Electrical Stimulation for Pain Relief PDF

PAIN Broadly defined as an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage. International Association for the Study of Pain TYPES OF PAIN (REVIEW) Acute: associated with distinct tissue trauma and ser...

PAIN Broadly defined as an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage. International Association for the Study of Pain TYPES OF PAIN (REVIEW) Acute: associated with distinct tissue trauma and serving biologic function Often either nocioceptive or neuropathic pain Chronic: may or may not be associated with tissue damge or trauma, no biologic function Often described as nociplastic pain Referred: painful sensation in location other than site of biologic injury. BASIC CONCEPTS FOR THE TRANSMISSION OF PAIN Cutaneous afferents (A delta) Transmits sensory information of pain First response C polymodal afferents Slow in transmitting 80 - 90% of the pain transmission Visceral nociceptive afferents Carry message of referred pain CUTANEOUS AFFERENTS (A-DELTA) Transmits some characteristics of pain Mechanical (primary) vs. Thermal Pain sensation is often sharp, stabbing, or pricking Heavily myelinated fibers Quick onset of pain transmission after stimulus Actual transmission of pain information to the CNS is rapid Localizes pain Not mediated by opiates C POLYMODAL NOCICEPTIVE AFFERENTS Small, unmyelinated nerve fibers Transmit action potentials (information about pain) more slowly Slower onset of pain sensation after the after the stimulus Pain sensations are longer lasting and not as localized. Often described as: Dull, aching, throbbing, or burning Responsive to multiple nociceptive stimuli Mechanical Thermal Chemical (related to inflammation after initial injury): Includes Substance P Can be mediated by opiates Can be sensitized and may be involved in hyperalgesia. NICE TO KNOW - SPINAL PATHWAYS Dorsal Horn Lamina 5 is responsible for a wide range of pain transmission. Dorsal Horn Lamina 1 is responsible for nonspecific nociception. NICE TO KNOW - CENTRAL PROCESSING OF NOCICEPTIVE INFORMATION The Spinothalamic tracts carry input to the thalamus, and the somatosensory cortex as well as the reticular formation, and the limbic system. The transmission of pain information to these areas in the brain can also impact affect and emotion MODULATION OF PAIN There are many known mechanisms by which the transmission of or experience of pain input may be altered or reduced. The most common proposed mechanisms of pain control and modulation are… Endogenous Opiate System Descending inhibition Gate control ENDOGENOUS OPIATES Pain perception can be altered endogenously when peptides known as opipetins (aka, endorphins) bind to specific opiate receptors in the nervous system The endogenous peptides are similar in action to exogenous opiates operating at opiate receptors When activated, opiate receptors: Reduce the release of Substance P and subsequent pain transmission at the level of the spinal cord (inhibitory effect) In the brainstem and limbic system, will inhibit pain transmission from some spinal dorsal horn neurons. Once released opipetins (endogenous opiates) will circulate through the blood stream and have effects at various points in the body. Nonspecific Moderately long lasting ENDOGENOUS OPIATE THEORY Accounts for the fact that tolerable, but painful stimuli such as acupuncture or motor/noxious level electrical stimulation can reduce less tolerable, pre-existing pain Proposed that the painful stimulus will cause neurons in the mid-brain and thalamus to release opipetins, which bind to opiate receptors to reduce the transmission of pain PRIMARY ENDOGENOUS OPIATES Beta Endorphin Enkephalins Serotonin NICE TO KNOW: ENDOGENOUS OPIATES Beta Endorphin is released from pituitary and hypothalamus into the circulatory and cerebrospinal fluid. Enkephalins are a five amino acid peptide released from the adrenal gland, and other organs which inhibit propagation of action potentials and release of substance P Serotonin is often considered to be a part of this class of substances because of its effects on pain. It also effects mood and sleep. DESCENDING INHIBITION General concept related to pain control/modulation Simply stated, pain messages can be modulated by the actions of descending neurons from areas of the brain through an inhibitory loop Can affect pain perception, motor responses to pain, and the emotional aspects of pain This mechanism is now thought to influence the gate control method of pain modulation GATE CONTROL This is the classic explanation upon which pain modulation has been explained. Sensory input from A beta fibers can inhibit the transmission of pain through C fibers, thereby reducing the overall sensation of pain. Real life example: The parent that rubs of hand of a child that has just fallen and scraped their knee Many physical agents and interventions can be used to modulate pain by activating these non-nociocepetive sensory nerve fibers including: TENS Interferential Stimulation GATE CONTROL PAIN MODALITIES Try to either interfere with the normal process by which pain messages are transmitted in the body Gate Control Theory (with descending inhibition) Trying to stimulate the internal mechanisms by which the body modulates pain transmission Endogenous Opiate Theory Need to be more effective than placebo ELECTRIC STIMULATION FOR MODULATION OF PAIN Transcutaneous Electric Nerve Stimulation (TENS) Interferential Current Therapy (IFC) TENS Transcutaneous electric nerve stimulation is a sensory level stimulation which is used to produce analgesia Low frequency device Three common modes of application Conventional (sensory or high rate) – most common Motor (Low Rate) Noxious (hyperstimulation) NICE TO KNOW: REVIEW OF THE LITERATURE Keep in mind… With physical agents/modalities, the literature is often plagued with problems when making comparisons. Type of pain treated Type of parameters used Type of electrode placement Type of measurement of pain or dysfunction Types of subjects NICE TO KNOW CONVENTIONAL (HIGH RATE TENS) Shown to be effective : Low back Pain (Ersek 1976) Pancreatitis (Roberts 1978) Post herpetic Neuralgia (Nathan 1974) Rheumatoid Arthritis (Mannaheimer 1979) Pain during Jaw exercises (Fagade 2003) Phantom Limb Pain (Mulvey 2012) Improve stretching outcomes (Capobianco 2017) CONVENTIONAL TENS Subject should feel a comfortable, sub-motor paraesthesia (buzzing/tingling) Pulse duration should be short Strength – duration curve: Avoid muscle contraction Pulse rate should be high Rapid activation of sensory, afferent nerve fibers Electrodes placed at/around site of pain or at a related spinal segment Time: 30-60 minutes typical up to several hours per day Mechanism of Action: Gate Control with some Descending Inhibition ADVANTAGES OF CONVENTIONAL TENS Fast acting – though effects will not be lasting once stimulation is removed Gives patient control over pain – machines often portable Evidence for decreased use of pain medications (J. Neurosurg Anesthesiol Sep 2009 ) MOTOR (LOW RATE TENS) Subject should feel a strong, but rhythmic muscle contraction Pulse duration should be long Strength – duration curve: Must reach motor threshold Pulse rate should be low Want a strong muscle twitch (not a fused muscle contraction) Electrodes placed at/around site of pain or at a segmentally related myotome Time: 40-60 minutes typical up to several hours per day Mechanism of Action: Endogenous Opiate Theory ADVANTAGES OF LOW RATE/MOTOR TENS Long lasting effects – though onset of pain relief is slow Better effects on referred pain and generalized pain Systemic impact of endogenous opiates May increase blood flow to area of pain which could contribute to tissue recovery HYPERSTIMULATION/NOXIOUS TENS Subject should feel a noxious, pricking sensation Pulse duration should be long Strength – duration curve: Easier to stimulate pain fibers Pulse rate should be low Electrodes placed at/around site of pain (trigger or acupuncture point) Time: Short bouts since stimulus is painful Mechanism of Action: Likely Descending Inhibition and Endogenous Opiate ADVANTAGES AND DISADVANTAGES OF HYPERSTIMULATION TENS ADVANTAGES DISADVANTAGES Fast acting relief Skill / ease of application Long lasting relief Lack of patient control Wide location of relief Unpleasant to patient Unlikely to achieve accommodation NICE TO KNOW: IS TENS LESS EFFECTIVE AS PATIENTS AGE? Pain Oct 2015, Bergeron-Vezina , et al. Compared High Rate and low Rate and placebo in age groups. Young subjects had reduction in pain perceived and pain threshold and no change with placebo Older subjects had only reduction of pain threshold in Low Rate Strong statistical results but small sample size NICE TO KNOW TENS AND LOW BACK PAIN Spine Dec. 2005 Systematic review of the literature using TENS for treatment of low back. TENS consistently better than placebo. However when used as part of a total treatment plan looking at various functional outcome measures there was no significant difference in RCT.’s NICE TO KNOW TENS AND LABOR PAIN RELIEF Cochrane database review 2009 Looked at 19 studies with randomized controls. No significant difference in pain scores or need for other interventions, or length of labour Women using TENS generally wanted to use it again in future labour. 2017 clinical trial (Shahoei et al. CTCP 2017) found significant differences NICE TO KNOW TENS AND FIBROMYALGIA Systematic review of pain relief modalities for Fibromyalgia; Honda et al. Pain Research and Management 2018 Included 11 studies Looked at LLLT; Thermal agents; TENS; and Electromagnetic field therapy TENS significantly reduced VAS scores Analgesic effect of TENS in Fibromyalgia a Systematic Review Megia Garcia et al. Aten Primaria Jul 2018 Included 8 studies Was shown to be effective at reducing pain No efficacy demonstrated in fatigue; quality of life; range of motion or depression NICE TO KNOW TENS AND SYMPATHETIC NERVOUS SYSTEM Stein C. et al., Transcutaneous Electrical Nerve stimulation at different frequencies on Heart Rate variability in healthy Subjects, Auton. Neurosci. (2011) Found a reduction in Heart rate with the Low frequency and an increase with the high frequency. This they associated with a change in balance between sympathetic and parasympathetic nervous systems. Okuyucu,EE. et. al., Does Transcutaneous Nerve Stimulation have an effect on Sympathetic Skin Response. (J Clin Neurosci Oct 2017) TENS had an inhibitory effect on SSR NICE TO KNOW GENETIC PREDISPOSITION FOR TENS Govil et. Al. Eur J Pain Oct 2019 Looked at patients with osteoarthiris and compared low frequency to high frequency to Sham TENS on different Genotypes. Found some genotypes experienced greater resting pain reduction with high frequency and some experienced higher magnitude of pain reduction with low frequency Take home message: there were differing responses based on who the subjects were. NICE TO KNOW FURTHER IMPLICATIONS FOR TENS Stimulation to prevent post op Nausea and Vomiting Lee and Fan 2015 Chocrane Database Sys Rev. Significant evidence to support but further research required to determine impact and optimal parameters. Reduce spasticity in SCI patients. Gulumser (2005) Am J Phys Med Rehabil. Found clinically significant results and comparable to Baclofen (oral). Constipation in children with lower urinary tract dysfunction. Veiga 2012. J. Pediatr Urol. Found significantly improved voiding and less residual urine post voiding. TENS and Dementia: Multiple studies from 2003 -2006 including a Chocrane database analysis showed potentially favorable evidence. INTERFERENTIAL CURRENT THERAPY The combination of two applied electric fields to produce a third distinct electric field, which can serve to modulate or control pain Medium frequency stimulation Less impedance Deeper penetration and more comfortable Produced by two distinct current generators in the machine BEAT FREQUENCY Describes the summative current produced by the intersection of two identically shaped wave trains at slightly different frequencies Interferential field is created at the point of intersection of two currents. It will have double the magnitude and depth of penetration of the originating currents The value of the beat frequency is simply the difference between the frequencies of the two wave trains BEAT FREQUENCY FREQUENCY DIFFERENCE The frequency difference is created by using one current generator at a constant frequency and the other at a variable frequency. This allows you to modulate the Interferential current created Higher beat frequencies (50-100 bps): Sensory stimulation Lower beat frequencies (1-5 bps): Motor stimulation APPLICATION OF INTERFERENTIAL STIMULATION Quadripolar electrode set-up around the area of pain Channel 1: Set carrier frequency intersects with Channel 2: Variable carrier frequency set by the user Depending on the beat frequency chosen, subject should feel either A comfortable, sub-motor paraesthesia (buzzing/tingling): High beat frequency A tolerable muscle contraction/twitch: Low beat frequency Pulse/phase duration: Based on the intersection of the two wave trains Higher beat frequency = short phase duration and sensory stimulation Lower beat frequency = longer phase duration and the potential for motor stimulation Time: 20-30 minutes typical up to several hours per day Mechanism of Action: Gate Control and Endogenous Opiate NICE TO KNOW: LITERATURE REVIEW Early work by Nemec (1948, 1950,1959) Scarcity of literature when compared to other modalities Much is comparative to TENS (medium frequency TENS) Early literature based on older equipment. NICE TO KNOW: BRIEF OVERVIEW OF LITERATURE Kloth (1982) showed to be effective at a variety of painful conditions Hobler (1991) showed to be effective in reducing post- traumatic edema and pain Snyder-Mackler et.al. showed to be effective at generating contractions sufficient for strength gains NICE TO KNOW: BRIEF OVERVIEW CONT. Several articles support effective on urinary incontinence Dougall (1985) Milliard (1984) Kajbafzadeh et. Al. Urology Aug 2009 Chronic back pain with multiple vertebral fx. Zambito et. Al. Osteoporos Nov 2007 Some preliminary support for the use of IFC for bone Healing. NICE TO KNOW: HOME INTERFERENTIAL THERAPY Jarit GJ, Mohr KJ, et.al. Clin J. Sports Med Jan 2003 RTC with home interferential vs. Sham units Multiple measures taken over time Found reduced pain and swelling, decreased pain meds, and increased range of motion NICE TO KNOW: INTERFERENTIAL AND TKA Kadi et. Al. Clin Reahbil 2019 Jun Double blinded randomized control study with nearly 100 subjects. Look at outcomes on Day 0, 5, and 30 No significant difference in pain, Range of motion, or edema between the two groups IFC group was significant for lower utilization of pain meds at day 5 ADVANTAGES OF IFC Pain relief when area is fairly large and deep. Pain relief is fast acting generally a few minutes and has some carry –over effect PREMODULATED INTERFERENTIAL CURRENT Still defined as the current (beat frequency) generated by the intersection of two distinct wave trains However, the intersection of the two distinct wave trains occurs that the level of the machine, not the body Therefore it is a single channel, bipolar electrode set-up around the area of pain Otherwise, all of the same principles of inferential current apply to premodulated current May be better for motor level stimulation INDICATIONS FOR TENS / IFC Acute trauma Post-op pain Local inflammation Inflammatory pain Painful treatment CONTRAINDICATIONS FOR TENS /IFC Application in certain anatomic locations Transthoracicaly Transcerebrally Abdominally in pregnant females Anterior neck Demand cardiac pacemakers Pain of unknown origin ADDITIONAL PRECAUTIONS Contact dermatitis Skin irritation is fairly common with TENS users as they tend to use electrodes for a longer time. NICE TO KNOW: TENS AND IFC THERAPY HAVE SIMILAR RESULTS DeAlmeida et al. Brazilian Journal of Physical Therapy, Oct 2018 Systematic review and Meta-analysis of 8 studies which pooled 825 patients. Dysfunctions included: Chronic back pain; neck discomfort; carpal tunnel; and osteoarthritis of the knee. Found both modalities had significant decreased in pain and positive effects on function based on WOMAC and RMDQ  REVIEW OF PAIN MODALITIES TENS TENS TENS Interferential Conventional Motor Hyperstimulation Action Fast Delayed Fast Fast Duration Short Lasting Lasting Some Lasting Primary Gate and Circulating Several Gate and Mechanism Descending Opioids Circulating Inhibition opioids Localized Yes Diffuse and Referred Larger area effects referred but local Patient Good Some No Some control