Pain, 49 (1992) 289-291 0 1992 Elsevier Science
289 Publishers
B.V. All rights
reserved
0304-3959/92/$05.00
PAIN 02047
Guest Editorial
Pain: paradigms and treatments William A. Macrae ‘INinewells Hospital and
‘, Huw T.O. Davies ’ and Iain K. Crombie
’
Medical School, Dundee, Scotland (UK) and ’ Department of Epidemiology and Public Health, Unic,ersity of Dundee, Dundee, Scotland (UK) (Received
and accepted
“Man masters nature not by force but by understanding. ”
(Bronowski, 1955-1956) Since ancient times doctors’ understanding of pathology, and consequent treatment of disease, has reflected prevailing theories of physiology and anatomy. The doctrine of ‘humours’, which dates back at least to Galen in the 2nd century and persisted until the 17th century, was invoked to account for many conditions otherwise unexplainable by current knowledge (McGrew and McGrew 1985). Treatments such as manipulation of diet and bloodletting were aimed at restoring the balance of the body humours. In pain too prevailing theories have influenced trends in treatment. Specificity theory, likened by Descartes in 1664 to pulling on one end of a rope to ring a bell at the other end (as described in Melzack and Wall 1988, p. 1501, had a powerful impact on pain therapy. It provided the rationale for interrupting nerve pathways by whatever means available. Models of pain evolved greatly over the first half of this century, culminating in the gatecontrol theory (Melzack and Wall 1965). The theory presented a new paradigm which might have been expected to influence the management of pain. Many advances in the management of pain over the past three decades are consequent upon the gate-control theory. Obvious examples are stimulation analgesia (Shealy et al. 1967; Wall and Sweet 1967) and the use of spinal opioids (Herz et al. 1970). Further, the explanation of possible mechanisms whereby higher centres affect the perception of pain has made psychological approaches respectable (Melzack and Wall 1988). At the same time, the realisation that there is no absolute link between peripheral stimulation and perceived pain has hastened the decline of many destructive tech-
Correspondence to: Dr. W.A. Macrae, Department of Anaesthetics, Ninewells Hospital and Medical School, Dundee, DDl 9SY, Scotland, UK. Tel.: (0382) 60111.
20 December
1991)
niques (Wall and Melzack 1984; Loeser 1990). More recently the focus on plasticity at the peripheral nociceptors (Raja et al. 1988) as well as in the spinal cord has produced another shift of paradigm and opened up new possibilities for explanation of the many puzzles surrounding pain. Further evidence of the impact of the gate-control theory comes from a recent survey of experts on pain (officers, councillors and chapter presidents of the International Association for the Study of Pain; editors of the leading pain journals) (Crombie et al. 1991). We asked for their views on changes in the management of pain since the publication of the gate-control theory. About half of the changes cited described advances in physical treatments. Improvements in drug therapy were mentioned by most, in particular, the better utilisation of opioids with improved delivery systems and the growing use of antidepressants. Increased use of stimulation analgesia received much attention, and many of the experts pointed to the benefits of psychological assessment in the management of chronic pain. Decline in the use of destructive neurosurgical techniques was described as beneficial by almost half the respondents. In addition to these comments on treatment, many replies described general advances such as increased knowledge about the physiology of pain, the organisation of pain services, the emergence of pain management as a specialty, and the development of effective means of disseminating knowledge about pain. Despite the. excitement generated by recent changes, treatment for the majority of patients in pain remains inadequate. Even cancer pain and postoperative pain, which can be treated very effectively with opioids (Saunders 1981; Schulze et al. 1988), are often poorly managed (Wilkes 1984; Donovan et al. 1987; Bruera et al. 1989; Dorrepaal et al. 1989; Kuhn et al. 1990). In many countries the prescribing of opioids is severely limited, and in some countries the consumption of morphine is actually falling (Doyle 1991). Thus, al-
290
though most of the experts we surveyed considered the improved use of opioids as a positive change, these benefits have clearly not reached all patients. Patients who suffer pain are seen by doctors from almost every branch of medicine. With the need to stay up-to-date in their own specialty, how many doctors are aware of recent advances in pain research? In another recent study (Davies et al. 1991) we surveyed doctors who would be expected to treat patients with pain resulting from nerve damage. The results showed widespread disagreement about the effectiveness of various forms of treatment. Many doctors still considered neuroablative techniques appropriate when there is evidence to suggest that these techniques are often counter-productive (Loeser 1990). Conversely, several treatments which should be widely employed for neuropathic pain (Rapeport et al. 1984; Withrington and Wynn Parry 1984; Neumann 1988; Glynn 1989; Anon 1990; Arner et al. 1990; Max 1990) are under-used, including TENS, antidepressants, anticonvulsants and sympathetic nerve blocks. Perhaps many clinicians retain outdated ideas of how the nervous system works. If so, is it surprising that pain treatment is so poor? Patients and doctors need explanations of illness and pain. Without an explanation, patients may feel guilt and blame themselves for their symptoms. For doctors. having to say “I don’t know” is difficult and may be threatening. It is often easier for doctors, and more comforting for patients, to fall back on old simplified notions. The history of medicine is littered with medical models that, in retrospect, stifled progress in treatment. A major challenge for the future lies in advancing the models of pain to stimulate physiological and clinical research. The gate-control theory has contributed much and will continue to be used as a tool to generate further ideas, but it is not perfect (Wall 1978). Even successful theories should not be mistaken for a complete representation of the real world (Popper 1982). There are two main dangers in the confusion between medical theory and scientific fact; useless therapies may be endorsed because they concur with the theory, and useful therapies may be rejected because they do not. The first of these is well known and is encouraged by the placebo effect. As for the second, the term ‘tomato effect’ ’ has been coined to describe the rejection or non-recognition of efficacious therapies because they do not fit in with the prevailing ideas on pathogenesis (Goodwin and Goodwin 1984). The
’ The effect is so named because for many years the tomato was thought to be poisonous by North Americans, belonging as it does to the nightshade (Solunaccae) family. This was despite obvious evidence to the contrary, as tomatoes were commonly consumed in Europe.
consequences for patients are twofold: at best, effective treatments are withheld; at worst, treatments are used which actually make the problem worse. Thus, there is a need to view all models with a critical eye, where possible using well designed randomised controlled trials as the final arbiter of a therapy’s utility. Progress in pain research will come from strengthening the alliance between basic science, which suggests therapeutic options, and clinical epidemiology, which evaluates them. Relief for patients will come from ensuring that practice is based on the best available knowledge. Recent physiological research has given new insights into the process of the perception of pain which have important implications for treatment, both in terms of embracing the new and discarding the old. Future research may hold great promise for future patients, but much greater benefit to existing patients can be gained from the proper application of current knowledge. It is the urgent duty of all concerned with pain relief to translate this knowledge into improved care for patients who suffer pain now. Mere education is not sufficient; changes in behaviour and changes in medical practice must be effected. In the past it has been assumed that bringing new knowledge to peoples’ attention is sufficient. Clearly this is not so (Mitchell and Fowkes 1985; Mugford et al. 1991). Effective means of translating advances in understanding to better patient care are needed. Today’s major challenge is changing doctors’ perception of pain and methods of treatment, not just amongst pain clinicians but in the wider medical community.
Acknowledgements Two of the authors (HD, IKC) are supported by Scottish Home and Health Department, and HD also funded by the Ian Mactaggart Trust. We thank North British Pain Association and its members their advice and support.
the was the for
References Anonymous, Postherpetic neuralgia (editorial). Lancet, 336 (1990) 537-538. Am&r, S., Lindblom, U.. Meyerson, B.A. and Molander, c‘.. Prolonged relief of neuralgia after regional anesthetic blocks. A call for further experimental and systematic clinical studies, Pain, 43 (1990) 287-297. Bronowski, J., Science and human values. Univ. Quart., 10 (1955-56) 247-259. Bruera, E., MacMillan, D., Hanson, J. and MacDonald, R.N.. The Edmonton staging system for cancer pain: preliminary report. Pain, 37 (1989) 202-210. Crombie, I.K., Davies, H.T.Q. and Macrae, W.A.. Developments in pain since the Gate Control Theory: a survey of experts, Eur. J. Pain, in press.
291 Davies, H.T.O., Crombie. I.K., Lonsdale, M. and Macrae, W.A., Consensus and contention in the treatment of chronic nervedamage pain, Pain, 47 (1991) 191-196. Donovan, M., Dillon, P. and McGuire, L. Incidence and characteristics of pain in a sample of medical-surgical inpatients. Pain. 30 (1987) 69-7X. Dorrepaal. K.L.. Aaronson. N.K. and van Dam, F.S.A.M., Pain experience and pain management among hospitalized cancer patients, Cancer, 63 (1989) 593-598. Doyle, D., Morphine: myths, morality and economics, Postgrad. Med. J., 67 (Suppi. 2) (1991) S70-S73. Glynn, C., An approach to the management of the patient with deafferentation pain, Pall. Med., 3 (1989) 13-21. Goodwin, J.S. and Goodwin. J.M.. The Tomato Effect: rejection of highly efficacious therapies.. J. Am. Med. Assoc., 251 (1984) 2387-2390. Herz. A.. Alhus, K., Metys, J.. Schubert, P. and Teschemacher, H., On the sites for the anti-nociceptive action of morphine and fentanyl, Neuropharmacology. 9 (1970) 539-551. Kuhn, S., Cooke. K., Collins, M.. Jones, J.M. and Mucklow, J.C., Perceptions of pain relief after surgery, Br. Med. J.. 300 (1990) 1687- 1690. Loeser. J.D., Ablative neurosurgical operations. In: J.J. Bonica (Ed.). The Management of Pain 2nd edn., Lea and Febiger, Philadelphia PA. 1990. pp. 2040-2043. Max, M.B., Towards physiologically based treatment of patients with neuropathic pain, Pain, 42 (1990) 131-133. McGrew, R.E. and McGrew, M.P., Encyclopaedia of Medical History, Macmillan Press, London, 1985. Melzack. R. and Wall, P.D., Pain mechanisms: a new theory, Science, 150 (1965) 971-979. Melzack, R. and Wall. P.D., The Challenge of Pain, Penguin, London, 1988, pp. 244-261. Mitchell, M.W. and Fowkes. F.G.R., Audit reviewed: does feedback
on performance change clinical behaviour?, J. Roy. Coil. Phys. (Land)., 19 (1985) 251-254. Mugford, M., Banfield, P. and M. O’Hanlon, Effects of feedback of information on clinical practice: a review, Br. Med. J., 303 (1991) 398-402. Neumann, M.M.. Nonsurgical management of pain secondary to peripheral nerve injuries. Orthop. Clin. N. Am.. 19 (1988) 165173. Popper. K.R. On theories as nets, New Sci., 29 July (1982) 319-320. Raja. S.N., Meyer, R.A. and Campbell, J.N. Peripheral mechanisms of somatic pain. Anesthesiology, 68 (198X) 571-590. Rapeport, W.G.. Rogers, K.M. McCubbin T.D., Agnew. E. and Brodie M.J., Treatment of intractable neurogenic pain with carbamazepine. Scot. Med. J., 29 (1984) 162-165. Saunders, C., Current views on pain relief and terminal care. The therapy of pain. In: M. Swerdlow (Ed.), Current Status of Modern Therapy, Vol. 6, MTP Press, Lancaster, 1981. pp. 215-241. Schulze, S., Roikjaer, 0. Hasselstrom, L. Jensen, N.H. and Kehlet, H., Epidural bupivacaine and morphine plus systemic indomethacin eliminates pain but not systemic response and convalescence after cholecystectomy. Surgery, 103 (1988) 321-327. Shealy, C.N.. Mortimer, J.T. and Reswick, J.B.. Electrical inhibition of pain by stimulation of the dorsal columns, Anesth. Analg., 46 (1967) 489-491. Wall, P.D., The Gate Control Theory of pain mechanisms: a re-examination and re-statement, Brain, 101 (1978) 1-18. Wall. P.D. and Melzack, R., Textbook of Pain. Churchill Livingston Edinburgh. 1984, pp. 577-676. Wall. P.D. and Sweet, W.H., Temporary abolition of pain, Science, 155 (1967) 108-109. Wilkes, E., Dying now, Lancet, i (1984) 950-952. Withrington. R.H. and Wynn Parry, C.B., The mangement of painful peripheral nerve disorders, J. Hand Surg., 9 (1984) 24-28.
289 Publishers
B.V. All rights
reserved
0304-3959/92/$05.00
PAIN 02047
Guest Editorial
Pain: paradigms and treatments William A. Macrae ‘INinewells Hospital and
‘, Huw T.O. Davies ’ and Iain K. Crombie
’
Medical School, Dundee, Scotland (UK) and ’ Department of Epidemiology and Public Health, Unic,ersity of Dundee, Dundee, Scotland (UK) (Received
and accepted
“Man masters nature not by force but by understanding. ”
(Bronowski, 1955-1956) Since ancient times doctors’ understanding of pathology, and consequent treatment of disease, has reflected prevailing theories of physiology and anatomy. The doctrine of ‘humours’, which dates back at least to Galen in the 2nd century and persisted until the 17th century, was invoked to account for many conditions otherwise unexplainable by current knowledge (McGrew and McGrew 1985). Treatments such as manipulation of diet and bloodletting were aimed at restoring the balance of the body humours. In pain too prevailing theories have influenced trends in treatment. Specificity theory, likened by Descartes in 1664 to pulling on one end of a rope to ring a bell at the other end (as described in Melzack and Wall 1988, p. 1501, had a powerful impact on pain therapy. It provided the rationale for interrupting nerve pathways by whatever means available. Models of pain evolved greatly over the first half of this century, culminating in the gatecontrol theory (Melzack and Wall 1965). The theory presented a new paradigm which might have been expected to influence the management of pain. Many advances in the management of pain over the past three decades are consequent upon the gate-control theory. Obvious examples are stimulation analgesia (Shealy et al. 1967; Wall and Sweet 1967) and the use of spinal opioids (Herz et al. 1970). Further, the explanation of possible mechanisms whereby higher centres affect the perception of pain has made psychological approaches respectable (Melzack and Wall 1988). At the same time, the realisation that there is no absolute link between peripheral stimulation and perceived pain has hastened the decline of many destructive tech-
Correspondence to: Dr. W.A. Macrae, Department of Anaesthetics, Ninewells Hospital and Medical School, Dundee, DDl 9SY, Scotland, UK. Tel.: (0382) 60111.
20 December
1991)
niques (Wall and Melzack 1984; Loeser 1990). More recently the focus on plasticity at the peripheral nociceptors (Raja et al. 1988) as well as in the spinal cord has produced another shift of paradigm and opened up new possibilities for explanation of the many puzzles surrounding pain. Further evidence of the impact of the gate-control theory comes from a recent survey of experts on pain (officers, councillors and chapter presidents of the International Association for the Study of Pain; editors of the leading pain journals) (Crombie et al. 1991). We asked for their views on changes in the management of pain since the publication of the gate-control theory. About half of the changes cited described advances in physical treatments. Improvements in drug therapy were mentioned by most, in particular, the better utilisation of opioids with improved delivery systems and the growing use of antidepressants. Increased use of stimulation analgesia received much attention, and many of the experts pointed to the benefits of psychological assessment in the management of chronic pain. Decline in the use of destructive neurosurgical techniques was described as beneficial by almost half the respondents. In addition to these comments on treatment, many replies described general advances such as increased knowledge about the physiology of pain, the organisation of pain services, the emergence of pain management as a specialty, and the development of effective means of disseminating knowledge about pain. Despite the. excitement generated by recent changes, treatment for the majority of patients in pain remains inadequate. Even cancer pain and postoperative pain, which can be treated very effectively with opioids (Saunders 1981; Schulze et al. 1988), are often poorly managed (Wilkes 1984; Donovan et al. 1987; Bruera et al. 1989; Dorrepaal et al. 1989; Kuhn et al. 1990). In many countries the prescribing of opioids is severely limited, and in some countries the consumption of morphine is actually falling (Doyle 1991). Thus, al-
290
though most of the experts we surveyed considered the improved use of opioids as a positive change, these benefits have clearly not reached all patients. Patients who suffer pain are seen by doctors from almost every branch of medicine. With the need to stay up-to-date in their own specialty, how many doctors are aware of recent advances in pain research? In another recent study (Davies et al. 1991) we surveyed doctors who would be expected to treat patients with pain resulting from nerve damage. The results showed widespread disagreement about the effectiveness of various forms of treatment. Many doctors still considered neuroablative techniques appropriate when there is evidence to suggest that these techniques are often counter-productive (Loeser 1990). Conversely, several treatments which should be widely employed for neuropathic pain (Rapeport et al. 1984; Withrington and Wynn Parry 1984; Neumann 1988; Glynn 1989; Anon 1990; Arner et al. 1990; Max 1990) are under-used, including TENS, antidepressants, anticonvulsants and sympathetic nerve blocks. Perhaps many clinicians retain outdated ideas of how the nervous system works. If so, is it surprising that pain treatment is so poor? Patients and doctors need explanations of illness and pain. Without an explanation, patients may feel guilt and blame themselves for their symptoms. For doctors. having to say “I don’t know” is difficult and may be threatening. It is often easier for doctors, and more comforting for patients, to fall back on old simplified notions. The history of medicine is littered with medical models that, in retrospect, stifled progress in treatment. A major challenge for the future lies in advancing the models of pain to stimulate physiological and clinical research. The gate-control theory has contributed much and will continue to be used as a tool to generate further ideas, but it is not perfect (Wall 1978). Even successful theories should not be mistaken for a complete representation of the real world (Popper 1982). There are two main dangers in the confusion between medical theory and scientific fact; useless therapies may be endorsed because they concur with the theory, and useful therapies may be rejected because they do not. The first of these is well known and is encouraged by the placebo effect. As for the second, the term ‘tomato effect’ ’ has been coined to describe the rejection or non-recognition of efficacious therapies because they do not fit in with the prevailing ideas on pathogenesis (Goodwin and Goodwin 1984). The
’ The effect is so named because for many years the tomato was thought to be poisonous by North Americans, belonging as it does to the nightshade (Solunaccae) family. This was despite obvious evidence to the contrary, as tomatoes were commonly consumed in Europe.
consequences for patients are twofold: at best, effective treatments are withheld; at worst, treatments are used which actually make the problem worse. Thus, there is a need to view all models with a critical eye, where possible using well designed randomised controlled trials as the final arbiter of a therapy’s utility. Progress in pain research will come from strengthening the alliance between basic science, which suggests therapeutic options, and clinical epidemiology, which evaluates them. Relief for patients will come from ensuring that practice is based on the best available knowledge. Recent physiological research has given new insights into the process of the perception of pain which have important implications for treatment, both in terms of embracing the new and discarding the old. Future research may hold great promise for future patients, but much greater benefit to existing patients can be gained from the proper application of current knowledge. It is the urgent duty of all concerned with pain relief to translate this knowledge into improved care for patients who suffer pain now. Mere education is not sufficient; changes in behaviour and changes in medical practice must be effected. In the past it has been assumed that bringing new knowledge to peoples’ attention is sufficient. Clearly this is not so (Mitchell and Fowkes 1985; Mugford et al. 1991). Effective means of translating advances in understanding to better patient care are needed. Today’s major challenge is changing doctors’ perception of pain and methods of treatment, not just amongst pain clinicians but in the wider medical community.
Acknowledgements Two of the authors (HD, IKC) are supported by Scottish Home and Health Department, and HD also funded by the Ian Mactaggart Trust. We thank North British Pain Association and its members their advice and support.
the was the for
References Anonymous, Postherpetic neuralgia (editorial). Lancet, 336 (1990) 537-538. Am&r, S., Lindblom, U.. Meyerson, B.A. and Molander, c‘.. Prolonged relief of neuralgia after regional anesthetic blocks. A call for further experimental and systematic clinical studies, Pain, 43 (1990) 287-297. Bronowski, J., Science and human values. Univ. Quart., 10 (1955-56) 247-259. Bruera, E., MacMillan, D., Hanson, J. and MacDonald, R.N.. The Edmonton staging system for cancer pain: preliminary report. Pain, 37 (1989) 202-210. Crombie, I.K., Davies, H.T.Q. and Macrae, W.A.. Developments in pain since the Gate Control Theory: a survey of experts, Eur. J. Pain, in press.
291 Davies, H.T.O., Crombie. I.K., Lonsdale, M. and Macrae, W.A., Consensus and contention in the treatment of chronic nervedamage pain, Pain, 47 (1991) 191-196. Donovan, M., Dillon, P. and McGuire, L. Incidence and characteristics of pain in a sample of medical-surgical inpatients. Pain. 30 (1987) 69-7X. Dorrepaal. K.L.. Aaronson. N.K. and van Dam, F.S.A.M., Pain experience and pain management among hospitalized cancer patients, Cancer, 63 (1989) 593-598. Doyle, D., Morphine: myths, morality and economics, Postgrad. Med. J., 67 (Suppi. 2) (1991) S70-S73. Glynn, C., An approach to the management of the patient with deafferentation pain, Pall. Med., 3 (1989) 13-21. Goodwin, J.S. and Goodwin. J.M.. The Tomato Effect: rejection of highly efficacious therapies.. J. Am. Med. Assoc., 251 (1984) 2387-2390. Herz. A.. Alhus, K., Metys, J.. Schubert, P. and Teschemacher, H., On the sites for the anti-nociceptive action of morphine and fentanyl, Neuropharmacology. 9 (1970) 539-551. Kuhn, S., Cooke. K., Collins, M.. Jones, J.M. and Mucklow, J.C., Perceptions of pain relief after surgery, Br. Med. J.. 300 (1990) 1687- 1690. Loeser. J.D., Ablative neurosurgical operations. In: J.J. Bonica (Ed.). The Management of Pain 2nd edn., Lea and Febiger, Philadelphia PA. 1990. pp. 2040-2043. Max, M.B., Towards physiologically based treatment of patients with neuropathic pain, Pain, 42 (1990) 131-133. McGrew, R.E. and McGrew, M.P., Encyclopaedia of Medical History, Macmillan Press, London, 1985. Melzack. R. and Wall, P.D., Pain mechanisms: a new theory, Science, 150 (1965) 971-979. Melzack, R. and Wall. P.D., The Challenge of Pain, Penguin, London, 1988, pp. 244-261. Mitchell, M.W. and Fowkes. F.G.R., Audit reviewed: does feedback
on performance change clinical behaviour?, J. Roy. Coil. Phys. (Land)., 19 (1985) 251-254. Mugford, M., Banfield, P. and M. O’Hanlon, Effects of feedback of information on clinical practice: a review, Br. Med. J., 303 (1991) 398-402. Neumann, M.M.. Nonsurgical management of pain secondary to peripheral nerve injuries. Orthop. Clin. N. Am.. 19 (1988) 165173. Popper. K.R. On theories as nets, New Sci., 29 July (1982) 319-320. Raja. S.N., Meyer, R.A. and Campbell, J.N. Peripheral mechanisms of somatic pain. Anesthesiology, 68 (198X) 571-590. Rapeport, W.G.. Rogers, K.M. McCubbin T.D., Agnew. E. and Brodie M.J., Treatment of intractable neurogenic pain with carbamazepine. Scot. Med. J., 29 (1984) 162-165. Saunders, C., Current views on pain relief and terminal care. The therapy of pain. In: M. Swerdlow (Ed.), Current Status of Modern Therapy, Vol. 6, MTP Press, Lancaster, 1981. pp. 215-241. Schulze, S., Roikjaer, 0. Hasselstrom, L. Jensen, N.H. and Kehlet, H., Epidural bupivacaine and morphine plus systemic indomethacin eliminates pain but not systemic response and convalescence after cholecystectomy. Surgery, 103 (1988) 321-327. Shealy, C.N.. Mortimer, J.T. and Reswick, J.B.. Electrical inhibition of pain by stimulation of the dorsal columns, Anesth. Analg., 46 (1967) 489-491. Wall, P.D., The Gate Control Theory of pain mechanisms: a re-examination and re-statement, Brain, 101 (1978) 1-18. Wall. P.D. and Melzack, R., Textbook of Pain. Churchill Livingston Edinburgh. 1984, pp. 577-676. Wall. P.D. and Sweet, W.H., Temporary abolition of pain, Science, 155 (1967) 108-109. Wilkes, E., Dying now, Lancet, i (1984) 950-952. Withrington. R.H. and Wynn Parry, C.B., The mangement of painful peripheral nerve disorders, J. Hand Surg., 9 (1984) 24-28.
