A substantial proportion of cancer patients have moderate to severe pain. Cancer pain is multifactorial and could be related to the disease process, metastasis, or treatment modalities. The World Health Organization's (WHO's) three-step “analgesic ladder” provides guidelines for pharmacologic management of cancer pain and is probably the most widely used in the clinical setting.1
Application of these guidelines provides good pain relief in approximately 80% to 90% of patients with cancer pain.2 It has been suggested that a fourth step—“interventional techniques”—should be considered in these patients, who do not get adequate pain relief from medication management.3,4
With few exceptions, noninvasive analgesic approaches should precede invasive treatments. Among these exceptions are palliative radiotherapy for pain at the site of a long bone metastasis or an isolated brain metastasis and celiac block for a patient with pancreatic or other retroperitoneal tumor who presents with pain. These procedures are designed to improve analgesia or minimize analgesic side effects. Most are intended for pain that is localized to a nerve or plexus distribution. Because of their complexity, risk, and cost, invasive procedures are reserved for patients with intractable pain despite full application of the WHO guidelines1 and those with intolerable side effects from systemic pharmacologic pain treatment. However, it is important not to delay excessively when conventional pharmacologic management appears inadequate. Referral to a multidisciplinary pain clinic might be considered early in the course of cancer pain management to optimize current pharmacologic, psychological, and physical management techniques and to educate the patient, family, and referring physician about pain progression and future treatment options.
INTERVENTIONAL PAIN MANAGEMENT PROCEDURES
Somatic and neuropathic pain localized to a single nerve, plexus, or dermatome distribution is amenable to local anesthetic block of the nerve. Although pain relief is often dramatic, the longest lasting local anesthetics wear off within 1 day. To prolong the effect of local anesthetics, anesthesiologists may insert a catheter for continuous delivery to a nerve or plexus. The brachial plexus and femoral nerve sheath are the usual sites of peripheral catheter placement. Maintenance of peripheral catheters is difficult because movement may easily displace them.
SOMATIC NEUROLYTIC BLOCKS
Neurolytic blocks are often performed after a successful local anesthetic block to extend relief for weeks to months.5,6 Because neural disruption causes motor, sensory, and autonomic dysfunction, these blocks are reserved for those who cannot get relief by other means. Phenol and ethanol are the most popular agents for chemical neurolysis. Both agents cause extensive damage to the neuron. Subsequent inflammation and fibrosis of the nerve and adjacent tissues may cause secondary neuralgic pain.7 Radiofrequency neurolysis coagulates nerves by heating a small area around the tip of a needle-shaped probe. The size and shape of the lesion are more controlled than with chemical neurolysis, ...