Analyzing Electrotherapeutic Options for Managing and Controlling Pain
Exploring viable alternatives to opiates, barbiturates and NSAIDs in managing acute and chronic pain has become a national priority. Concern about managing pain is highlighted by the recent National Pain Care Policy Act of 2009 (FN1) requiring the Secretary of Health and Human Services to seek an agreement with the Institute of Medicine to convene a conference on pain to:
1) Increase the recognition of pain as a significant public health problem in the United States; 2) Evaluate the adequacy of assessment, diagnosis, treatment, and management of acute and chronic pain; 3) Identify barriers to appropriate pain care; and 4) Establish an agenda to reduce such barriers and significantly improve the national state of pain care research, education and clinical care.
This bill amended the Public Health Service Act and required the Director of the National Institutes of Health (NIH) to continue to expand, through the Pain Consortium, an aggressive program of basic and clinical research on the causes of and potential treatments for pain. Further, it requires the Pain Consortium to develop and make recommendations on appropriate pain research initiatives. It also mandates education and training for health care professionals in pain care and the implementation of a national pain care education outreach and awareness campaign to educate consumers, patients, their families and other caregivers. This has spawned a powerful emerging interest in alternatives to pharmacotherapy in managing and treating pain.
Pain is an extremely complex phenomenon. The human nervous system features a variety of nerve ?bers, each carrying a different type of sensation to the spinal cord, which, in turn, forwards messages to the brain. Of particular interest are A beta ?bers, A delta fibers, and C ?bers, each of which has distinctive properties. A beta ?bers transmit nonpainful mechanical sensations, such as those generated from rubbing and touching. A delta ?bers transmit sharp, intense, immediate pain that signals that injury is taking place and that some action is urgently needed to evade the source of injury. C ?bers transmit the dull, aching, long-term pain that is the hallmark of chronic pain syndromes. Both A beta and A delta ?bers are insulated by myelin sheaths, so they transmit signals to the spinal cord very quickly. C ?bers are unmyelinated, so their signals travel slowly in comparison.
Distinctions in Therapy
Transcutaneous electrical nerve stimulation, or TENS, is the most commonly known of the electrotherapy armamentarium. This is a relatively simple waveform that provides adequate short-term pain relief, generally lasting for the duration of stimulation therapy. Once TENS is turned off, there is minimal residual pain control.
A more effective electrotherapeutic option is interferential stimulation (IF), which produces a complex waveform that relieves pain by delivering deeper penetration. It is stronger, more effective and longer lasting than TENS. Soon after TENS is removed the pain will return, while IF has a lasting residual effect. IF, first introduced in the U.S. in 1981, involves two circuits of medium frequency sine waves. The intersection of those circuits sets up an interference pattern that produces a beat frequency of the two circuits and results in a higher amplitude. This higher amplitude results in deeper penetration with less surface sensation, allowing for more effective pain control. Unlike the superficial penetration of TENS, the high frequency of IF penetrates beyond the skin’s barrier and goes deeper into the substrate to treat the underlying condition more effectively. This promotes greater toleration and increased comfort. It also has the clinical advantage of creating deeper levels of tissue stimulation.
Sequential stimulation involves a sequence of therapy that begins with interferential and is followed by muscle stimulation (NMES). Research published in Osteoarthritis and Cartilage has shown that 15 minutes of interferential followed by 30 minutes of muscle stimulation is effective and can be comfortably used two to three times per day. Sequential stimulation reduces pain, strengthens muscles, decreases spasm and enhances metabolic processes. Unlike TENS, there is no need to wear the sequential stimulation unit all day long, and therefore one does not experience accommodation to the signal. The 45-minute treatment can address the need for pain relief and treat the underlying cause of the pain.
An emerging electrotherapeutic technology is cutaneous field stimulation (CFS), a new technique used to assist in the management of chronic pain. The technique is based on the idea that stimulating A delta and C nerve fibers is more effective for treating pain than stimulating A beta fibers. Low-frequency stimulation of A delta and C fibers in the skin creates powerful inhibition of pain-related signals (C-fiber pain) in the spinal cord. CFS was found to induce a long-term depressive (LTD) effect on the perception of pain, which provides pain relief for three to four hours after stimulation has stopped.