May 26, 2009

The Gate Control Theory of Pain Management in Childbirth and the Epidural

Last night I was teaching a refresher childbirth education class to a couple. The father is a physician and the mother is an occupational therapist – so when I started talking about non-pharmacological methods of pain relief, specifically those related to the Gate Control Theory, they knew exactly what I was referring to. They added to the conversation by sharing that this method of pain relief can really help a mother during her first labor. This particular mom labored submerged in a warm birth tub up to the time she was ready to push. She explained that the water really helped relieve a lot of the pain she was experiencing.

You may be asking how something as simple as a warm bath could act as a pain reliever. This is explained by the Gate Control Theory of Pain, which was developed in 1962 by Ron Melzack and Patrick Wall and details the role of the mind and brain in pain perception. They explain that 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. There are two types of nerve fibers that descend from the brain through the spinal cord: C-fibers, or slow/small neural fibers; and A-delta nerve fibers, or fast or large pain fibers. If impulses along the slow pain fibers outnumber impulses along the fast pain fibers, the gate is opened and pain impulses are transmitted to, and perceived by, the brain. However, the same holds true that if there is more stimulation of the fast fibers the gate closes, inhibiting transmission of pain impulses, reducing pain perception, and stimulating the release of endorphins. To put it in REALLY simple terms, the brain can only process so many signals at a time.

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. 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. All of these methods are so accessible and can be used by the laboring mother or offered by a partner or doula.

I find it interesting that the Gate Control Theory and these nonpharmcological methods produce an outcome similar to the relief of an epidural. Ok, granted, an epidural takes much less effort to sustain pain relief, offers a chance for the laboring mother to sleep and has a very high rate of success. (Although it is important to note that the epidural does not offer total pain relief. For some women, it offers none at all.) Here is a very simplified explanation of how the epidural works: a hollow needle is inserted into the epidural space below the spinal cord, and the epidural anaesthesia passes through a catheter that remains in the back for the remainder of labor. The anaesthesia blocks the A-delta and C-fibers from transmitting pain to the brain, offering relief and numbness from the waist down.

It is comforting to know that there are several options for pain relief during childbirth. Even for those choosing to have an unmedicated birth, there are still plenty of ways to relieve the innate pains of labor. Prepare in advance, arranging for a birth tub if you are birthing at home or investigating whether your birth center or hospital has a tub/shower. Purchase a hot water bottle, get an ice pack, and have a rice sock or massage tools available.

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