Anesthesiologists Have Increasing Role in Managing Pain

NEW YORK—In recent years, the practicing anesthesiologist has become more involved in the management of pain and has to be aware of the increasing number of treatments available, said Carol A. Warfield, MD, chief, Division of Pain Services, Beth Israel Deaconess Hospital, Boston.

Speaking at the Third Conference on Pain Management and Chemical Dependency, Dr. Warfield addressed some of the more common problems seen in a multidisciplinary pain management center, including back, neck, neuropathic, and cancer-related pain. The conference was sponsored by the American Pain Society, the National Institute on Drug Abuse (NIDA), Beth Israel Medical Center, New York, and others.

Lower Back Pain

Lower back pain affects about four out of five people at some point in life and may be addressed through many treatment options, she said. Of the injection therapies, the most common is the epidural steroid injection.

“In discogenic disease, these injections will not only reduce the edema, but also reduce the patient’s pain,” Dr. Warfield said. Epidural steroid injections are most effective in patients with acute radiculop-athy and those with acute exacerbations of chronic pain. “Unfortunately, patients who have had previous back surgery do not do as well,” she added.

Use of an epi-duroscope offers the advantage of allowing the physician to visualize adhesions during an epidural injection. Unfortunately, the data have not supported that its use provides any better relief than a blind epidural injection. “However, when the role of the epiduroscope is further defined, it may serve as a diagnostic measure, defining situations in which surgical or other interventional techniques should be used,” Dr. Warfield said.

The selective nerve root block also allows the physician to identify the correct nerve root and can help identify which patients may be amenable to interven-tional surgical procedures, she said.

Discogram Technique

In the discogram, another technique for identifying the inflamed nerve root, a saline injection may mimic the patient’s usual pain. It is especially useful for the patient with axial low back pain, which is common among chronic back pain sufferers.

Many patients have had previous surgery that relieved the radicular pain component in their leg, but are left with the axial low back pain without radiation to the leg. “The discogram technique will help us determine which disks are involved and tell the surgeon whether the patient is a candidate for spinal fusion to prevent further irritation at the level of the disk,” Dr. Warfield pointed out.

Facet syndrome is a pain syndrome occurring particularly postsurgically. “It is a difficult diagnosis to make because there are no diagnostic techniques that are pathognomonic for it,” Dr. Warfield noted. A past study looking for predictive factors found that patients who had positive x-rays, CT scans, or MRIs, and had awakenings from pain, tenderness over a facet joint, and absence of positive straight leg raising, were the patients most likely to benefit from facet blocks.

Although most patients experience short-term relief from a series of facet injections, many do not get long-term relief, she said. A newer radiofrequency denervation technique offers longer term relief. The response has been generally good, although there are varying study findings.

“Many patients who have initial pain relief with this technique go on to experience long-term or permanent relief,” Dr. Warfield said.

In chronic regional pain syndrome (CRPS), patients will typically have burning and heightened aesthetic pain related to an over- or understimula-tion of the sympathetic nervous system. “These patients can be very dysfunctional, with severe hyperpathic pain,” Dr. Warfield said. CRPS type I, also called RSD (reflex sympathetic dystrophy), is not associated with major nerve trauma in contrast to CRPS type II, or causalgia, which does involve major nerve trauma. Among tests for CRPS are sympathetic blocks, she said. A series of such injections is usually enough to provide adequate pain relief.

In some circumstances, radiofrequency lesioning (or denervation) can help patients with RSD. Radiofrequency denervation may also be effective for those with intractable pain from vascular disease or other vascular problems in the lower extremities. Regional IV infusions of vasodilators have also been reported to offer long-term relief to some patients with hypersympathetic mediated pain syndromes.

Regarding neuropathic pain, Dr. Warfield noted several innovative techniques. Capsaicin (Zostrix), which depletes substance P from the nerve endings, has been used to treat burning neuropathic pain. Transcutaneous electrical nerve stimulation (TENS) has been particularly useful in neuropathic pain.

Spinal Cord Stimulation

Spinal cord stimulation effected via an externally placed transmitting device has been especially effective for patients with failed back syndrome or previous laminectomy, particularly when the patient has unilateral leg pain, Dr. Warfield said. The technique is also useful for ischemic limb pain, CRPS, and some types of neuropathic pain such as postamputation, spinal cord injuries, and postherpetic neuralgia.

“For patient’s who respond to spinal cord stimulation, this can really be a miraculous relief for their chronic pain,” Dr. Warfield commented.

A few patients who require long-term opioid treatment but cannot tolerate the intractable side effects of nausea and sedation may be candidates for spinally administered opiates. In a study of more than 1,200 chronic pain cancer patients, only 1% fell into this category. Catheters for epidural opiates can be internally or externally implanted, giving patients the freedom to receive treatment at home.

Targeting Neurotransmitters

Because endorphins are not the only neurotransmitters to mediate pain, many non-opioid drugs may be helpful. For example, agonists of serotonin, norepinephrine, GABA, and somatostatin can also be injected to provide pain relief independent of the opioid system.

Patients tolerant to opioids or those with neuropathic pain can benefit from injections of clonidine, the most common of these non-opioid drugs, Dr. Warfield observed.

Rounding out the list of useful approaches in chronic pain settings, Dr. Warfield included spinal alcohol blocks, other neurolytic blocks, cryoanalgesia, and a few neurosurgical procedures. She concluded with the reminder that proper patient evaluation is critical to correct treatment.