Thoracic Intervertebral Foramen Block

Overview

The investigators hypothesize an alternative way to perform thoracic paravertebral block, by placing the needle tip over and behind the transverse process of vertebra, via the thoracic intervertebral foramen. This anesthetic procedure is called thoracic intervertebral foramen block. The study aims to verify the spread of dye on to the the nervous structures of retropleural space (the ventral rami, the communicating rami, and the sympathetic trunk), and into the thoracic paravertebral space and epidural space. To accomplish this, a prospective cadaveric study was designed.

This is a prospective cadaveric study. The anesthetic procedure is performed on 2 corpses for which autopsy is requested, in accordance with Italian Low. Before performing the autopsy, the corps is placed in the left and then in the right lateral position, to perform bilateral block. The anesthetic procedure is performed at second (T2), fifth (T5), ninth (T9), and twelfth (T12) thoracic vertebra. The ultrasonography is performed by using a high-frequency linear-array US transducer. A Tuohy needle is inserted in-plane to the ultrasound beam in a lateral-to-medial direction gently to contact the spinous process, into the skeletal muscle plane of the erector spinae muscle. Then, the needle tip is moved to reach the angle between the transverse process and spinous process. Subsequently, the needle tip is gently inserted and advanced for 2 mm along with the superior limit of the vertebral pedicle, until losing contact with the bone. Five ml methylene blue 1% dye (MB) were subsequently injected. The anesthetic procedure is bilaterally performed. Two continuous catheter sets are used and threaded 1 cm from the needle tip, for a bilateral continuous block. The catheters are inserted from the caudal to the cephalic direction. At the end of the anesthetic procedure, a second look ultrasound scan of thoracic paravertebral space was performed. Subsequently, the corps is put in supine position, and autopsy is started.