Transcutaneous Electric Nerve Stimulation (TENS)

Feels kinda like a buzzing or a vibrating buzz, if that makes any sense at all. I think it "distracts" one from feeling the actual pain in the area, in other words, it distracts the nervous system from interpreting the pain and instead, it tells us that there is a different sensation to interpret there. Don't know the proper jargon for the neurological adjustment/adaptation....hope this helps. It does work! I've used it before, my neighbor has used it, and I've helped lots of pts. with it, most of them stated that they got relief while the TENS unit was applied and turned on. Neat, huh?

I personally have used TENS therapy and have had the gate control theory explained many times but I think my understanding is rudimentary (sp?) at best. Basically the TENS unit sends out an electrical signal that can be steady or tapping, fast or slow depending on what setting is used. The idea is that the electrical signal interrupts/blocks the pain signal that nerves are sending to the brain and thus the brain doesn't get the pain signal. In regard to what conditions warrant TENs therapy I believe I have heard it is used for neuropathic pain, endometriosis, low back pain, myofascial and arthritis pain, bladder incontienance, visceral pain, and one website even noted post op pain control.

The one warning I have is to never go to remove the pads from someone before turning off the unit. I have done it myself and the high impulse I could stand on my back was a bit of a shock to my fingers.

There are several types of electrotherapies: TENS, Electroacupuncture (TENS on active acupoints), and PENS (percutaneous electrical nerve stimulation, which is TENS applied to needles inserted into active acupoints). TENS, PENS, and EA all stimulate the release of natural neurochemicals (such as endorphines) in the CNS, but PENS also causes the local effects of needling, such as activation of the immune system.

All three stimulate A-beta and A-delta nerve fibers causing a frequency-dependent endorphin release. Remember that the input of pain signals come from C- and A-delta fibers and this input can be modified from A-beta fibers before the pain signals reach the brain. Endorphin release from stimulation of the A-beta and A-delta fibers strongly inhibit the incoming pain signals.

So far, we know that low frequency stimulation [2Hz] stimulate the release of endomorphin and enkephalin while high frequency stimulation [100 Hz] stimulates the release of dynorphin. Beta-endorphin is initially stimulated at 2Hz and its release is inversely proportional to frequency. In addition to the release of enogenous opioids, other neurochemical analgesic factors are triggered by TENS/EA/PENS, such as serotonin and norephinephrine.

In addition to endogenous endorphins, TENS/EA/PENS also stimulate the release of anti-endorphins, which reduce the analgesic effect. High frequency stimulation causes a greater release of the anti-endorphins, which is why frequencies between 2 - 5 Hz are normally used, although some believe a mixed/alternating frequency between 2Hz and 100Hz elicits the greatest release of endorphins. Also, prolonged stimulation [approaching 3h] causes the release of anti-endorphins, which reduces the analgesic effect.




Loosely referenced from: Clinical Acupuncture:Scientific Basis by G. Stux and R. Hammerschlag (Eds) and Biomedical Acupuncture for Pain Management: An Integrative Approach by Ma et al.

I would like to reactivate this thread to say that the physiology of pain is well covered in chapter 8 of Thelan's Critical Care Nursing 5th Edition. Thelan's had the best coverage of the topic of any nursing text I've seen, although I must admit my exposure is somewhat limited.