Abstract
Acupuncture (AP) is widely practiced for acute and chronic pain management. National Institute of Health (NIH) consensus statement in 1997 demonstrated favorable results of AP treatments in postoperative pain, chemotherapy nausea and vomiting, and postoperative dental pain, or applicable as adjunct option in various comprehensive medicine programs.
AP may modulate pain pathways by activating a mixture of bioactive chemicals through peripheral, spinal, and supraspinal mechanisms, and potentially reversing neuroplasticity in animal experimental models.
Clinical studies on the efficacy of AP treatments supported more temporary benefits. AP is most likely to provide improvement in neck pain, tension headache, migraines, and pain from osteoarthritis of the knee and low back. Other encouraging but less conclusive results are seen in myofascial pain, fibromyalgia, functional bowel disorders, premenstrual syndrome, dysmenorrhea, and pregnancy-related conditions. The criteria of frequency and duration of AP treatments to achieve the ultimate efficacy has not reached widespread consensus yet.
The precautions for adverse effects of AP may include vasovagal responses (nausea, pallor, dizziness, and syncope), drowsiness, generalized fatigue, and needle discomfort in the initial stage. Less common but more critical events, such as bleeding, hematoma, and pneumothorax, would need judicious evaluation and appropriate treatment.
The existing literature on AP consists of case studies, systematic review, and meta-analysis. There is increased interest in future translational studies based on exciting advances in bench research. The integration of AP to augment multimodal analgesia might reduce the adverse effects related to polypharmacy in conventional pain management.
Keywords
acupoints, acupuncture, complementary and alternative medicine, electro-acupuncture, meridians, neuromodulation
Acupuncture (Jin jiu) is an essential component of traditional Chinese medicine (TCM). The term acupuncture comes from the Greek words acus (needle) and punctura (puncture). Scientific evidence has demonstrated the physiologic effects of acupuncture (AP) and electro-acupuncture (EA) stimulation over the last four decades. AP consists of mechanical stimulation via needle insertion and thermal input by Moxa (a Chinese herb) or by a heat lamp applied over the needles (moxibustion [Mox]).
History and Theories
The history of AP can be traced back over 3000 years with origin in China. The first written medical text on AP was in the Huang Di Nei Jing (The Yellow Emperor’s Internal Classic) written by Chi Po around 2nd century BC. AP became well publicized in the Western world thanks to New York Times’ writer James Reston’s article in 1971. He described his first-hand experience of AP during the emergency appendectomy and perioperative care while accompanying President Nixon on a visit to China.
Theories: Taoist philosophy underlies the hypothetical framework of AP. Tao (way) was described by Lao-tse in the Tao Te Ching around 500 BC, which assumed nature is constantly changing. Tao is the source of all creation and acts through two opposing but balancing forces: the yin and the yang. Yin refers to dark, cold, rest, passivity, inward, decrease, wet, and female. Yang refers to bright, hot, activity, outward, increase, dry, and male. People exist within the tensions created by these two forces in a dynamic interaction with nature. Illness occurs when yin and yang fall out of balance and harmony. AP restores the balance by promoting yin and yang energy within organ systems.
The concept of qi (vital energy) is fundamental to the practice of classic AP. Qi is the energy that flows through different “meridians” or channels that connect the internal body with the external environment. There are different types of qi that serve functions such as hereditary, protective, and nourishing energy. The network of meridians runs throughout the body while each meridian is associated with an organ system. There are 12 paired principal, 2 unpaired, and 8 extra meridians. Obstruction of qi may result in disequilibrium of yin and yang that may manifest as pain or illness. The meridians emerge at the surface of the body via AP points (acupoints) where external stimulation may modulate the qi.
There are six pathologic factors that cause disease such as wind, cold, heat, dampness, dryness, and fire in TCM. There are four steps in the assessment of a patient’s symptoms: observation; listening and smelling; palpation; and history taking. The goal is to assess balance of yin and yang, and to gain insight into other symptoms. There are eight diagnostic principles for classifications of symptoms including yin or yang, external or internal, cold or hot, and deficiency or excess.
There are more than 361 established AP points (acupoints) that distribute along the meridians. Acupoints are sites of low skin resistance and are accessible for stimulation. Acupoint is identified by its meridian, a Chinese name, and number. Acupoints are located through anatomic landmarks such as bony structures, muscles, and external features. The “cun” is a defined unit of measurement to locate acupoints via specific landmarks. “Cun” is the distance between the joint creases of interphalangeal joints of a patient’s flexed middle finger or equivalent to the width of a patient’s thumb.
Meridians, Acupoints, and Myofascial Trigger Points
Melzack et al. reported a remarkably high degree (71%) of correlation between myofascial trigger points and acupoints on the basis of two criteria: spatial distribution and the associated pain pattern. This close correlation suggests that trigger points and acupoints for pain, though discovered independently and labeled differently, represent the same phenomenon and can be explained in terms of the same underlying neural mechanisms. Dorsher updated references and confirmed the conceptual comparison of trigger points to acupoints in pain and clinical correspondence was likely 95% or higher. Although separated by 2000 years, the AP and myofascial pain traditions have fundamentally clinical similarities in the treatment of pain disorders.
Dorsher examined whether myofascial referred-pain data can provide independent physiologic evidence of AP meridians. Trigger point regions were subdivided from previously validated trigger point region-classical acupoint correspondence results into subsets according to the 12 AP organs and their anatomically corresponding acupoints. For all 12 subsets of trigger point regions, their summed referred pain patterns accurately predicted the distributions of corresponding AP meridians, particularly in the extremities. Dorsher demonstrated that myofascial referred pain data may provide the physiologic evidence of AP meridians.
Technique
No consensus exists about which technique of needle insertion in AP is most favorable or efficacious. Positions of patients may include prone or supine to allow adequate access and optimal comfort. A lateral decubitus or sitting position may also work. The skin is wiped with an alcohol pad and stretched prior to needle insertion to minimize discomfort. Tubular guides can assist needle insertion. The usual angle of insertion is perpendicular or oblique. More horizontal insertion is often used over face and chest.
The selection of acupoints may follow various schools of AP. Tender or trigger points are used as local acupoints. Distal points are selected according to involved meridians. The insertion of the needle is usually accompanied by “de qi” (obtaining qi) described as soreness, heaviness, and numbness around the site. There is a feedback as if surrounding tissue were grabbing and holding the needle that confirms accurate placement. The disposable stainless steel needle consists of a body or shaft with a handle. Common sizes are 30–32 gauge with lengths ranging from 20 to 125 mm. Manipulation of the needle depends on either excess or deficiency state of the qi. AP stimulation can be accomplished manually or with EA stimulators. Mox or a heat lamp may be applied over needles. Patients need to avoid strenuous activities since generalized fatigue occurs in the beginning of AP treatment.
Mechanism of Acupuncture Analgesia
There are three domains (neurohumoral, neuromodulation, and neuroimaging) of scientific evidence ( Box 60.1 ).
- 1.
Manual acupuncture (MA) caused suppression of mRNA expression of pain-related genes (fos, opioid receptor-like 1, tachykinin receptor 1, mu-opioid receptor, and 5-hydroxytryptamine receptor 2A) in spinal cord and enhanced antinociceptive effect on formalin-induced pain in a rat model.
- 2.
Gate-control theory (Melzack and Wall) of pain describes the modulation of sensory nerve impulses by inhibitory mechanisms in the central nervous system.
- 3.
Electro-acupuncture (EA) of 2 Hz accelerates the release of encephalin, beta-endorphin, and endomorphin, while EA of 100 Hz selectively increases the release of dynorphin.
- 4.
EA may modulate pain via activation of bioactive chemicals (monoamines such as serotonin and norepinephrine in addition to opioids) through peripheral, spinal, and supraspinal mechanisms.
- 5.
MA induced specific “de qi” response and its association with distinct nerve fibers via functional magnetic resonance imaging (fMRI) study in contrast to sham control with tactile stimulation.
- 6.
Acupuncture (AP) yielded broad deactivation in limbic system, pain status, and default mode network (DMN) and evoked activations in attentional and somatosensory systems via fMRI study in subjects with acute low back pain (LBP).
- 7.
AP induced more deactivations and less activation via fMRI study as compared with sham control. AP may modulate multiple brain networks beyond somatosensory-guided mind-body therapy according to fMRI study in subjects with acute LBP.
- 8.
AP restored less connectivity within the DMN in the dorsolateral prefrontal cortex, medial prefrontal cortex, anterior cingulate gyrus, and precuneus via fMRI study in chronic LBP subjects. The reductions in clinical pain were correlated with increases in DMN connectivity.
Neurohumoral and Neuromodulation Data
Pomeranz proposed that AP appears to cause release of various endorphins and monoamine neurotransmitters in both peripheral and central nervous systems (CNS). AP activates sensory nerve fibers in muscles and sends signals to the spinal cord. This activates other centers in midbrain and the hypothalamic–pituitary axis that cause release of neuropeptides. Enkephalin and dynorphin are released at the level of the spinal cord and may block afferent pathways. Enkephalin produced at midbrain may stimulate the inhibitory raphe descending system and release the monoamines serotonin and norepinephrine. These neurotransmitters may further modulate pain transmission in the spinal cord. Beta-endorphin released from the hypothalamic–pituitary axis may result in analgesia through both systemic circulation and cerebrospinal fluid.
To apply appropriate AP stimulation, different needle manipulation techniques are required. These manipulations are performed in many ways such as twirling the needle or varying the insertion angle. Kim et al. designed a study to evaluate the antinociceptive effect of these manipulations to acupoint ST36 on formalin-induced pain in rats. Several pain-related gene expressions were investigated in the spinal cord using reverse transcriptase-polymerase chain reaction analysis. Needle manipulation suppressed the mRNA expression of pain-related genes such as fos, opioid receptor-like 1, tachykinin 1, tachykinin receptor 1, mu-opioid receptor, and 5-hydroxytryptamine receptor 2A in the spinal cord. The authors proposed that needle manipulation enhanced analgesia by suppression of the transcription of pain-related genes. The growing popularity of the gate-control theory of pain by Melzack and Wall led to electrical stimulation therapies and development of the transcutaneous electrical nerve stimulation (TENS) unit. Electrical stimulation has been frequently employed for needle stimulation in EA and related techniques. Han et al. demonstrated that EA of 2 Hz accelerates the release of enkephalin, beta-endorphin, and endomorphin, while EA of 100 Hz selectively increases the release of dynorphin. A combination of the two frequencies produced simultaneous release of all four opioid peptides resulting in maximal therapeutic effects. Zhang et al. summarized that EA activates the nervous system differently in health and in various pain conditions, alleviates both sensory and affective inflammatory pain, and inhibits inflammatory and neuropathic pain more effectively at 2 and 10 Hz than at 100 Hz. They suggested that EA may modulate pain by activating a mixture of bioactive chemicals (opioids, serotonin, and norepinephrine) through peripheral, spinal, and supra-spinal mechanisms.
Neuroimaging Data
Updates in biophysiologic and imaging techniques offer enhanced evaluation of the sequential events following AP-induced stimulation. Functional magnetic resonance imaging (fMRI) is a noninvasive technique that depends on differences in relative concentration of oxygenated to deoxygenated hemoglobin within the brain in response to stimuli. AP stimulation elicits “de qi,” a composite of unique sensations that are essential for clinical efficacy according to TCM. Manual acupuncture (MA) was performed in randomized order during fMRI in 42 AP naïve healthy adult volunteers. The most significant differences in de qi sensations between AP and tactile stimulation (sham) control were observed with aching, soreness, pressure, and dull pain. Hui et al. provided scientific data on the characteristics of de qi response in AP and its association with distinct nerve fibers. Shi et al. presented network response to AP in models of experimental acute low back pain (a LBP). As compared with the baseline, the pain state had higher regional homogeneity (ReHo) values in the pain matrix, limbic system, and default mode network (DMN) and lower ReHo values in frontal gyrus and temporal gyrus. AP yielded broad deactivation in subjects, including nearly all of the limbic system, pain status, and DMN, and also evoked numerous activations in the attentional and somatosensory systems. AP induced more deactivations and less activation in the subjects compared with sham. Shi et al. proposed that AP may modulate multiple brain networks beyond somatosensory-guided mind-body therapy. Li et al. studied 4-week AP in chronic low back pain (c LBP) with fMRI. Less connectivity within the DMN was found in c LBP than controls, mainly in the dorsolateral prefrontal cortex, medial prefrontal cortex, anterior cingulate gyrus, and precuneus. The DMN connectivity after AP was restored almost to the control levels. Reductions in clinical pain were correlated with increases in DMN connectivity. Li et al. proposed that imaging of the DMN may offer objective assessment of AP analgesia in c LBP.
Indications
The National Institute of Health (NIH) organized a conference of experts to evaluate the available literature in 1997. AP was widely practiced for treatment of postoperative and chemotherapy-related nausea and vomiting, and dental pain. Other promising results were seen in headache, low back pain (LBP), asthma, menstrual cramps, fibromyalgia, and myofascial pain. Wang et al. critically examined prospective randomized controlled trials (RCTs) and suggested that AP and stimulation were effective in the short-term management of LBP, neck pain, and osteoarthritis (OA) of the knee. Another group evaluated the Cochrane reviews that were concerned specifically with the effectiveness of AP for pain management. Four reviews concluded that AP is effective for migraines, tension-type headaches, neck disorders, and peripheral joint OA; one review failed to demonstrate effectiveness of AP for rheumatoid arthritis; and three reviews were inconclusive for shoulder pain, lateral elbow pain, and LBP.
Adverse Effects, Complications, and Medical Consent of Acupuncture
Witt et al. conducted a prospective AP study for OA pain of the knee or hip, LBP, neck pain or headache, allergic rhinitis, asthma, or dysmenorrhea. A total of 229,230 patients received an average of 10 AP treatments. There were 8.6% of patients who reported at least one adverse effect and 2.2% reported one that required treatment. Common adverse effects were bleeding or hematoma (6.1%), pain (1.7%), and vegetative symptoms (0.7%). Two patients experienced a pneumothorax and the longest duration of a side effect was 180 days. There was a proposed medical consent that consists of five modules: Introduction to AP and Mox, Risks of AP treatment, Conditions that can increase the risk, Doctor’s statement, and Consent. Witt et al. concluded that AP is a relatively safe treatment and a more detailed consent form could support both patients and professionals. Other investigators analyzed AP-related complications and adverse events in case reports published between 1980 and 2013 in China. There were 182 incidents identified in 133 relevant papers. Internal organ and nerve injury were the main complications of AP, especially pneumothorax and CNS injury. Adverse effects may also include syncope, infections, hemorrhage, allergy, burn, aphonia, hysteria, cough, thirst, fever, somnolence, and broken needles ( Box 60.2 ). The investigators proposed to standardize the practice of AP to minimize adverse events and to promote global popularity of AP treatment.
- 1.
Bleeding/hematoma
- 2.
Syncope
- 3.
Somnolence
- 4.
Aphonia
- 5.
Hysteria
- 6.
Central nervous system injury
- 7.
Pneumothorax
- 8.
Infection
- 9.
Broken needles
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