September 11, 2012

TENS Machine- Transcutaneous electrical nerve stimulation

Among the many pain management techniques and methods, there is one that gets little attention here in the US. It is called the TENS Machine- Transcutaneous electrical nerve stimulation, and it is used throughout much of Europe.

What is the TENS machine? How Does It Work?

It is a non-invasive, drug free method of pain management. TENS machines is a small hand held device that delivers small amounts of electrical stimulation through two electrodes placed on the mother’s lower back region. This electrical stimulation triggers nerve fibers and works to block pain receptors to the brain. In a sense, it is primarily using the “Gate Theory of Pain Management” to achieve these positive effects.

What is the Gate Theory of Pain Management?
Before pain messages reach the brain, those messages encounter “nerve gates” in the spinal cord that open or close depending upon a number of factors (possibly including instructions coming from the brain). When the gates are open, pain messages “get through” more or less easily and pain can be intense. When the gates close, pain messages are prevented from reaching the brain and may not even be experienced.(1) In terms of pain, think about when you burn yourself. If you apply ice or cold compress to the burn area, relief is perceived even though the burn is still there, but if you take the ice or cold compress away the pain returns. The stimulation from the cold overrides and “close the gate” of the pain to be received by the brain.

For relief of pain during childbirth, the “gate” is the dorsal horn of the lumbar, a horn-shaped projection of gray matter in the posterior region of the spinal cord.(2) It relays information related to touch and pressure from muscles as well as regulating precise movement and unconscious proprioception. So when we apply sensory stimulation – such as heat, cold, water in a bath/shower, firm pressure, intradermal water blocks, Transcutaneous electrical Nerve Stimulation (TENS) and massage – the fast fibers are activated, endorphins are released, and the transmission and perception of pain never reaches the brain.

Does TENS have side effects? Can it cause problems for my baby?

Since TENS is a non-invasive technique, there are very few, if any side effects for most women and none for the baby. The most common issue that may arise is an allergic reaction due to the material of the electrodes, the conductive gel or the tape used to hold the electrodes in place. About 2% of patients experience such a reaction.(3)

What are the results?

Several studies support the use of TENS machines providing a very favorable result for labor and delivery. One study published in the Journal of American Physical Therapy Association showed a very favorable outcome among participants. The patients served as their own control and turned the unit off for several contractions during the middle and late periods of the first stage of labor to judge the effectiveness of TENS. Twenty-four hours after delivery, a physical therapist recorded the subjective response of patients and obstetricians separately on a questionnaire, which gave a rating scale of poor, moderate, or excellent for relief. We found TENS provided some form of relief to 87 percent of
the participants, and 20 percent reported excellent relief. Most participants expressed a willingness to use TENS if they gave birth again.(4)

Another study from the Department of Obstetrics and Gynaecology, Queen Mary Hospital, Pokfulam, Hong Kong shows a similar outcome. The result of this survey showed that TENS alone with or without the addition of entonox was sufficient for pain relief in 38% of the women. Furthermore, the use of TENS was associated with the shortest first and second stages of labour, and highest rate of spontaneous delivery. The role and merits of TENS for pain relief in uncomplicated labour should be explored further.(5)

How to get a TENS machine?
You can buy one online or rent one from a local physical therapist.

I often advise my students to build their “tool box” with a variety of pain management techniques since the length of labor or the desired approach are things that will not be discovered until in the process. Having a TENS machine available is just another tool that may become useful.




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