1514
study of amputees in the USA neglected to mention vibration as a possible treatment,9.10 and many physicians, even in the area of chronic pain management, may be unaware of the effectiveness of this approach. One drawback with vibrators may be the relative user-unfriendliness of the equipment. Stationary vibrators--eg, those incorporated into a chair of bed-are difficult to apply to specific painful areas with enough force to be effective. Moreover, the chairs or beds tend to be extremely expensive and unsuited to patients who are physically active. Hand-held vibrators are often bulky and noisy, require a mains power supply, and are obtrusive in use. Small battery-operated vibrators may lack the power for long-term use and have sexual connotations that can embarrass some patients. However, the small machines are easy to apply, and the high frequencies (100-200 Hz) of some models may be more comfortable and effective than the low-frequency vibrators.l1 Even so, vibrators are much more obvious in use than a small transcutaneous nerve stimulator and for this reason patients may reject them even though they are more effective. Vibration works best if it is applied at around 100 Hz near or distal to the painful site7with moderate (at least 69 kPa or 10 psi) pressure; vibration should be maintained for about 45 min. Lower frequencies, less pressure, or shorter duration all reduce effectiveness.4 The surface area covered is unimportant.8 In a few patients vibration will increase pain. The benefits are most pronounced in pain arising in nerve or muscle;5 chronic pain responds better than acute pain.4 It used to be thought that hyperstimulation
analgesia was produced by an acupuncture-like mechanism, by distraction, by self-hypnosis, or simply as a result of suggestion in a patient who is desperate enough to believe anything. Vibration does not work via endogenous opioids12 but probably via a pre-gate or efferent control system. 13,11 Most workers agree that large-diameter afferents from lowthreshold rapidly adapting receptors 14 and/or Pacinian corpusclesll are involved (so vibration is much
more
selective than
transcutaneous
nerve
stimulation). 14,15Whether the subsequent response is segmental6,16 or via diffuse noxious inhibitory controls17,18 is unclear. 19 The noxious control mechanism provides a much more satisfactory explanation not only for the development of analgesia but also for its persistence far beyond the usual period for techniques such as transcutaneous nerve stimulation. There has lately been increased interest in the use of vibration for facial pain management, with excellent results being reported; other applications are well described20 but little used. Transcutaneous nerve stimulation commands a very large share of the market for stimulation-produced analgesia; vibration is simple, safe, and highly effective and has the added advantage of being cheap to establish and maintain.
1. Gammon DG, Starr J. Studies on the relief of pain by counter-irritation J Clin Invest 1941; 20: 13-20. 2. Ritchie Russell W, Spalding JMK. Treatment of painful amputation stumps. Br Med J 1950; 2: 68-736. 3. McCulloch WS, Cronley-Dillon JR, Duchane EM, et al. Effect of touch stimuli on pain and temperature sensations. MIT Quart Prog Rep 1959; 52: 168-76. 4. Lundeberg T, Nordemar R, Ottoson D. Pain alleviation by vibratory
stimulation. Pain 1984; 20: 25-44. Lundeberg T. Long term results of vibratory stimulation as a pain relieving measure for chronic pain. Pain 1984; 20: 13-23. 6. Ekblom A, Hansson P. Extrasegmental transcutaneous electrical nerve stimulation and vibratory stimulation as compared to placebo for the relief of acute oro-facial pain. Pain 1985; 23: 223-29. 7. Sherer CL, Clelland JA, O’Sullivan P, Doleys DM, Canan B. The effect of two sites of high frequency vibration on cutaneous pain threshold. 5.
Pain 1986; 25: 133-38. 8. Palmesano TJ, Clelland JA, Sherer C, Stullenbarger E, Canan B. Effect of high frequency vibration on experimental pain threshold in young women when applied to areas of different size. Clin J Pain 1989; 5: 337-42. 9. Sherman RA, Sherman CJ, Gall NG. A survey of current phantom limb treatment in the United States. Pain 1980; 8: 85-99. 10. Sherman RA, Sherman CJ, Parker L. Chronic phantom and stump pain among American Veterans: results of a survey. Pain 1984; 18: 83-95. 11. Pantaleo T, Duranti R, Bellini F. Effects of vibratory stimulation on muscular pain threshold and blink response in human subjects. Pain
1986; 24: 239-50.
Lundeberg T. Naloxone does not reverse the pain-reducing effect of vibratory stimulation. Acta Anesthesiol Scand 1985; 29: 212-16. 13. Torebjork HE, Hallin RG. Identification of afferent C units in intact 12.
human skin nerves. Brain Res 1974; 67: 387-403. 14. McGlone FP, Marsh D. Stimulators for treatment of pain. In: Lipton S, Tunks E, Zoppi M, eds. Advances in pain research and therapy, vol 13. New York: Raven, 1990: 79-82. 15. Lundeberg T, Ottoson D, Hakansson S, Meyerson BA. Vibratory stimulation for the control of intractable chronic orofacial pain. In: Bonica JJ, Lindblom U, Iggo A, eds. Advances in pain research and therapy. New York: Raven, 1983: 555-61. 16. Melzack R, Schecter B. Itch and vibration Science 1965; 147: 1047-48. 17. Talbot JD, Duncan GH, Bushnell MC, Boyer M. Diffuse noxious inhibitory controls (DNIC): psychophysical evidence in man for intersegmental suppression of noxious heat perception by cold pressor pain. Pain 1987; 30: 221-32. 18. Le Bars D, Chitour D, Clot AM. Diffuse noxious inhibitory controls (DNIC). Relationship between conditioning stimulus intensity and inhibitory effect. In: Bonica JJ, Lindlom U, Iggo A, eds. Advances in pain research and therapy, vol 5. New York: Raven, 1983: 549-54. 19. Kakigi R, Shibasaki H. Mechanism of pain relief by vibration and movement. J Neurol Neurosurg Psychiatry 1992; 55: 282-86. 20. McCaffery M, Beebe A. Pain: clinical manual for nursing practice. St Louis: Mosby, 1989: 142-56.
Detecting vitamin A deficiency early So much attention has been paid to the control of nutritional blindness that elimination of this disorder is one of the more realistic goals of the World Health Organisation’s Health for All by the Year 2000 strategy. Ironically, just as this was becoming a possibility, evidence began accumulating that subclinical deficiency of vitamin A may be an important contributory factor in the death of young children in the third world.1-3 Amid the considerable controversy over this association, researchers sought to devise methods for detection of hypovitaminosis A at this very early stage. Serum retinol under these conditions is insensitive. Techniques have been developed for indirect assessment of liver stores,4,5 but biochemical tests are complex and blood sampling carries the risk of transmission of various infections including human immunodeficiency virus. Moreover, liver stores may not truly represent total body reserves in deficiency.66
1515
Consequently there is much to commend a simple, non-invasive, cheap test such as conjunctival impression cytology (CIC), which is rapidly gaining wide acceptance.7-9 There is lack of agreement on several technical details, perhaps the most important being how to interpret as normal or abnormal the
10. Carlier C, Coste J, Etchepare M, et al. Conjunctival impression cytology with transfer as a field-applicable indicator of vitamin A status for mass screening. Int J Epidemiol 1992; 21: 373-80. 11. World Health Organisation. Control of vitamin A deficiency and xerophthalmia. Tech Rep Ser no 672, 1982. 12. Sommer A. Vitamin A deficiency and childhood mortality. Lancet 1992;
339: 864.
appearances of the cellular elements of the bulbar
epithelium. Accompanying eye infections such as trachoma, or irritation due to smoke or dust, may sometimes give false-positive results. The importance of the quality of the cytological preparations has not been thoroughly assessed. Carlier and colleagues1o in France, one of the foremost groups in the use of CIC, have lately proposed a formula for a prevalence criterion for subclinical vitamin A deficiency. As they point out, this was done by WHO for clinical xerophthalmia and the WHO recommendations have been widely adopted.l1 From a meta-analysis of six controlled community-based prophylaxis-mortality trials,
Horse
conjunctival
Sommer12 reports
an
overall reduction in child
mortality of 34%. This meta-analysis has not been published, but even if the percentage is an overestimate it is difficult to escape the conclusion that
marginal or subclinical deficiency of vitamin A is an important determinant of deaths in young children throughout the world. 12 years have now passed since WHO expert group met to consider the control of vitamin A deficiency and xerophthalmia. The grave consequences of the new dimension that has been unearthed mean that another meeting is overdue. High on its agenda should be achievement of a consensus on the detailed technique of CIC and all aspects of its application and interpretation, together with recommendations concerning the control of the marginal deficiency of vitamin A it is designed to detect. Until then, the deceptive simplicity of CIC lays it wide open to abuse. a
1. Sommer A, Tarwotjo I, Hussaini G, Susanto D. Increased mortality in children with mild vitamin A deficiency. Lancet 1983; ii: 585-88. 2. Sommer A, Tarwotjo I, Djunaedi E, et al. Impact of vitamin A supplementation on childhood mortality: a randomised controlled community trial. Lancet 1986; i: 1169-73. 3. Rahmathullah L, Underwood BA, Thulasiraj RD, et al. Reduced mortality among children in southern India receiving a small weekly dose of vitamin A. N Engl J Med 1990; 323: 929-35. 4. Flores H, Campos FACS, Araujo CRC, et al. Assessment of marginal vitamin A deficiency in Brazilian children using the relative dose response procedure. Am J Clin Nutr 1984; 40: 1281-89. 5. Tanumihardjo SA, Muhilal, Yuniar Y, et al. Assessment of vitamin A status in preschool-age Indonesian children by the modified relative dose response (MRDR) assay. Am J Clin Nutr 1990; 52: 1064-67. 6. Blomhoff R, Green MH, Green JB, et al. Vitamin A metabolism: new perspective on absorption, transport, and storage. PhysiolRev 1991;71: 951-90. 7. Natadisastra G, Wittpenn JR, West KP, et al. Impression cytology for detection of vitamin A deficiency. Arch Ophthalmol 1987; 105: 1224-28. 8. Gadomski AM, Kjolhede CL, Wittpenn J, et al. Field trial of conjunctival impression cytology (CIC) to detect subclinical vitamin A deficiency, part II: comparison of CIC with biochemical assessments. Am J Clin Nutr 1988; 48: 695-701. 9. Carlier C, Moulia-Pelat JP, Ceccon JF, et al. Prevalence of malnutrition and vitamin A deficiency in the Diourbel, Fatick and Kaolack regions of Senegal: feasibility of impression cytology with transfer. Am J Clin
Nutr 1991; 53: 66-69.
manure
after Rio
When Malthus painted his dismal population scenario he was not to know how birth control, technology, and education would come to the rescue. But relief proved only temporary. Today we have the "demographic trap"1 and technological fixes for that are nowhere in sight. It is the same with horse droppings. If horse-drawn transport had continued to grow from the rate of, say, 1792 the streets of our cities would now be deep in manure. Along came the horseless carriage and once more we were freed by the ingenuity of scientists and engineers-yet within less than a century cities such as Athens and Los Angeles are deep in a different sort of ordure, one to which the internal combustion engine contributes heavily. There are things that can be done with technology, often low technology but at the Rio de Janeiro environmental summit that finished last weekend little was heard of the notion that technological solutions to the world’s environmental problems are just around the comer. So, the two weeks that were the "last chance to save our planet" are over. The earth is still there, just. So are the politicians, full of sound and even fury sometimes, but with no vision and signifying nothing because they suspect that those who put them into office back home are not yet persuaded of the need for sacrifice. Sustaining the environmental debate after Rio is the challenge that faces those who found the Earth Summit a crashing disappointment (but see p 1529 for a view from someone who was there). That task will have to be shared by the projected
Sustainable Development Commission, The Lancet has argued that there is a substantial medical dimension to the current destruction of the environment.2That case is well made in the World Health Organisation’s excellent contribution to the Rio jamboree. In her foreword to the reportSimone Veil wrote that "the kind of development needed to safeguard health and welfare will depend on many
conditions, including respect for the environment,
development without regard for the environment would inevitably result in impairment of human health". WHO did not neglect population. How sad, then, that population per se got so little publicity in Brazil. It is there in Agenda 21, one of the products of the UN Conference on Environment and Development, but separated from "protection and promoting human health" (with its obvious WHO input). Some argue that poverty must first be corrected, and limitation on family size will follow. It while
is
too
more
late. On the road to that destination how many nations in Africa and elsewhere will fall into the
study of amputees in the USA neglected to mention vibration as a possible treatment,9.10 and many physicians, even in the area of chronic pain management, may be unaware of the effectiveness of this approach. One drawback with vibrators may be the relative user-unfriendliness of the equipment. Stationary vibrators--eg, those incorporated into a chair of bed-are difficult to apply to specific painful areas with enough force to be effective. Moreover, the chairs or beds tend to be extremely expensive and unsuited to patients who are physically active. Hand-held vibrators are often bulky and noisy, require a mains power supply, and are obtrusive in use. Small battery-operated vibrators may lack the power for long-term use and have sexual connotations that can embarrass some patients. However, the small machines are easy to apply, and the high frequencies (100-200 Hz) of some models may be more comfortable and effective than the low-frequency vibrators.l1 Even so, vibrators are much more obvious in use than a small transcutaneous nerve stimulator and for this reason patients may reject them even though they are more effective. Vibration works best if it is applied at around 100 Hz near or distal to the painful site7with moderate (at least 69 kPa or 10 psi) pressure; vibration should be maintained for about 45 min. Lower frequencies, less pressure, or shorter duration all reduce effectiveness.4 The surface area covered is unimportant.8 In a few patients vibration will increase pain. The benefits are most pronounced in pain arising in nerve or muscle;5 chronic pain responds better than acute pain.4 It used to be thought that hyperstimulation
analgesia was produced by an acupuncture-like mechanism, by distraction, by self-hypnosis, or simply as a result of suggestion in a patient who is desperate enough to believe anything. Vibration does not work via endogenous opioids12 but probably via a pre-gate or efferent control system. 13,11 Most workers agree that large-diameter afferents from lowthreshold rapidly adapting receptors 14 and/or Pacinian corpusclesll are involved (so vibration is much
more
selective than
transcutaneous
nerve
stimulation). 14,15Whether the subsequent response is segmental6,16 or via diffuse noxious inhibitory controls17,18 is unclear. 19 The noxious control mechanism provides a much more satisfactory explanation not only for the development of analgesia but also for its persistence far beyond the usual period for techniques such as transcutaneous nerve stimulation. There has lately been increased interest in the use of vibration for facial pain management, with excellent results being reported; other applications are well described20 but little used. Transcutaneous nerve stimulation commands a very large share of the market for stimulation-produced analgesia; vibration is simple, safe, and highly effective and has the added advantage of being cheap to establish and maintain.
1. Gammon DG, Starr J. Studies on the relief of pain by counter-irritation J Clin Invest 1941; 20: 13-20. 2. Ritchie Russell W, Spalding JMK. Treatment of painful amputation stumps. Br Med J 1950; 2: 68-736. 3. McCulloch WS, Cronley-Dillon JR, Duchane EM, et al. Effect of touch stimuli on pain and temperature sensations. MIT Quart Prog Rep 1959; 52: 168-76. 4. Lundeberg T, Nordemar R, Ottoson D. Pain alleviation by vibratory
stimulation. Pain 1984; 20: 25-44. Lundeberg T. Long term results of vibratory stimulation as a pain relieving measure for chronic pain. Pain 1984; 20: 13-23. 6. Ekblom A, Hansson P. Extrasegmental transcutaneous electrical nerve stimulation and vibratory stimulation as compared to placebo for the relief of acute oro-facial pain. Pain 1985; 23: 223-29. 7. Sherer CL, Clelland JA, O’Sullivan P, Doleys DM, Canan B. The effect of two sites of high frequency vibration on cutaneous pain threshold. 5.
Pain 1986; 25: 133-38. 8. Palmesano TJ, Clelland JA, Sherer C, Stullenbarger E, Canan B. Effect of high frequency vibration on experimental pain threshold in young women when applied to areas of different size. Clin J Pain 1989; 5: 337-42. 9. Sherman RA, Sherman CJ, Gall NG. A survey of current phantom limb treatment in the United States. Pain 1980; 8: 85-99. 10. Sherman RA, Sherman CJ, Parker L. Chronic phantom and stump pain among American Veterans: results of a survey. Pain 1984; 18: 83-95. 11. Pantaleo T, Duranti R, Bellini F. Effects of vibratory stimulation on muscular pain threshold and blink response in human subjects. Pain
1986; 24: 239-50.
Lundeberg T. Naloxone does not reverse the pain-reducing effect of vibratory stimulation. Acta Anesthesiol Scand 1985; 29: 212-16. 13. Torebjork HE, Hallin RG. Identification of afferent C units in intact 12.
human skin nerves. Brain Res 1974; 67: 387-403. 14. McGlone FP, Marsh D. Stimulators for treatment of pain. In: Lipton S, Tunks E, Zoppi M, eds. Advances in pain research and therapy, vol 13. New York: Raven, 1990: 79-82. 15. Lundeberg T, Ottoson D, Hakansson S, Meyerson BA. Vibratory stimulation for the control of intractable chronic orofacial pain. In: Bonica JJ, Lindblom U, Iggo A, eds. Advances in pain research and therapy. New York: Raven, 1983: 555-61. 16. Melzack R, Schecter B. Itch and vibration Science 1965; 147: 1047-48. 17. Talbot JD, Duncan GH, Bushnell MC, Boyer M. Diffuse noxious inhibitory controls (DNIC): psychophysical evidence in man for intersegmental suppression of noxious heat perception by cold pressor pain. Pain 1987; 30: 221-32. 18. Le Bars D, Chitour D, Clot AM. Diffuse noxious inhibitory controls (DNIC). Relationship between conditioning stimulus intensity and inhibitory effect. In: Bonica JJ, Lindlom U, Iggo A, eds. Advances in pain research and therapy, vol 5. New York: Raven, 1983: 549-54. 19. Kakigi R, Shibasaki H. Mechanism of pain relief by vibration and movement. J Neurol Neurosurg Psychiatry 1992; 55: 282-86. 20. McCaffery M, Beebe A. Pain: clinical manual for nursing practice. St Louis: Mosby, 1989: 142-56.
Detecting vitamin A deficiency early So much attention has been paid to the control of nutritional blindness that elimination of this disorder is one of the more realistic goals of the World Health Organisation’s Health for All by the Year 2000 strategy. Ironically, just as this was becoming a possibility, evidence began accumulating that subclinical deficiency of vitamin A may be an important contributory factor in the death of young children in the third world.1-3 Amid the considerable controversy over this association, researchers sought to devise methods for detection of hypovitaminosis A at this very early stage. Serum retinol under these conditions is insensitive. Techniques have been developed for indirect assessment of liver stores,4,5 but biochemical tests are complex and blood sampling carries the risk of transmission of various infections including human immunodeficiency virus. Moreover, liver stores may not truly represent total body reserves in deficiency.66
1515
Consequently there is much to commend a simple, non-invasive, cheap test such as conjunctival impression cytology (CIC), which is rapidly gaining wide acceptance.7-9 There is lack of agreement on several technical details, perhaps the most important being how to interpret as normal or abnormal the
10. Carlier C, Coste J, Etchepare M, et al. Conjunctival impression cytology with transfer as a field-applicable indicator of vitamin A status for mass screening. Int J Epidemiol 1992; 21: 373-80. 11. World Health Organisation. Control of vitamin A deficiency and xerophthalmia. Tech Rep Ser no 672, 1982. 12. Sommer A. Vitamin A deficiency and childhood mortality. Lancet 1992;
339: 864.
appearances of the cellular elements of the bulbar
epithelium. Accompanying eye infections such as trachoma, or irritation due to smoke or dust, may sometimes give false-positive results. The importance of the quality of the cytological preparations has not been thoroughly assessed. Carlier and colleagues1o in France, one of the foremost groups in the use of CIC, have lately proposed a formula for a prevalence criterion for subclinical vitamin A deficiency. As they point out, this was done by WHO for clinical xerophthalmia and the WHO recommendations have been widely adopted.l1 From a meta-analysis of six controlled community-based prophylaxis-mortality trials,
Horse
conjunctival
Sommer12 reports
an
overall reduction in child
mortality of 34%. This meta-analysis has not been published, but even if the percentage is an overestimate it is difficult to escape the conclusion that
marginal or subclinical deficiency of vitamin A is an important determinant of deaths in young children throughout the world. 12 years have now passed since WHO expert group met to consider the control of vitamin A deficiency and xerophthalmia. The grave consequences of the new dimension that has been unearthed mean that another meeting is overdue. High on its agenda should be achievement of a consensus on the detailed technique of CIC and all aspects of its application and interpretation, together with recommendations concerning the control of the marginal deficiency of vitamin A it is designed to detect. Until then, the deceptive simplicity of CIC lays it wide open to abuse. a
1. Sommer A, Tarwotjo I, Hussaini G, Susanto D. Increased mortality in children with mild vitamin A deficiency. Lancet 1983; ii: 585-88. 2. Sommer A, Tarwotjo I, Djunaedi E, et al. Impact of vitamin A supplementation on childhood mortality: a randomised controlled community trial. Lancet 1986; i: 1169-73. 3. Rahmathullah L, Underwood BA, Thulasiraj RD, et al. Reduced mortality among children in southern India receiving a small weekly dose of vitamin A. N Engl J Med 1990; 323: 929-35. 4. Flores H, Campos FACS, Araujo CRC, et al. Assessment of marginal vitamin A deficiency in Brazilian children using the relative dose response procedure. Am J Clin Nutr 1984; 40: 1281-89. 5. Tanumihardjo SA, Muhilal, Yuniar Y, et al. Assessment of vitamin A status in preschool-age Indonesian children by the modified relative dose response (MRDR) assay. Am J Clin Nutr 1990; 52: 1064-67. 6. Blomhoff R, Green MH, Green JB, et al. Vitamin A metabolism: new perspective on absorption, transport, and storage. PhysiolRev 1991;71: 951-90. 7. Natadisastra G, Wittpenn JR, West KP, et al. Impression cytology for detection of vitamin A deficiency. Arch Ophthalmol 1987; 105: 1224-28. 8. Gadomski AM, Kjolhede CL, Wittpenn J, et al. Field trial of conjunctival impression cytology (CIC) to detect subclinical vitamin A deficiency, part II: comparison of CIC with biochemical assessments. Am J Clin Nutr 1988; 48: 695-701. 9. Carlier C, Moulia-Pelat JP, Ceccon JF, et al. Prevalence of malnutrition and vitamin A deficiency in the Diourbel, Fatick and Kaolack regions of Senegal: feasibility of impression cytology with transfer. Am J Clin
Nutr 1991; 53: 66-69.
manure
after Rio
When Malthus painted his dismal population scenario he was not to know how birth control, technology, and education would come to the rescue. But relief proved only temporary. Today we have the "demographic trap"1 and technological fixes for that are nowhere in sight. It is the same with horse droppings. If horse-drawn transport had continued to grow from the rate of, say, 1792 the streets of our cities would now be deep in manure. Along came the horseless carriage and once more we were freed by the ingenuity of scientists and engineers-yet within less than a century cities such as Athens and Los Angeles are deep in a different sort of ordure, one to which the internal combustion engine contributes heavily. There are things that can be done with technology, often low technology but at the Rio de Janeiro environmental summit that finished last weekend little was heard of the notion that technological solutions to the world’s environmental problems are just around the comer. So, the two weeks that were the "last chance to save our planet" are over. The earth is still there, just. So are the politicians, full of sound and even fury sometimes, but with no vision and signifying nothing because they suspect that those who put them into office back home are not yet persuaded of the need for sacrifice. Sustaining the environmental debate after Rio is the challenge that faces those who found the Earth Summit a crashing disappointment (but see p 1529 for a view from someone who was there). That task will have to be shared by the projected
Sustainable Development Commission, The Lancet has argued that there is a substantial medical dimension to the current destruction of the environment.2That case is well made in the World Health Organisation’s excellent contribution to the Rio jamboree. In her foreword to the reportSimone Veil wrote that "the kind of development needed to safeguard health and welfare will depend on many
conditions, including respect for the environment,
development without regard for the environment would inevitably result in impairment of human health". WHO did not neglect population. How sad, then, that population per se got so little publicity in Brazil. It is there in Agenda 21, one of the products of the UN Conference on Environment and Development, but separated from "protection and promoting human health" (with its obvious WHO input). Some argue that poverty must first be corrected, and limitation on family size will follow. It while
is
too
more
late. On the road to that destination how many nations in Africa and elsewhere will fall into the
