Oscar A. de Leon-Casasola, MD, Department of Anesthesiology, Roswell Park CancerInstitute, Buffalo, NY.

Abstract and Introduction
Abstract
Background: Patients with pain caused by cancer frequently experience visceral pain. In addition to oral pharmacologic therapy to manage pain, neurolytic blocks of the sympathetic axis are also effective in controlling visceral cancer pain.
Methods: Four types of neurolytic blocks (interpleural phenol, celiac plexus, superior hypogastric plexus, and ganglion impar) used in the treatment of visceral cancer pain are reviewed.
Results: Several studies have documented the efficacy of neurolytic blocks in reducing pain intensity and opioid consumption. However, the narrow risk-benefit ratio associated with neurolysis techniques requires knowledge of the implications associated with the different neurolytic blocks to minimize undesirable effects.
Conclusions: Neurolysis of the sympathetic axis has been shown to be an effective and safe approach to treat visceral pain in cancer patients and should be incorporated in the armamentarium of the pain specialist as a useful adjunct to oral pharmacologic therapy.

Introduction
Pain associated with cancer may be somatic, visceral,or neuropathic in origin. Approximately 50% of cancer patients experience a combination of paintypes at the time of diagnosis. Stretching, compressing,invading, or distending visceral structures can result in a poorly localized noxious pain. Patients experiencing visceral pain often describe the pain as vague, deep,squeezing, crampy, or colicky. Other signs and symptomsinclude referred pain (eg, shoulder pain thatappears when the diaphragm is invaded with tumor)and nausea/vomiting due to vagal irritation.

Visceral pain associated with cancer may be relieved with oral pharmacologic therapy that includes combinations of nonsteroidal anti-inflammatory drugs(NSAIDs), opioids, and coadjuvant therapy. In additionto pharmacologic therapy, neurolytic blocks of thesympathetic axis are also effective in controlling visceralcancer pain and should be considered as important adjuncts to pharmacologic therapy for the relief ofsevere pain experienced by cancer patients. These blocks rarely eliminate cancer pain because patients frequently experience coexisting somatic and neuropathic pain as well. Therefore, oral pharmacologic therapy must be continued, albeit at lower doses. The goals of performing a neurolytic block of the sympatheticaxis are to maximize the analgesic effects of opioid ornonopioid analgesics and reduce the dosage of theseagents to alleviate side effects.

Since neurolysis techniques have a narrow risk-benefitratio, undesirable effects due to neurolytic blockscan be minimized with sound clinical judgment and byassessing the probable effect of the technique on eachpatient. A detailed description of the techniques forthese blocks is beyond the scope of this review but isavailable elsewhere.^[1] This report describes several differentapproaches to achieve neurolysis, including theinterpleural phenol block, celiac plexus block, superiorhypogastric block, and ganglion impar block.

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Cancer Control 7(2):142-148, 2000. © 2000 H. Lee Moffitt Cancer Center and Research Institute, Inc