Ultrasound-guided intercostal nerve block is utilized in a variety of clinical scenarios as a diagnostic, prognostic, and therapeutic maneuver as well as to provide surgical anesthesia for thoracic and upper abdominal surgeries. As a diagnostic tool, ultrasound-guided intercostal block allows accurate placement of the needle tip within the intercostal space when performing differential neural blockade on an anatomic basis in the evaluation of chest wall and upper intra-abdominal pain. As a prognostic tool, ultrasound-guided intercostal block can be utilized as a prognostic indicator of the degree of motor and sensory impairment that the patient may experience if intercostal nerves are going to be destroyed in an effort to palliate intractable pain in patients too sick to undergo neurosurgical neurodestructive procedures. In the acute pain setting, ultrasound-guided intercostal block with local anesthetics may be used to palliate acute pain emergencies while waiting for pharmacologic, surgical, and/or antiblastic methods to become effective. This technique has great clinical utility in both children and adults when managing acute postoperative and posttrauma pain including fractured ribs and flail chest and to provide anesthesia for placement of chest and nephrostomy tubes (Fig. 92.1). Pain of malignant origin of the chest wall, flank, and upper abdomen as well as liver and lung tumors that involve the pleura and peritoneum is also amenable to treatment with local anesthetics and/or steroids and neurolytic agents such as phenol administered into the intercostal space.

Exiting their respective intervertebral foramen and passing just below the transverse process are the paravertebral nerves. After exiting the intervertebral foramen, the intercostal nerve gives off a recurrent branch that loops back through the foramen to provide innervation to the spinal ligaments, meninges, and its respective vertebra and can be an important contributor to spinal pain. The paravertebral nerve also provides fibers to the sympathetic nervous system and the thoracic sympathetic chain via the myelinated preganglionic fibers of the white rami communicantes as well as the unmyelinated postganglionic fibers of the gray rami communicantes. The intercostal nerve then divides into a posterior and an anterior primary division (Fig. 92.2). The posterior division courses posteriorly and, along with its branches, provides innervation to the facet joints and the muscles and skin of the back. The larger, anterior division courses laterally to pass into the subcostal groove beneath the rib along with the intercostal vein and artery to become the respective intercostal nerves (Fig. 92.3). The 12th thoracic nerve courses beneath the 12th rib and is called the subcostal nerve and is unique in that it gives off a branch to the first lumbar nerve, thus contributing to the lumbar plexus. The intercostal and subcostal nerves provide the innervation to the skin, muscles, ribs, and the parietal pleura and parietal peritoneum.

Ultrasound-guided intercostal block can be carried out by placing the patient in the sitting position with the patient’s head resting comfortably on a padded bedside table and the arms resting comfortably on the patient’s lap (Fig. 92.4). A total of 5 mL of local anesthetic is drawn up in a 10-mL sterile syringe. If the painful condition being treated is thought to have an inflammatory component, 40 to 80 mg of depot steroid is added to the local anesthetic. The rib at the level to be blocked is then identified by palpation and then traced posteriorly to the posterior angulation of the affected rib (Fig. 92.5). A linear high-frequency ultrasound transducer is then placed in the longitudinal plane with the superior aspect of the ultrasound transducer rotated ˜15 degrees laterally over the affected rib at the posterior angulation of the ribs, and an ultrasound survey scan is obtained (Figs. 92.6 and 92.7). The rib will be identified as a hyperechoic curvilinear line with an acoustic shadow beneath it. The three layers of intercostal muscle, the external, internal, and innermost, will be identified in the intercostal space between the adjacent ribs (Figs. 92.8 and 92.9). Color Doppler will help identify beneath the adjacent intercostal artery and vein (Fig. 92.10). This space between adjacent ribs provides an excellent acoustic window, which allows easy identification of the intercostal space and the pleura beneath it. Adjacent ribs
with the intercostal space in between have been described as having the appearance of a “flying bat” (Fig. 92.11A and B). The clinician should then identify the pleura that appears as a bright hyperechoic line having the appearance of a bright sunset on the ocean beneath the innermost intercostal muscle, which can be seen to slide back and forth with respiration (see Fig. 92.7). The pleura and the lung beneath it have been described as having the appearance of “waves on a sandy beach” (Fig. 92.12A and B). The depth of the pleura is noted. When these anatomic structures are clearly identified on transverse ultrasound scan, the skin is prepped with anesthetic solution, and a 1½-inch, 22-gauge needle is
advanced from the inferior border of the ultrasound transducer using an in-plane approach with the trajectory being adjusted under real-time ultrasound guidance until the needle tip is resting within the internal layer of intercostal muscle (Fig. 92.13). At that point, after careful aspiration, a small amount of solution is injected under real-time ultrasound imaging to utilize hydrodissection to reconfirm the position of the needle tip (Fig. 92.14). Once the position of the needle tip is reconfirmed, the needle is carefully advanced into the innermost layer of intercostal muscle just short of the previously identified depth of the pleura. After careful aspiration, a small amount of solution is again injected to aid in identification of the position of the needle tip with attention paid to the relative location of the bright hyperechoic pleural line. After careful aspiration, the remainder of the solution is slowly injected. There should be minimal resistance to injection. The needle is then removed, and a sterile pressure dressing and ice pack are placed at the injection site.