Atlas of Pain Medicine Procedures 1st Edition

SECTION IV

SYMPATHETIC BLOCKS

CHAPTER 47

Lumbar Sympathetic Block

Joshua P. Prager

SYMPATHETIC NERVE BLOCKS

Indications

Pain specialists use sympathetic nerve blocks for diagnostic, prognostic, prophylactic, and therapeutic purposes (Table 47-1). Sympathetic nerve blocks have been used to:

TABLE 47-1. Neural Blockade as Part of Integrated Pain Management

Diagnostic blocks

• Determine source of chronic pain.
• Determine contribution of sympathetic nervous system to patient’s pain.
• Differentiate peripheral from central pain.
• Evaluate the patient’s reaction to treatment.

Prognostic blocks

• Allow patients to experience pain relief of the nerve block.
• Can predict the effect of spinal cord stimulation.

Prophylactic blocks

• Delay onset of postoperative pain.
• Prevent exacerbation of chronic pain syndromes, such as complex regional pain syndrome, when trauma (such as surgery) is anticipated.

Therapeutic blocks

• Optimize short-term pain relief.
• Provide pain relief that permits more effective physical therapy and rehabilitation.
• Improve peripheral blood flow.
• Gain patient’s cooperation in addressing physiologic and psychologic aspects of pain.
• Diagnose sympathetically mediated pain
• Control pain during surgery
• Treat pain associated with complex regional pain syndrome (CRPS)
• Treat herpes zoster infections
• Treat Raynaud disease
• Treat phantom limb pain
• Treat scleroderma
• Treat cancer pain

Sympathetic nerve blocks are used routinely to provide short-term regional analgesia, and their efficacy for this application is well established. Though the effect of local anesthetics can be prolonged by the addition of epinephrine, any resulting analgesia eventually diminishes. Thus, even successful therapeutic blockade is not curative. In the context of interdisciplinary pain management, however, sympathetic blocks can be used to facilitate rehabilitation in patients with chronic noncancer pain.

Although the popularity of sympathetic blocks has generally decreased, mainly due to the scarcity of evidence from randomized controlled trials, the procedure continues to be valuable in treating CRPS. An interdisciplinary treatment protocol for CRPS, developed under the aegis of the International Association for the Study of Pain, positions sympathetic blocks early to support physical rehabilitation (Figure 47-1). If blockade is not sustained or progressively longer with each injection, sympathetic blockade should be abandoned and a trial of spinal cord stimulation (SCS) initiated. Among the advantages of sympathetic blocks and SCS are that both are minimally invasive and neither involves neuroablation.

Figure 47-1. Multidisciplinary care continuum for complex regional pain syndrome. This algorithm was developed by the International Association for the Study of Pain for the multidisciplinary treatment of complex regional pain syndrome. It emphasizes functional rehabilitation utilizing various forms of progressive physical therapy, with adjuvant interventional pain management techniques, including neuromodulation and behavioral therapy. (Adapted from Stanton-Hicks, et al. Pain Pract. 2002;2:1-16.)

• Sympathetically maintained pain requires a coupling of sympathetic noradrenergic neurons and primary afferent neurons in the periphery of the body.
• The long-lasting pain relief achieved by temporary sympathetic blockade clearly implies that sympathetic neurons, which are of central origin, maintain a positive feedback circuit through the primary afferent neurons.
• A temporary block of the sympathetically mediated activity—lumbar sympathetic ganglia (anterior L2 and L3), for example—affects both the central state of hyperexcitability and the afferent neurons.
• Sympathetic blocks consist of injecting local anesthetic around the sympathetic paravertebral ganglia that communicate with affected body part.
• The contribution of the sympathetic system to a patient’s pain can be determined by selectively blocking autonomic pathways that are separate from somatic nerve fibers.
• Injection of local anesthetics near sympathetic ganglia is intended to disrupt pain transmission temporarily and may reset sympathetic tone to a normal state.
• Tissue damage may also be minimized by the increase in peripheral blood flow that accompanies sympathetic block.
• Pain relief or reduction following the procedure confirms that the patient’s acute or chronic pain was sympathetically mediated.
• Decreased pain may allow inflamed tissues to heal and physical therapy or rehabilitation to commence.
• There is also some evidence that early sympathetic blocks may prevent development of CRPS.

Contraindications

Patients who should not receive a sympathetic block include those patients who:

• Cannot discontinue their anticoagulant medication
• Have a bleeding diathesis
• Have an active infection near the injection site

RELEVANT ANATOMY

Anatomy

• The lumbar sympathetic chain consists of 4 to 5 paired ganglia that are located over the anterolateral surface of the second through fourth lumbar vertebra.
• Lumbar sympathetic ganglia are variable in number and location from one individual to another.
• The cell bodies that connect to the lumbar sympathetic ganglia lie in the anterolateral region of the spinal cord from T11 to L2 and contributions vary from T10 to L3.
• The preganglionic fibers exit the spinal canal via the corresponding ventral spinal nerve root, and join the sympathetic chain as white rami communicantes and then synapse within the corresponding ganglion.
• Postganglionic fibers leave the chain to join the diffuse perivascular plexus around the femoral and iliac arteries, via the grey rami communicantes to join the nerve roots that produce the lumbar and lumbosacral plexuses.
• Sympathetic fibers associate with all major nerves to the lower extremities and produce the majority of sympathetic innervation to the lower extremities.
• The largest portion of the lumbar sympathetic ganglia is located in the area of the lower second and upper third lumbar vertebrae. Thus, blockade of these ganglia result in near complete sympathetic block of the lower extremities.
• In the lumbar region, the two-bilateral sympathetic chains are connected segmentally to the spinal cord by preganglionic neurons, whose cell bodies are situated in the lateral horn, intermediate nucleus, and paracentral nuclei of the thoracolumbar spinal cord. These nerves are responsible for vasoconstriction in the lower limbs.
• The preganglionic fibers travel as thewhite rami communicans, which communicate in the paravertebral ganglia with postganglionic efferents and in the prevertebral ganglia by postganglionic efferents leaving the sympathetic trunk as gray rami communicans.
• Each lumbar sympathetic chain enters the retroperitoneal space under the right and left crura, continuing inferiorly between the anterolateral aspect of the vertebral bodies and the psoas muscle to enter the pelvis.
• The sympathetic ganglia of the lumbar sympathetic chain are variable in numbers, size, and position.

Landmarks

The needle is placed 1 cm below the ipsilateral rib approximately 8 cm from the midline (depending on body habitus). The needle is then directed to the anterolateral aspect of the body of L2 and then, after the needle is withdrawn, to the body of L3.

PREOPERATIVE CONSIDERATIONS

Sympathetic blocks should be performed by experienced pain specialists, because diagnostic and prognostic information can be lost if the block is not properly performed or evaluated. Requirements for optimal results are listed in. The procedure should be performed where the patient can be adequately monitored and managed should an adverse event occur (Table 47-2).

TABLE 47-2. Obtaining Optimal Results from Sympathetic Blocks

Physician requisites

• Thorough knowledge of pain syndromes and their pathophysiology, and of the range of diagnostic and therapeutic measures available for each patient.
• Understanding of the risks and benefits of sympathetic blocks.
• Knowledge of anatomy, pharmacology of local anesthetics, expected results and possible side effects.

Patient evaluation and communication

• Physicians must be willing to devote adequate time to the patient’s previous and current history, physical and neurologic examination, and to continued pain assessment and management.
• Should be conducted within the framework of a multidisciplinary pain program where nerve block is not the only available option.
• Patients should understand that nerve block is not curative.

Requirements for diagnostic or prognostic blocks

• Target nerve should be identified with localized radiography. Contrast media should be used to determine appropriate flow of the medication. Even with appropriate needle placement, it is possible to move medication into the wrong tissue plane or intrasvascularly (Figure 47-2K).
• Small volumes of local anesthetic should be used to avoid block of adjacent nerves.
• The duration of the block should be correlated with subjective pain relief.
• Sedation should be avoided when blocks are performed for diagnostic and prognostic purposes, because the effects of sedation can confound the results.

Assessment by medical personnel

• Note patient’s reaction to initial needle insertion as indicator of personal pain threshold.
• Assess block with neurologic examination.
• Evaluate efficacy of block in relieving pain.
• Correlate duration of pain relief with duration of neural block.
• Accurately record results in patient’s record.

Limitations

• Nerve block is not a panacea.
• Results of a nerve block must be interpreted in the context of all of the diagnostic and prognostic information available.
• Blocks represent only part of a multimodal rehabilitation or management program for chronic pain.

Before performing a sympathetic block for noncancer pain, the physician should review the patient’s previous and current history, perform a physical and neurologic examination, and discuss any prescription and over-the-counter medications the patient is currently taking. This evaluation should be conducted in the context of a multidisciplinary pain program, where nerve block is not the only available option, and patients should understand that sympathetic block is not curative. The patient’s response to the block should be carefully noted if it is being performed for diagnostic or prognostic reasons.

Fluoroscopic Views

Lateral, AP and anterolateral views are helpful in correctly positioning needles for injection.

Positioning of Patient

For a lumbar sympathetic block, the patient is placed in the prone position.

Selection of Needles, Medications, and Equipment

Equipment includes:

• 18-gauge needle to use as radiological marker at L2
• Sterile towels
• Multiple 10-mL syringes with local anesthetic
• Sterile gloves
• Marking pen
• 6- to 7-in, 22- or 25-gauge spinal needles
• 3-mL syringe with 30-gauge needle to anesthetize skin
• 18-gauge introducer
• 5-mL syringe for contrast with extension tubing

Medications include:

• Lidocaine 1% with bicarbonate for skin
• 10 mL 0.25% bupivacaine per level
• Contrast (Isovue or Omnipaque)

If performing bilateral sympathetic blockade, it is essential to administer 500 to 1000 mL of normal saline or lactated Ringer’s solution prior to the procedure to avoid hypotension or orthostatic hypotension from the sympathetic blockade. It is also essential that vasopressors be available in the room and be readily identified prior to starting the procedure, although they need not be opened because they are rarely needed.

INTRAOPERATIVE TECHNICAL STEPS

• For a lumbar sympathetic block, with the patient in the prone position, the body of L2 is radiographically marked.
• Approximately 1 cm below the ipsilateral costal margin and about 8 cm from the midline (depending on body habitus), the skin is infiltrated with short-acting local anesthetic with bicarbonate using a fine needle.
• With the 2-needle technique, an introducer is placed and then a 6- to 7-in sharp spinal needle is inserted through the introducer (Figure 47-2A).

Figure 47-2. Radiographic imaging of sympathetic blockade. (A) AP view of the radiographic marker at L2 with placement of the needle at L3. (B) Lateral view of the needle at L3. (C) Lateral view of injection of contrast media at L3. (D) AP view of contrast media at L3. (E) Lateral view of inadvertent intravascular injection, lumbar sympathetic block, see text. (F) AP view of needle and radiographic marker at L2. (G) AP view of radiographic marker and needle at L2 after contrast injection. (H) Lateral view of contrast media at L2 before local anesthetic. Note contrast at L3 from prior injection. This view should be utilized when first injecting contrast. (I) AP view of contrast media followed by local anesthetic at L2. (J) Oblique needle placement. (Used with permission from Dr. Andrea Trescot.) (K) CT view of needle placement. (Used with permission from Dr. Andrea Trescot.)

• The needle is then advanced to L2 or L3. In the lateral view (Figure 47-2B), after negative aspiration, nonionic contrast solution is injected at L3 (Figure 47-2C, D).
• Special care should be exercised to avoid and detect immediately intravascular injection (Figure 47-2E). InFigure 47-2E, the needle can be seen in the appropriate position and yet, even after negative aspiration, almost all the contrast is seen intravascular. The flow extends into the spinal canal from anterior to the spine. Care should be applied to ensure that injection of medication be avoided if such intravascular flow is noted. Typically, 10 mL of local anesthetic is injected around the anterolateral aspect of the L3 vertebral body under fluoroscopic guidance.
• The needle in this case is moved to L2 where it and the marker is again visualized (Figure 47-2F).
• Contrast media is injected at L2 (Figures 47-2G AP),Figure 47-2H in a lateral view with needle at L2 (note the contrast diluted with local anesthetic at L3 from the prior injection).
• Medication is injected following the contrast injection (Figure 47-2I). Injection at L2 generally blocks the leg. For better results near the foot, a second block at L3 must be performed.

Alternative Technique

• Use ipsilateral oblique fluoroscopy view of the needle.
• The camera is obliqued until the transverse process is at the edge of the vertebral body (Figure 47-2J).
• The needle is then advanced to the target area.
• Both lateral and AP views should still be used to assure appropriate placement of the medication.

POSTPROCEDURE CONSIDERATIONS

Pain relief can be measured by subjective means (visual analogue scale, quality of life measure), as well as by assessing function and use of pain medication postprocedure.

• Pain relief: YES. The patient may be asked to move the painful body part shortly after injection.
• Increased temperature: YES. Temperature monitoring of the involved part should be performed before and after the first block. Increased warmth or redness may be noticeable at first, but this effect usually resolves within 4 to 18 hours.
• Motor or sensory deficit: NO. After a lumbar block, the legs should never feel weak or numb.

MONITORING OF POTENTIAL COMPLICATIONS

As with any invasive procedure, sympathetic nerve blocks carry some risks, but complications are rare when the procedure is performed by an experienced physician and the patient is adequately monitored. Patients should be monitored using the same protocol as for epidural anesthesia. Infection, hematoma, vascular puncture, local anesthetic toxicity, nerve injury, and hypotension are possible complications. Infection can be minimized by using strict aseptic technique and avoiding multiple needle punctures. The risk of local anesthetic toxicity is greater with large volumes of long-lasting anesthetics than with smaller volumes of shorter-acting medications. This is particularly true for older and frailer patients. Local anesthetic should never be injected if a patient complains of pain or if resistance is felt during injection. Hypotension can occur and may result from sympatholysis. This is unusual with unilateral block except in the frail or intravascularly depleted patient.

CLINICAL PEARLS AND PITFALLS

Epidural Sympathetic Blockade

• Low-concentration continuous epidural infusions have been used in lieu of pure lumbar sympathetic blockade in CRPS to facilitate physical therapy. Although more popular in the past, this technique is still commonly used.
• An advantage of this approach is that it obviates the need for frequent repeat injections.
• Disadvantages include diminished normal sensation, including proprioception, which can hamper or render unsafe some aspects of physical therapy.
• Spinal cord stimulation can diminish sympathetically-mediated pain without disturbing normal sensation.
• Historically, there was belief that sympathetic fibers could be selectively blocked in the epidural space by using low concentrations of local anesthetic. This belief was based on the concept that sympathetic fibers are nonmyelinated and small, and therefore, more likely to be affected differentially by local anesthetic before other nerve fibers. There are no data to verify this belief.
• Single-shot epidural sympathetic blockade should never be used diagnostically or prognostically.
• Low concentration of local anesthetic will inevitably block normal sensory fibers and it willnot be possible to determine whether the pain is sympathetically mediated using epidural technique.

Lumbar Sympathetic Neurolysis

Destruction of the lumbar sympathetic chain (lumbar sympathectomy), chemically, surgically or by radio frequency is likely to have excellent short-term success if pure lumbar sympathetic blockade has been successful but of insufficient duration. Meta-analysis by Furlan et al suggests that long-term risks are potentially significant, and that informed consent for such procedures should include discussion of persistent neuropathic pain, among other sequelae, as a consequence.

Some physicians perform lumbar sympathetic block at L3 and L4 rather than at L2 and L3. This often spares the leg from sympathetic blockade despite good results at the foot.

Suggested Reading

Boswell MV, Trescot AM, Datta S, et al. Interventional techniques: evidenced-based practice guidelines in the management of chronic spinal pain. Pain Physician. 2007;10:7-111.

Cepeda MS, Carr DB, Lau J. Local anaesthetic sympathetic blockade for complex regional pain syndrome. Cochrane Systematic Rev. 2005:4:art. no. CD004598.

Furlan AD, Lui PW, Mailis A. Chemical sympathectomy for neuropathic pain: does it work? Case report and systematic literature review. Clin J Pain. 2001;17(4):327-336.

Prager J, Aprill C. Complications related to sedation and anesthesia for interventional pain therapies. Pain Med. 2008;9(S1):S121-S127.

Stanton-Hicks MD, Burton AW, Bruehl SP, et al. An updated interdisciplinary clinical pathway for CRPS: report of an expert panel. Pain Pract. 2002;2:1-16.