Patient Selection

Patients requiring lumbar sympathetic block can be divided into two primary groups: (1) those requiring sympathetic block because of ischemic vascular disease to the lower extremities (these patients are often older); and (2) patients requiring the block for diagnosis or treatment of complex regional pain syndromes of the lower extremities (these patients have a much wider age range).

Pharmacologic Choice

Block of the sympathetic nervous system can be performed with lower concentrations of local anesthetics than almost any other regional block. For example, 0.5% lidocaine, 0.125% or 0.25% bupivacaine, or 0.1% or 0.2% ropivacaine are appropriate choices.

Anatomy

The lumbar sympathetic chain, with its accompanying ganglia, is located in the fascial plane immediately anterolateral to the lumbar vertebral bodies (Fig. 46-1). The sympathetic chain is separated from the somatic nerves by the psoas muscle and fascia. The lumbar regions L1, L2, and sometimes L3 provide white rami communicantes to the sympathetic chain, and all five lumbar vertebrae are associated with gray rami communicantes. These rami are longer in the lumbar region than in the thoracic region. This is anatomically important because it allows needle placement nearer the anterolateral border of the vertebral body in the lumbar region. Conceptually, the anatomy important to anesthesiologists performing lumbar sympathetic nerve block is also the anatomy important for celiac plexus nerve block.

Figure 46-1. Lumbar sympathetic block: cross-sectional anatomy. Ao, aorta; IVC, inferior vena cava.

Position

My experience suggests that lumbar sympathetic nerve block is most effectively carried out in a manner similar to that used for celiac plexus block (see Chapter 47, Celiac Plexus Block). The patient should be prone with a pillow under the mid-abdomen to help reduce lumbar lordosis. (Despite this recommendation, many clinicians continue to use the lateral position successfully.)

Needle Puncture

Most experienced anesthesiologists now carry out this block through a single needle. This is possible because placing the needle tip at the anterolateral border of the second or third lumbar vertebral body allows the local anesthetic solution to spread along the fascial plane enveloping the sympathetic chain. As an example, the second lumbar vertebral spine is identified, and a mark is made lateral to it in the horizontal plane, 7 to 9 cm from the midline, as illustrated in Figure 46-2. A skin wheal is raised, and a 15-cm, 20- or 22-gauge needle is directed in the horizontal plane at an angle of 30 to 45 degrees from a vertical plane through the patient’s midline. It is inserted until it contacts the lateral aspect of the L2 vertebral body. If it comes into contact with the vertebral transverse process at a more superficial level (at only 3 to 5 cm), the needle can simply be redirected cephalad or caudad to avoid the transverse process. The vertebral body is usually located at a depth of 7 to 12 cm.

Figure 46-2. Lumbar sympathetic block: surface (A) and cross-sectional (B) technique.

Once the needle’s position on the lateral aspect of the vertebral body is certain, the needle is withdrawn and redirected at a steeper angle until it slides off the anterolateral surface of L2. This needle insertion and redirection process is almost identical to that described for the celiac plexus block. For the lumbar sympathetic block, once the needle is in position, approximately 15 to 20 mL of local anesthetic solution is injected. With proper needle tip position, this volume will allow spread along the axis of the sympathetic chain (Fig. 46-3).

Figure 46-3. Lumbar sympathetic block: fluoroscopic spread of contrast in typical lumbar sympathetic block. Needle placement anterolateral to L3 and spread of 1.5 mL of contrast. A, Posteroanterior view. B, Lateral view.