The Massachusetts General Hospital Handbook of Pain Management
May C. M. Pian-Smith
In any path of study, knowledge never comes entirely at once but piecemeal. Truth presents herself in fragmentary form, and we put pieces together.
I. The growing significance of complementary therapies
II. Classical and modern mechanisms of acupuncture
III. The scientific basis of the acupuncture effect
IV. Suitability, efficacy, and safety of acupuncture
I. THE GROWING SIGNIFICANCE OF COMPLEMENTARY THERAPIES
There is increasing patient demand for, and acceptance of, “unconventional” therapies. It is now incumbent on healthcare practitioners to have knowledge of complementary therapies and to understand their clinical implications. In a national survey published in the Journal of the American Medical Association in 1998, Eisenberg and colleagues found that 42% of American adults use some form of “unconventional” therapy. The number of visits for alternative therapy was 629 million in 1997, which far exceeded the number of visits to all primary care physicians that year, totaling 386 million. That year, the total expenditure for complementary therapy was estimated to be $27 billion, compared to out-of-pocket expenditures for conventional care of $29 billion. Back pain, headache, depression, and anxiety were the main clinical entities for which people were interested in pursuing unconventional therapies. The survey also revealed that most patients do not inform their regular physicians when they seek help outside the realm of standard medical care.
The United States government has made several initiatives in response to the evolving acceptance of unconventional therapies in Western medical practice. In 1996, the U.S. Food and Drug Administration relabeled acupuncture needles as medical equipment rather than experimental equipment. The marketing and use of acupuncture needles is therefore now under the same strict quality control standards that are demanded for medical needles, syringes, or surgical scalpels. In 1997, the National Institutes of Health (NIH) convened a consensus conference on acupuncture. The NIH Consensus Statement on Acupuncture concluded that sufficient evidence exists to support the efficacy of acupuncture for postoperative and chemotherapy-induced nausea and vomiting, nausea of pregnancy, and postoperative dental pain. The conference panel also determined that acupuncture may be an effective adjunctive therapy for other conditions, including addiction, headache, low back pain, asthma, and carpal tunnel syndrome. The NIH Office of Alternative Medicine has since been expanded to the Center for Complementary and Alternative Medicine. A 1998 survey revealed that alternative medicine coursework is now offered at 75 American medical schools. As an indication of how complementary therapies are being integrated into regular medical practices, there has been reevaluation of third-party reimbursements for these alternative therapies, and more insurance plans are covering these services.
II. CLASSICAL AND MODERN MECHANISMS OF ACUPUNCTURE
Acupuncture is a medical practice that has been used for about 3,000 years. Acupuncture methods promote natural healing and functional restoration. This is achieved by inserting very thin needles, and sometimes applying manual stimulation, heat, or electrical stimulation, at very precise acupuncture points.
There are many hundreds of acupuncture points located over the entire body. Some of the points are theoretically connected with one another energetically. According to classical Chinese teachings, channels of energy (“qi”) run in regular patterns through the body and over its surface. These energy channels are called meridians and are analogous to rivers that irrigate and nourish the body’s tissues. Disease and pain are thought to reflect imbalances in the flow of energy, with energy deficiencies occurring in some areas and energy excesses in others. The principal meridians are named after organ systems and are often linked to one another on the basis of having either complementary or opposing effects. The meridians can be influenced by needling of acupuncture points; the needles can unblock obstructions and/or allow excess energy to be dissipated and thus correct imbalances.
Different acupuncture traditions trace roots back to various regions in Asia as well as Europe. On the basis of the traditions or beliefs of a particular acupuncture school (e.g., Traditional Chinese Medicine, Five-Elements theory, Korean Hand acupuncture, scalp or ear acupuncture, Japanese acupuncture, and the French energetics system), various acupuncture points are selected and manipulated in different ways. Points might be selected on the basis of the clinical symptoms to be treated, because of intrinsic properties or the “spirit” of the points, or because of their location in a theoretical energy pathway or network. Once needled, the points can be stimulated to either add energy to a depleted system or to dissipate excess energy. Heat or electrical (electroacupuncture) stimulation can be used to tonify, or add energy to, acupuncture needles; alternatively, heat energy, from a heat lamp or from burning herbs (moxa), can be applied over acupuncture points even in the absence of needling. In many acupuncture traditions, the elicitation of “deqi” sensation, an achy, warm, tingly, or swollen feeling at the needle insertion site, is thought to be necessary for therapeutic effect.
III. THE SCIENTIFIC BASIS OF THE ACUPUNCTURE EFFECT
Since the 1970s there has been a great deal of laboratory research to elucidate a more “scientific” basis for acupuncture’s effects. Neurophysiologic data support the efficacy of acupuncture for painful syndromes. In summary, the central nervous system, peripheral nerves, various endorphins, and monoamine neurotransmitters have all been implicated in the process. Different types of acupuncture stimulation (depending on the location of the needle and its relationship to the site of pain, and depending on the electrical frequency with which the acupuncture needles are stimulated) elicit different mechanisms of pain inhibition.
In the most widely accepted acupuncture model, needling of nerve fibers in the muscle sends impulses to the spinal cord and then activates three centers: (1) areas of spinal cord, (2) the midbrain, and (3) the hypothalamus-pituitary system. The spinal cord site uses enkephalin and dynorphin to block incoming messages during electroacupuncture at low frequency (2 to 4 Hz). Other neurotransmitters (e.g., gamma-aminobutyric acid, or GABA) are stimulated with high-frequency acupuncture stimulation (on the order of 50 to 500 Hz).
The midbrain uses enkephalin to activate the raphe descending system, which inhibits spinal cord pain transmission by a synergistic effect of monoamines, serotonin, and norepinephrine. The midbrain also has a circuit that bypasses the endorphin steps during high-frequency electroacupuncture. At the hypothalamuspituitary level, the pituitary releases B-endorphin into the blood and cerebrospinal fluid (CSF) to cause analgesia at a distance. The hypothalamus also sends long axons to the midbrain, and via B-endorphin, it activates the descending analgesia system. This center is not activated at high frequency but with low-frequency electroacupuncture stimulation.
The following findings (coming from several laboratories) support the role of endorphins during some forms of electroacupuncture:
The acupuncture effect is not immediate; rather, analgesia occurs after a 20- to 30-minute induction period, as might be expected with a humorally mediated mechanism.
Analgesia persists 1 to 2 hours after the cessation of acupuncture.
Naloxone and other opiate antagonists inhibit acupuncture analgesia.
Animals genetically deficient in opiate receptors or deficient in endorphins show poor acupuncture analgesia.
Endorphin levels rise in the blood and in the CSF during acupuncture.
Acupuncture effects are enhanced by inhibitors of endorphin enzymatic degradation.
Acupuncture analgesia can be transferred to a second animal via CSF transfer or blood cross-circulation between two animals, and this effect is blocked by naloxone given to either animal.
On the other hand, during high-frequency electroacupuncture, it seems that other neurotransmitters (e.g., serotonin and norepinephrine) mediate the effects. This is supported by the following findings:
Under these conditions, there is a rapid onset of analgesia, without a long induction period.
When lesions are made in parts of the brain that are rich in serotonin-releasing cells (e.g., in the raphe magnus of the brainstem and the medial medulla oblongata), acupuncture-induced analgesia is abolished.
Agents that block biosynthesis of serotonin (e.g., parachlorophenylalanine) block acupuncture analgesia.
Agents that block serotonin receptors also block acupuncture.
Analgesia is enhanced when serotonin levels are increased.
Norepinephrine has also been implicated in studies showing inhibition of acupuncture’s effects with yohimbine and phentolamine.
A recent study from Massachusetts General Hospital reported the use of functional magnetic resonance imaging (fMRI) to investigate the effects of acupuncture in the brain. This study provides a foundation for future studies on mechanisms of acupuncture as a therapeutic intervention. Functional MRI signals are thought to reflect changes in metabolic activity or blood flow. The results of this study suggest that acupuncture needling modulates the activity of the limbic system and subcortical structures. Further studies are underway to correlate signal changes with changes in pain thresholds.
IV. SUITABILITY, EFFICACY, AND SAFETY OF ACUPUNCTURE
Diehl and colleagues recently conducted a survey of American physicians who use acupuncture as well as conventional therapies in their practice. The study estimated that there are about 3,000 physician acupuncturists in the United States. These physicians choose acupuncture over conventional therapy most often for low back pain, myofascial pain, simple headache, sciatica, and shoulder pain. Reasons for using acupuncture in these settings included efficacy of acupuncture and failed or inadequate standard medical therapy.
Many benefits of acupuncture are reported in the literature; the World Health Organization (WHO) has published a list of clinical indications for which acupuncture may be helpful that includes illnesses involving virtually every organ system. Despite these reports, there is little support from randomized controlled trials (RCTs), and there are several impediments to conducting RCTs of acupuncture. True blinding of either the patient or the treating acupuncturist is clearly impossible. At the same time, controversy surrounds the development of appropriate controls for acupuncture studies, as even nonspecific needling (i.e., not at recognized acupuncture sites, or not site specific for the disease in question) can elicit responses that may be similar to the response to active treatment. Most of the published reports about clinical applications of acupuncture are case reports or case series. In many cases, individual subjects have served as their own historical controls. Very few studies include long-term follow-up data. It has been difficult to make generalized conclusions based on the results of different studies because of the variation in acupuncture points used for a given clinical condition, the mode of needle stimulation, variations in treatment duration and intervals between treatments, and variations in electrical frequency where electroacupuncture was employed.
The effectiveness of acupuncture for managing the pain of primary dysmenorrhea was demonstrated in a randomized clinical study by Helms in 1987. Forty-three women were followed for a year, and they were allocated to receive weekly acupuncture for three menstrual cycles (n = 11), weekly sham acupuncture (at random points; n = 11), weekly visitations but no acupuncture (n = 11), or no intervention (n = 10). There was an improvement in dysmenorrhea in 10 patients in the real acupuncture group (90.0%), 4 in the sham acupuncture group (36.4%), 2 in the visitation control group (18.2%), and 1 in the no care group (10%). The improvement in the group receiving real acupuncture was significantly better than all other groups combined (p < .001) and there was a 41% reduction in analgesic medication used by the women who received acupuncture.
The efficacy of electroacupuncture for low back pain was described by Ghoname in 1999. Sixty adults with chronic low back pain associated with degenerative disc disease were studied in a randomized, single-blind, sham-controlled cross-over study. Four therapeutic modalities, percutaneous electrical nerve stimulation (PENS, a form of electroacupuncture), sham PENS, transcutaneous electrical nerve stimulation (TENS), and physical therapy were each given for a period of 30 minutes three times per week for 3 weeks. PENS was significantly more effective in decreasing pain scores after each treatment than sham PENS, TENS, or physical therapy. The average daily oral intake of nonopioid analgesics was decreased by PENS significantly more than by sham-PENS, TENS, or physical therapy (p < .008). The majority of study patients (91%) reported that PENS was most effective in decreasing their low back pain. The PENS therapy was also significantly more effective in improving physical activity, quality of sleep, and sense of wellbeing (p < .05 for each).
Several notable studies have been done on acupuncture that do not relate directly to pain, but they are so beautifully designed and controlled that they warrant mention. For example, Dundee and colleagues have published many reports of studies in which acupuncture was effective for management of chemotherapy-induced nausea and vomiting. In one illustrative study, statistically significant differences were found in a small sample of 10 men undergoing cisplatin therapy for testicular cancer. Patients were treated with electroacupuncture stimulation at MH-6 (on the ventral wrist) or with electroacupuncture at a dummy point on the arm. The patients were then asked to rate their nausea on a scale of 0 to 4 (4 being maximal relief of symptoms). The group receiving real electroacupuncture gave a mean score of 3.76, compared to 1.6 for the control group (p < .001).
Cardini and colleagues reported in 1998 the results of a study carried out in the People’s Republic of China in which moxibustion (burning of herbs near the skin) over an acupuncture point on the fifth toe resulted in version of breech fetus presentation. Specifically, 260 healthy primigravida women at 33 weeks gestation and with breech fetuses were randomized to two groups. One group received daily moxibustion therapy and the other group received no special intervention. Two weeks later, at 35 weeks gestation, 75% of those who had received moxibustion had fetuses that had flipped to the head-down position, compared to 48% in the control group (p < .001). The results correlated with an increased number of fetal movements perceived by the mothers (48 movements per hour in the treatment group versus 35 movements per hour in the control group; p < .001). Although the subjects were not blinded to the treatment, the level of significance of the results, and the potential impact on rates of cesarean sections and birth complications, makes this an important study.
Acupuncture, properly performed, is a procedure that is rarely associated with complications. The most common include minor bruising or a transient vasovagal response that responds quickly and completely to body repositioning. When sterile, disposable needles are placed carefully and skillfully, complications such as transmission of infection, nerve injury, and pneumothorax are avoided.
Acupuncture therapy can play an important role as part of a multidisciplinary approach to the management of chronic and acute pain. Analgesia is thought to be mediated by the activation of several pathways involving neurotransmitters and hormones. Alterations in neurotransmitter handling, or “balancing of energy,” are thought to also affect associated symptoms of fatigue and depression, and to improve the overall sense of well-being. Physician acupuncturists cite the following reasons for choosing acupuncture:
Useful adjunct to standard care
Use as part of a multidimensional, holistic, mind–body–spirit approach
Preferred by some patients
Avoidance of side effects and complications of standard treatments
Worth trying when standard therapies have failed
Acupuncture has become increasingly popular in the West as people of Western culture become more familiar with the customs and cultures of the East, and as the healing qualities of acupuncture and other Eastern therapies are recognized. Acupuncture has a very long history of success in the East, but we are still learning the scientific basis of its effects, how it interacts with conventional therapies, and how effective it is in Western patients.
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