Acupuncture analgesia

TI%'S - Julr IqT,~

21

Acupuncture analgesia P. W. Nathan i

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4cupltPlCttlrt' is bei,g used i,creasblgir throughout the ~ orld.]br the treatment q f (hseo~e. II'hr it worl, s is still a subject f o r conjecture. Perhaps surprtstngl.r, acupuncture a'lalgestu is the.[irst part o f acupuncture to be explained on the bast ~ o f ph.wioh)er and anatom'..

It is often difficult to separate the facts from the rauonaie gi,,en for them. Irrational though th,s -nay be. It ts more difficult to do so ~hen ~,-." are faced with a culture so different from our o,,~n as that of tradmonal C h m a To anyone brought up m ~,~,c,,tcrn culture, the tradmonal explanations of acupuncture are so strange and archaic that th; facts are often thrown out along with their explanations. Acupuncture analgesia seems to ne ,:ten more inexph,-able. Although oper ,ions pertormed under acupuncture am Igesia have been ,,hown on tele~ IMOfl and a fe~ dottor,, ha~e seen th~s really happening m Ch,na. most r,:ople ~ere so amazed ihal thc~ rultr, cd to f" :he,,e their eyes. The efforts to account ft r the fat.Is led We,,tern do~.tor,, to ,,ugge,,! that the patmnts v, ere bern,_, secreti3, h~pnouzt:d, or that they w'ere ,,.,'rctl~ be,ng g ~ e n large dw, es of analgesic mtravenousl) under the drape,,,, or that Chmese patients were so tough and stoical that the; d~d not mind be,ng operated upon w~thout an) form of general anaesthetic. The advantages claimed for acupuncture analgesia are that it can b,: used anywhere. that it avoids overdosage ~ t h general anaesthetic, that ,t has no toxic side-effects. that there is no need It) gn, e drugs lalthough ,,omeume,, ,,mall do,,e,, are g~scn m c o n j u n c t m n v.~th acupuncture) that there ,,, least ",nterference with the patient's physio logical ,date'. and that Ihere m "acuse cooperation between the surgeon and the patient'.

Operalions in China under acupuncture analgesia

Reports of large numbers of patients ha,.mg heen operated upon under a~.upuncture analgesia ha~,e been gl,~en ,n the Chinese Medical Journal, with adequate abstracts in English. From these and other reports ~,t can assess to some degree the results of Chinese exper,ence o f this techtuque. For example, acupuncture does

,~ot produce complete analge.~)a l-he degree of analgesm sartes from pat;ent t,, patient, dependmg on the r ' e , h o d of reduction and mamtendnce Certam part', of the ,,perauon are more pamful than olher., h)r example. InCl,.,ion,~ t)l the ,,kin are pam~ul Tclemctr,c re~.,~rdmg,, made h,. ,i group of anae-,thctr, l,, f r o m Vienna ~,r,mng ( hma, ,,ho~,ed that dur,ng -,urger> under acupuncture ,,malge.qa -,~,mc ol I [ C p:ati=nt, produced no electro~.ardmgraph~. cha age,,, nor am, ,dteratmn,, m pul,e rate dur ng ,,km mctsmn, allhouoh manx olhcr l at,ent ,, did. There ,ire .,ome ( h m c , c ,,argeon,, ~ h o addmon,tll~ mhltrate the skmn v,,th local anaesthetic. ,,olut,on ~.h.)c ,,om~ d,) ~qterco,,lal bl-uk., l'ulhnt, ,,n the ~l~ccr.I Is p,unful and man~ ~t,rdc,)n~ tnd [ , t )pc,in ()b+cr+cr,, found thdt Ih),, 2,111~. x,,,r, )n,ldequatel? ,,uppres,,cd b'. ,~,~up ~n,.lure. The analg¢,,ht r, lea,,t th+od t~ll the hmh,,, onl,, f,url,, goud I,,r .,bd,,l~ ~n.ll t)pc'atmt,n,,, and he,,t I',)r ,,per.lib,n., ,n the f a i r . head. thesl, and lhxr,))d elant

-~nderv, on and hr. ~c,lleague., t,n a,.upun~turc .Lnalge,~ ! dlTeuun~ the teeth the m,,,,t eomprehen,t,,e r, that b,. -\nders,~on and H t d m ~ r e n ~ The,, u-ed t ~ o ,,orl, ,q a,t,puncture,,t~-uul.tt~on ~n,,erte,l hnc nee lie,,

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gamed b} our Chme,,e colleagues, the pt mt t~xer the middle ol the tir~t mlero',.,,et u,, muscle ts p lrt,cularl.~ effectl,.e lor analgc ta and a[.,o tor the treatment of rtlam, patho logical Colldltl.~n ~, tlo~e,,er. ,,ttmulatam ol thr, pomt +ca, I¢,,, ettcct~+e thdn ".tm~ul.mng the ,.hock,tnd

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Experimenls on pain Ihre~hold,,

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Exper,ments on pain thresholds m nor real subjec,+ and m those about t> ha+e operations under acupuncture analge~m ha+e been cmried out m China. America. and Europe. One group tn Shanghm rept.,c ted that under aeupuvcture analgesia there v.as a rise mn pare thrt ,hold; but tactde and pre',~ure senstbdlt), t~,o po:nt di~cr,mm auun. and temperatur- scnslblht~ remained unaffe~.ted, One notes, ho,~e,,er, that the r:,,e in threshold obtained b~ most m,,estl t:at,,rs under experimental condmon~ v,a~ ~ot such as would be needed lot major

ha~e t,,und the opp..+,,tte l)¢r, tal pain thre,,ho.d v.a,, al~o c,t,tmmcd h', %la~er an ~ ht~ ,,,Ik JI~LIC'. I h. ', -1 .:'. kited the mter,~.,,,¢ou., p,,;nt hd.ltcr.t]l~ i.,,. tv, lrhi:g .t needle. ~h~.h thc~ ,,ni~ .l,t l , r

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tn kurope, acupum.turt,,t~ ha,.c bccn induc+lg analgesia for dental treatment. mclud ng extractions, for man.', ~,ear~. Perhap~ it ~ a s for this reason that the first e~perlment., on p,un thre,,hold ~cre d,me t n teem. O f the man) e,tcellent papers b)

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pr~,:n~ t hat a ,:h ,,u, h na,'.cq', tic .,, u p u , , ture the,. t+ .tq ~gcd 1,, Drt,.lu,.t .t,~. ¢0~.,.l .t" all In the group r~.,c:,,m- .~,,.p.:'~,'~,'~ there ,~a~ a 2" rt.,c ,u tt.r~ ,h, i ~, ,~c.,, m a group re,.e x~ng h~lp:, . . . . . +~. ~,a- .t:~ b'~ rt,,¢ In a'h+thcr ~tmerh.,tn ,tud.~'. t~,, pomt,~ m the f. cc ~erc ,,t,mul.ttcd b~ ctc,.tr,. ,.al ,,I~mul ~t~,, ~ at . t r j t c ol ] II~ ,,,nt,r:u~ue l,,r St)n+,)+ ~,~ th thi,.,.,,rtc, t;. ,ppl,cd k.nd o f a c u p u n c t , ' r e ,,tlnluldll,)n. there +,.a,, a rt+c ,n pare it:re+hold o f I","

It is to be loted f i a t olten m a series ol e-~penment, ,n human +ub3+cts. and also t;; ot~er an tr als. thert is a s n ail number of -. I. -',~ : ' %,,r~h-H

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T I N S . July 1978

22 subjects wh,~ do not get analgesia with the same wethod of induction as induces analgesia ir~ others. This fact upsets scientists and doctors who feel a need for consistency and tidiness: which is not often satisfied by the material of biology. Interaction of somatosensory inputs in the central nervous system Although acupuncture analgesia for surgical operations is new to the Chinese, just as it is to us. using acupuncture to alleviate pain is a part of traditional Chinese medicine. T:fis invasion of surgery by acupuncture led physiologists in China to investigate ~ mechanisms. It may be mereiy coinCidence that over the last decade neurophysio.ogists everyw,here have been mvesttgatin~ ehe interaction oftwoneuronal inputs: eithe: of simultaneous volleys of impu!ses, or of the effects of a preceding volley on a subsequent volley. The particular interact.on that has interested most workers is the inhibition of a noxious input, the inhibition of the input that causes pain. The gate-control theory of Melzack and Wall6 that has aroused so much interest in the W e s t almost as much as has acupuncture - is a theory based on interaction of this kind. This theory proposes that at the entrance to the central nervous system and at many sttes within it, there are gating mechanisms. The gate can be kept shut, allowing no input from the smaller delta and non-myelinated fibres to pass, kept ajar, or left open to allow this small fibre input to pass through synapses and on to further regions of the central nervous system. The guardians of the gates are excitatory and inhibitory neurones present at the synapses where the gate is to be found. That interactions such as these are likely to furnish the explanation of acupuncture analgesia has been realized by most investigators.

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Neumpaedia 1. ~e-synapticinhibition

Chang, who was probably the first contraction of abdominal muscles physiologist to investigate the mechanism associated with a painful disorder of the of acupuncture analgesia, looked at the abdominal or thoracic contents. They found interactions of the two inputs ~ - that from that electrical acupuncture of either the the acupuncture stimulation and that from fore- or hindlimbs stopped or decreased this the noxious ;~npot. He examined neurones of rt:flex response; the same effect was obthe thalamus that are known to he a pa:-t of tained from the electrical stimulation of a the pathway for feeling pain. In rabbits and deep afferent nerve of the lower fimb at an rats he found "'an inhibitor)" interaction intensity to activate fibres that would cause between the afferent impulses arising from pain in man. Acupuncture analgesia, as the points of acupuncture and those from judged by its effects in reducing this reflex, the site of pain". But the effect was slight. could not be induced after the spinal cord When he stimulated the sciatic nerve of a was cut just below the brain. They conrabbit at an intensity that would have been eluded that some supraspinal region was below pain threshold in man, the inhibitory necessary, and they made various cuts of effect was feeole. A strong stimulus to a the neuraxis to find out what this structure nerve that would have teen unbearably was. They localized it to the bralnstem. painfpl in man evoked both excitatory and From differential sections of the spinal inhibitory actions on the thalamic neurone. cord, they showed the afferent pathway to Thus his evidence did not go ,~ery far to the brainstem was in the anterolateral account for acupuncture analgesia. columns of the cord and the descending Another investigation in China, this time pathway was in the posterolateral columns, on the cat, showed that the nearer the near the posterior horns. acupuncture input was to the noxious input, By this time (! 975) the following position the more effective it was; most effective was had been reached by physiologists in China. when both the acupuncture and the noxious Acupuncture analgesia was due to the stimulation were within the same peripheral impulses from the acupuncture inhibiting nerve territory. Acupuncture never caused those from the surgical operation. This complete obliteration of impulses set up by inhibition was occurring in the thalamus. noxious stimulation. These workers con- The afferent pathway to the thalamus taken eluded that acupuncture was inhibiting by impulses arising from the stimulation nociceptive neurones of Lamina V of the was within the anterolateral columns of the spinal cord. As these experiments were cord. There were also descending influences carried out on cats in which the spinal cord from the brainstem suppressing nociceptive had been divided from the brain, they reflexes and likely to be suppressing pain; concluded that regardless of the effects these descending inhibitory effects reached found by Chang in the thalamus, there were the spinal cord via fibres running adjacent also inhibit(,r~ effects at spinal level. to the posterior horns in the posterolateral Shen. Ts'ai and Lan' used a viscero- column. Some Chinese investigators, somatic reflex in the cat as the measure of Clearly influenced by. Melzack-and Wall's analgesia. This is a reflex contraction of the gate-control theory, thought that the desfibres induced presynaptic abdominal wall arising from excitation of cending afferent nerves from the viscera. It is the inhibition of the small posterior root fibres reflex responsible for what is known as that reported noxious events. Some physio"guarding' in clinical medicine: that is, the logists thought that there was an analgesic effect of acupuncture stimulatiort taking place within the spinal cord, with local acupuncture inpnt inhibiting local nociceptire neurones. Endorpbins and acupuncture analgesia What is likely to be the essential mechanism of acupuncture analgesia was discovered in the West after acupuncture analgesia had been in general use for surgery in China for some years. We now know that there is an endogenous paininhibitory" system within the brain and spinal cord. There is an inhibitory tract running caudally from the more caudal raphe nuclei, through the medulla obiongata and the posterolateral columns of the spinal cord, adjacent to the posterior horns.

TINS July 1978

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The fibres of this tract inhibit the posterior inhibitory tract, it causes local inhibition at horn neurones that receive a noxious input ~pinal level, and it may liberate endorphin from any source, be it the skin. the muscles to reinforce inhibition at the nociceptive and joints, or the viscera. Th~s inhibition is synapses. Thus, although we have not yet so effective that when the raphe neurones obtained the full proof, it is apparent that are electrically stimulated, operations can the mechanism of acupunctvre analgesia be performed on animals, while they carry invol~es an activation of the ¢adogenous antinocieeptive system, incorporating both on unconcernedly with their daily lives. e The endogenous system, that is now its inhibitory synaptic division and its sometimes clumsily, though correctly, call- peptide hormonal division. ed antinociceptive, prevents the receptit~n of noxious input at the first synapse made Parameters of dectrkal stimulation With acupuncture analgesia, a new way by posterior root fibres. This is achieved by the descending tract just mentioned and by cf stimulating the nervous system was local spinal inhibitior. At least a part ,)f the introduced: excitation at a low rate. This antinociception is a presynaptic inhibition was done in imitation of putting the needles in and twiddling by Fand. In Western of afferent fibres. The evidence now shows that the neurones causing presynaptic medicine, stimulation has always been at a inhibition are peptidergic, emitting the fast rate. "Slow" means up to lO Hz and short-chain peptides, methionine and "fast" means more than 100 Hz. These leucine enkephalin. In addition to this local boundaries are of course not rigorous: in mechanism stoppine a noxious input being some of the physiological investigations in received, there is a more general .,:,a- China the acupuncture stimulation was at 100 Hz. in China, acupuqcture analgesia is nociceptive mechanism: the circulation in th~ blood-stream, and maybe in the usually induced at stimulation rates of 2-4 cerebrospinal fluid, of long-chain peptides. Hz. Slow stimulation is more effective at certain points: these are the points already alpha, beta. and ~amma endorphins. known in Chinese traditional medicine to Recently Sjtlund, Terenius and Eriksson have estimated s the endorphin content of be effective in the acupuncture treatment of disease. Both Chlne.,e and European lumbar cerebrospinal fluid before and after workers have examined the effects of giving acupuncture to patients with chronic ~umulation at various slow rates. pain. They found a "'marked rise of e n dorphin ,'raction! in lumbar cerebrospmal Stimulation at 100 llz has been found to be fluid in 4 out of 9 patients after electro the best rate~; better ,,till was to ~ar~ the acupuncture", whereas there was a low rate. This is al~a)> done nowada.~s in China. and a changing rhythm is built i n t o level of cndorphin in all patients gith the usual acupuncture st+mulator a~allable chronic pain. As this pain inhibiting system came to m China. From what on- knov~s of neuro ph) slologlc,l habltua~ =on and dts light, the question arose whether a foreign substance known to be an effective habituatior, this is lik¢,~ to be a good . a~algesic, morphine, was working on the suggestion. The rate of stimulati¢n ts one factor in ,,ystem. Much work in the United States has led to the conclusion that opiates fit into the inducing analgesia: int:nmty is a~,,~thet Usually tl+¢ intensity is maintamed at a level sites on membrapes normally occupied by which the patient can tolerate without i~. enkephalins; endorphins act at the same sites. Two of the main sites are peri- being pmnful, and it ~s progresmveb increased during the induction period. The aqueductal grey matter of the brainstem. actual re,i-ease in voltage is large: ~[ may stimulation of which causes antinociception, and Laminae I! and 111 of the start at 0 25 V and finals be 50 V. Anders-on and Holmgren ~ wrote: "'The posterior horns of the spinal cord where the pain threshold increase ~as clearly related small afferent fibres excited by noxious to the intensity of the conditioning stimulastimuli synapse. It appears, then, that tion (by which they meant 15 30 rain of opiates are analgesic substances in that they electroacupuncturc before testing). A high activate the raphe-spinal inhibitory tract intensit) giving powerful muscular conand because they inhibit the noxious input at the spinal levd. traction~ anti a strong beating sensation was required. No change of the pain threshAn antagonist of morphine is naloxone. This drug pre-empts the morphine-binding old was found at low intensities." They exasites on the membranes of neurones. The mined the effect of step-wise increases in accumulating evidence that acupuncture stimulatiot~ intensity. "'At each level the analgesia ~ reversed by naloxone ~hows us intensit) was kept constant for 20 rain.'" that acupuncture analgesia is like Low intensities of electrical stimulation. morphine: it activates the descending with currents of 15-20 mA did not raise the

pain threshold. With a stimulus intens=t~ of 25 m A m the first interosseous muscle at;d 48 mA m the face, which caused strong beating sensations and large muscle contractions and that could just De tolerated for 60 rain, the rise =n thre:.hold occurrtd: the stronger r~e stimulation, the greater the rise in pai.~ threshold. The gradu'~! rise in pain tireshold ~,.,.:,~rc both with a gradual ira.reuse m acupuncture stimulation intensit:~ and ~,~h a sudden increase in intensity, To be effective, stimulation had to be ~trt,ng enough to give repeated muscle comraction, it max be noted too. that acupuncture points recommended for in ducmg analgesia are what are called motor points: these are points at which dectric+:i stimulation most r+.tdll~ causes muscle :o~traction. IndeeC. all motor points are act~puncture points, th.,,ugh not all acupu++cture points are motor points ~ Andersson and Holmgren sax "'Undo =otedl>, this st,~mulat=on activates afteren+ nerve fibres both d.rectly and +la xar+ous t.~pes of cutaneous and muscle receptors activated during the mu:cle contra:tions, and the pare threshold increase mt~,t be dtrectl~ rel tied to central nervous eff+cts of these afferent d~scha:'ges." I:mure prospects ~ox+ that neuroph~ siolog~.~ts are ~pentng tip Ile~ ~cglon5 of ,r,., .,, "rid are In,:klll~

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unJer~landing of the nl¢chanz,,m.~ of pare. I¢1 us look forx~ard to the tlme x',llCll ~t.' ha:¢ an ue+derstallding of lh¢ f~C~h,lfll,ll1'~ tll+~¢rl) in~ th~ effC~;tl++' Us~" of ,tcupul+#lur¢ In the [ r e , l l l n c n [ Of dP~c,l'~¢.

Acknowledgements

=~am rnn~t grateful to Dr. Joh[I Lm~ and Dr. Jo.~ph Needham F . R S fi~r their + o m m e n l s a n d c o n t r i b u t i o n s to ~hl,~ paper. Reading List !

'tlndcr,.,~Lm. b Ii and liol;iilArl:n t I 19";~ -I,,. d ~. hm I h , / L 311 .;.~4 2 Chant. i! [ (I9".~).%+,,mu.%,m, l~ 2"." r,tl .; Ch,tpman t ' R . ( hen. A C and t~,,nJ~a. I J , I ~ " ~ P,,,I 3.21 : 22" 4 Ctuen. P. ~, . t ' h , h . t " C and Yen.~ V. ~1'+'4, ~, lt'tltltl o~Hlit'~J | ". 0 ~

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_~ Ma~,¢r. l ) J . Price. l ) D . BarL~'r. J and R.,th A (19"Tt) In: J J B o m c a and D ~ll'm~:e~ard (Eds). .4d~ames :n Ptitn R,'~',tr~ll Fhc~apt. Vol 7. Ra~.en Pre,~..%¢v~ ~ ork +" M,:ltat.k.M and ~8,all. P l) |l')h.cl.~.+/t,'. ¢'. % ~' 7 %hen. E . Ts'a~. T a n d Lan. C ( I O " ~ j ('hm g f r d J. I. 431 440

8. Sjolund. D, Tereniu~, L. and Ersk~on. M

~1977) A~taph)sm/ 100. 382 384. II

p IV. %tathan is a m e m b e r o f the ~! R C, ~"tternal sc¢¢nrth¢ sin.ft, working at the Institute of Veurvlog=. The Vational Hospital ~ff %er~ous Dtv¢*,~c~. Queen Square. London ~VC" "~ 3BG. L .K