Phase 1 aimed to validate an ultrasound-guided approach for a lumbosacral trunk blockade proximal to the cranial gluteal nerve using cadavers. In Phase 2, sympathetic responses were evaluated for nociception detection through electrical stimulation of the deep gluteal muscles in living dogs. In Phase 1, 0.1% methylene blue (0.2 mL kg-1) was injected alongside the lumbosacral trunk in the bilateral pelvic limbs of three adult cadavers. The median length of the stained lumbosacral trunk proximal to the cranial gluteal nerve was 16 mm. Cranial gluteal nerves were stained in all pelvic limbs. In Phase 2, under general anesthesia, ten healthy adult beagle dogs received injections of 0.5% bupivacaine (0.2 mL kg-1) in one limb and saline (0.2 mL kg-1) in the contralateral limb in a blinded, randomized fashion, following the Phase 1 methodology. Percutaneous electrical stimulation of the deep gluteal muscles was performed before, 15 min, and 60 min after administering 0.5% bupivacaine. Suppression of sympathetic response was defined as < 10% increase in heart rate (HR) and mean arterial blood pressure (MAP) following electrical stimulation. Differences in relative changes of HR and MAP were analyzed using the Kruskal-Wallis and Dunn's multiple comparison tests. After 0.5% bupivacaine injection, the sympathetic response to electrical stimulation of the deep gluteal muscles was suppressed. Ultrasound-guided, lumbosacral trunk blockade proximal to the cranial gluteal nerve inhibits the sympathetic response to deep gluteal muscle stimulation.
ONISHI et al. (Thu,) studied this question.