Anatomical bases for paravertebral anesthetic block: fluid communication between the thoracic and lumbar paravertebral regions.

An injection of a local anesthetics in the paravertebral region produces an analgesic field on the same side of the body, a paravertebral block. One point in question about this block is whether the local anesthetic spreads from the thoracic to the lumbar level of the paravertebral region. The purpose of this study was to find how the anesthetic fluid traveled to the lumbar paravertebral region, if at all. Twelve cadavers were used in this study. 15 ml of crimson dye was injected into the paravertebral region at the 11th thoracic level. The viscerae were removed so that we could examine the dye spread. While the crimson dye spread in the endothoracic fascia posterior to the parietal pleura, it also spread downward in the fascia mostly along the splanchnic nerves. At the upper surface of the diaphragm the dye spread laterally in the fascia, and entered the abdominal cavity through the medial and lateral arcuate ligaments. In the abdominal cavity, the dye was found to have spread so widely in the transversalis fascia that the subcostal, iliohypogastric, ilioinguinal, genitofemoral, lateral femoral cutaneous and femoral nerves were involved. We concluded that the dye in the thoracic paravertebral region can enter the abdominal cavity through the medial and lateral arcuate ligaments. This study explained possible fluid communication between the thoracic and lumbar paravertebral regions and confirmed our former clinical observations. The result is important for the future clinical application of paravertebral anesthesia.