INTRODUCTION

To incorporate acupuncture as an effective medical procedure for pain management and trauma rehabilitation, health care practitioners need a basic understanding of needling mechanisms.

GENERAL PRINCIPLES OF HEALING PROCESS INDUCED BY ACUPUNCTURE NEEDLING

Researchers have accumulated an impressive amount of evidence of the cellular and molecular events underlying tissue response to needling. Clinical observation shows that acupuncture needling achieves at least four therapeutic goals:

Needling reduces bodily stress by stimulating the secretion of endorphins, relaxing the cardiovascular and muscular systems, and restoring the physiologic and autonomic balance (homeostasis), which includes normalizing visceral functions that are impaired during stressful assault via neurohormonal pathways.

Our clinical evidence shows that acupuncture is an effective modality in controlling inflammation. Needling and needle-induced lesions are foreign invaders to our body. Needling and its lesions stimulate and increase the number and the activity of immune cells and control the inflammatory process (see Chapter 4), which reduces both acute and chronic inflammation.

Needling promotes and accelerates soft tissue healing. Soft tissue includes nerves, muscles, connective tissues (tendons, ligaments, joint capsules, fascial coating of muscles), and some functional structures like blood and lymphatic vessels. Soft tissue damage may be caused by physical activities, injuries from accidents, or inflammation from repetitively overusing the muscles. In addition, almost all internal diseases, for example, asthma, gastritis, nephritis, and especially arthritis, cause discomfort, pain, or inflammation in superficial soft tissues. After acupuncture treatments, soft tissue inflammation and pain subside. Often internal diseases are alleviated or cured along with peripheral tissue healing.

Finally pain relief is achieved by homeostatic balancing and soft tissue healing in most cases, whereas immediate pain relief frequently happens even before tissue healing is complete.

NEEDLING AND DE QI SENSATION

Modern sterile stainless steel acupuncture needles with plastic guide tubes make needling safe, technically easy, and less painful. Needling, however, always produces a certain sensation. The nonpainful sensations produced by needling are traditionally called de qi (deh chee) in traditional Chinese medicine (TCM).

The needling process includes the following procedures:

During procedure no. 3, a needle can be manipulated by unidirectional or bidirectional (i.e., clockwise or counterclockwise) rotation or “pistoning” (up and down motion). This manipulation creates winding of connective tissue around the needle, which makes the practitioner feel the needle being grasped by body tissue.³

Once the needle has punctured the deeper tissues, especially the muscles, the patient will feel nonpainful sensations termed de qi (deh chee) in traditional Chinese acupuncture, which means that qi (i.e., the vital energy flow) has obtained or arrived. About 90% of needling will produce some sort of de qi sensation, depending on the nerve fibers encountered by needling and surrounding tissue milieu, such as tissue perfusion and inflammatory mediators.⁴ Needling the points on limbs may produce a de qi sensation of brief electric shock running up or down along the entire length of the limb. When needling the points on the back, a de qi sensation could be experienced more as localized sensations, like deep aching, soreness, and heaviness.

The phenomenon of de qi sensations can be explained by the types of nerve fibers stimulated by the needling (Table 3-1). Types II, III, and IV muscular afferent fibers not only generate de qi, but they also produce pain sensation if they are injured or pathophysiologically excited; so they represent de qi and pain-transmission nerves. Patients should be warned that some needling sensations such as aching or soreness may last 1 or 2 days.

Table 3-1 De Qi Sensation and Its Related Nerve Fibers in the Muscles

A needling-induced lesion stimulates the epidermis, dermis, underlying connective tissues (elastic fibers, collagen, basal lamina, deeper fascia), muscular tissues (skeletal muscles and smooth muscles of blood vessels), and nervous tissues (nerve fibers of sensory neurons and postganglionic neurons). The cells lesioned by the needling will be replaced with the same type of fresh cells without scar formation, since the lesions are very fine and tiny.

A needling activates chain reactions in both local tissues and the CNS (the spinal cord and brain). Thus we categorize needling mechanisms as peripheral and central. Both peripheral and central mechanisms, however, are physiologically inseparable. This chapter describes some of the major peripheral tissue reactions and the next chapter discusses the central mechanisms.

The following local chain reactions are started right after needling:

LOCAL SKIN REACTION AND CUTANEOUS MICROCURRENT MECHANISM

The neurovasculoimmune function of the skin is the first line of the body’s defense system. Needling stimulates the following skin tissues:

When an acupoint transits from latent phase (normal tissue) to passive phase, it becomes tender (Chapter 2). Around a tender acupoint the skin electrical conductance increases and the resistance decreases as discussed in Chapter 2. Inserting a needle into this acupoint will provoke an acute local inflammatory defensive response from all the previously mentioned tissues. The first visible response is the flare response, resulting in the appearance of redness around the needle. This vasodilatation function of the autonomic nervous system (ANS) is mediated by substance P secreted by cutaneous nociceptive sensory nerves. Then the immune reaction is triggered by mast cells, which produce histamine, platelet activating factor (PAF), and leukotrienes. The needle-induced lesion simultaneously activates interaction between the blood coagulation system and the immune complement system.

The body surface wears a layer of electric charges because the human body bathes in the electromagnetic field of the earth. Normally, dry skin has a DC resistance in the order of 200,000 to two million ohms. At acupuncture points this resistance is down to 50,000 ohms.⁵ Melzack and Katz⁶ found no difference in conductance between acupuncture points and nearby control points in patients with chronic pain.

This phenomenon can be explained by the dynamic nature of the acupoints. In a healthy person, DC resistance of the acupoints is the same as that of nonacupoints. In a chronically sick person, the acupoints transit from the latent phase (healthy tissue) to the passive phase (tender or sensitized tissue) in a predictable sequence and location (see Chapter 2). The sensitive area of acupoints is getting larger in chronic conditions, which contributes to high electrical conductance and low resistance.

In acute injury, acupoints appear around injured tissue. There is 20 to 90 mV of resting potential across the intact human skin, outside negative and inside positive.⁷ Most acupoints are measured at 5 mV higher than in nonacupoint areas.⁵ This higher voltage at acupoint loci can be explained histologically and pathologically. The configuration of most acupoints is rich in nerve fibers and/or vasculolymphatic structures, and once sensitized, inflammation may accumulate more fluids in the tissues of an acupoint. All these conditions may increase conductance and compensate the loss of resistance at acupoint loci according to Ohm’s formula: V = IR.

Insertion of a metal needle makes a short circuit from the skin battery and thus creates a microcurrent, called a current of injury, moving from inside to outside. The tiny lesion created by an acupuncture needle causes negativity at the needling site and produces 10 mA of current of injury, which benefits tissue growth and regeneration.⁸

These microcurrents induced by the needling are not sufficient to initiate nerve pulses to the spinal cord; thus the microcurrents will not generate effects of “needling tolerance” like “morphine tolerance,” meaning that repetitive needling will not reduce its therapeutic effect. In case of electroacupuncture stimulation of more than 3 hours’ duration, the analgesic effect will gradually decline. Professor J.S. Han of the Beijing Medical University explained that possibly long-lasting electrical stimulation, especially with high frequencies such as 100 Hz, increases the release of cholecystokinin octapeptide (CCK-8), which is an endogenous antiopioid substance.⁹

NEEDLE MANIPULATION: MECHANICAL SIGNAL TRANSDUCTION THROUGH CONNECTIVE TISSUE

During acupuncture treatments, more than 90% of the needling elicits de qi sensation. De qi elicited by manipulation of the needles increases the effectiveness of muscle relaxation and helps relieve pain. (Warning: Caution should be taken in treating weak or older patients because they may not be able to tolerate even weak manipulation and may suffer from flare-up pain after treatment. For these patients, simple insertion of the needle to the proper depth is sufficient. Flare-up pain can be alleviated easily by inserting one or two needles at the painful site. No manipulation is suggested for some facial points because of the dense capillary bed in such areas, which could cause bleeding or bruising on the face.)

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