Ultrasound-Guided Intercostal Approach to Thoracic Paravertebral Block

Abstract

To the Editor: In the first report of ultrasound-guided thoracic paravertebral block (USG-TPVB),1 the authors imaged the transverse process and the thoracic paravertebral space (TPVS) in a longitudinal parasagittal plane, the needle was inserted out-of-plane to the probe using a conventional technique, and loss-of-resistance to saline was used as the end point for needle placement rather than ultrasonographic visualization of needle-tip position. Our USG-TPVB technique is typically performed using in-plane technique that utilizes direct visualization of needle-tip position and local anesthetic spread as the end point. USG-TPVB is performed using a high-frequency linear array probe. A convex probe is also useful in obese patients. The patient is placed in a lateral decubitus position with the side to be blocked uppermost or in a prone position. After aseptic preparation of the skin and the probe, the probe is placed on the rib at the selected level with the medial edge of probe in contact with the spinous process, so that the horizontal view of the rib is visualized as a hyperechoic line with posterior acoustic shadowing. The probe is then moved caudally into the intercostal space between adjacent ribs. The inferior part of transverse process is visualized as a hyperechoic convex line with posterior acoustic shadowing. The apex of TPVS is visualized as a wedge-shaped hypoechoic space surrounded by the hyperechoic line of the pleura below and the internal intercostal membrane above (Fig. 1). The apex of TPVS is laterally continuous with the intercostal space2 (Fig. 2). The internal intercostal ligament is medially continuous with the superior costotransverse membrane; these two membranes cannot be distinguished by ultrasonography. A 20-gauge Tuohy needle is inserted in a lateral-to-medial direction from the outer edge of probe with the bevel facing the probe using an in-plane approach and advanced until the needle tip penetrates through the internal intercostal membrane. After a negative aspiration test for blood, 15–20 mL of local anesthetic is injected into the TPVS slowly. The pleura is seen being pressed ventrally during local anesthetic injection (Fig. 3).Figure 1.: Ultrasound image of the thoracic paravertebral space at the level of T3. TP = transverse process; TPVS = apex of thoracic paravertebral space; IICM = internal intercostal membrane; EICM = external intercostal muscle; PL = pleura.Figure 2.: Ultrasound image of the needle-tip placement into the thoracic paravertebral space. TP = transverse process; EICM = external intercostal muscle; N = Tuohy needle; PL = pleura.Figure 3.: Ultrasound image of local anesthetic spread. N = Tuohy needle; EICM = external intercostal muscle; LA = local anesthetic; PL = pleura.The technique we describe has been modified from that reported by Kappis3 in 1912. A 10-cm needle was introduced three finger breadths from the midline at an angle of 45° to the skin and advanced into the TPVS until the needle tip was in contact with the posterolateral aspect of the vertebral body. Kappis’s technique was eventually abandoned because of the risk of needle penetration through the intervertebral foramen resulting in intrathecal injection or spinal cord injury. With the ultrasound-guided technique, however, needle contact with the vertebral body is not necessary, and the complications associated with Kappis’s technique can be avoided. Moreover, Tuohy needle insertion and advancement tangential to the pleura can lessen the risk of pleural and intercostal vascular puncture. The safety and reliability of USG-TPVB await future confirmation. Yasuyuki Shibata, MD Kimitoshi Nishiwaki, MD, PhD Department of Anesthesiology Nagoya University, School of Medicine Nagoya, Japan [email protected]