The indications for paravertebral lumbar sympathetic ganglion block include the diagnosis and treatment of sympathetically mediated pain (including the sympathetic component of complex regional pain syndrome), and vascular insufficiency of the lower extremities. Today with decreasing availability of surgical centers for pain procedures the likelihood of being able to perform lumbar sympathetic blocks under fluoroscopic guidance is quickly disappearing. The option of using a lumbar sympathetic ganglion block technique guided by anatomical landmarks instead of fluoroscopy may be advantageous.
Anatomy
The lumbar sympathetic ganglia lie along the anterolateral surface of the lumbar vertebral bodies and medial border of the psoas muscle. The anatomical distance between the vertebral spinous and transverse processes and the transverse process and to where the sympathetic ganglia lie is fairly constant. The distance between the transverse process and the ganglia is fairly constant at 4-5 cm, because the anteroposterior dimension of the lumbar vertebrae varies less than 0.6 cm irrespective of the patient's build. Though the distance from spine to the transverse process is usually 3-½ cm in depth, the size of the overlying muscle and adipose varies greatly. The major sympathetic innervation to the lower extremity is through the L2 ganglion, with contributions through the L3, and L4 ganglia. Therefore when a single needle placement technique is utilized the block is usually performed at the L2 ganglion.
Technique:
There are two ways to locate the L2 body:
1. Palpate the costal margins bilaterally and draw a line connecting them. This
line should pass through the L2 spine or the L1-2 interspace.
2. Palpate the two iliac crests and draw a line connecting them. This line will
intersect either the L4 spine or the L4-5 interspace.
To be sure that the L2 vertebral body had been identified count from both the upper and lower approaches. A line is then drawn through the middle of the L2 spinous process and the skin marked 4 to 5 cm from the midline; a skin wheal with local anesthetic is raised at this point. A 10 to 15 cm 22-gauge needle (Spinal, Havel, or Chiba) can be used for this block with the length dependent on the patient's habitus. A minimum of 7-1/2 cms is inserted to reach the area of the sympathetic ganglion in the thinnest patients. The initial insertion to skin is cephalad at a 45-degree angle until contact with the transverse process is made. The depth is marked on the needle; the needle withdrawn to skin and inserted at a 90-degree angle 4 cm past the marked insertion. The needle is aspirated for blood or CSF. A test dose of 3 cc of local anesthetic is given. A total of 30-cc volume (not to exceed the toxic dose of local anesthetic by body weight) is injected.
Choice of local anesthetics
Because the placement of the needle by anatomic landmarks may not be as accurate as that of placement under fluoroscopic guidance, choosing a local anesthetic with the greatest diffusibility is important. Local deposition of anesthetic depends on bulk flow of the solution, diffusion of the molecules, binding of the anesthetic to protein and lipid, and metabolism of the drugs. Both lidocaine and mepivacaine have lower protein and lipid binding than bupivacaine. These solutions should be used only with freshly added epinephrine, because the lower pH of commercially prepared epinephrine containing solutions affects diffusion. Lidocaine has the best diffusibility of the local anesthetics and may be the drug of choice for this particular block, which is based on anatomical needle placement. Alkalinization of the drugs may be of benefit to increase diffusion. Sympathetic nerves can be blocked with very low concentrations of local anesthetics, i.e., lidocaine 0.5%, mepivacaine 0.5%, and bupivacaine 0.125%. The volume used in adults through a one- needle insertion at L2, or L3 is 30 cc. Temperature monitoring should be done for adequacy of the block. A rise of at least 1-degree Celsius or more should occur after the block.
Pearls
Contact of the periosteum of the transverse process is painful. Touch gently and do not probe, otherwise the patient will become apprehensive and agitated. After determining the depth for appropriate needle placement, quickly move the needle to this location. Slow movement with the needle though all tissue planes can cause more discomfort than a swift needle placement. Sedation on the first block should be minimal if the desired end point is pain relief. Giving narcotics or benzodiazepines may cloud the issue. If the patient refuses the block without any or minimal analgesia, propofol may be the drug of choice for its rapid onset and offset. Advantages include lower cost, and the ability to perform the block without fluoroscopic guidance or the use of contrast media. Disadvantages include possible paresthesia or injury to the paravertebral somatic nerve. Complications include epidural or subarachnoid injection, somatic nerve block, and retroperitoneal injection.
Bibliography
Moore D: Regional Block, Springfield, Charles C. Thomas, 1981,
p.211-218.
Cousins MJ, Bridenbaugh P: Neural Blockade. Philadelphia, Lippincott, 1998,
p 55-92.
Saldman S, Winnie A: Interventional Pain Management. Philadelphia, WB Saunders,
1996, p 354-356.
Jerry Berger, MD
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