Fast Fact and Concept #97: Blocks of the sympathetic axis for visceral pain

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Title: Fast Fact and Concept #97: Blocks of the sympathetic axis for visceral pain

Author(s): Gary M. Reisfield, M.D. and George R. Wilson, M.D.

The sympathetic nervous system is present along the length of the axial skeleton; most of the various plexi and ganglia are readily accessible to percutaneous interruption. In the palliative care setting, the most common indication for interrupting the sympathetic axis is to control pain arising from malignancies of the abdomino-pelvic viscera. Visceral pain is often described as constant, deep and is difficult to localize and characterize. When such a pain syndrome is recalcitrant to meticulous application of drug and behavioral therapy, or if the patient is intolerant to drug therapy, consultation should be sought for consideration of anesthetic and neurolytic procedures. In particular, the following procedures have an established record of success in well-selected patients.

  1. Celiac plexus block. Used for upper abdominal pain, most commonly for pancreatic cancer pain; it is also appropriate for pain involving the GI tract from the distal third of the esophagus to the transverse colon, the liver and biliary tract, the adrenals and mesentery.
  2. Superior hypogastric plexus block. Applicable to malignant pain of the gastrointestinal tract from the descending colon to the rectum, as well as the urogenital system.
  3. Ganglion impar block. Pain involving the rectum and perineum.

These procedures are performed under radiographic guidance (fluoroscopy or CT) to prevent damage to nearby organs, vessels and spinal cord. Initially, a diagnostic/prognostic block is performed using local anesthetic; the analgesic response is assessed by patient and physician. Note: an analgesic response to a diagnostic block is the only pathognomonic test for success. If the response is satisfactory, a therapeutic neurolytic block is performed with ethyl alcohol or phenol. Neurolytic blocks may provide several months of analgesia and may be repeated. The diagnostic and therapeutic blocks are usually separated by at least a day in order to fully assess the response; however, logistical difficulties or extremely debilitated patients occasionally warrant performance of both blocks on a single occasion.

Contraindications to these procedures include bleeding diathesis and local infection. Side effects referable to loss of sympathetic tone may include transient hypotension and increased intestinal motility. Complications include needle injury to visceral, neural and vascular structures, pain at the injection site, and failure to obtain an analgesic response.

Crucial to the success of sympatholysis is professional expertise, in terms of both patient selection and technical excellence, Sympathetic blocks are not a panacea and generally do not obviate the need for ongoing pharmacological management of the remaining nociceptive and neuropathic pain components. However, they can substantially improve analgesia and quality of life, and may allow for opioid dosage reduction. Note: attempts at post-block opioid reduction should be done with care to avoid unmasking existing nociceptive/neuropathic pain and precipitating opioid withdrawal. Potential advantages of a neurolytic procedure, compared to spinal and epidural anesthetic techniques, include cost savings and avoidance of hardware (e.g. catheters, tubes, pump), which can be cumbersome and are subject to malfunction, and pose an infection risk.


Waldman SD (ed.): Interventional Pain Management. 2nd ed. Philadelphia: WB Saunders Company, 2001.

De Leon-Casasola OA: Critical evaluation of chemical neurolysis of the sympathetic axis for cancer pain. Cancer Control. 2000;7(2):142-148.

Plancarte R, Velazquez R, Patt RB: Neurolytic blocks of the sympathetic axis. In: Patt RB. Cancer Pain. Philadelphia: JB Lippincott Company, 1993:377-425.

Copyright/Referencing Information: Users are free to download and distribute Fast Facts for educational purposes only. Citation for referencing: Reisfield GM and Wilson GR. Fast Facts and Concepts #97. Blocks of the sympathetic axis for visceral pain. August 2003. End-of-Life Physician Education Resource Center www.eperc.mcw.edu.

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Creation Date: 8/2003

Format: Handouts

Purpose: Instructional Aid, Self-Study Guide, Teaching

Training: Fellows, 3rd/4th Year Medical Students, PGY1 (Interns), PGY2-6, Physicians in Practice
Specialty: Anesthesiology, Emergency Medicine, Family Medicine, General Internal Medicine, Geriatrics, Hematology/Oncology, Neurology, OB/GYN, Ophthalmology, Pulmonary/Critical Care, Pediatrics, Psychiatry, Surgery
Non-Physician: Nurses

ACGME Competencies: Medical Knowledge, Patient Care

Keyword(s): Addiction, Chronic non-malignant pain, Controlled substance regulations, Pain, Pain assessment, Pain treatment

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