OTs and PTs can use transcutaneous electrical nerve stimulation (TENS) to help patients better manage pain after surgery throughout rehabilitation.
By John V. Rider, PhD, OTR/L, MSCS, CPAM, CEAS 

Technological advancements and high-quality studies have led to improved surgical techniques and better rehabilitation outcomes; however, most post-surgical patients still report a significant amount of pain impacting recovery.1 Occupational and physical therapists can use non-pharmacological approaches, such as transcutaneous electrical nerve stimulation (TENS), to help patients better manage post-surgical pain throughout rehabilitation. 

Post-Surgical Pain

Despite surgical advancements, surgery still causes tissue damage to somatic, visceral, and neural structures, resulting in peripheral and central sensitization of the nociceptive system and post-surgical pain.2 Post-surgical pain may be nociceptive and/or neuropathic in origin. Nociceptive pain arises from actual or threatened damage to non-neural tissue and is due to the activation of nociceptors (eg, soft tissue damage after an incision).3 In contrast, neuropathic pain is pain caused by a lesion or disease of the somatosensory nervous system (eg, nerve damage during surgery).3 While acute post-surgical pain is often localized around the incision site, soft tissue injury from surgical trauma may cause pain to spread to other areas. 

Beyond incision-site pain, stretching, contusions, transection, or inflammation of nerves during surgery can also lead to significant post-surgical neuropathic pain. Among surgical cases, more than 85% of patients report post-surgical pain, and 75% of those describe the pain severity as moderate to extreme during the immediate postoperative period.1

Poor post-surgical pain management negatively affects quality of life, interferes with rehabilitation, and increases the risk of post-surgical complications and the development of moderate-to-severe acute and chronic post-surgical pain.2 Conversely, effective pain management is associated with improved patient satisfaction, earlier mobilization, shorter hospital stays, and decreased healthcare costs.4 Fortunately, therapists can use TENS to not only combat post-surgical pain, but also increase engagement in therapy and improve post-surgical rehabilitation outcomes. 

Electrotherapy

The use of electrotherapy is far from a novel approach. In fact, using electrical currents to relieve pain pre-dates the discovery of electricity. Stone carvings which date from the Egyptian Fifth Dynasty (around 2500 BC) suggest that electric fish and rays (capable of generating 300-400 volts) were used to treat multiple painful ailments.5 The use of medical electricity began in the 1700s, with significant advancements in the 1900s as battery-powered TENS units became available in 1919.5 Fast forward to the 21st century: electricity continues to be used as a pain management tool with pocket-sized battery-powered TENS units that are affordable and user-friendly. Occupational and physical therapists can capitalize on these technological advancements and use TENS to help patients better manage post-surgical pain. 

Post-Surgical Benefits  

TENS is a non-invasive technique that has been shown to be effective at decreasing post-surgical pain associated with incision and soft tissue trauma across multiple procedures, such as orthopedic, thoracic, and abdominal surgeries. Its use has also been shown to reduce analgesic consumption and associated side effects.6 Beyond the direct benefits of pain management, the use of TENS has also demonstrated improvements in pulmonary mechanics and general mobilization, reducing the risk of chest infections, hypoxia, pressure sores, and deep vein thrombosis, and therefore warranting serious consideration in post-surgical rehabilitation.1

Conventional TENS and General Guidelines

The use of the term “TENS” has been inconsistent and somewhat loose in the literature, leading to much confusion among clinicians and patients. This inconsistent use may also fuel misunderstandings and misuse of TENS in clinical practice. By strict definition, TENS is any technique that delivers electricity across the intact surface of the skin to activate underlying nerves7; however, when talking about TENS, most literature and clinicians tend to refer to “conventional” TENS, rather than the broad definition. Conventional TENS is the most widely used TENS technique and is often used for pain control. While parameters vary across devices and within the literature, conventional TENS typically uses low intensity (meaning it causes paresthesias without an increase in pain), high frequency (generally between 50 to 100 Hz), and small pulse width (typically ranging from 50 to 200 μs).7,8

TENS can be used as a stand-alone treatment or in combination with skilled therapy. For example, TENS can be a preparatory intervention used to manage pain before skilled therapy. It can be applied during therapeutic activities, occupational engagement, or exercises to decrease pain. TENS can also be used to help address pain after therapy. Because TENS is safe and effective for post-surgical pain, occupational and physical therapists can utilize it in multiple ways during rehabilitation to address pain and increase patient participation in therapy. TENS can also be incorporated into a patient’s daily routine as a part of their pain self-management plan. 

Electrode Placement

Electrode placement for conventional TENS is generally on the outer margins of the pain. For post-surgical pain, electrodes can be placed on skin with adequate sensation around the margins of the surgical site or other areas of reported pain. Electrodes are typically positioned approximately 5 cm on either side of the suture line to reduce the chance of any damage to the incision when removing the electrodes.1 If the patient cannot tolerate TENS near the incision site, electrodes can be positioned along peripheral nerves proximal to the pain, at contralateral sites that mirror the pain, on acupuncture or trigger points, or paravertebrally on relevant dermatomes.1

While it may seem complicated at first, remember that electrode placement often requires repositioning, and therapists should follow the patient’s lead. The intensity of the applied current is dependent on the person’s tolerance and may need to be adjusted frequently for optimal pain management. Gently increase the intensity until the patient feels “strong but comfortable” paresthesias and reports decreased pain. If needed, turn the unit off, reposition, and test again. Qualitative research from patients using TENS suggests that therapists should incorporate a learning phase when introducing TENS to allow patients to optimize its usage.9 It is important to remind patients that they may need to personalize the positioning of the electrodes and the TENS settings and readjust them over time. It may take some exploration and occasional readjustment to find the optimal electrode placement.

Most over-the-counter TENS units come with lay instructions and are user-friendly. However, some electrical stimulation units in rehabilitation settings may have multiple channels and waveforms, allowing for more advanced customization. If using a single channel, you can place two electrodes on opposite sides of the outer margins of the painful area. Horizontal versus vertical placement depends on the location of pain and available tissue with functional sensation. For larger areas, a dual-channel TENS with two pairs of electrodes may be necessary. Currents from each channel can remain independent using parallel electrode positions or currents can intersect using crisscross electrode positions.5 Therapists should be aware that the positioning of the black (cathode) lead versus red (anode) lead electrodes can affect the intensity, distribution, and quality of TENS sensation.5 However, the outcome is often unpredictable and may vary according to the device manufacturer. In general, the black lead is the active electrode and will excite neural tissue, so it should be positioned over the peripheral nerve to be stimulated.5

Therapists should recognize the benefits of various electrode placements, but in the end, the best approach is to explore various placements with the patient and find what works for them within safe parameters. The same general rule applies to intensity, frequency, and pulse width. Consider how this modality is being used when determining duration. For example, when using it before or after therapy for pain relief, recommendations are typically in the 30-minute range. However, using TENS during therapy or activity engagement may warrant longer use. As with other parameters, explore effectiveness with the patient and remember that pain relief after using TENS can vary and patients may choose to use it multiple times throughout the day.

Safety Considerations

Contraindications to using TENS are often listed as cardiac pacemakers and implantable cardioverter defibrillators.1 Precautions commonly include pregnancy, epilepsy, deep-vein thrombosis, active malignancy, and impaired sensation.1 It is possible to use TENS in some of these situations when it is applied to treat an unrelated pain that is far enough away from the affected area. However, therapists should consult with the primary physician first and patients should be monitored carefully.1 TENS should not be used next to transdermal drug delivery because the currents may interfere. When using TENS, therapists should always inspect the skin beforehand to ensure it is healthy and sensate, and afterward to assess for any irritation. Although adverse reactions to TENS are uncommon, when present, they generally include minor skin irritation. 

How Will My Patient Respond to TENS?

Unfortunately, there are no factors that have been found to identify whether or not an individual will respond favorably to TENS. If possible, it may be beneficial to have the patient try it before surgery to see how they respond. Some patients may be apprehensive about electrotherapy, while others find they do not like the sensation of TENS in particular. The truth is TENS may not be beneficial for everyone. For all of these reasons, therapists should empower patients with an opportunity to safely explore TENS as part of their pain management plan. 

To do this, therapists should always perform a comprehensive assessment before using TENS and provide skilled education and training. For example, therapists should educate patients on the neurophysiology of pain, tissue healing, graded exposure, and the use of electrotherapy modalities for pain management, and provide training on the safe and correct use of the TENS unit. To ensure patient comprehension, therapists can employ teach-back techniques. 

Comprehensive Pain Management

While TENS can be a very beneficial modality for post-surgical pain, it is often only one piece of the puzzle. Pain management should always be approached from a biopsychosocial perspective utilizing the interdisciplinary team and multimodal interventions. Therapists should consider incorporating additional evidence-based interventions alongside TENS for a more holistic approach to post-surgical pain management and long-term carryover. 

For example, therapists can assist patients in developing a pain self-management plan and implement self-regulation interventions such as sensory reeducation, desensitization training, and graded exposure. They can also provide pain neuroscience education, explore pain coping strategies, utilize other physical agent modalities, practice activity pacing or mindfulness, use virtual reality, and incorporate manual techniques as appropriate. Pain management is complex, and pain is always a personal experience. Therapists should strive to respect each patient’s unique pain experience throughout the rehabilitation process. 

Conclusion

Conventional TENS is a non-invasive, inexpensive, safe, and easy-to-administer modality that can help address post-surgical pain with minimal side effects. Current evidence suggests that it is effective at reducing post-surgical pain and reducing analgesic consumption when used appropriately.1,6,10 It is important to provide clear, simple instructions for the safe use of TENS as patients may continue to use it outside of therapy or after discharge. Lastly, therapists should use TENS intentionally and within a biopsychosocial approach to pain management alongside other evidence-based pain management interventions. Depending on the evaluation and the needs of the patient, therapists can utilize TENS to manage pain in preparation for therapy, during therapy, while engaging in meaningful activities, after therapy, or as part of a pain self-management program throughout the patient’s daily routine. 

John V. Rider, PhD, OTR/L, MSCS, CPAM, CEAS, is an assistant professor at Touro University Nevada in the School of Occupational Therapy and works as a community-based occupational therapist for Good Life Therapy in Las Vegas. For more information, contact [email protected]

References

1.     Gan TJ. Poorly controlled postoperative pain: prevalence, consequences, and prevention. J Pain Res. 2017;10:2287-2298. 

2.     Johnson, M. Post-surgical pain: the status of evidence for the use of transcutaneous electrical nerve stimulation (TENS). Analgesia & Resuscitation: Current Research, 2017, 6(1);1000e109

3.     Merskey H, Bogduk N, eds. Classification of Chronic Pain. 2nd ed. International Association of the Study of Pain; 2011.

4.     Nambiar VK. Role of transcutaneous electrical nerve stimulation (TENS) in management of post-operative pain (Thoracotomy). Int J Health Sci Res. 2017; 7(7):336-339.

5.     Johnson M. Transcutaneous Electrical Nerve Stimulation (TENS): Research to Support Clinical Practice. New York, NY. OUP Oxford, 2014. 

6.     Parseliunas A, Paskauskas S, Kubiliute E, Vaitekunas J, Venskutonis D. Transcutaneous electric nerve stimulation reduces acute postoperative pain and analgesic use after open inguinal hernia surgery: a randomized, double-blind, placebo-controlled trial. The Journal of Pain. 2020;22(5);533-544.

7.     Johnson M. Transcutaneous Electrical Nerve Stimulation: Mechanisms, Clinical Application and Evidence. Rev Pain. 2007;1(1):7-11. doi:10.1177/204946370700100103

8.     Charlton J. Core Curriculum for Professional Education in Pain. 3rd ed. Seattle: IASP Press. 2005

9.     Gladwell PW, Badlan K, Crapm F, Palmer S. Problems, solutions, and strategies reported by users of transcutaneous electrical nerve stimulation for chronic musculoskeletal pain: qualitative exploration using patient interviews. Physical Therapy. 2016;96(7);1039-1048.

10.  Li J, Song Y. Transcutaneous electrical nerve stimulation for postoperative pain control after total knee arthroplasty: A meta-analysis of randomized controlled trials. Medicine (Baltimore). 2017;96(37):e8036.