatomal anesthesia.
Eight volunteers were included in a randomized, observer-blinded study. Sixty milliliters of ropivacaine 0.375% was administered: 1 injection of 30 mL as a lateral classic TAP block, followed by a sham upper intercostal TAP block, and on the contralateral side, 2 separate 15-mL injections at the upper intercostal and lateral classic TAP plexuses, respectively. The primary outcome measure was magnetic resonance imaging-assessed area expansion of all injectates over a 6-hr period. Dermatomal anesthesia and sequential serum ropivacaine levels were recorded at the same time intervals.
All injectate areas expanded in a statistically significant manner in the anterior abdominal wall. Lateral classic TAP blocks with 30-mL injectates did not extend into the upper intercostal TAP plexus. The dual 15-mL injectates on the other hemiabdomen remained within the upper intercostal and lateral classic TAP compartments and resulted in significantly (P