TURN DOWN THE VOLUME!

                   Pain: Surviving the Body's Alarm System

Mechanisms of Pain, Approaches to Prevention
With Insights Gained from Studies of Phantom Limb Pain


by Thom Bloomquist, MS, CRNA-FAAPM

 
    Pain is part of human existence.  Pain has been depicted from the time of the earliest cave paintings, in oral history and down through the ages to our written history.  Descriptions include the hurt involved in childbirth, in hunting and warfare; the full gamut of pain-producing experiences.  Pain is reported in terms like aching, burning, lightning, lancinating, throbbing, pressure and a host of other adjectives.  Pain is symbolized in gestures and apparent in facial expressions.  Mothers remark on the difference between a baby's ordinary cry and one that communicates real hurt.  Amputees are acquainted with all these aspects of pain, plus one form of suffering unique to amputees: Phantom Limb Pain (PLP).  Although braces and prosthetics are known to have been used as far back as the ancient Egyptians, PLP did not appear in medical literature until the French surgeon Pare described it in 1551.  Phantom Limb Pain is labeled as such because patients describe pain in places that no longer exist: their absent limbs.  Recent studies of PLP have shed new light on pain and now suggest further improvements in pain management for all patients.

How significant a problem?

    The economic toll for chronic pain (other than cancer) in the US exceeds $100 billion per year.  Approximately 185,000 surgical amputations were performed in 1996, according to the U.S. Department of Health and Human Services.  70 percent of amputees suffer some degree of burning, cramping and other types of phantom pain in the first few weeks after amputation.  In addition,  painless phantom sensations, or the patient's occasional "feeling" of the missing part, are almost universal.

    You may have had a phantom sensation.  If you had a nerve block in the dental chair, you may have experienced a feeling of a swollen lip.  You did not perceive a hole in your face where that nerve was blocked; rather, you probably felt a fat lip.  This is a form of a phantom sensation.  Bodily perceptions can be confused.

    Although most common with limb amputation, PLP sometimes also can follow the loss of teeth, fingers, intestines, breasts and the genitals. Unfortunately, even seven years after amputation, about half of amputees still suffer burning, cramping, throbbing or crushing Phantom Limb Pain.  Phantom pain can be a temporary phenomenon or a lifelong, even life-altering pain problem.  This particular discomfort is difficult to manage because, unlike most other forms of pain, PLP does not have a simple "tissue injury produces pain" explanation.

    People who have a painful limb prior to surgery have a greater chance of developing bothersome chronic phantom limb pain after amputation; therefore, it's in the amputee's best interest to become familiar with the body's internal alarm signal : pain.   In fact, gaining information about pain is recommended for anyone facing surgery or dealing with a pain problem.

    As the real leader of your own healthcare team, you the consumer should be an active participant in decisions about your care.  It starts by being as accurate as possible when talking with your anesthetist about pain and anesthesia.  Ask questions.  Request answers in understandable terms.  These are busy professionals, yes, but it's your body, and you deserve to know what's going on.  You can be a better team leader if you have a clear understanding of events and how things work.

Mechanisms of pain

The tissue level

    When a body part is damaged, as during surgery, the broken cells release a group of chemicals including histamine, bradykinin and prostaglandins.  These chemicals start the process of inflammation and stimulate the body's alarm system to notify the brain that something is wrong.  The same alarm can be sounded directly by nerve sensors with specific alarms for problems like temperature or pressure.  It is at the tissue level that NSAIDs (nonsteroidal anti-inflammatory drugs) like ibuprofen work to relieve pain.  Narcotic analgesics, although more potent drugs, have little value here because the body does not build narcotic receptors at the tissue level.

Other effective pain relief measures here include:

  • Local anesthetics or numbing medicine, like lidocaine
  • Warm or cold packs
  • Elevating an injured part above the heart to limit swelling
  • Massage and some muscle relaxants
  • Transcutaneous Electrical Muscle Stimulation (TENS)
  • Micro-current technology (a refinement on TENS) like the Alpha-Stim or Trio-Stim.

  •     For amputees, correct stump-wrapping and precise prosthetic fit are crucial in limiting discomfort.  Proper stump-wrapping aids blood flow back toward the heart (venous return) and aids in the repair of interrupted blood vessels responsible for the "throbbing pain" patients describe.

        All medicines have side effects and pain managers will often combine safer low-potency drugs with stronger more potent drugs to get the best combination of safety and effectiveness, i.e. the most beneficial risk/benefit ratio.   For example, natural pain relief measures like massage, warm packs, acupuncture and physical therapy are often combined with the selected medicines and with advanced techniques like nerve blocks in a plan specifically tailored for the individual patient.

    Mechanisms of pain -- the spinal cord

        The spinal cord carries information to and from the brain, including pain signals.  In the process, the signal must cross nterconnections, or "synapses" between nerve cells.  The alarm signal going toward the brain comes to the end of one nerve, where it causes the release of chemical messengers called neurotransmitters.  These attach only to coded receptors on the beginning of the next nerve cell.  The process continues passing the signal upward much like a voice is converted from sound waves to electrical signals and back to sound over a phone system.

        The spinal cord, which does the sending/receiving for the brain, contains many types of synapses and at these sites the "volume" or intensity of incoming pain signals can be influenced.  For example, the spinal cord includes narcotic receptors.  Thus, narcotics can work very effectively directly on the spinal cord to decrease the volume of the body's alarm signals.  These pain relieving drugs can be given by mouth, by intramuscular or IV injection, through skin patches or, for maximum effect, given in the back close to the spinal nerves. Obviously, administering a drug at the spinal cord level is far more complex than getting a shot in the arm.  Such techniques as spinals, epidurals and other nerve blocks are used only by specially trained nurse anesthetists and anesthesiologists after careful patient selection and preparation in a hospital or clinic setting.

        Some drugs that were originally developed as antidepressants can also be helpful at this level.  Working on different synapses than narcotics, they help turn down the volume of the pain alarm without blocking normal body functions or causing numbness like local anesthetics.  Amitryptyline (Elavil) and trazodone (Desyrel) are examples of this class of drugs.

    Mechanisms of pain -- the brain

        In the brain, the alarm signal from the spinal cord is processed in the memory and emotion centers to become the sensory and emotional experience we call pain.  The brain also has its own specialized sites where medicines and non-drug pain relief measures work to decrease pain volume and affect how we react to, and cope with, discomfort.

        Recently researchers have found a gene that determines how our body's alarm system gets constructed before birth.   Like hair color, skin pigmentation and eye color, our alarm systems are unique to each individual.  Furthermore, pain is always a subjective experience: each person feels pain and manages it differently.  Because of these variables, pain and suffering are not exactly synonymous.  Some people seem to suffer very little discomfort from major surgery while others suffer greatly from minor injuries.  Anesthesia providers involved in pain management tailor their approach to suit each individual patient's unique and special requirements.
     
     

    On the bright side -- positive measures

        Authors have reported that patients with painful body parts before surgical amputation sometimes experience less PLP when aggressive pain relief measures were initiated BEFORE surgery, and then combined with effective sustained pain relief measures continued after surgery.  This suggests that nurse anesthetists and anesthesiologists can better benefit their patients by assuming a more active role in providing pain relief.  Perhaps now we can begin to think in terms of preventing lifelong pain problems such as PLP.

    Toward a deeper understanding of pain

        Another new finding has been the manner in which pain pathways in the nervous system can actually change in response to sustained pain signals.  It appears that the presence of strong, long lasting pain actually alters the body's alarm receptors and causes them to become more sensitive -- a phenomenon known as "wind-up."  Under such conditions, usually silent receptors become activated and the area of the nervous system responsible for recognizing pain in that region of the body can become so acutely sensitive that it reports a pain alarm from usually non-painful stimuli, for example gently brushing the skin near a fresh incision.  These changes in the body and other changes in the brain can produce Phantom Limb Pain.  Phantom pain is not necessarily a false alarm; it is rather the pain signaling system gone awry. Perception, once again, is key.  Even though the stimulus that started that alarm might not normally produce such a disproportionate reaction, still, pain perceived by the brain is as real as real can be.

        When nerves are cut during amputation, some will attempt to regrow, slowly forming branches that sometimes reconnect to themselves, forming a bundle of nerve tissue or a neuroma, which can then become a "pain generator."  This pain alarm sensor is much bigger and more sensitive that the body's original design.

        The nervous system's ability to adapt is a wonderful attribute; it can help the body heal, respond to our changing environment and keep us going.  Yet, in this one special case, that adaptability can lead to ongoing discomfort.  These new findings suggest that the adaptability or "plasticity" associated with PLP might be caused by severe sustained pain.  Therefore, we might be able to limit this change if we aggressively manage the patient's discomfort in the perioperative period.

    What can be done?

        Preliminary evidence suggests that if we effectively control pain signaling around the time of surgical amputation, we might be able to help patients heal, with fewer individuals developing PLP.  I say, "might be able to" because these are new concepts and we are still learning about these systems, about how the body adapts, and how to do a better job of controlling pain.  More research needs to be done to confirm these findings and to discover better ways of helping the body turn down the alarm when it is no longer needed.  Revision of our ideas over the course of time is not a failure of science or medicine; rather, revisions demonstrate how anesthesia and medicine are constantly evolving.  New discoveries indeed should make us reconsider our understanding of how the body works.

        Long ago, pain was thought to come from evil influences and the heart was thought to contain our center of consciousness.  Burning phantom pain might be treated in those ancient times by digging up the amputated part and throwing it in a cold lake.  We have come a long way since those days.  The search for more of our body's secrets will always be an ongoing process.  It's not simple.  We use the term "Multimodal Approach" to mean combining different types of drugs and techniques to relieve patients' suffering.  There are some six billion types of bodies on this planet, all individuals, and it seems each one does things in a slightly different way. This signifies that for pain control, as for anesthesia care, there is no one "right" formula for everybody.  Your anesthetist or anesthesiologist will consider your medical history, list of medicines, allergies, laboratory results, reason for surgery, and local resources, among other factors, to make an anesthetic plan tailored just for you.  Anesthesia and pain relief are not "one-size-fits-all" ideas.
     
     

    Conclusion

        There is tempting evidence that the suffering from Phantom Limb Pain may be decreased and perhaps even prevented.  We will probably never be able to completely control how people's bodies respond to injury and illness, nor should we expect a complete absence of pain in our lives; however, we may be able to do a better job of controlling pain.  We can turn down the volume.

        Preoperatively, in most cases your nurse anesthetist or anesthesiologist will be informed of your scheduled case in time to plan for your anesthesia care.  Ideally, the pain and anesthesia teams would be consulted early enough to use this new information to your best advantage.  You, as an active informed consumer, can start the process of pain management yourself.

        Together, we need to continue to study how our bodies work and how they adapt and reconfigure after injury and illness. Since the earliest days of human beings, when knocked down, we have picked ourselves up, dusted off, and gone on again.  With new knowledge and tools, we are still learning improved ways to help people do that very most human thing -- to be a survivor.

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    About the author:

    Thom Bloomquist, MS, CRNA-FAAPM is a Certified Registered Nurse Anesthetist in practice with other nurse anesthetists at Cottage Hospital Woodsville, New Hampshire.  Thom is a Fellow in the American Academy of Pain Management.  His article is adapted from one he wrote originally for the Journal of the American Association of Nurse Anesthetists, and which was later published by InMotion, the official magazine of the  Amputee Coalition of America.  It is published here with permission.

    Thom is also a below-knee amputee.

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