Hypothermia
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1027 LEADING ARTICLES Hypothermia THE LANCET LONDON: SATURDAY, NOV. 14, 1953 IN the past few years the deliberate induction of hypothermia has come to the fore as a means of lessening certain operative and anaesthetic risks. Reduction of body-temperature, and therefore of metabolism, cuts down the oxygen needs of highly specialised organs such as the brain and heart to the level of less important tissues -; and the blood-supply to these organs can then be temporarily interrupted or diminished. There are, however, dangers in hypo- thermic states, and a considerable amount of experi- mental work has been carried out in attempts to assess the various factors concerned. In this issue Dr. CHUBCHiLL-DAViDSON and his colleagues describe experiments on surface cooling, by immersion in iced water, designed to assess the dangers of this technique. Their results in dogs, which do not differ greatly from those previously reported, suggest that surface cooling is a simple and safe method of reducing the body- temperature, provided this is not allowed to fall below 26°C. Clinically, this method is likely to be restricted to children ; while cooling of the blood- stream by means of the extracorporeal circulation, as described by DELORME,1 may be preferable for adults. Special blankets through which ice-cold water is circulated in pipes, and on which the patient lies, is an alternative. With this method skin necrosis may very occasionally ensue, owing to the uneven pressure of the dependent parts of the body on the blanket ; but this slight risk has to be set against the physiological disadvantages of the extracorporeal circulation with the associated need to insert a cannula into a large artery and vein. All these methods produce an effect only slowly-upwards of four hours may be -needed to bring a normal-sized adult to a temperature of 26°C-and cooling of the peritoneal or the pleural cavity, which is mentioned by CHUBCHILL-DAVIDSON and his colleagues, certainly warrants further trial. These investigators have clearly shown the dangers, first of ventricular fibrilla- tion at temperatures below 26°C, and secondly, of unexplained fatal pulmonary complications after rewarming. Cardiac arrhythmias are usual below 26°C, and occasionally ventricular fibrillation develops which is irreversible at temperatures below 22°C. This work has been done on normal dogs, in which the margin of safety was found to decrease with increasing age. The most obvious clinical applica- tion of hypothermia is in the operative treatment of congenital heart-disease in children ; but, though young, these patients have far from normal hearts, and the complications of cooling might easily arise at higher temperatures than those found experi- mentally to be safe. Further experimental work 1. Delorme, E. J. Lancet, 1952, ii, 914. 2. Lewis, F. J., Taufic, M. Surgery, 1953, 33, 52. 3. Laborit, H., Huguenard, P. Pr. méd. 1951, 59, 1329. 4. Huguenard, P. Anesth. Analg. 1953, 10, 16. will no doubt be directed to averting these dangerous complications, since there is little doubt that hypo- thermia is of practical value. One reason why it has been developed is in order to work safely in a dry heart ; and this ideal will not be achieved solely with hypothermia, except for brief periods, unless very low temperatures can be obtained. In the light of our present knowledge there is little or no justification for using this technique for surgical operations which can be properly done without its aid. In cardiac surgery the clearest occasions for its use seem to be for operations on the great vessels which cannot be completed without temporarily stopping the blood-supply to a vital organ such as the brain, and for operations to repair septal defects in the heart. LEWIS and TAUFIC 2 have already reported the closure of an atrial defect with the aid of hypothermia in a girl aged 5 years who recovered fully, and other workers have had similar successes ; but the dangers of the operation are considerable. Unless the cardiac outflow is occluded low enough to include the origin of the coronary arteries, air may enter these during the opening of the heart ; and even if this is avoided ventricular fibrillation is always likely. Hypothermia has been used clinically as an ancillary to the surgical treatment of the tetrad of Fallot by the Blalock-Taussig operation. This would as yet hardly seem an acceptable indication : the operation has been done without hypothermia in many thousands of cases, with so low an immediate mortality as to suggest that in most cases reduction of body-tempera- ture may enhance rather than decrease the risk. Moreover the fall of pressure in the right ventricle that accompanies the general fall of blood-pressure when the body is cooled may prove disadvantageous- and even dangerous-in the presence of obstruction at the pulmonary valve. In very severe cases, where a high operative mortality is to be expected, there may be some justification for cooling ; but the wish to assess the practical value of this new method should not obscure the possibility that there is no real need for it. Hypothermia may prove useful in neurosurgery and, in a limited form, in cases needing anaesthesia with controlled hypotension, since some of the hazards of hypotension could be diminished by decreasing the oxygen needs. A moderate reduction of temperature may become a valuable adjunct to the use of the artificial heart. It may also be of value in the treatment of shock, and in toxic illnesses in which fever is prominent and the normal defensive mechanism of the body inadequate. In some Continental clinics various agents are given before, during, and after operation to lower metabolism by producing a state of " artificial hibernation" 3 4; and French work in this connection is reviewed by a correspondent on a later page. Hypothermia is often used as an ancillary to this method-in fact many of the drugs prescribed facilitate cooling by depressing the temperature-regulating mechanisms-though, irrespective of deliberate cooling, the body-temperature will fall a degree or so. Much of the success of the technique apparently depends on chlorpromazine hydro-
Transcript of Hypothermia
1027LEADING ARTICLES
Hypothermia
THE LANCETLONDON: SATURDAY, NOV. 14, 1953
IN the past few years the deliberate induction ofhypothermia has come to the fore as a means of
lessening certain operative and anaesthetic risks.Reduction of body-temperature, and therefore ofmetabolism, cuts down the oxygen needs of highlyspecialised organs such as the brain and heart to thelevel of less important tissues -; and the blood-supplyto these organs can then be temporarily interruptedor diminished. There are, however, dangers in hypo-thermic states, and a considerable amount of experi-mental work has been carried out in attempts toassess the various factors concerned.In this issue Dr. CHUBCHiLL-DAViDSON and his
colleagues describe experiments on surface cooling,by immersion in iced water, designed to assess
the dangers of this technique. Their resultsin dogs, which do not differ greatly from those
previously reported, suggest that surface coolingis a simple and safe method of reducing the body-temperature, provided this is not allowed to fallbelow 26°C. Clinically, this method is likely tobe restricted to children ; while cooling of the blood-stream by means of the extracorporeal circulation,as described by DELORME,1 may be preferable foradults. Special blankets through which ice-coldwater is circulated in pipes, and on which the patientlies, is an alternative. With this method skin necrosis
may very occasionally ensue, owing to the unevenpressure of the dependent parts of the body on theblanket ; but this slight risk has to be set againstthe physiological disadvantages of the extracorporealcirculation with the associated need to insert a
cannula into a large artery and vein. All these methodsproduce an effect only slowly-upwards of four hoursmay be -needed to bring a normal-sized adult to atemperature of 26°C-and cooling of the peritonealor the pleural cavity, which is mentioned byCHUBCHILL-DAVIDSON and his colleagues, certainlywarrants further trial. These investigators have
clearly shown the dangers, first of ventricular fibrilla-tion at temperatures below 26°C, and secondly,of unexplained fatal pulmonary complications after
rewarming. Cardiac arrhythmias are usual below26°C, and occasionally ventricular fibrillation developswhich is irreversible at temperatures below 22°C.This work has been done on normal dogs, in whichthe margin of safety was found to decrease withincreasing age. The most obvious clinical applica-tion of hypothermia is in the operative treatmentof congenital heart-disease in children ; but, thoughyoung, these patients have far from normal hearts,and the complications of cooling might easily ariseat higher temperatures than those found experi-mentally to be safe. Further experimental work
1. Delorme, E. J. Lancet, 1952, ii, 914.
2. Lewis, F. J., Taufic, M. Surgery, 1953, 33, 52.3. Laborit, H., Huguenard, P. Pr. méd. 1951, 59, 1329.4. Huguenard, P. Anesth. Analg. 1953, 10, 16.
will no doubt be directed to averting these dangerouscomplications, since there is little doubt that hypo-thermia is of practical value. One reason why ithas been developed is in order to work safely in a dryheart ; and this ideal will not be achieved solelywith hypothermia, except for brief periods, unless
very low temperatures can be obtained.In the light of our present knowledge there is little
or no justification for using this technique for surgicaloperations which can be properly done without itsaid. In cardiac surgery the clearest occasions forits use seem to be for operations on the great vesselswhich cannot be completed without temporarilystopping the blood-supply to a vital organ such asthe brain, and for operations to repair septal defectsin the heart. LEWIS and TAUFIC 2 have alreadyreported the closure of an atrial defect with the aidof hypothermia in a girl aged 5 years who recoveredfully, and other workers have had similar successes ;but the dangers of the operation are considerable.Unless the cardiac outflow is occluded low enoughto include the origin of the coronary arteries, air
may enter these during the opening of the heart ;and even if this is avoided ventricular fibrillation is
always likely.Hypothermia has been used clinically as an ancillary
to the surgical treatment of the tetrad of Fallot bythe Blalock-Taussig operation. This would as yethardly seem an acceptable indication : the operationhas been done without hypothermia in many thousandsof cases, with so low an immediate mortality as tosuggest that in most cases reduction of body-tempera-ture may enhance rather than decrease the risk.Moreover the fall of pressure in the right ventriclethat accompanies the general fall of blood-pressurewhen the body is cooled may prove disadvantageous-and even dangerous-in the presence of obstructionat the pulmonary valve. In very severe cases, wherea high operative mortality is to be expected, theremay be some justification for cooling ; but thewish to assess the practical value of this new methodshould not obscure the possibility that there is noreal need for it. Hypothermia may prove usefulin neurosurgery and, in a limited form, in cases
needing anaesthesia with controlled hypotension,since some of the hazards of hypotension could bediminished by decreasing the oxygen needs. Amoderate reduction of temperature may become avaluable adjunct to the use of the artificial heart.It may also be of value in the treatment of shock,and in toxic illnesses in which fever is prominentand the normal defensive mechanism of the bodyinadequate.
In some Continental clinics various agents are
given before, during, and after operation to lowermetabolism by producing a state of " artificialhibernation" 3 4; and French work in this connectionis reviewed by a correspondent on a later page.Hypothermia is often used as an ancillary to thismethod-in fact many of the drugs prescribed facilitatecooling by depressing the temperature-regulatingmechanisms-though, irrespective of deliberate
cooling, the body-temperature will fall a degreeor so. Much of the success of the techniqueapparently depends on chlorpromazine hydro-
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chloride (’ Largactil ’), which has been developedfrom compounds of the anti-histamine group,though it is almost devoid itself of anti-histamineacti vity. This drug is said to depress various partsof the autonomic and central nervous systems, andalso the endocrine system. The patient will gaingreat advantage if it proves possible to depressdifferentially the body-readjustments that followthe trauma of surgery and anaesthesia, so that harmfulprocesses are retarded and reparative ones allowedto progress. -
Many problems concerning hypothermia are still
unsolved ; and meanwhile its clinical applicationshould be confined to patients whom it is clearlylikely to benefit.
1. Melnick, J. L. Amer. J. Hyg. 1947, 45, 240.2. Collins, S. D. Publ. Hlth Rep., Wash. 1946, 61, 327.3. Howe, H. A. In Viral and Rickettsial Diseases of Man. Edited
by T. M. RIVERS. Philadelphia, 1952.4. Bradley, W. H. Papers and Discussions of 2nd International
Conference on Poliomyelitis. Philadelphia and London, 1952.5. Agerholm, M. Lancet, Aug. 8, 1953, p. 287.6. Melnick, J. L., Ledinko, N. Amer. J. Hyg. 1953, 58, 207.
Subclinical Poliomyelitis InfectionsEPIDEMIOLOGISTS concerned with the prevention of .
poliomyelitis need to know how many silent sub-clinical cases accompany each overt paralytic infec-tion. Estimates, based on indirect methods, havevaried from 100 to 1000 subclinical infections to each
paralytic case. Thus, MELNICK 1 measured the amountof virus excreted into New York sewage at a timewhen the incidence of poliomyelitis was low, and heconcluded that there were about 1000 silent excretorsof virus to each paralytic case. COLLINS 2 found that
only about 1% of young adults aged 20-24 gavea history of paralytic poliomyelitis, and since theattack-rates are negligible above this age he concludedthat adult immunity had been gained at a cost of1 paralytic illness to about 100 abortive infections.HOWE 3 compared attack-rates of measles and polio-myelitis, and by reasoning similar to that of COLLINShe concluded that there were about 200 subclinicalinfections to each paralytic case. Many epidemio-logists, however, regard these figures as excessive.Thus, BRADLEY 4 speaks of " the probability thatthe infection moves through a relatively narrow streamof the population " ; and AGERIIOLM,’5 taking up thisidea, suggests that damming the stream might haltthe flow of the disease and should not prove toodifficult administratively.MELNICK and LEDINKO 6 have now found strong
evidence against the hypothesis of a narrow streamof infection. These workers used the new tissue-culture techniques for studying neutralising anti-bodies to the poliomyelitis viruses. They investi-
gated samples of serum from 200 children in Winston-Salem, North Carolina, who were bled in 1948,first just before a poliomyelitis epidemic and againsix months afterwards. Tests of the pre-epidemicsera revealed a very low previous incidence of infec-tion with any of the three types of poliomyelitis virusin children under 4 years of age ; but a higher propor-tion of older children showed antibodies-a findingwhich correlated well with the fact that the lastoutbreak of poliomyelitis before that of 1948 was in1944. Sera taken after the 1948 epidemic showedthat quite a high proportion of children had developedantibody to poliomyelitis viruses of types 1 and 2
during the summer; ; no evidence was found of
infection with typc-3 virus. MELNICK and LEDINKOcalculated the proportions of children in different
age-groups infected during the epidemic. Theseinfection-rates were then compared with the knownparalysis-rates in the epidemic ; and it was found thatthe number of subclinical infections per paralyticcase was 175 for infants under 1 year of age, 100 forchildren aged 1-2 years, 73 for children aged 3-4years, 62 for children aged 5-9 years, and 95 forchildren aged 10-14 years. It was also found that
previous infection with virus of type 2 or 3 did notprevent infection with type-1 virus in 1948. MELNICKand LEDINKO did not investigate whether adults wereundergoing subclinical infections during the epidemic;and this may be an additional source of spread.
These findings suggest that poliomyelitis cannotbe accurately pictured as moving in narrow streamsthrough the community, and that the major part ofthe flow is through wide subterranean channels.Quarantine restrictions against poliomyelitis havebeen likened to closing the stable door after thehorse has bolted. They are better compared to
mending a leaking bottle after most of its noxiouscontents have already escaped ; the attempt to pre-vent the last few drops from escaping, howeverdesirable, should be viewed in the light of the damagealready done. This new evidence will discouragethe adoption of stricter quarantine measures. Themain hope at present is from vaccines 7; but,because of the large number of subclinical infectionsand the low paralytic rates, it may prove difficultto assess their protective power. The aim will be to
produce either a live attenuated-virus vaccine whichwill confer lifelong immunity, or else a killed-virusvaccine which will convert the paralytic cases intosilent subclinical infections.
7. See Lancet, 1953, i, 777.
Diarrhœa after GastrectomyA NOT uncommon consequence of gastrectomy is
looseness of the bowels, sometimes amounting to
diarrhoea, starting two or three days after the opera-tion. Though usually transient this may last forweeks or even months. It has usually been attributedto the greatly diminished secretion of hydrochloricacid in the days immediately after the operation, andthe neutralisation of any acid present by the pain-creatic and intestinal juices which now have free accessto the cavity of the stomach remnant. Ingestedbacteria, no longer destroyed by the acid, pass intothe jejunum where they find conditions eminentlysuitable for propagation. The upper part of the smallintestine reacts by becoming inflamed and pouringout large quantities of exudate. How exactly accom-modation to the strange new state of affairs takesplace we do not know. On an earlier page Mr.WILLIAM and Mr. PULLAN describe the illness of tenpatients in whom the diarrhoea was so severe as tocause death in five and to threaten life in the remain-der. Fortunately the condition can rarely be as
serious as this, for they could find only these ten casesin all the St. Thomas’s Hospital records. The patientspresent a characteristic picture. The operationproceeds as usual, and for forty-eight hours all seemsto be well. Then diarrhoea sets in, and with it circu-latory collapse so great that within two or three daysthe patient may die. The pulse is rapid and thready,
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