Pain Forum最新文献

The International Association for the Study of Pain (IASP) definition of pain, by its emphasis on verbal communication, may contribute to the lack of recognition and treatment of pain in certain vulnerable groups of people. Additionally, the definition possesses an inherent Cartesian dualism, which may undermine effective treatment and contribute to stigmatization. Although the definition is valuable in that it addresses the irreducible subjectivity and lack of specificity of the pain experience, certain aspects deserve discussion and revision.

The current definition of pain adopted by the International Association for the Study of Pain (IASP) and the American Pain Society (APS) chapter of the IASP is unacceptable because its claims and consequences are inconsistent with the IASP's stated purpose. The definition's apparent claims that (1) only effective communication of pain brings pain into existence, and that (2) researchers and clinicians are merely objective evaluators of whether such communication has occurred are inconsistent with the lASP's purpose to improve care of patients with acute and chronic pain through attention to patients, to the relationship between them and their caregivers, and to social policy. The definition's success at rejecting the consequences of Cartesian dualism is only partial. The definition contributes to a lack of justice for nonverbal patients.

Cunningham has delivered a critique of the International Association for the Study of Pain (IASP) definition of pain from a very narrow standpoint. The reference to subjectivity and the multidimensional aspects of the definition were reduced to mean nothing more than an ability of “verbal report.” This indefensible straw man position was then demolished and replaced with a “signaling” theory of pain that was only minimally described. Cunningham's argument unfairly presents current medical practice as the enemy, oversimplifies the complexity of treating pain, and too easily dismisses our theoretical understanding of pain expressed through the IASP definition.

I agree with Bernard Rollin (in “Some Conceptual and Ethical Concerns About Current Views of Pain”) that it is implausible to hold that linguistic competence is a necessary condition for consciousness of pain. However, Rollin is incorrect to characterize this criterion as insulated from empirical disproof, because the best current theories of phenomenal consciousness that would support the criterion are themselves open to empirical disproof. Although I agree with Rollin that it would be implausible to deny that any nonhuman animals can feel pain, when we look closely at the relevant behavioral and neurophysiological evidence, we see that a good case can be made for saying that invertebrates (with the possible exception of cephalopods) probably cannot feel pain.

Cunningham raises important issues about the ethical issues facing pain researchers and practitioners and the need to ensure that far more must be done to eliminate needless pain. I suggest that inadequate knowledge and lack of will are more of a problem than lack of agreement about a suitable definition of pain. In the absence of a universal definition, education and legislation are needed to ensure competent treatment, particularly for those whose capacity to communicate is limited.

Erroneous beliefs prevent effective management of infant pain, with the focus on self-report of the current definition of pain leading to neglect of nonverbal diagnostic information. Models of pain should consider not only experience but pain expression and how this is decoded and interpreted. The common-sense appeal of the belief that pain is a conscious experience is deficient, because there is no consensus on the nature of consciousness. Caregivers tend to self-reference and search for adult capacities for focal awareness in infants. The search seems to obfuscate our understanding of infant pain. Greater attention should be devoted to age-specific experience, the emotional distress of pain in infancy, and the important role of implicit information processing, or an impact for pain outside of focal attention.

There is a growing body of evidence that implicates the role of excitatory amino acids (EEAs), in particular the N-methyl-D-aspartate (NMDA) receptor, in the development of opioid tolerance. In their Focus article, Fundytus and Coderre have proposed a model of opioid tolerance that highlights the importance of metabotropic glutamate receptors (MGIuRs) in the contribution of EEAs to opioid tolerance. The authors conclude that drugs that target MGIuRs may provide a therapeutic tool for the prevention of tolerance to morphine analgesia in humans. However, although the authors provide clear evidence that MGIuRs play a critical role in the development of tolerance to morphine analgesia, we should practice caution in ascribing a single mechanism to a complex phenomenon. The aim of this Commentary is to examine some broader issues that surround tolerance to morphine analgesia to highlight the complexity of the problem.

Morphine acts at μ-opioid receptors within the brain and spinal cord to induce analgesia. However, tolerance and dependence are potentially undesirable side effects encountered with repeated opiate administration. Opiate withdrawal, the physical correlate of dependence, is involved in the negative reinforcement of opiate addiction. Recently, blockers of ionotropic subtypes of glutamate receptors have been suggested to have therapeutical potential for opiate withdrawal. Fundytus and Coderre have also shown that antagonism of metabotropic glutamate receptors (mGluRs) and δ-opioid receptors can separately alleviate the behavioral symptoms of withdrawal. They propose that mGluRs and δ-opioid receptors share intermediates and products of the same second messenger pathways as μ-opioid receptors, thereby enhancing the desensitization of this receptor. Thus, mGluRs appear to be involved in the development of opiate tolerance and dependence and may provide a key target for adjunct therapy with opiate analgesia.