Transcutaneous Electrical Nerve Stimulation - TENS

TENS

Transcutaneous Electrical Nerve Stimulation (TENS)

In this method two or more electrodes are applied on the skin around the painful area and weak electric current is applied. When given TENS, the patient feels typical tingling produced by the electric current. Modern TENS devices are capable of producing electric current of varying intensity and pulsation, which is adjusted for each individual patient in order to get best results.

The mechanism of action of TENS is though to be through the activation of opioid receptors in the brain. In other words, the electric current works in the same way as the injection of morphine. Another possible mechanism is that the the impulses produced by the electric current compete with the pain signals conducted by nerves to the brain and by doing so reduce the intensity of pain. This is also one of the mechanisms of action of acupuncture. TENS devices are available in many hospitals and may also be rented by patients for the time of their labor.

TENS is appealing to patients as there are virtually no risks for the mother and the baby, and there has been considerable interest in this way of relieving pain in various conditions, such as chronic back pain, arthritis, cancer, pain after surgical operations and so on. There is also research on TENS in regards to relieving pain in labor.

As with many similar methods of treating pain, there is considerable controversy regarding the efficiency of TENS. Some studies show great results while others show no difference at all. In the Cochrane Database, the golden standard of medical evidence, there is the review on TENS for chronic pain updated in 2008. Its conclusion is that the effectiveness of this method in the treatment of chronic pain is uncertain and suggest that more studies are needed. There are no completed reviews regarding the effectiveness of TENS in acute or labor pain.

Older review on TENS in labor that reviewed eight trials and was published in 1997 came to similar conclusion that there was ‘no compelling evidence for TENS having any analgesic effect during labour’. Only one of the eight trials showed good effect of TENS in some patients. Even so, over 80% of them still needed additional pain relief. Despite this women did seem to appreciate some of the features of TENS by stating that they would use it for future births. Reporting in the British Journal of Obstetrics and Gynaecology, the author of the review Dawn Carroll and her colleagues said: ‘the argument may be that something that appears to do no harm, and which may do some good, is worth using’. The downside to this argument, they pointed out, is that resources which might better be directed to the provision of more effective treatment of pain, are being used inappropriately.

The bottom line is, the efficiency of TENS is questionable. To me, it does not come as a surprise. I believe that it can bring some relief to patients with mild or moderate pain in chronic conditions. Labor pain, on the other hand, is very intense and requires serious interventions. Believe me, if TENS was really effective, we would use in every patient in labor.

References:

1. Nnoaham KE, Kumbang J. Transcutaneous electrical nerve stimulation (TENS) for chronic pain. Cochrane Database of Systematic Reviews 2008, Issue 3. Art. No.: CD003222. DOI: 10.1002/14651858.CD003222.pub2.

2. Carroll D. et al. (1997) Transcutaneous electrical nerve stimulation in labour pain: a systematic review. British Journal of Obstetrics and Gynaecology 104, 169-175.

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Dr. Eugene Smetannikov is a practicing anesthesiologist with the interest in obstetric anesthesia. He is the author of the most comprehensive book on the subject, The Truth About Labor Epidural