Lumbar Paravertebral Nerve Blocks
Lumbar paravertebral nerve blocks may be useful in evaluating pain due to disorders involving the lum-bar spine or spinal nerves.
The lumbar spinal nerves enter the psoas compart-ment as soon as they exit through the intervertebral foramina beneath the pedicles and transverse pro-cesses. This compartment is formed by the psoas fascia anteriorly, the quadratus lumborum fascia posteriorly, and the vertebral bodies medially.
The approach to lumbar spinal nerves is essentially the same as for thoracic paravertebral blockade (Figure 47–13). An 8-cm 22-gauge needle is usually used. Radiographic confirmation of the correct level is helpful. For diagnostic blocks, only 2 mL of local
anesthetic is injected at any one level, because larger volumes may block more than one level. Larger vol-umes of local anesthetic are used for therapeutic blocks, or to produce complete somatic and sympa-thetic block of the lumbar nerves.
Complications are primarily those of unintentional intrathecal or epidural anesthesia. Patients may experience paresthesias if inadvertent nerve injury occurs during needle placement. Some physicians advocate the use of a blunt-tipped needle to (theo-retically) decrease the chance of accidental intraneu-ral injection. Digital subtraction angiography with radiopaque contrast may lessen the risk of intravas-cular injection of local anesthetic or steroid.