Indications

PVBs can be utilized to provide anesthesia and analgesia for a variety of procedures (Box 126-1). PVBs provide excellent analgesia after thoracotomy and have unique advantages in patients with anatomic abnormalities, such as kyphoscoliosis and ankylosing spondylitis, in which thoracic epidural placement may be difficult or impossible. PVBs provide better deafferentation than does a thoracic epidural technique, which may help explain why PVBs result in better preservation of pulmonary function, compared with epidural analgesia. There is also evidence that the intensive deafferentation provided by PVBs may attenuate chronic pain and, when used during surgery for resection of (breast) malignancy, may decrease the incidence of metastasis.

PVBs are particularly useful in patients with multiple rib fractures and associated spinal or cranial trauma, in which placement of a thoracic epidural catheter is contraindicated. In these clinical situations, PVBs, especially if a continuous technique is used, obviate the need for systemic analgesia or sedation, which facilitates continuous neurologic assessment.

PVBs have been documented to reverse ischemic cardiac pain and, thus, may provide a treatment option for patients who have had medical and surgical treatment but continue to have ischemic symptoms.

PVBs can be utilized for obstetric analgesia and are particularly useful in situations in which anatomic abnormalities, such as Harrington rods, preclude the use of epidural analgesia.

Contraindications

Contraindications to performance of PVBs include generic contraindications to any peripheral nerve block, including infection at the site of insertion, indeterminate neuropathy, major coagulopathy, and patient refusal. The need for subsequent anticoagulation is a relative contraindication to the use of a continuous technique.

Regional anatomy

The paravertebral space is a wedge-shaped anatomic compartment adjacent to the vertebral bodies. The space is defined anterolaterally by the parietal pleura; posteriorly by the superior costotransverse ligament (thoracic levels); medially by the vertebra, vertebral disk, and intervertebral foramina; and superiorly and inferiorly by the heads of the ribs. Within this space, the spinal root emerges from the intervertebral foramen and divides into dorsal and ventral rami (Figure 126-1).

Patients are seated with the neck flexed forward with the chin to the chest, the back is arched posteriorly, and shoulders are relaxed forward (similar to performance of a thoracic epidural).

Landmarks

The spinous process of each level is identified, and a mark is placed at the most superior aspect. From the midpoint of these marks, a needle-entry site is marked 2.5 cm laterally (Figure 126-2). In the thoracic area, these marks should overlie the transverse process of the immediately caudal vertebra (because of the extreme angulation of the thoracic spinous processes). In the lumbar area, the transverse process is at the same level as the spinous process or even one level above the spinous process.

Nerve stimulation technique

A nerve stimulation technique can be used, performed similarly to the anatomic technique described earlier. In the author’s opinion, nerve stimulation techniques should be utilized in lumbar and lower thoracic levels only to minimize complications such as pneumothorax, which might occur secondary to the multiple needle manipulations that may be required with the nerve stimulation technique. The same anatomic landmarks as discussed in the anatomic technique are utilized.

Ultrasound guidance

As with the practice of regional anesthesia in other applications, ultrasound-guided PVBs have proved to be useful, particularly in patients with anatomic abnormalities, such as significant scoliosis.

Choice of local anesthetic agent

Similar to other peripheral nerve blocks, PVBs can be performed utilizing an intermediate agent such as lidocaine or mepivavaine with onset 5-10 minutes, time to surgical anesthesia is 20 minutes and duration is 4-6 hours. Long acting agents such as bupivacaine or ropivacaine have onset times of 10-15 minutes, time to surgical anesthesia 20-30 minutes and duration 18-24 hours (longer duration with increasing concentration). For continuous PVB, ropivacaine 0.2% is utilized.

Complications

Complications associated with PVBs include possible intraneural injection, significant epidural spread of the local anesthetic agent, pneumothorax, and local anesthetic toxicity.