Erector spinae plane block is an excellent alternative to paravertebral nerve block and thoracic and lumbar epidural block to provide surgical anesthesia for surgeries involving the thorax, cervical and thoracic spine, reconstructive breast and chest wall surgery, implantable drug delivery systems including ports and reservoirs, thoracoscopic sympathectomy, and lower segment caesarean section. This technique has great clinical utility in both children and adults when managing acute postoperative and posttrauma pain in the area subserved by erector spinae plane block including thoracic and abdominal surgeries and postcesarean section pain (Fig. 97.1). Recent case reports have identified the utility of erector spinae plane block in the palliation of the pain associated with rib fractures and acute herpes zoster involving the thoracic dermatomes. Continuous erector spinae plane block techniques have been utilized to provide prolonged analgesia following chest wall trauma and postoperative pain. The area of anesthesia following erector spinae block is determined in part by the volume of local anesthetic injected as well as the level at which the block is performed. Clinical experience suggests that it will require between 3 and 5 mL of local anesthetic to block a dermatome and that if a catheter is being used for continuous blockade, the use of a curved epidural needle to direct the catheter either cephalad or caudad can also influence the area of anesthesia.

The primary target of the erector spinae plane block is the dorsal and ventral rami of the spinal nerves, which are blocked when local anesthetic is placed between the anterior fascia of the erector spinae muscle and the transverse process (Fig. 97.2). Exiting their respective intervertebral foramen and passing just below the transverse process are the spinal 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 anatomic basis for the erector spinae plane block is the proximity of the erector spinae muscles to the exiting spinal nerve roots combined with the fact that the fascia surrounding these muscles of posture creates potential compartments that can contain local anesthetics when injected within the facial compartments (Fig. 97.3). Because the nerves contained within these fascial compartments traverse these fascial compartments, they are amenable neural blockade at various points along their paths. Since these fascial compartments can potentially prevent the

spread of local anesthetic to block other nerves, repositioning of the needle tip into adjacent fascial compartments may be required in order to provide complete anesthesia and analgesia for the area desired.

Ultrasound-guided erector spinae plane block can be carried out by placing the patient in the sitting position, although the block may be performed in the lateral decubitus or prone position as the clinical situation dictates. A total of 20 mL of local anesthetic is drawn up in a 20-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 spinous process of the thoracic spine at the desired level of blockade is identified with T3, a suitable level for lower cervical and high thoracic applications, T5 a suitable level for most upper thoracic applications, T7 for most lower thoracic applications, and T10 for most upper lumbar applications. A linear high-frequency ultrasound transducer is then placed in the parasagittal position about 3 cm from the midline at the desired level of blockade (Fig. 97.4). A survey scan is taken to identify the transverse process of the vertebral body and the overlying muscles (Fig. 97.5). The number of identifiable muscle layers will depend on the level chosen for needle insertion. From T1 to T5, three distinct layers of muscle will be identifiable from superficial to deep: (1) the trapezius; (2) the rhomboid; and (3) the erector spinae (see Fig, 97.5). Since the lower extent of the rhomboid is between T5 and T6, if a lower level is chosen for needle insertion, only two layers of muscle will be identifiable from superficial to deep: (1) the trapezius and (2) the erector spinae (Fig. 97.6). Intentional identification of the bright sunset line of the pleura should be undertaken to allow the operator to avoid placing the needle too deeply and risking pneumothorax (see Fig. 97.5).