Transcutaneous Electrical Nerve Stimulation Unit: Pain Treatment (Rehabilitation Therapy)

ALERT

Transcutaneous electrical nerve stimulation (TENS) should not be used with patients who present with impaired cognition or understanding of instructions, epilepsy, or impaired sensation at or around the treatment area.

Never place TENS electrodes:

• Over the trunk or abdomen of a pregnant patient, with the exception of use for labor pain
• On a patient with a pacemaker
• On a patient who has an allergic response to the electrode pads or gel
• Over a patient’s eyes
• Over the anterior aspect of the neck or carotid sinus

Do not remove the electrodes until the TENS unit is off to avoid electrocution.

Use caution when using TENS with a patient who has sensitive skin, including dermatitis and eczema.

OVERVIEW

TENS is a physical agent modality used to treat pain. TENS provides electrical stimulation with modulated current directed at peripheral nerves through electrode placement.^{undefined#ref6">6} Therapists use TENS to reduce pain to prepare patients for functional activities. Indications for use of TENS include patients with acute or chronic pain (e.g., postoperative pain, osteoarthritis, diabetic neuropathy, chronic pelvic pain, chronic lower back pain, complex regional pain syndrome).^1,3,6 Additionally, TENS is used with patients with fibromyalgia⁴ and spinal cord injury with neuropathic pain.³

Parameters including frequency (pulse rate), intensity (amplitude), and pulse width (pulse duration) may be adjusted on the TENS unit. The therapist determines the parameters and the duration of treatment, depending on the patient’s diagnosis and tolerance of the treatment.

Frequency, or pulse rate, targets different nerve groups depending on the setting. When applied to the peripheral nerves, high frequencies (50 to 150 Hz)⁴ activate the delta-opioid receptors, blocking the perception of pain in the brain.⁶ Low frequencies (1 to 10 Hz)⁴ activate the mu-opioid receptors and cause the brain to release endorphins, which reduces the sensation of pain.⁶ Lower frequencies may be ineffective in patients with an opioid tolerance.⁴

Intensity, or amplitude, is critical to the successful use of TENS. The strongest intensity that is comfortable to the patient should be used.¹ Studies have shown that there is a positive cumulative effect with the use of TENS; however, repeated use at the same frequency, intensity, and duration may lead to a buildup of a tolerance of TENS, resulting in an analgesic tolerance.⁴ To counteract analgesic tolerance and to continue achieving positive outcomes, the therapist should change the frequency and intensity as the patient builds up a tolerance.

Pulse width, or pulse duration, can range from 1 to 400 microseconds.⁴ The higher the pulse width, the more stimulation the patient feels.

TENS treatment is considered either conventional TENS or acupuncture-like TENS.

• Conventional TENS has a high frequency, low intensity, and low pulse width (50 to 200 microseconds).⁴ Conventional TENS is used to treat pain.⁴
• Acupuncture-like TENS has a low frequency, high intensity, and high pulse width (100 to 400 microseconds).⁴ Acupuncture-like TENS is used for patients who are unable to tolerate conventional TENS.⁴

SUPPLIES

See Supplies tab at the top of the page.

EDUCATION

• Provide developmentally and culturally appropriate education based on the desire for knowledge, readiness to learn, and overall neurologic and psychosocial state.
• Explain to the patient and caregiver the purpose of TENS.
• Explain to the patient and caregiver the expectations for duration of treatment.
• Explain that the patient should feel a sensation or tingling during treatment, but not pain.
• Explain to the patient and caregiver that minor redness at the site of electrode placement is normal and will fade quickly.
• Explain to the patient and caregiver that lasting redness or skin irritation is not expected and should be reported.
• Instruct the patient to report pain experienced during treatment.
• Encourage questions and answer them as they arise.

PROCEDURE

1. Perform hand hygiene. Don appropriate personal protective equipment (PPE) based on the patient’s need for isolation precautions or the risk of exposure to bodily fluids.
2. Introduce yourself to the patient.
3. Verify the correct patient using two identifiers.
4. Explain the procedure and ensure that the patient agrees to treatment.
5. Assess the patient for pain.
6. Assess the patient’s cognition for understanding TENS treatment.

   Ensure that the patient consents to treatment and will be able to provide feedback throughout treatment.

7. Position the patient comfortably, exposing the treatment area for electrode placement.
8. Prepare the patient’s skin for electrode pad placement by cleansing the area with water or alcohol pads and letting it air dry.
9. Apply gel as needed to the bottom of each electrode pad, depending on the type of TENS unit and electrode pads used. Follow the instructions for the specific TENS unit and pads.

   Rationale: The use of gel on each electrode pad may be required, depending on the manufacturer.

10. Place either two or four electrode pads on the patient’s skin around the painful area, at least 5 cm (1 inch) apart.² Electrode pads may be placed vertically, horizontally, or diagonally. A variety of electrode placements may be effective, depending on where the patient is experiencing pain. Follow the instructions for the specific TENS unit.

    Rationale: TENS units come with either two or four pads, depending on the manufacturer.

    1. For a patient with lower back pain, place two or four electrode pads on either side of the spine, on the lower back, at least 5 cm (1 inch) apart (Figure 1).²
    2. For a patient with shoulder pain, place two or four electrode pads around the painful area at least 5 cm (1 inch) apart (Figure 2).²
    3. For a patient with knee pain, place two or four electrode pads around the painful area, two above the patella and two below, ensuring that they are at least 5 cm (1 inch) apart.²
11. Cover the electrode pads with medical tape or a patch of sticky adhesive to keep them in place.
12. Hook the pin connectors on the end of the electrode wires to the electrode pads.
13. Connect the wires to the TENS unit (Figure 3).
14. Determine and set the parameters for treatment, depending on the patient and goal of treatment.
    1. Frequency (pulse rate)
       1. Conventional TENS: Use a high frequency (50 to 150 Hz) to treat pain (in most cases).⁴
       2. Acupuncture-like TENS: Use a low frequency (1 to 10 Hz) for a patient who cannot tolerate a high frequency.⁴
    2. Intensity (amplitude)
       1. Conventional TENS: Apply up to the patient’s tolerance, which may be when the patient reports a tingling sensation.
       2. Acupuncture-like TENS: Apply until a visible contraction is observed in the muscle.
    3. Pulse width (pulse duration)
       1. Conventional TENS: Set at 50 to 200 microseconds.²
       2. Acupuncture-like TENS: Set at 100 to 400 microseconds.²
15. Set the treatment time from 20 to 60 minutes, depending on the patient’s needs.⁵
16. Turn the TENS unit on. Continue to monitor the patient throughout treatment. Watch the patient’s face for signs of intolerance. If the patient is unable to tolerate treatment, stop the procedure.
17. At the end of the treatment time, turn the TENS unit off and remove the electrode pads.
18. Remove any excess gel, if applicable, from the patient’s skin with a towel.
19. Discard supplies, remove PPE, and perform hand hygiene.
20. Document the procedure in the patient’s record.

MONITORING

1. Observe the patient for signs and symptoms of pain. If pain is suspected, report it to the authorized practitioner.
2. Monitor the patient for any signs of intolerance of TENS when turning on the unit and during the allotted treatment time, such as skin irritation, pain, and redness that does not fade at the electrode pad site. Slight redness that fades quickly at the site is normal.

EXPECTED OUTCOMES

• Patient tolerates TENS treatment without incident.
• Patient reports decreased pain after treatment.

UNEXPECTED OUTCOMES

• Patient is unable to tolerate TENS treatment.
• Patient experiences pain during TENS treatment.
• Redness persists at the site of the electrode pads.

DOCUMENTATION

• Education
• Patient’s progress toward goals
• Unexpected outcomes and related interventions
• TENS unit settings (frequency, intensity, pulse width)
• Placement of electrode pads
• Patient’s response to TENS treatment

OLDER ADULT CONSIDERATIONS

• Older adult patients’ skin may be sensitive as a result of age-related physiologic changes, which should be considered when placing electrode pads.

REFERENCES

1. Bracciano, A.G. (2021). Chapter 24: Physical agent modalities and biofeedback. In D.P. Dirette, S.A. Gutman (Eds.), Occupational therapy for physical dysfunction (8th ed., pp. 487-510). Philadelphia: Wolters Kluwer.
2. Cameron, M.H., Ocelnik, M. (2023). Chapter 13: Electrical currents for pain control. In M.H. Cameron (Ed.), Physical agents in rehabilitation: An evidence-based approach to practice (6th ed., pp. 269-283). St. Louis: Elsevier.
3. Hatch, M.N. and others. (2018). Neuropathic pain and SCI: Identification and treatment strategies in the 21st century. Journal of Neurological Sciences, 384, 75-83. doi:10.1016/j.jns.2017.11.018 (Level VII)
4. Johnson, M.I. and others. (2017). Transcutaneous electrical nerve stimulation (TENS) for fibromyalgia in adults. Cochrane Database of Systematic Reviews, 10, Art. No.: CD012172. doi:10.1002/14651858.CD012172.pub2 (Level I) (classic reference)*
5. Martimbianco, A.L.C. and others. (2019). Transcutaneous electrical nerve stimulation (TENS) for chronic neck pain. Cochrane Database of Systematic Reviews, 12, Art. No.: CD011927. doi:10.1002/14651858.CD011927.pub2 (Level I)
6. Walter, J.R., Winston, K. (2018). Chapter 29: Therapeutic occupations and modalities. In H.M. Pendleton, W. Schultz-Krohn (Eds.), Pedretti’s occupational therapy: Practice skills for physical dysfunction (8th ed., pp. 710-727). St. Louis: Elsevier.

*In these skills, a “classic” reference is a widely cited, standard work of established excellence that significantly affects current practice and may also represent the foundational research for practice.

Elsevier Skills Levels of Evidence

• Level I - Systematic review of all relevant randomized controlled trials
• Level II - At least one well-designed randomized controlled trial
• Level III - Well-designed controlled trials without randomization
• Level IV - Well-designed case-controlled or cohort studies
• Level V - Descriptive or qualitative studies
• Level VI - Single descriptive or qualitative study
• Level VII - Authority opinion or expert committee reports

Clinical Review: Meghan Jackson, OTR/L

Published: September 2023