TENS is an inexpensive non-pharmacological method of treating acute and chronic pain without the adverse side effects often associated with pain medications. The addition of properly dosed TENS to the patient's pain management program can minimize or even eliminate the use of pain medication.
High-frequency TENS, also known as conventional TENS, is the most commonly used electrotherapy approach for pain management. In this approach, the clinician increases the stimulation until the patient feels a pleasant tingling sensation associated with sensory nerve depolarization. The A-beta sensory nerve is targeted by selecting parameters that include a high frequency (80-120 pps), a short phase duration (20-100 microseconds), and a treatment duration that can range from 15 minutes to hours.
High-frequency TENS is indicated for the treatment of acute pain. Short-term pain relief is achieved through the gating mechanism in combination with the activation of delta-opioid receptors.3 However, it is less effective for chronic pain.
Acupuncture-Like TENS
Acupuncture-like TENS (ALT), also known as low-frequency TENS, has been shown to increase the magnitude and duration of pain relief in chronic pain patients.4 ALT specifically targets the A-delta nerve fiber by dosing the intensity to produce a strong, tremor-like twitch. The A-delta nerve fiber is targeted by using a low frequency (1-10 pps) and a longer phase duration (200-300 microseconds) for a duration of 15-45 minutes.
Recent data suggests a 15-minute treatment in subjects with chronic, nonspecific low back pain provides similar duration of pain relief to a 30-minute treatment.4 Acupuncture-like TENS provides longer-term pain relief by activating the mu-opioid receptors. Pain relief post treatment lasts 3-9 hours.5
Dosing Intensity
The intensity is a critical parameter for properly delivering ALT. Higher intensity stimulation is associated with greater analgesia. Sufficient intensity to produce strong, slightly painful (2/10 pain), and rhythmical muscle twitching produces greater analgesia.6 As the patient accommodates to the stimulus, the intensity should be titrated upward.
TENS studies using lower intensity levels show less analgesic effects than those using higher intensity of stimulation.1,3
Combining TENS With Movement Increases Analgesia
TENS does reduce resting pain; however, greater analgesia has been reported when TENS is combined with movement.7 Traditionally, TENS has been used solely before or after therapy. Evidence supports the use of electrophysical agents as adjuncts to standard active care, but not as stand-alone interventions.8
Contemporary approaches recommend that the patient actively perform basic therapeutic exercise and/or functional activity during the TENS treatment.7 This paradigm shift will provide better pain relief deter the passive use of electrophysical agents.
It is important to grade the therapeutic exercise and functional activity using good clinical discretion, since the analgesic response will decrease the patient's perception of pain. If the tremor-like muscle twitching associated with ALT interferes with the appropriate execution of a therapeutic exercise or functional task, high-frequency (conventional) TENS can be used during the session, and the patient can use ALT at home.
Issuing a Portable TENS Device
If the patient experiences clinically meaningful pain relief in the office with a clinical line-powered device, the patient should be issued and trained to use a portable TENS device at home.
Traditionally, TENS has been limited to 10- to 20-minute treatments, 1-3 times per week during office visits only. Issuing a portable TENS device expands the patient's pain management options outside of office visits and allows them to take full advantage of the analgesic effect of TENS.
Unlike pharmaceutical interventions, TENS can be used as much as needed to modulate pain with no adverse side effects or risk of addiction.
Once patients are able to manage their own pain with TENS, the doctor can focus on hands-on, active care during subsequent office visits. A portable prescription device allows patients to perform a TENS treatment at home one hour prior to their doctor visit. This decreases patients' pain, spasms, and muscle guarding, allowing for a more effective office visit with their doctor.
Adjusting TENS for Patients With Opioid Tolerance
If the patient has developed an opioid tolerance through long-term, repeated opioid drug use, they will not experience ALT-induced analgesia since the mechanism of action involves the activation of the same mu-opioid receptors as opioid drugs. In these instances, conventional (high-frequency) TENS can be used. Because it relies on the gating mechanism of pain modulation and is less reliant on the endogenous opioid mechanism, conventional TENS can be a better option for these types of patients.9
The Impact of Caffeine
It is believed that caffeine can block the analgesic effect of TENS.10 It also has been shown that chronic pain patients ingest higher amounts of caffeine.11 Given that the half-life of caffeine is 4-6 hours, it is recommended that caffeine intake be limited overall and not be ingested in the six hours prior to TENS treatment.9
Key Points
- Acupuncture-like TENS is an effective nondrug intervention for reducing subacute and chronic pain without adverse side effects or risk of addiction.
- ALT increases the duration of analgesia for 3-9 hours posttreatment through the activation of mu-opioid receptors.
- Appropriately dosed TENS combined with movement has been shown to maximize analgesic effects both in the office and at home.
References
- Bjordal JM, Johnson MI, Ljunggreen AE. Transcutaneous electrical stimulation (TENS) can reduce postoperative analgesic consumption. A meta-analysis with assessment of optimal treatment parameters for postoperative pain. Eur J Pain, 2003;7:181-188.
- Van Der Ark GD, McGrath KA. Transcutaneous electrical stimulation in treatment of post-operative pain. AM J Surg, 1975;130(3):338-340.
- Sluka KA, Bjordal JM, Marchand S, Rakel BA. What makes transcutaneous electrical nerve stimulation work? Making sense of the mixed results in the clinical literature. Phys Ther, 2013; 93(10): 1397–1402.
- Tousigant-Laflamme Y, Laroche C, Beauileu C, et al. A randomized trial to determine the duration of analgesia following a 15- and a 30-minute application of acupuncture-like TENS on patient with chronic low back pain. Physiother Theory Pract, 2017:5;1-9.
- Cameron, MH. Physical Agents in Rehabilitation: From Research to Practice, 4th Edition. Elsevier-Saunders: St. Louis, MO; 2013.
- Granot M, Weissman-Fogel I, Crispel Y, et al. Determinants of endogenous analgesia magnitude in a diffuse noxious inhibitory control (DNIC) paradigm: do conditioning stimulus painfulness, gender, and personality variables matter? Pain, 2008;20:2702-2709.
- Rakel B, et al. Transcutaneous electrical nerve stimulation (TENS) for control of pain during rehabilitation following total knee arthroplasty (TKA): a randomized, blinded, placebo-controlled trial. Pain, 2014:155(12);2599-2611.
- Poitras S, Brosseau L. Evidence-informed management of chronic low back pain with transcutaneous electrical nerve stimulation, interferential current, electrical muscle stimulation, ultrasound, and thermotherapy. Spine J, 2008;8:226-233.
- Leonard G, Cloutier C, Marchand S. Reduced analgesic effect of acupuncture-like TENS but not conventional TENS in opioid-treated patients. J Pain, 2011;12(2):213-221.
- Marchand S, Li J, Charest J. Effects of caffeine on analgesia from transcutaneous electrical nerve stimulation. N Engl J Med, 1995;333:325-326.
- McPartland S, Mitchell JA. Caffeine and chronic back pain. Arch Phys Med Rehabil, 1997;93:1397-1402.
Dr. Joseph A. Gallo is a professor and director of the athletic training program at Salem State University in Salem, Mass.
Kevin J. Silva is the program assistant and adjunct faculty for the athletic training program at Salem State University.