September 7, 2005
Reaching The Point Of Acceptance: How Does It Work?
Now that we’ve explored the philosophy behind acupuncture and some of those theories in practice, you may be wondering about the science behind the technique and if there is any clinical evidence of efficacy that will withstand modern Western scrutiny. The answer is a qualified “yes.” Some modern practitioners feel that at its most basic level, acupuncture is applied neurophysiology.
We may one day be able to explain acupuncture in those terms. Today, its mechanisms still are poorly understood by Western science; however, the body of anecdotal evidence supporting its effectiveness is overwhelming. One only has to watch surgery under acupuncture anesthesia to comprehend that something significant and unfamiliar to the Western way of thinking is going on. The World Health Organization concluded in 1979 that “acupuncture is clearly not a panacea for all ills; but sheer weight of evidence demands that acupuncture must be taken seriously as a clinical procedure of considerable value.” Acupuncture has had field tests, too. Some 4,000 years of application on a sizable segment of the world’s population makes acupuncture arguably the most widely practiced and thoroughly tested medical technique in history. In 1998 the American Veterinary Medical Association took this position in its “Guidelines for Complementary and Alternative Veterinary Medicine” approved by the American Veterinary Medical Association: “Veterinary acupuncture and acutherapy are considered an integral part of veterinary medicine. These techniques should be regarded as surgical and/or medical procedures under state veterinary practice acts. It is recommended that educational programs be undertaken by veterinarians before they are considered competent to practice veterinary acupuncture.” Besides acupuncture courses that currently are available, there also are some popular textbooks including “Veterinary Acupuncture” by Alan Klide and Shiu Kung. A more recent book is “Veterinary Acupuncture: Ancient Art of Modern Medicine.” For a more general, traditional Chinese medicine text suitable for the layperson, we suggest “Four Paws, Five Directions” by Cheryl Schwartz.
To understand how the theories of acupuncture translate to pain relief, it is necessary to know a little about how pain is transmitted and experienced by the body. Pain is a double-edged sword. On one hand it protects us from damage by warning us of harmful situations, but in chronic conditions it is as debilitating as the disease process itself. Abnormal chronic pain states are thought to result from damage within the pain pathway itself, either in the peripheral nerves or the central nervous system. The normal protective pain mechanism, which warns of impending or actual damage, is activated by mechanical, heat or other noxious stimuli impinging on pain receptors that then transmit the pain impulse to the CNS through afferent nerve fibers. Unlike other sensory input, pain recognition is subjective, and previous experiences can influence one’s perception of it. This is true of dogs, too, as some breeds generally are more stoic than others. Pain perception also is a function of sex as females have demonstrated a much higher pain threshold. How is this possible? It seems the body has its own pain-suppression mechanisms. This built-in analgesic system depends on the presence of endogenous opiates, which include endorphins. Most Western theories suggest acupuncture either instigates the production of these opiates or blocks pain transmission. Not unexpectedly, when East meets West and when philosophy meets science, confusion undoubtedly will occur. Similarly, when old meets new, questions of quackery from both sides will arise. Even in light of this, some Western theories have sought to explain the reported pain-relief benefits of acupuncture. One of those is the gate or inhibition theory, which proposes that pain is blocked by stimulating sensory neurons that travel faster than those that transmit pain. Several types of nerve fibers are involved in pain transmission. As mentioned before, there are three types of pain receptors. Stimuli received from the mechanical and thermal pain receptors are transmitted over large myelinated A-delta fibers at a speed close to 30 meters per second. Impulses received by the other type of receptors travel much more slowly on the C fibers at the rate of 12 meters per second. A-alpha fibers, which are necessary for the proper perception of where we are in three-dimensional space, i.e., where our feet are located, are found in muscles and joints. Alpha-beta neurons are involved in feeling light touch and the bending of hairs. A-alpha and A-beta fibers transmit nerve impulses many times faster than A-delta or C fibers. Acupuncture stimulation may induce nonpainful sensory information that travels along A-beta fibers. When the information reaches something called the inhibitory interneurons, it shuts a nerve transmission “gate” that blocks the conduction of the slower traveling A-delta and C fibers. The gate theory may account for some part of the mechanism of acupuncture analgesia, but it does not explain the delayed effects of treatment or the results of cross-circulation studies (studies in which the blood circulations of two animals were connected, and the procedure performed on one produced results in both). These factors are much better explained by the competing humoral theory, which states that acupuncture instigates the release of endogenous (developed from within) opiates that produce a self-induced analgesia. Some believe that acupuncture’s pain relief derives from a combination of the neurologic and humoral explanations. Another theory suggests acupuncture may have localized vasodilatation effects, which would explain the procedure’s benefits specific to musculoskeletal disorders. Dilated blood vessels are better able to eliminate pain-producing substances such as bradykinin (a substance released from blood plasma by some snake venoms and certain other enzymes that lowers blood pressure and triggers pain), prostaglandins and other inflammatory products. Another explanation is the autonomic theory, which maintains that internal organs can be stimulated by external acupuncture points that selectively excite parasympathetic and sympathetic nerves regulating the autonomic nervous system.28 Topping off this confusing mix of theories is the bioelectric theory, which suggests acupuncture meridians are like direct current pathways and acupuncture points function as amplifiers. What these theories have in common is the stimulation of acupuncture points via insertion of small needles, application of pressure, cupping (suction) and application of heat through moxibustion (which can be used to raise the temperature of the needles), or infrared, laser or electrical stimulation.
Interpreting Scientific Studies
Although the successes of acupuncture have been tested in practice throughout history and have attracted a following of practitioners and patients, rigorous scientific analysis of acupuncture trials has yielded mixed results. Unfortunately, there is no tight control of patient suitability/responsiveness or practitioner expertise, and even studies with statistical analyses may be flawed because of inappropriately small or nonrandom samples. One well-known text used to teach biostatistics to medical and veterinary students maintains that in general, major errors are made in the statistical treatment of data in at least 50 percent of all the papers submitted for peer review in journals. Significant efforts have been made to improve the validity of statistical inferences drawn in journal articles. Flaws in the statistical treatment of experimental data especially are damaging in clinical studies. Veterinarians and physicians consider their treatment options (including acupuncture) based on the outcomes of clinical trials. If erroneous conclusions are drawn from experimental data, the patient could be exposed to unnecessary risks, discomfort and expense. Worst of all, more efficacious treatment may be delayed or not even attempted. It is therefore important to read the claims made about acupuncture with a discerning eye. This is not to say the use of statistics is an invalid and unrecognized strategy, but be aware that errors can be made in both the experimental design and in the conclusions drawn, so what you read always must be questioned with those caveats in mind. Some detractors absolutely are convinced that acupuncture is little more than “nonsense with needles” and hope it will pass from the contemporary scene and fall into disuse like other obsolete treatments such as purging, leeching and bleeding. A lack of evidence, however, is not proof that a treatment is not effective. In the words of a colleague, “If there are no benefits derived from the process, acupuncture would have to be categorized as one of the longest playing scams in the history of mankind.”
Reaching The Point Of Acceptance: