PT 606 UE 2025 ELECTRO PAIN CONTROL

Therapeutic Uses of Electrical Currents

Focus on TENS (Transcutaneous Electrical Nerve Stimulation)

Author: DM Selkowitz

Page 1: Introduction

The therapeutic uses of electrical currents have garnered significant interest due to their potential in pain management. Transcutaneous Electrical Nerve Stimulation (TENS) is a widely recognized technique that employs low-voltage electrical currents to alleviate pain and improve patient comfort. The efficacy of TENS is attributed to its ability to modulate pain pathways through various mechanisms.

Page 2: Definition of Pain

Pain: An unpleasant sensory and emotional experience associated with actual or potential tissue injury. Understanding pain requires a value judgment based on individual perceptions of threats to the body, showcasing the complex nature of pain experiences different individuals may have.Reference: IASP (International Association for the Study of Pain) by DM Selkowitz.

Page 3: Components of Pain

Pain can be classified into several components:

  • Pathological: Directly relates to identifiable tissue damage.

  • Perceptual: Involves the subjective experience and interpretation of pain by the affected individual.

  • Psychological: Encompasses emotional reactions to pain, such as anxiety or depression which can exacerbate pain experiences.

  • Cognitive: Involves individual thoughts and beliefs about pain, influencing one’s pain threshold and coping strategies.

  • Behavioral: Describes the actions or responses a person exhibits when experiencing pain, which can vary widely among individuals.

Page 4: Theories of Pain Control

Various theories are vital in understanding pain control:

  • Gate Control Theory: Introduces the concept that non-painful input can close the gates to painful input, implying that large sensory fibers can inhibit pain signals transmitted by smaller fibers.

  • Opiate-Mediated Control: Highlights the natural pain modulation through the release of endogenous opiates, which bind to specific opioid receptors in the central and peripheral nervous systems, reducing pain perception.

Page 5: Gate Control Mechanism

The gate control mechanism functions by:

  • Activating large sensory fibers that inhibit signals carried by small nociceptive fibers associated with pain.

  • This inhibition leads to a rapid onset of pain relief during TENS treatment, with potential for prolonged responses due to engagement of supraspinal pathways and serotonin release, indicating complex neurochemical interactions. References: Melzack & Wall 1965, 1982; Sluka et al.

Page 6: Gate Control Evidence

Evidence supporting the gate control theory includes:

  • Reduction of nociceptive activity observed in the dorsal horn and spinothalamic tract cells during animal studies.

  • Decreased flexion reflex responses in animal models when exposed to certain electrical stimuli.

  • Evidence from human studies showing diminished pressor responses in reaction to painful stimuli under TENS treatment. References: Hollman & Morgan 1997; Wang et al 1997; Garrison & Foreman 1994; Shin et al 1986.

Page 7: Opiate-Mediated Control Mechanism

The opiate-mediated control mechanism involves:

  • Release of endogenous opiates which bind to specific receptors in both the central nervous system (CNS) and peripheral nervous system (PNS) — μ, δ, and κ receptors.

  • Reduction of pain perception and nociceptive responses is noted, characterized by a delayed effect which provides prolonged pain relief.

Page 8: Opiate-Mediated Control Evidence

Evidence supporting this mechanism shows:

  • Decreased nociceptive transmission observed in the spinothalamic tract and reduced flexion reflex in animal models subjected to TENS.

  • Increased levels of endorphins in cerebrospinal fluid correlate with significantly decreased pain perception in patients with neurological issues.

  • Effects observed can be blocked by Naloxone, which serves as an opioid receptor antagonist, indicating the role of opioids in this mechanism. References: Han et al 1991; Almay et al 1985; Chung et al 1984; Salar et al 1981.

Page 9: Opiate-Mediated Control Evidence (Sluka et al)

Animal study results demonstrated:

  • High-frequency antihyperalgesia that is blocked by naltrindole, indicating a key role of the δ-receptor.

  • Low-frequency antihyperalgesia blocked by naloxone, suggesting reliance on the μ-receptor.

  • Transmission blockage occurring at both supraspinal and spinal levels, revealing intricacies in pain modulation at varying frequencies (High: 50-150 pps, Low: 1-10 pps).

Page 10: Opiate-Mediated Control with TENS and Medications

Findings indicate:

  • Co-application of both high and low-frequency TENS with analgesics like Morphine or Clonidine enhance antihyperalgesic effects.

  • Low frequency TENS is notably less effective in subjects who have developed morphine tolerance.

  • Continuous daily exposure to TENS suggests the possibility of developing tolerance, highlighting the need to consider dosage and therapy duration carefully.

Page 11: TENS Treatment Methods

TENS therapy can be categorized into four distinct levels:

  1. Subsensory-level: Below the sensory perception threshold.

  2. Sensory-level: Above threshold but not painful.

  3. Motor-Level: Induces muscle contraction, thereby offering therapeutic benefits.

  4. Noxious-level: Painful stimulation aimed at chronic pain management.

Page 12: Sensory-Level TENS

Known also as Conventional or High-Rate TENS:

  • This method displays effectiveness in treating hyperalgesia associated with acute pain as opposed to chronic conditions.

  • Mechanistically engages the gate control theory via diminished activity in the dorsal horn, providing rapid pain relief during treatment.References: Proctor et al 2002/2010; Sluka et al; Osiri et al 2000/2009.

Page 13: Sensory-Level TENS Efficacy

Prolonged pain relief occurs through:

  • Enhanced release of opiates and increased serotonin levels, with a noted reduction in norepinephrine.

  • Higher amplitude settings tend to yield more effective outcomes, and it is particularly applicable for conditions such as knee osteoarthritis (OA) and primary dysmenorrhea.

  • Electrode placement considerations may involve a contralateral approach for optimal results.

Page 14: Motor-Level TENS

Also known as Acupuncture-like or Low-Rate TENS:

  • More prominently effective in managing chronic pain, showing a reduction of 20% in hyperalgesia.

  • Operates through an opiate-mediated mechanism, providing delayed and longer-lasting relief, which is critical for chronic pain management. References: Sluka et al; Osiri et al 2000/2009; Tanaka et al 2015.

Page 15: Motor-Level TENS Additional Points

The significance of gate control effect is also noteworthy, as it reduces dorsal horn activity substantially.

  • Notable serotonin involvement is observed, making this approach particularly recommended for knee OA treatments, with contralateral electrode placements yielding superior results compared to sensory-level approaches.

Page 16: Noxious-Level TENS

Termed Hyperstimulation:

  • Specifically aimed at chronic pain management via quicker onset times and shorter session durations, utilizing opiate-mediated mechanisms akin to previous TENS methods.

  • Notably effective in managing post-operative pain situations, providing essential insights for post-surgical protocols.Reference: Bjordal et al 2003, 2007.

Page 17: Subsensory-Level TENS

This method is also referred to as Subliminal, Microcurrent, or MENS:

  • Typically operates at microamperes, which are below threshold levels for nerve depolarization.

  • Clinical efficacy remains mixed, with ongoing discussions surrounding the validity of publication outcomes and general utility.Reference: Allen JD et al 1999 and others.

Page 18: Overall Efficacy of TENS

The effectiveness of TENS is contingent on several parameters, including:

  • Current amplitude, duration, frequency, and precise electrode placement which are crucial in maximizing therapeutic outcomes.

  • Conventional TENS has been particularly effective in mitigating pressure-induced and thermal pain sensations.

  • Intense TENS has demonstrated effectiveness across various pain models, while combined methodologies yield superior results compared to singular approaches. Reference: Claydon et al 2011.

Page 19: General Recommendations for TENS

Key recommendations for TENS application include:

  • Employing stimulation that is strong, yet tolerable to elicit neurophysiologic responses effectively.

  • Incrementally increasing intensity during treatment sessions promotes cumulative pain reduction benefits.

  • Adjusting frequency during sessions can help mitigate the effects of opioid tolerance over prolonged therapy.

  • Optimal use of high-frequency TENS alongside concurrent opioid administration is advised for enhanced outcomes.

Page 20: Evidence-Based Recommendations for TENS

A summary of clinical recommendations includes:

  • Maximizing the tolerated current output (in mA) to achieve desired therapeutic impacts.

  • Adjusting frequency throughout treatment sessions to prevent the development of patient tolerance to TENS.

  • Emphasizing the need for high-frequency TENS in combinations with opioid analgesics for improved results.

Page 21: Outcome Measures for TENS

It is essential to evaluate TENS effectiveness using various assessment measures, including:

  • Visual Analog Scale (VAS) to quantify pain at rest and during activities.

  • Monitoring medication usage, healthcare utilization, and assessing functional outcome measures.

  • Quality of life surveys to capture patient perspective continuously throughout treatment phases.

Page 22: TENS Effectiveness in Patient Populations

Research confirms the efficacy of TENS across several conditions such as:

  • Osteoarthritis (OA), Fibromyalgia, and Neuropathic Pain.

  • Effective in treating both acute and chronic pain conditions, underscoring its versatility.

  • Noteworthy is the cumulative effect observed over prolonged use of TENS, suggesting significant contributions to overall pain management.

  • Importantly, TENS is not intended as a standalone therapy but rather as an adjunct to comprehensive pain management strategies.

Pages 23-25: Recommended Parameter Settings for TENS

Table 11-7: Sensory-Level TENS parameters include:

  • Pulse duration: 20-100 μs; Frequency: 50-200 pps; Treatment time: minutes to hours.Table 11-8: Motor-Level TENS parameters include:

  • Pulse duration: 100-600 μs; Rate: 30-50 pps; Treatment time: 15-60 min.Table 11-9: Noxious-Level TENS parameters include:

  • Pulse duration: 20-600 μs; Maximum tolerated painful stimulation; Treatment time: minutes.Electrode configuration is vital to effectively target neuroanatomical and neurophysiological regions associated with pain in patients, enhancing therapeutic outcomes.