Lesson 1 of 4
When TENS helps, and when not to use it
What TENS is for, what the trials show, and the patients and sites to avoid.
TENS passes pulsed current through the intact skin from self-adhesive pads. The aim is to stimulate skin nerves and so reduce the transmission of pain, which Johnson describes as electrically “rubbing the pain away” (Johnson 2014, p. 2). It is used as an adjunct for musculoskeletal, neuropathic and inflammatory pain: alone for mild to moderate pain, with medication for moderate to severe pain (Johnson 2014, p. 2).
The largest review pooled 381 randomised trials of strong, non-painful TENS at or close to the site of pain. Pain was lower during or immediately after TENS than with placebo, with moderate-certainty evidence (91 trials, 4841 participants); adverse events were poorly reported, generally mild and no different from comparators (Johnson 2022, abstract). Its onset and offset are rapid, so judge it while the unit is on (Pallett 2014, p. 224).
Guidelines still disagree. NICE recommends TENS as an adjunct for osteoarthritis and rheumatoid arthritis but not for non-specific chronic low back pain or in labour, and its 2021 guidance on chronic pain recommends not offering it (Johnson 2022, introduction). Trials that used an appropriate technique and dose were more likely to find an effect (Johnson 2014, p. 1; lesson 3).
There are no reliable predictors of who will respond, so run a supervised trial to screen for suitability and teach safe electrode positions and settings (Johnson 2014, p. 4).
Benefit and risk
Benefit
- Pain during use
Lower than placebo during or immediately after stimulation, moderate certainty (Johnson 2022, abstract).
- Self-administered
Patients titrate the dose themselves; there is no toxicity or overdose (Johnson 2014, p. 2).
Risk
- Skin
Adverse events were minor, mostly redness and itching at the electrode sites (Johnson 2022, discussion).
- Device interference
An implanted cardiac device can misread the TENS current as heart activity (Johnson 2014, p. 5).
Contraindications and precautions
- Implanted defibrillator
Contraindicated: there is strong evidence that TENS interferes with cardioverter defibrillators (Johnson 2014, p. 5).
- Pacemaker
Contraindicated. Some centres use TENS with ECG testing and monitoring at the first application, but not if the pacemaker cannot override a spontaneous tachycardia or there is no demand (VVI) pacing of at least 40 bpm; a cardiologist must be involved (Johnson 2014, p. 5).
- Pregnancy, epilepsy
Not over the abdomen in pregnancy or the head in epilepsy. Manufacturers list both as contraindications; evidence of harm is limited, and some practitioners use TENS away from the area of concern with careful monitoring (Johnson 2014, pp. 4–5).
- Implants and attachments
Ask about implants and external attachments first. Over stents, percutaneous drains and central venous catheters, use low-intensity conventional TENS without muscle contraction and monitor closely (Johnson 2014, p. 5).
- Skin and vessels
Not over damaged skin, skin with altered sensation, deep vein thrombosis or recent haemorrhage; not on irradiated skin in the immediate weeks after radiotherapy (Johnson 2014, pp. 5–6).
- Malignancy
Not over active malignancy in patients with treatable tumours in acute oncology; in palliative care, under the supervision of a palliative care specialist (Johnson 2014, p. 5).
- Hazardous sites
The anterior neck over the carotid sinus, across the eyes, across the chest front to back, and temple to temple (Johnson 2014, p. 6).