Pain (from Ancient Greek ποινή - poine) is defined by the International Association for the Study of Pain (IASP) as “an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage”.
Pain may be experienced in response to any of four events: stimulation of a pain nerve sensor at the end of a nerve, actual damage to a pain nerve, damage in the brain where the nerve travels, and/or psychogenic causes that originate in the brain but the mechanism is not understood.
Psychogenic pain caused entirely by mental illness is exceedingly rare.
Pain is part of the body's defense system, triggering mental and physical behavior to end the painful experience. It promotes learning so that repetition of the painful situation will be less likely.
Description edit
To establish an understanding of an individual's pain, health-care practitioners will typically try to establish certain characteristics of the pain:
- Quality
- Intensity
- Localization
- Radiation
- Exacerbating Factors
- Ameliorating Factors
By using the gestalt of these characteristics, the source or cause of the pain can often be established.
Quality edit
The quality of the pain remains a key characteristic, and is often the first question a practitioner will ask. Typical descriptions of pain quality include sharp, stabbing, tearing, squeezing, cramping, burning, lancinating (electric-shock like), or heaviness. It may be experienced as throbbing, dull, nauseating, shooting or a combination of these. Indeed, individuals who are clearly in extreme distress such as from a myocardial infarction may not describe the sensation as pain, but instead as an extreme heaviness on the chest. Another individual with pain in the same region and with the same intensity may describe the pain as tearing which would lead the practitioner to consider aortic dissection. Inflammatory pain is commonly associated with some degree of itch sensation, leading to a chronic urge to rub or otherwise stimulate the affected area; but see discussion under itch. The difference between these diagnoses and many others rests on the quality of the pain.
Intensity edit
Pain may range in intensity from slight through severe to agonizing and can appear as constant or intermittent. The threshold of pain varies widely between individuals. Many attempts have been made to create a Pain scale that can be used to quantify pain. The purpose of these scales is to monitor an individual's pain over time, allowing care-givers to monitor response to therapy for example. Accurate quantification can also allow researchers to compare results between groups of patients. Pain may be quantified on a pain numeric rating scale (NRS) that ranges from 1-10 points; the accuracy of such as scale (using a cut point of 4 or more) for predicting pain that interferes with functioning is:[1]
- sensitivity 64%
- specificity 83%
Localization edit
A well-known example is when heart damage is felt to radiate down the left shoulder.[2]
This subjective localization of pain to an area of the body defines some kind of pain as neck pain, cutaneous pain, kidney pain, or the painful uterine contractions occurring during childbirth. This common usage of pain is not entirely consistent with the scientists' model of pain being a subjective experience.
Insensitivity to pain edit
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Inability to experience pain, as in the rare condition congenital insensitivity to pain or congenital analgesia, can lead to physical damage because of unawareness. Insensitivity to pain may also be caused by Hansen's disease or other forms of nerve damage.
CIP presents in early childhood, with children frequently getting injuries such as broken bones and bruises because they fail to develop the normal avoidance of pain, thus taking risks others would not.
Management and therapy of pain edit
Pain can be acute or chronic. The distinction between acute and chronic pain is not based on its duration of sensation, but rather the nature of the pain itself. Management and therapy is adequated to this distinction.
Acute pain edit
In general, physicians are more comfortable treating acute pain, which usually is caused by soft tissue damage, infection and/or inflammation among other causes. It is usually treated simultaneously with pharmaceuticals or appropriate techniques for removing the cause and pharmaceuticals or appropriate techniques for controlling the pain sensation, commonly analgesics. Acute pain serves to alert after an injury or malfunction of the body.
Chronic pain edit
General physicians have only elementary training in chronic pain management and patients suffering from it are referred to specialists.
Chronic pain may have no apparent cause or may be caused by a developing illness or imbalance. This disorder can trigger multiple psychological problems that confound both patient and health care provider, leading to various differential diagnoses and to patient's feelings of helplessness and hopelessness. Sometimes chronic pain can have a psychosomatic or psychogenic cause.[3] Chronic pain is sometimes referred to as the "disease of pain"
The failure to treat acute pain properly may lead to chronic pain in some cases.[4]
Other therapies edit
Hypnosis as well as diverse perceptional techniques provoking altered states of consciousness have proven to be of important help in the management of all types of pain.[5] Some kinds of physical manipulation or exercise are showing interesting results as well.[6]
CNS edit
If the signals are sent to the reticular formation and thalamus, the sensation of pain enters consciousness in a dull poorly localized manner. From the thalamus, the signal can travel to the somatosensory cortex in the cerebrum, when the pain is experienced as localized and having more specific qualities.
Analgesia edit
The body possesses an endogenous analgesia system, which can be supplemented with analgesic drugs to regulate pain. There is both an analgesia system in the central nervous system and peripheral receptors that decreases the grade in which pain reaches the higher brain areas. The perception of pain can be modified by the body according to gate control theory of pain.
Central edit
The central analgesia system is mediated by 3 major components : the periaquaductal grey matter, the nucleus raphe magnus and the nociception inhibitory neurons within the dorsal horns of the spinal cord, which act to inhibit nociception-transmitting neurons also located in the spinal dorsal horn.
Peripheral edit
The peripheral regulation consists of several different types of opioid receptors that are activated in response to the binding of the body's endorphins. These receptors, which exist in a variety of areas in the body, inhibit firing of neurons that would otherwise be stimulated to do so by nociceptors.
Factors edit
The gate control theory of pain, proposed by Patrick Wall and Ronald Melzack, postulates that nociception (pain) is "gated" by non-nociception stimuli such as vibration. Thus, rubbing a bumped knee seems to relieve pain by preventing its transmission to the brain. Pain is also "gated" by signals that descend from the brain to the spinal cord to suppress (and in other cases enhance) incoming nociception (pain) information.
Genotype and pain edit
Pain may be experienced differently depending on genotype; as an example individuals with red hair may be more susceptible to pain caused by heat[7] but redheads with a non-functional melanocortin 1 receptor (MC1R) gene are less sensitive to pain from electric shock.[8] Although the identification of human genes influencing pain has just begun, more than 230 genes are known to affect pain or analgesic sensitivity in mice.[citation needed]
Gene Nav1.7 has been identified as a major factor in the development of the pain-perception systems within the body. A rare genetic mutation in this area causes non-functional development of certain sodium channels in the nervous system, which prevents the brain from receiving messages of physical damage, resulting in congenital insensitivity to pain.[9] The same gene also appears to mediate a form of pain hyper-sensitivity, while other mutations may be the root of paroxysmal extreme pain disorder.[9] Various other forms of somatic sensitivity are unaffected.[10]
Pain and alternative medicine edit
A survey of American adults found pain was the most common reason that people use alternative medicine. Among American adults who used complementary and alternative medicine (CAM) in 2002, 16.8% used CAM to treat back pain; 6.6% for neck pain; 4.9% for arthritis; 4.9% for joint pain; 3.1% for headache; and 2.4% used CAM to treat recurring pain, with some using CAM to treat more than one condition.[11]
Traditional Chinese medicine views pain as a 'blocked' qi, akin to electrical resistance, with treatments such as acupuncture claimed as more effective for nontraumatic pain than traumatic pain. Although the mechanism is not fully understood, acupuncture may stimulate the release of large quantities of endogenous opioids.[12] A 2004 NCCAM-funded study showed that acupuncture provides pain relief and improved function in patients with osteoarthritis of the knee, causing some managed care organizations to support acupuncture as adjunctive therapy for this purpose.[13] The National Institutes of Health's 1997 Consensus Statement on Acupunture notes that research has been mixed, partly due to difficulties with designing clinical studies with the proper controls.[14]
CAM may also involve the use of nutritional supplements in pain treatment. Options include curcumin, a polyphenol found in turmeric and a natural COX-2 inhibitor,[15] glucosamine, chondroitin, bromelain and omega-3 fatty acids. Glucosamine and chondroitin were found to be effective only in a minority of pain patients, those suffering from moderate to severe pain, but was otherwise equivalent to a placebo.[16]
Philosophy of pain edit
The concept of pain has played an important part in the study of philosophy, particularly in the philosophy of mind. The question of what pain actually consists in is still open since any evaluation is dependent upon what subject one approaches the question from. Identity theorists assert that the mental state of pain is completely identical with some physical state caused by various physiological causes. Functionalists consider pain to be defined completely by its causal role (ie in the role it has in bringing about various effects) and nothing else. Some theologians and other spiritual traditions have much to say about the nature of pain and its various spiritual consequences, especially its role in growth, understanding, compassion, and in providing an aspect of life to be overcome.
Survival benefit edit
Despite its unpleasantness, pain is an important part of the existence of humans and other animals; in fact, it is vital to survival. Pain encourages an organism to disengage from the noxious stimulus associated with the pain. Preliminary pain can serve to indicate that an injury is imminent, such as the ache from a soon-to-be-broken bone. Pain may also promote the healing process, since most organisms will protect an injured region in order to avoid further pain. People born with congenital insensitivity to pain usually have short life spans, and suffer numerous ailments such as broken bones, bed sores, and chronic infection.
The study of pain has in recent years diverged into many different fields from pharmacology to psychology and neurobiology. It is also a separate sub-discipline in some terminal illnesses specializations.
Interestingly, the brain itself is devoid of nociceptive tissue, and hence cannot experience pain.
Chronic pain, in which the pain becomes pathological rather than beneficial, may be an exception to the idea that pain is helpful to survival, although some specialists believe that psychogenic chronic pain exists as a protective distraction to keep dangerous repressed emotions such as anger or rage unconscious.[3] It is not clear what the survival benefit of some extreme forms of pain (e.g. toothache) might be; and the intensity of some forms of pain (for example as a result of injury to fingernails or toenails) seem to be out of all proportion to any survival benefits.
Pain as pleasure edit
Pain and nociception in other species edit
Pain is defined as a subjective conscious experience. The presence or absence of pain even in another human is only verifiable by their report; "Pain is whatever the experiencing person says it is, and exists whenever he says it does."[17] Currently, it is not scientifically possible to prove whether an animal is in pain or not, however it can be inferred through physical and behavioral reactions.
In veterinary science all uncertainty is overcome by assuming that if something would be painful for a human then it would be painful for an animal.[18] Where possible, analgesics are used preemptively if there is any likelihood of pain being caused to an animal.
See also edit
References edit
- ^ Krebs, Carey, and Weinberger, “Accuracy of the Pain Numeric Rating Scale as a Screening Test in Primary Care,” Journal of General Internal Medicine 22, no. 10 (October 21, 2007): 1453-1458, doi:10.1007/s11606-007-0321-2 (accessed September 28, 2007).
- ^ Ann Waugh, Allison Grant (2001). Anatomy and Physiology in Health and Illness. Edinburgh: Churchill Livingstone. pp. pp 174-175. ISBN 0443-06468 7.
{{cite book}}:|pages=has extra text (help) - ^ a b Sarno, John E., MD, et al., The Divided Mind: The Epidemic of Mindbody Disorders 2006 (ISBN 0-06-085178-3)
- ^ Dahl JB, Moiniche S (2004). "Pre-emptive analgesia". Br Med Bull. 71: 13–27. PMID 15596866.
- ^ Robert Ornstein PhD, David Sobel MD (1988). The Healing Brain. New York: Simon & Schuster Inc. pp. pp 98-99. ISBN 0-671-66236-8.
{{cite book}}:|pages=has extra text (help) - ^ Douglas E DeGood, Donald C Manning MD, Susan J Middaugh (1997). The headache & Neck Pain Workbook. Oakland, California: New Harbinger Publications. ISBN 1-57224-086-5.
{{cite book}}: CS1 maint: multiple names: authors list (link) - ^ Liem EB, Joiner TV, Tsueda K, Sessler DI (2005). "Increased sensitivity to thermal pain and reduced subcutaneous lidocaine efficacy in redheads". Anesthesiology. 102 (3): 509–14. PMID 15731586.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ Mogil JS, Ritchie J, Smith SB; et al. (2005). "Melanocortin-1 receptor gene variants affect pain and mu-opioid analgesia in mice and humans". J. Med. Genet. 42 (7): 583–7. doi:10.1136/jmg.2004.027698. PMID 15994880.
{{cite journal}}: Explicit use of et al. in:|author=(help)CS1 maint: multiple names: authors list (link) - ^ a b Fertleman CR, Baker MD, Parker KA; et al. (2006). "SCN9A mutations in paroxysmal extreme pain disorder: allelic variants underlie distinct channel defects and phenotypes". Neuron. 52 (5): 767–74. doi:10.1016/j.neuron.2006.10.006. PMID 17145499.
{{cite journal}}: Explicit use of et al. in:|author=(help)CS1 maint: multiple names: authors list (link) - ^ Hopkin, M (2006-12-13). "The mutation that takes away pain". Nature News. doi:10.1038/news061211-11. Retrieved 2008-03-29.
- ^ Barnes, P (2004-05-27), CDC Advance Data Report #343. Complementary and Alternative Medicine Use Among Adults: United States, 2002, U.S. National Center for Complementary and Alternative Medicine
{{citation}}: Unknown parameter|coauthors=ignored (|author=suggested) (help); news release. - ^ Sapolsky, Robert M. (1998). Why zebras don't get ulcers: An updated guide to stress, stress-related diseases, and coping. New York: W.H. Freeman and CO. ISBN 0-585-36037-5.
- ^ Berman BM, Lao L, Langenberg P, Lee WL, Gilpin AM, Hochberg MC (2004). "Effectiveness of acupuncture as adjunctive therapy in osteoarthritis of the knee: a randomized, controlled trial". Ann. Intern. Med. 141 (12): 901–10. PMID 15611487.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ Ramsay (1997-11-5). "The National Institutes of Health (NIH) Consensus Development Program: Acupuncture". Retrieved 2008-03-29.
{{cite web}}: Check date values in:|date=(help); Text "first DJ" ignored (help) - ^ Sharma S, Kulkarni SK, Agrewala JN, Chopra K (2006). "Curcumin attenuates thermal hyperalgesia in a diabetic mouse model of neuropathic pain". Eur. J. Pharmacol. 536 (3): 256–61. doi:10.1016/j.ejphar.2006.03.006. PMID 16584726.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ Clegg DO, Reda DJ, Harris CL; et al. (2006). "Glucosamine, chondroitin sulfate, and the two in combination for painful knee osteoarthritis". N. Engl. J. Med. 354 (8): 795–808. doi:10.1056/NEJMoa052771. PMID 16495392.
{{cite journal}}: Explicit use of et al. in:|author=(help)CS1 maint: multiple names: authors list (link) - ^ cite sourced from McCaffery M. Nursing management of the patient in pain. Philadelphia, Pa: JB Lippincott 1972.
- ^ American College of Veterinary Anesthesiologists' position paper on the treatment of pain in animals retrieved 2007-01-06
External links edit
- SmithBlue/PainExperience at Curlie
- Acute Pain Medicine: Scientific Evidence (2nd ed) (2007 updated version)