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CURRENT PRACTICE OF HYPOTHERMIA IN BRITISH CARDIAC SURGERY
Br.J. Anaesth. (1975), 47, 1011
CURRENT PRACTICE OF HYPOTHERMIA IN BRITISH CARDIAC SURGERY D. J. F. MACDONALD SUMMARY
Following the work of Bigelow and others in the early 1950s (Bigelow, Callaghan and Hopps, 1950; Bigelow, Mustard and Evans, 1954; Swan et al., 1955), clinically induced hypothermia made possible dramatic advances in cardiac surgery and neurosurgery. More recently, as a result of the continued development of other surgical and parasurgical techniques, for example the improvement in pumpoxygenators, the indications for the use of hypothermia in cardiac surgery have become less clear and the advantages of its use, without some form of extracorporeal circulation, are open to question. In 1971, McDowall investigated the use of hypothermia in British neurosurgery and reported that the practice was decreasing, 12 of the 31 centres having abandoned the technique completely, while another 13 centres used it rarely. No such information is available about the current practice of hypothermia in British cardiac surgery and it was felt that a survey similar to that of McDowall, but related to cardiac surgery, would be of value. Consequently, a questionnaire was sent to the 35 hospitals in the United Kingdom where open heart surgery is practised. The questionnaire is reproduced in table I. In order to simplify an already complicated proforma it was decided not to ask for percentage use but simply to ask the question, "Do you employ hypothermia for . . . ? " The questionnaire was addressed to D. J. F. MACDONALD, M.B., D.A., F.F.A.R.C.S., Division of
Anaesthesia, Royal Infirmary, Glasgow.
"senior anaesthetists in cardiac sugery" at the various hospitals. Four weeks later a duplicate questionnaire was sent to the heads of the anaesthetic departments at those hospitals from which a reply had not been received, with a request that they pass it on to the anaesthetists concerned. Questionnaires were also sent to 13 surgeons known to have, or to have had, an interest in the clinical use of hypothermia, for their comments. Replies were received from 29 of the anaesthetists circulated and from 10 of the surgeons. In one hospital the surgeon completed the questionnaire but the anaesthetist did not. In this case the surgeon's return was included among the anaesthetists' for the analysis of the figures, but his opinions were included with those from the other surgeons. Thus we have data on the current use of hypothermia in 30 of the 35 centres of open heart surgery in this country. RESULTS
The reply from one centre indicated that they do not use hypothermia in any form. Moderate hypothermia alone using the method of surface cooling is still employed in two centres. In one they employ it for secundum atrial septal defects in both adults and children and also for pulmonary valvotomy and state that its use is unchanging as compared with 5 yr ago. In the second centre, moderate hypothermia is used only for secundum
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A questionnaire was sent to all centres of cardiac surgery in the United Kingdom, enquiring into their current use of hypothermia. Moderate hypothermia without cardiopulmonary bypass and the Drew technique of profound hypothermia are becoming less popular, each technique being used in only two of the 30 centres which replied. Moderate hypothermia as an integral part of the cardiopulmonary bypass is used on occasions in 24 centres. Although some centres use moderate hypothermia out of habit, the main benefits from its use are considered to be the protection afforded to the myocardium and a greater safety margin in the event of technical difficulties. Profound hypothermia, usually induced by means of the pump oxygenator, followed by circulatory arrest is becoming increasingly popular for the correction of complex congenital anomalies in infants.
1012
BRITISH JOURNAL OF ANAESTHESIA TABLE I. Questionnaire sent to all centres of open heart surgery in the United Kingdom. If you are not currently practising cardiac surgery, please tick If you never employ hypothermia, please tick
and return.
and return. Moderate Moderate hypothermia hypothermia with C-P Profound alone bypass hypothermia
Do you employ hypothermia for: Downloaded from http://bja.oxfordjournals.org/ at University of Regina on September 6, 2015
Valve replacements—single ? —multiple? Coronary Artery Surgery? Secundum Atrial Septal Defects, —children? —adults ? More complex congenital anomalies ? Others? (please specify) Is your use of hypothermia increasing/decreasing/ static as compared to 5 years ago? How do you treat arrhythmias ? How do you measure temperature ? What temperature do you aim for? What do you consider the safe period of circulatory arrest at that temperature ? State, in order of importance, the advantages of hypothermia. Similarly, state the disadvantages. Any other comments please?
atrial septal defects in children, and its use is decreasing. The advantages of this technique, claimed by those in centres in which it is still used, are circulatory arrest for short procedures with total safety, and its simplicity. The disadvantages stated are that it is time-consuming, it creates acid-base problems and recovery of consciousness is slowed. Moderate hypothermia in conjunction with cardiopulmonary bypass is used on occasions in 24 of the 30 centres which replied to the questionnaire. Table II
TABLE II. No. of centres employing moderate hypothermia as part of their technique of cardiopulmonary bypass. Multiple valve replacements Complex congenital anomalies Single valve replacements V.S.Ds (adult) V.S.Ds (child) Coronary artery surgery Secundum A.S.Ds (adult) Secundum A.S.Ds (child)
19 18 17 15 14 13 9 8
V.S.D.=venticular septal defect; A.S.D.=atrial septal defect.
HYPOTHERMIA IN BRITISH CARDIAC SURGERY is a breakdown of this usage for specific operations. As might be expected, it is employed more commonly in the more complicated and time-consuming procedures. The use of moderate hypothermia with cardiopulmonary bypass is said to be increasing in five centres, two of which have changed from profound to moderate hypothermia; it is decreasing in seven and remains static in 12. The advantages and disadvantages of this use of hypothermia as quoted by those centres which use the technique are given in table III.
TABLE I I I .
younger children or neonates. The advantages and disadvantages of profound hypothermia as stated by those centres which use it are given in table IV. The temperature preferred and the duration of arrest permitted at that temperature are shown graphically (fig. 1). Where a range of temperature or time or both were indicated, this is shown by a continuous line. The duration of circulatory arrest allowed in relation to temperature is reasonably uniform throughout Britain and at temperatures above 25°C conforms closely with the recommendations of Benazon (1970). At lower temperatures there is a much wider scatter of opinion and the clinical impression is that hypothermia affords even greater protection than has been assumed previously. Temperature monitoring is performed most commonly at two sites, the most popular being the oesophagus and the nasopharynx in 14 centres, the oesophagus and the rectum being used in two centres and the oesophagus and skin in one; in one centre the temperature is measured in the oesophagus, rectum and skin and two groups measure it in the oesophagus, nasopharynx, rectum and muscle. In seven hospitals the temperature is measured at one site only, four using the oesophagus and three the nasopharynx. Of these seven hospitals, five never use profound hypothermia. In three replies this question was not answered. "How do you treat arrhythmias?" was not an easy question to answer succinctly. The precipitating
Advantages and disadvantages quoted for moderate hypothermia with cardiopulmonary bypass {nos. refer to number of centres).
Advantages Myocardial protection without coronary perfusion Increased safety Reduced oxygen requirements; less blood damage Better operating conditions
Disadvantages Time consuming Deranged physiology (acid-base and electrolytes) Postoperative vasoconstriction Depressed clotting Unnecessary extra complication Arrhythmia Difficulty starting heart Overswing of temperature
1st choice 9 6 7 2
1st choice 6 3 1 1 1
2nd choice 3 7 1 1
2nd choice
3rd choice 4
3rd choice
4th choice
2 2 1 1 2 1
1 1
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Profound hypothermia is employed routinely for adult patients in three centres, two using the Drew technique, and the third using conventional cardiopulmonary bypass whilst another 19 centres state that they employ profound hypothermia on occasions for the more complex cases. Nine of these centres specify work on young children and 18 state that their technique involves the use of a pump-oxygenator. Six of these 18 centres use surface cooling before thoracotomy. In the 19th centre, deep hypothermia alone (without cardiopulmonary bypass) is used in infants weighing less than 5 kg. The use of profound hypothermia was stated to be decreasing in three centres, two of which have changed from the Drew technique to one of moderate hypothermia with cardiopumonary bypass, static in two centres, and increasing in eight centres, seven of which state that the increase is in relation to work on
1013
BRITISH JOURNAL OF ANAESTHESIA
1014 TABLE IV.
Advantages and disadvantages quoted for profound hypothermia (nos. refer to number of centres).
1st choice
Advantages
2nd choice
3rd choice
4th choice
2nd choice
3rd choice
4th choice
14 1 1
Improved surgical access: dry heart No postperfusion lung problems Cerebral protection Avoidance of long cardiopulmonary bypass in children No problem with coronary perfusion More than adequate perfusion Cannulae removable from operating field Low priming volume
1st choice
Disadvantages
4 3
2 —
3 1
1
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Time consuming Time limited Deranged physiology (acid-base; oxyhaemoglobin dissociation; clotting) Hepato-renal failure Requires four cannulations No indication of damage to Bundle of His Difficult to control Postoperative arrhythmia Slow recovery of consciousness Possible c.n.s. damage Higher mortality Less successful in elderly patients
1 1
1 1 1 1 1 1 1
1
90 85 Single values from one centre
80 O—o
Range of values from one centre
75
'//A Derived from re'ecommendations of Benazon (1970)
70 65 60 55 50 45 40 35 30 25 20 15 10 5
10
12
13
15
16
18
21
22
Te.p.
23
2S
27
fc)
FIG. 1. Duration of arrest at different temperatures.
28
30
31
3Z
33
3S
HYPOTHERMIA IN BRITISH CARDIAC SURGERY
1015
Four surgeons commented on the promising results from the use of profound hypothermia for the correction of complex congenital lesions in neonates and infants, but one of them thought it might eventually be superseded by conventional perfusion. Further correspondence with the surgeons and anaesthetists who employ profound hypothermia in conjunction with cardiopulmonary bypass for infants indicated that they were equally divided between those who employ bloodstream cooling and rewarming alone and those who favour surface cooling followed by blood-stream cooling and rewarming. The overriding determinants of success or failure are the pathology and state of health of the patient. Hypothermia to 15-20°C with circulatory arrest is "Any other comments, please?" evoked responses considered to be a safe procedure which carries little varying from "none" to a full accompanying letter morbidity per se and has made it possible to offer giving details of technique and opinions on the value surgery to many infants who would previously have of hypothermia. It should be noted that the surgeons been considered inoperable. Several hundred infants who were questioned were those known to have had have now undergone such surgery in Britain. an interest in hypothermia at one time and therefore their views are not necessarily representative. DISCUSSION
Moderate hypothermia alone. No opinions were expressed by anaesthetists. Two surgeons commented on the techniques, one claiming that it is not associated with morbidity or mortality, and the other stating that it should never be used in cardiac surgery. Moderate hypothermia with cardiopulmonary bypass. One anaesthetist stated that it is a satisfactory technique, whilst four expressed the opinion that hypothermia offered no advantages in uncomplicated cases. Instances in which hypothermia would be worthwhile were, when difficulty was experienced in cannulating the coronary ostia and when it was necessary to interrupt the extracorporeal circulation. Two surgeons said that hypothermia was not important, and three felt that it gave protection to the myocardium and allowed them to proceed without coronary perfusion. Profound hypothermia. The anaesthetists in centres where the Drew technique is used stated that the results are particularly good in treating congenital disease in children. Another anaesthetist stated that, in his opinion, the only virtue in hypothermia was in the treatment of complicated congenital heart disease. Another centre stated that they are considering the re-introduction of selective cardiac cooling—a technique which is already in use in one centre in combination with moderate whole-body hypothermia on cardiopulmonary bypass.
The popularity of any technique may fluctuate considerably (fig. 2) before it becomes established practice. Twenty years after its introduction, we are still seeing considerable interest in hypothermia.
FIG. 2. Popularity of any new technique (modified from Williams, 1954): P wave—initial research, Q—first publications, R—adverse reports and T—final place in practice.
Until recently, hypothermia for cardiac surgery has been used in three ways: (1) Cooling by surface or blood-stream methods to a temperature not less than 28°C before the operation, thus allowing a period of 10-12 min of circulatory arrest for the performance of the cardiac operation (Swan et al., 1955; Sellick, 1957; Forrester, 1962). (2) Blood-stream cooling and rewarming as an integral part of the cardiopulmonary bypass technique (Sealy et al., 1957; Galleti and Brecher, 1962). (3) Blood-stream cooling in conjunction with cardiac, but not pulmonary, bypass to a temperature less than
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factors of mechanical stimulation and variations in coronary perfusion and temperature are difficult to separate. In contrast with neurosurgery, arrhythmias in cardiac surgery are seen as an expected hazard to be dealt with appropriately when encountered. The frequency with which specific drugs and methods are quoted is: lignocaine, 13 centres; electric defibrillation, 12; control of serum potassium, 11; beta blocking drugs, nine; isoprenaline, five; maintenance of acid-base and carbon dioxide concentrations, four; epanutin, four; electrical pacing, two; calcium, two; glycosides, one; bretylium, one. One centre emphasized discontinuing the use of digoxin before operation.
1016 20°C, followed by circulatory arrest (Drew, Keen and Benazon, 1959; Feldman, 1971).
1971, 55 infants less than 1 yr of age had operations for correction of total anomalous pulmonary venous drainage. There were 36 deaths, a mortality of 65%. Since then another 22 similar operations have been performed with eight deaths giving a mortality of 36% (Waterston, personal communication). Whilst this dramatic improvement may be attributable to several factors, there is no doubt that the reintroduction of profound hypothermia with circulatory occlusion has contributed to this advance in no small measure. A warning note has been sounded by Fisk and colleagues (1974), who demonstrated histological evidence of cerebral damage in new born piglets subjected to 1 hr of circulatory occlusion at 20°C. Clinically recognizable cerebral damage in human patients following hypothermic circulatory arrest is not a problem to those workers who responded to this questionnaire. In assessing this risk, one must consider the prognosis of alternative treatment. Not only has hypothermia given many infants the chance of an operation with an acceptable risk, but it has been the major influence in the trend towards total correction in preference to palliation (Subramanian, 1974). CONCLUSION
Moderate hypothermia without cardiopulmonary bypass is now seldom used for open heart surgery. As an integral part of the bypass technique it is still popular. Profound hypothermia with circulatory arrest, usually achieved by means of cardiopulmonary bypass, has made possible considerable advances in the surgery of severe congenital malformations in infants. ACKNOWLEDGEMENTS
The Honorary Secretary of the Society of Thoracic and Cardiovascular Surgeons of Great Britain and Ireland, Mr R. J. M. McCormack, supplied me with the list of centres where open heart surgery is performed regularly in the United Kingdom, and suggested the names of the surgeons known to have been interested in the clinical use of hypothermia. For his interest and help I am most grateful. I thank the 49 anaesthetists and 10 surgeons who responded to my enquiry with time and thought. Miss S. Sandeman, Secretary of the Division of Anaesthesia, Glasgow Royal Infirmary, went the second mile in preparing and distributing the questionnaire. REFERENCES
Barratt-Boyes, B. G., Simpson, M.j and Neutze, J. M. (1971). Intracardiac surgery in neonates and infants using deep hypothermia with surface cooling and limited cardiopulmonary bypass. Circulation, 43, (Suppl. 1), 25. Benazon, D. (1970). In Scientific Foundations of Anaesthesia (eds. Scurr, C. F. and Feldman, S. A.), p. 272. London: Heinemann. Bigelow, W. G., Callaghan, J. C , and Hopps, J. A. (1950). Hypothermia: its possible role in cardiac surgery. Ann. Surg, 132, 849.
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It is not the purpose of this paper to compare the various techniques, nor would it be possible to do so. However, we do have a fairly clear picture of the extent to which they are being used throughout the country at present. Moderate hypothermia alone in cardiac surgery has virtually passed into history. It is still used enthusiastically in only one centre and on occasions in only one other centre. The reason for its unpopularity is presumably the increasing efficiency of oxygenators and expertise in their use. The Drew technique is also less popular than it was a few years ago. It is the routine method for all open heart surgery in two hospitals. No hospital uses it for the occasional case for whom profound hypothermia is indicated. This is understandable, as it is a relatively complicated technique, especially when it is not used regularly (Clement, 1971). Hypothermia to varying levels, in conjunction with cardiopulmonary bypass, is still very fashionable, being used for the longer operations in approximately two-thirds of the hospitals. Some anaesthetists admit that their routine use of moderate hypothermia is mainly from habit, but concern for the myocardium with the difficulties of providing adequate coronary perfusion and the increased safety margin for the brain and other tissues in the event of breakdown or unforeseen complications are the main factors influencing its employment. The main disadvantage quoted was that the technique was time-consuming. The majority of persons using profound hypothermia quoted the most important advantage as being improved surgical access with a dry heart. The value of this is enhanced when the patient is small and the surgery is complex. Just as corrective surgery becomes more difficult in tiny hearts, so do the technical problems of cannulation and perfusion increase. For this reason we have recently seen the development of several methods employing profound hypothermia in infants (Mohri et al., 1969; Barratt-Boyes, Simpson and Neutze, 1971; Subramanian et al., 1971; Mori, et al., 1972). These methods involve the use of surface cooling, with or without the assistance of cardiopulmonary bypass for later cooling and rewarming. Any comparison of survival rates in different centres would be meaningless in view of the variability of case selection and other factors, but the experience at The Hospital for Sick Children, Great Ormond Street, illustrates the encouraging results being experienced in several centres. Breckenridge and colleagues (1973) reported that, between 1963 and
BRITISH JOURNAL OF ANAESTHESIA
HYPOTHERMIA IN BRITISH CARDIAC SURGERY
PRATIQUE ACTUELLE DE L'HYPOTHERMIE EN CHIRURGIE CARDIAQUE EN GRANDE-BRETAGNE RESUME
On a envoye un questionnaire a tous les centres de chirurgie cardiaque du Royaume-Uni pour obtenir des informations sur l'usage qu'ils font de l'hypothermie. L'hypothermie
moderee sans derivation cardio-pulmonaire et la technique de Drew sur l'hypothermie profonde deviennent de moins en moins populaires, chacune de ces techniques n'etant utilisee que dans seulement deux des 30 centres qui ont repondu. L'hypothermie moderee en tant que partie integrate de la derivation cardio-pulmonaire est occasionnellement utilisee dans 24 centres. Bien que certains centres utilisent l'hypothermie moderee plutot par habitude, on considere que son usage presente comme principaux avantages: la protection accordee au myocarde et la plus grande marge de securite en cas de difficultes techniques. L'hypothermie profonde, que l'on provoque habituellement au moyen d'un oxygenateur a pompe, suivi d'un arret de la circulation, est de plus en plus utilisee pour corriger certaines anomalies congenitales complexes chez les bebes.
DIE GEGENWARTIGE ANWENDUNG VON HYPOTHERMIE IN DER BRITISCHEN HERZCHIRURGIE ZUSAMMENFASSUNG
An alle britischen Herzchirurgie-Zentren in GroBbritannien wurde ein Fragebogen entsandt, der AufschluB iiber deren gegenwartige Anwendung von Hypothermie verlangte. MaBige Hypothermie ohne Herz-Lungenumleirung sowie die Drew-Methode der Profunden Hypothermie sind weniger popular geworden, und jede dieser Methoden wurde nur in 2 von den 30 Zentren angewendet, die den Fragebogen ausfullten. MaBige Hypothermie als integraler Teil der Herz-Lungenumleitung wird gelegentlich in 24 dieser Zentren verwendet. Obwohl manche Zentren die mafiige Hypothermie aus Gewohnheit yerwenden, sieht man die Hauptvorteile dieser Methode in ihrem Schutz fur das Myokardium und in ihrer grofieren Sicherheitsspanne im Falle technischer Schwierigkeiten. Profunde Hypothermie, meist durch eine Sauerstoffpumpe eingeleitet und gefolgt von Kreislaufsperre, wird fur die Korrektur komplexer Erbanomalien bei Kindern immer beliebter.
PROCEDIMIENTO PRACTICO ACTUAL DE HIPOTERMIA EN LA CIRURGIA CARDIACA BRITANICA SUMARIO
Se envio a todos los centros de cirugia cardiaca del Reino Unido un cuestionario relativo a su actual utilizacion de la hipotermia. La hipotermia moderada sin derivation cardiopulmonar y la tecnica de Drew de hipotermia profunda se estan haciendo cada vez menos populares, utilizandose solamente cada tecnica en dos de los 30 centros que respondieron al cuestionario. La hipotermia moderada como parte integral de la derivaci6n cardiopulmonar se utilizaba en algunas ocasiones en 24 centros. Aunque algunos centros utilizan hipotermia moderada por cosrumbre, las principales ventajas de su utilizacion se considera que son la protection que ofrece al miocardio y mayor margen de seguridad en el caso de dificultades tecnicas. La hipotermia profunda, por regla general inducida mediante un oxigenador de bomba, seguida de interrupcion circulatoria, se esti haciendo cada vez mas popular para la correccion de anomalias cong^nitas complejas en los beb^s.
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Bigelow, W. G., Mustard, W. T., and Evans, J. G. (1954). Some physiologic concepts of hypothermia and their applications to cardiac surgery. J. Thorac. Cardiovasc. Surg. 28, 463. Breckenridge, I. M., Oelert, H., Graham, G. R., Stark, J., Waterston, D. J., and Bonham-Carter, R. E. (1973). Open heart surgery in the first year of life. J. Thorac. Cardiovasc. Surg., 65, 58. Clement, A. J. (1971). The physiological background of and apparatus used for extracorporeal circulation. Br. J. Anaesth., 43, 233. Drew, C. E., Keen, G., and Benazon, D. B. (1959). Profound hypothermia. Lancet, 1, 745. Feldman, S. A. (1971). Profound hypothermia. Br. J. Anaesth., 43, 244. Fisk, G. C , Wright, J. S., Turner, B. B., Baker, W. de C , Hicks, R. G., Lethlean, A. K., Stacey, R. B., Lawrence, J. C , Lawrie, G. M., Kalnins, I., and Rose, M. (1974). Cerebral effects of circulatory arrest at 20°C in the infant pig. Anaesth. Intens. Care, 2, 33. Forrester, A. C. (1962). Personal communication quoted by Hunter, A. R., in Neurosurgical Anaesthesia, p. 160 (1964). Oxford: Blackwell. Galleti, P. M., and Brecher, G. A. (1962). Heart-lung bypass, p. 287. New York and London: Grune and Stratton. McDowall, D. G. (1971). Current usage of hypothermia in British neurosurgery. Br. J. Anaesth., 43, 1084. Mohri, H., Dillard, D. H., Crawford, E. W., Martin, W. E., and Merendino, K. A. (1969). Method of surface-induced deep hypothermia for open heart surgery in infants. J. Thorac. Cardiovasc. Surg., 58, 262. Mori, A., Muraoka, R., Yokota, Y., Okamoto, Y., Ando, F., Fukumasu, H., Oku, H., Ikeda, M., Shirotani, H., and Hikasa, Y. (1972). Deep hypothermia combined with cardiopulmonary bypass for cardiac surgery in neonates and infants. J. Thorac. Cardiovasc. Surg., 64, 422. Sealy, W. C , Brown, I. W., Young, G. W., Stephen, R. C , Harris, J. S., and Merrit, D. (1957). Hypothermia, low flow extracorporeal circulation and controlled cardiac arrest for open heart surgery. Surg. Gynecol. Obstet., 104, 441. Sellick, B. A. (1957). A method of hypothermia for open heart surgery. Lancet, 1, 443. Subramanian, S. (1974). Early correction of congenital cardiac defects using profound hypothermia and circulatory arrest. Ann. R. Coll. Surg. Engl., 54, 176. Wagner, H., Vlad, P., and Lambert, E. (1971). Surface-induced deep hypothermia in cardiac surgery. J. Pediatr. Surg., 6, 612. Swan, H., Virtue, R. W., Blount, S. G., jr, and Kircher, L. T., jr (1955). Hypothermia in surgery. Ann. Surg., 142, 382. Williams, R. H. (1954). Clinical investigator and his role in teaching, administration and the care of the patient. J.A.M.A., 156, 131.
1017
CURRENT PRACTICE OF HYPOTHERMIA IN BRITISH CARDIAC SURGERY D. J. F. MACDONALD SUMMARY
Following the work of Bigelow and others in the early 1950s (Bigelow, Callaghan and Hopps, 1950; Bigelow, Mustard and Evans, 1954; Swan et al., 1955), clinically induced hypothermia made possible dramatic advances in cardiac surgery and neurosurgery. More recently, as a result of the continued development of other surgical and parasurgical techniques, for example the improvement in pumpoxygenators, the indications for the use of hypothermia in cardiac surgery have become less clear and the advantages of its use, without some form of extracorporeal circulation, are open to question. In 1971, McDowall investigated the use of hypothermia in British neurosurgery and reported that the practice was decreasing, 12 of the 31 centres having abandoned the technique completely, while another 13 centres used it rarely. No such information is available about the current practice of hypothermia in British cardiac surgery and it was felt that a survey similar to that of McDowall, but related to cardiac surgery, would be of value. Consequently, a questionnaire was sent to the 35 hospitals in the United Kingdom where open heart surgery is practised. The questionnaire is reproduced in table I. In order to simplify an already complicated proforma it was decided not to ask for percentage use but simply to ask the question, "Do you employ hypothermia for . . . ? " The questionnaire was addressed to D. J. F. MACDONALD, M.B., D.A., F.F.A.R.C.S., Division of
Anaesthesia, Royal Infirmary, Glasgow.
"senior anaesthetists in cardiac sugery" at the various hospitals. Four weeks later a duplicate questionnaire was sent to the heads of the anaesthetic departments at those hospitals from which a reply had not been received, with a request that they pass it on to the anaesthetists concerned. Questionnaires were also sent to 13 surgeons known to have, or to have had, an interest in the clinical use of hypothermia, for their comments. Replies were received from 29 of the anaesthetists circulated and from 10 of the surgeons. In one hospital the surgeon completed the questionnaire but the anaesthetist did not. In this case the surgeon's return was included among the anaesthetists' for the analysis of the figures, but his opinions were included with those from the other surgeons. Thus we have data on the current use of hypothermia in 30 of the 35 centres of open heart surgery in this country. RESULTS
The reply from one centre indicated that they do not use hypothermia in any form. Moderate hypothermia alone using the method of surface cooling is still employed in two centres. In one they employ it for secundum atrial septal defects in both adults and children and also for pulmonary valvotomy and state that its use is unchanging as compared with 5 yr ago. In the second centre, moderate hypothermia is used only for secundum
Downloaded from http://bja.oxfordjournals.org/ at University of Regina on September 6, 2015
A questionnaire was sent to all centres of cardiac surgery in the United Kingdom, enquiring into their current use of hypothermia. Moderate hypothermia without cardiopulmonary bypass and the Drew technique of profound hypothermia are becoming less popular, each technique being used in only two of the 30 centres which replied. Moderate hypothermia as an integral part of the cardiopulmonary bypass is used on occasions in 24 centres. Although some centres use moderate hypothermia out of habit, the main benefits from its use are considered to be the protection afforded to the myocardium and a greater safety margin in the event of technical difficulties. Profound hypothermia, usually induced by means of the pump oxygenator, followed by circulatory arrest is becoming increasingly popular for the correction of complex congenital anomalies in infants.
1012
BRITISH JOURNAL OF ANAESTHESIA TABLE I. Questionnaire sent to all centres of open heart surgery in the United Kingdom. If you are not currently practising cardiac surgery, please tick If you never employ hypothermia, please tick
and return.
and return. Moderate Moderate hypothermia hypothermia with C-P Profound alone bypass hypothermia
Do you employ hypothermia for: Downloaded from http://bja.oxfordjournals.org/ at University of Regina on September 6, 2015
Valve replacements—single ? —multiple? Coronary Artery Surgery? Secundum Atrial Septal Defects, —children? —adults ? More complex congenital anomalies ? Others? (please specify) Is your use of hypothermia increasing/decreasing/ static as compared to 5 years ago? How do you treat arrhythmias ? How do you measure temperature ? What temperature do you aim for? What do you consider the safe period of circulatory arrest at that temperature ? State, in order of importance, the advantages of hypothermia. Similarly, state the disadvantages. Any other comments please?
atrial septal defects in children, and its use is decreasing. The advantages of this technique, claimed by those in centres in which it is still used, are circulatory arrest for short procedures with total safety, and its simplicity. The disadvantages stated are that it is time-consuming, it creates acid-base problems and recovery of consciousness is slowed. Moderate hypothermia in conjunction with cardiopulmonary bypass is used on occasions in 24 of the 30 centres which replied to the questionnaire. Table II
TABLE II. No. of centres employing moderate hypothermia as part of their technique of cardiopulmonary bypass. Multiple valve replacements Complex congenital anomalies Single valve replacements V.S.Ds (adult) V.S.Ds (child) Coronary artery surgery Secundum A.S.Ds (adult) Secundum A.S.Ds (child)
19 18 17 15 14 13 9 8
V.S.D.=venticular septal defect; A.S.D.=atrial septal defect.
HYPOTHERMIA IN BRITISH CARDIAC SURGERY is a breakdown of this usage for specific operations. As might be expected, it is employed more commonly in the more complicated and time-consuming procedures. The use of moderate hypothermia with cardiopulmonary bypass is said to be increasing in five centres, two of which have changed from profound to moderate hypothermia; it is decreasing in seven and remains static in 12. The advantages and disadvantages of this use of hypothermia as quoted by those centres which use the technique are given in table III.
TABLE I I I .
younger children or neonates. The advantages and disadvantages of profound hypothermia as stated by those centres which use it are given in table IV. The temperature preferred and the duration of arrest permitted at that temperature are shown graphically (fig. 1). Where a range of temperature or time or both were indicated, this is shown by a continuous line. The duration of circulatory arrest allowed in relation to temperature is reasonably uniform throughout Britain and at temperatures above 25°C conforms closely with the recommendations of Benazon (1970). At lower temperatures there is a much wider scatter of opinion and the clinical impression is that hypothermia affords even greater protection than has been assumed previously. Temperature monitoring is performed most commonly at two sites, the most popular being the oesophagus and the nasopharynx in 14 centres, the oesophagus and the rectum being used in two centres and the oesophagus and skin in one; in one centre the temperature is measured in the oesophagus, rectum and skin and two groups measure it in the oesophagus, nasopharynx, rectum and muscle. In seven hospitals the temperature is measured at one site only, four using the oesophagus and three the nasopharynx. Of these seven hospitals, five never use profound hypothermia. In three replies this question was not answered. "How do you treat arrhythmias?" was not an easy question to answer succinctly. The precipitating
Advantages and disadvantages quoted for moderate hypothermia with cardiopulmonary bypass {nos. refer to number of centres).
Advantages Myocardial protection without coronary perfusion Increased safety Reduced oxygen requirements; less blood damage Better operating conditions
Disadvantages Time consuming Deranged physiology (acid-base and electrolytes) Postoperative vasoconstriction Depressed clotting Unnecessary extra complication Arrhythmia Difficulty starting heart Overswing of temperature
1st choice 9 6 7 2
1st choice 6 3 1 1 1
2nd choice 3 7 1 1
2nd choice
3rd choice 4
3rd choice
4th choice
2 2 1 1 2 1
1 1
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Profound hypothermia is employed routinely for adult patients in three centres, two using the Drew technique, and the third using conventional cardiopulmonary bypass whilst another 19 centres state that they employ profound hypothermia on occasions for the more complex cases. Nine of these centres specify work on young children and 18 state that their technique involves the use of a pump-oxygenator. Six of these 18 centres use surface cooling before thoracotomy. In the 19th centre, deep hypothermia alone (without cardiopulmonary bypass) is used in infants weighing less than 5 kg. The use of profound hypothermia was stated to be decreasing in three centres, two of which have changed from the Drew technique to one of moderate hypothermia with cardiopumonary bypass, static in two centres, and increasing in eight centres, seven of which state that the increase is in relation to work on
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BRITISH JOURNAL OF ANAESTHESIA
1014 TABLE IV.
Advantages and disadvantages quoted for profound hypothermia (nos. refer to number of centres).
1st choice
Advantages
2nd choice
3rd choice
4th choice
2nd choice
3rd choice
4th choice
14 1 1
Improved surgical access: dry heart No postperfusion lung problems Cerebral protection Avoidance of long cardiopulmonary bypass in children No problem with coronary perfusion More than adequate perfusion Cannulae removable from operating field Low priming volume
1st choice
Disadvantages
4 3
2 —
3 1
1
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Time consuming Time limited Deranged physiology (acid-base; oxyhaemoglobin dissociation; clotting) Hepato-renal failure Requires four cannulations No indication of damage to Bundle of His Difficult to control Postoperative arrhythmia Slow recovery of consciousness Possible c.n.s. damage Higher mortality Less successful in elderly patients
1 1
1 1 1 1 1 1 1
1
90 85 Single values from one centre
80 O—o
Range of values from one centre
75
'//A Derived from re'ecommendations of Benazon (1970)
70 65 60 55 50 45 40 35 30 25 20 15 10 5
10
12
13
15
16
18
21
22
Te.p.
23
2S
27
fc)
FIG. 1. Duration of arrest at different temperatures.
28
30
31
3Z
33
3S
HYPOTHERMIA IN BRITISH CARDIAC SURGERY
1015
Four surgeons commented on the promising results from the use of profound hypothermia for the correction of complex congenital lesions in neonates and infants, but one of them thought it might eventually be superseded by conventional perfusion. Further correspondence with the surgeons and anaesthetists who employ profound hypothermia in conjunction with cardiopulmonary bypass for infants indicated that they were equally divided between those who employ bloodstream cooling and rewarming alone and those who favour surface cooling followed by blood-stream cooling and rewarming. The overriding determinants of success or failure are the pathology and state of health of the patient. Hypothermia to 15-20°C with circulatory arrest is "Any other comments, please?" evoked responses considered to be a safe procedure which carries little varying from "none" to a full accompanying letter morbidity per se and has made it possible to offer giving details of technique and opinions on the value surgery to many infants who would previously have of hypothermia. It should be noted that the surgeons been considered inoperable. Several hundred infants who were questioned were those known to have had have now undergone such surgery in Britain. an interest in hypothermia at one time and therefore their views are not necessarily representative. DISCUSSION
Moderate hypothermia alone. No opinions were expressed by anaesthetists. Two surgeons commented on the techniques, one claiming that it is not associated with morbidity or mortality, and the other stating that it should never be used in cardiac surgery. Moderate hypothermia with cardiopulmonary bypass. One anaesthetist stated that it is a satisfactory technique, whilst four expressed the opinion that hypothermia offered no advantages in uncomplicated cases. Instances in which hypothermia would be worthwhile were, when difficulty was experienced in cannulating the coronary ostia and when it was necessary to interrupt the extracorporeal circulation. Two surgeons said that hypothermia was not important, and three felt that it gave protection to the myocardium and allowed them to proceed without coronary perfusion. Profound hypothermia. The anaesthetists in centres where the Drew technique is used stated that the results are particularly good in treating congenital disease in children. Another anaesthetist stated that, in his opinion, the only virtue in hypothermia was in the treatment of complicated congenital heart disease. Another centre stated that they are considering the re-introduction of selective cardiac cooling—a technique which is already in use in one centre in combination with moderate whole-body hypothermia on cardiopulmonary bypass.
The popularity of any technique may fluctuate considerably (fig. 2) before it becomes established practice. Twenty years after its introduction, we are still seeing considerable interest in hypothermia.
FIG. 2. Popularity of any new technique (modified from Williams, 1954): P wave—initial research, Q—first publications, R—adverse reports and T—final place in practice.
Until recently, hypothermia for cardiac surgery has been used in three ways: (1) Cooling by surface or blood-stream methods to a temperature not less than 28°C before the operation, thus allowing a period of 10-12 min of circulatory arrest for the performance of the cardiac operation (Swan et al., 1955; Sellick, 1957; Forrester, 1962). (2) Blood-stream cooling and rewarming as an integral part of the cardiopulmonary bypass technique (Sealy et al., 1957; Galleti and Brecher, 1962). (3) Blood-stream cooling in conjunction with cardiac, but not pulmonary, bypass to a temperature less than
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factors of mechanical stimulation and variations in coronary perfusion and temperature are difficult to separate. In contrast with neurosurgery, arrhythmias in cardiac surgery are seen as an expected hazard to be dealt with appropriately when encountered. The frequency with which specific drugs and methods are quoted is: lignocaine, 13 centres; electric defibrillation, 12; control of serum potassium, 11; beta blocking drugs, nine; isoprenaline, five; maintenance of acid-base and carbon dioxide concentrations, four; epanutin, four; electrical pacing, two; calcium, two; glycosides, one; bretylium, one. One centre emphasized discontinuing the use of digoxin before operation.
1016 20°C, followed by circulatory arrest (Drew, Keen and Benazon, 1959; Feldman, 1971).
1971, 55 infants less than 1 yr of age had operations for correction of total anomalous pulmonary venous drainage. There were 36 deaths, a mortality of 65%. Since then another 22 similar operations have been performed with eight deaths giving a mortality of 36% (Waterston, personal communication). Whilst this dramatic improvement may be attributable to several factors, there is no doubt that the reintroduction of profound hypothermia with circulatory occlusion has contributed to this advance in no small measure. A warning note has been sounded by Fisk and colleagues (1974), who demonstrated histological evidence of cerebral damage in new born piglets subjected to 1 hr of circulatory occlusion at 20°C. Clinically recognizable cerebral damage in human patients following hypothermic circulatory arrest is not a problem to those workers who responded to this questionnaire. In assessing this risk, one must consider the prognosis of alternative treatment. Not only has hypothermia given many infants the chance of an operation with an acceptable risk, but it has been the major influence in the trend towards total correction in preference to palliation (Subramanian, 1974). CONCLUSION
Moderate hypothermia without cardiopulmonary bypass is now seldom used for open heart surgery. As an integral part of the bypass technique it is still popular. Profound hypothermia with circulatory arrest, usually achieved by means of cardiopulmonary bypass, has made possible considerable advances in the surgery of severe congenital malformations in infants. ACKNOWLEDGEMENTS
The Honorary Secretary of the Society of Thoracic and Cardiovascular Surgeons of Great Britain and Ireland, Mr R. J. M. McCormack, supplied me with the list of centres where open heart surgery is performed regularly in the United Kingdom, and suggested the names of the surgeons known to have been interested in the clinical use of hypothermia. For his interest and help I am most grateful. I thank the 49 anaesthetists and 10 surgeons who responded to my enquiry with time and thought. Miss S. Sandeman, Secretary of the Division of Anaesthesia, Glasgow Royal Infirmary, went the second mile in preparing and distributing the questionnaire. REFERENCES
Barratt-Boyes, B. G., Simpson, M.j and Neutze, J. M. (1971). Intracardiac surgery in neonates and infants using deep hypothermia with surface cooling and limited cardiopulmonary bypass. Circulation, 43, (Suppl. 1), 25. Benazon, D. (1970). In Scientific Foundations of Anaesthesia (eds. Scurr, C. F. and Feldman, S. A.), p. 272. London: Heinemann. Bigelow, W. G., Callaghan, J. C , and Hopps, J. A. (1950). Hypothermia: its possible role in cardiac surgery. Ann. Surg, 132, 849.
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It is not the purpose of this paper to compare the various techniques, nor would it be possible to do so. However, we do have a fairly clear picture of the extent to which they are being used throughout the country at present. Moderate hypothermia alone in cardiac surgery has virtually passed into history. It is still used enthusiastically in only one centre and on occasions in only one other centre. The reason for its unpopularity is presumably the increasing efficiency of oxygenators and expertise in their use. The Drew technique is also less popular than it was a few years ago. It is the routine method for all open heart surgery in two hospitals. No hospital uses it for the occasional case for whom profound hypothermia is indicated. This is understandable, as it is a relatively complicated technique, especially when it is not used regularly (Clement, 1971). Hypothermia to varying levels, in conjunction with cardiopulmonary bypass, is still very fashionable, being used for the longer operations in approximately two-thirds of the hospitals. Some anaesthetists admit that their routine use of moderate hypothermia is mainly from habit, but concern for the myocardium with the difficulties of providing adequate coronary perfusion and the increased safety margin for the brain and other tissues in the event of breakdown or unforeseen complications are the main factors influencing its employment. The main disadvantage quoted was that the technique was time-consuming. The majority of persons using profound hypothermia quoted the most important advantage as being improved surgical access with a dry heart. The value of this is enhanced when the patient is small and the surgery is complex. Just as corrective surgery becomes more difficult in tiny hearts, so do the technical problems of cannulation and perfusion increase. For this reason we have recently seen the development of several methods employing profound hypothermia in infants (Mohri et al., 1969; Barratt-Boyes, Simpson and Neutze, 1971; Subramanian et al., 1971; Mori, et al., 1972). These methods involve the use of surface cooling, with or without the assistance of cardiopulmonary bypass for later cooling and rewarming. Any comparison of survival rates in different centres would be meaningless in view of the variability of case selection and other factors, but the experience at The Hospital for Sick Children, Great Ormond Street, illustrates the encouraging results being experienced in several centres. Breckenridge and colleagues (1973) reported that, between 1963 and
BRITISH JOURNAL OF ANAESTHESIA
HYPOTHERMIA IN BRITISH CARDIAC SURGERY
PRATIQUE ACTUELLE DE L'HYPOTHERMIE EN CHIRURGIE CARDIAQUE EN GRANDE-BRETAGNE RESUME
On a envoye un questionnaire a tous les centres de chirurgie cardiaque du Royaume-Uni pour obtenir des informations sur l'usage qu'ils font de l'hypothermie. L'hypothermie
moderee sans derivation cardio-pulmonaire et la technique de Drew sur l'hypothermie profonde deviennent de moins en moins populaires, chacune de ces techniques n'etant utilisee que dans seulement deux des 30 centres qui ont repondu. L'hypothermie moderee en tant que partie integrate de la derivation cardio-pulmonaire est occasionnellement utilisee dans 24 centres. Bien que certains centres utilisent l'hypothermie moderee plutot par habitude, on considere que son usage presente comme principaux avantages: la protection accordee au myocarde et la plus grande marge de securite en cas de difficultes techniques. L'hypothermie profonde, que l'on provoque habituellement au moyen d'un oxygenateur a pompe, suivi d'un arret de la circulation, est de plus en plus utilisee pour corriger certaines anomalies congenitales complexes chez les bebes.
DIE GEGENWARTIGE ANWENDUNG VON HYPOTHERMIE IN DER BRITISCHEN HERZCHIRURGIE ZUSAMMENFASSUNG
An alle britischen Herzchirurgie-Zentren in GroBbritannien wurde ein Fragebogen entsandt, der AufschluB iiber deren gegenwartige Anwendung von Hypothermie verlangte. MaBige Hypothermie ohne Herz-Lungenumleirung sowie die Drew-Methode der Profunden Hypothermie sind weniger popular geworden, und jede dieser Methoden wurde nur in 2 von den 30 Zentren angewendet, die den Fragebogen ausfullten. MaBige Hypothermie als integraler Teil der Herz-Lungenumleitung wird gelegentlich in 24 dieser Zentren verwendet. Obwohl manche Zentren die mafiige Hypothermie aus Gewohnheit yerwenden, sieht man die Hauptvorteile dieser Methode in ihrem Schutz fur das Myokardium und in ihrer grofieren Sicherheitsspanne im Falle technischer Schwierigkeiten. Profunde Hypothermie, meist durch eine Sauerstoffpumpe eingeleitet und gefolgt von Kreislaufsperre, wird fur die Korrektur komplexer Erbanomalien bei Kindern immer beliebter.
PROCEDIMIENTO PRACTICO ACTUAL DE HIPOTERMIA EN LA CIRURGIA CARDIACA BRITANICA SUMARIO
Se envio a todos los centros de cirugia cardiaca del Reino Unido un cuestionario relativo a su actual utilizacion de la hipotermia. La hipotermia moderada sin derivation cardiopulmonar y la tecnica de Drew de hipotermia profunda se estan haciendo cada vez menos populares, utilizandose solamente cada tecnica en dos de los 30 centros que respondieron al cuestionario. La hipotermia moderada como parte integral de la derivaci6n cardiopulmonar se utilizaba en algunas ocasiones en 24 centros. Aunque algunos centros utilizan hipotermia moderada por cosrumbre, las principales ventajas de su utilizacion se considera que son la protection que ofrece al miocardio y mayor margen de seguridad en el caso de dificultades tecnicas. La hipotermia profunda, por regla general inducida mediante un oxigenador de bomba, seguida de interrupcion circulatoria, se esti haciendo cada vez mas popular para la correccion de anomalias cong^nitas complejas en los beb^s.
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Bigelow, W. G., Mustard, W. T., and Evans, J. G. (1954). Some physiologic concepts of hypothermia and their applications to cardiac surgery. J. Thorac. Cardiovasc. Surg. 28, 463. Breckenridge, I. M., Oelert, H., Graham, G. R., Stark, J., Waterston, D. J., and Bonham-Carter, R. E. (1973). Open heart surgery in the first year of life. J. Thorac. Cardiovasc. Surg., 65, 58. Clement, A. J. (1971). The physiological background of and apparatus used for extracorporeal circulation. Br. J. Anaesth., 43, 233. Drew, C. E., Keen, G., and Benazon, D. B. (1959). Profound hypothermia. Lancet, 1, 745. Feldman, S. A. (1971). Profound hypothermia. Br. J. Anaesth., 43, 244. Fisk, G. C , Wright, J. S., Turner, B. B., Baker, W. de C , Hicks, R. G., Lethlean, A. K., Stacey, R. B., Lawrence, J. C , Lawrie, G. M., Kalnins, I., and Rose, M. (1974). Cerebral effects of circulatory arrest at 20°C in the infant pig. Anaesth. Intens. Care, 2, 33. Forrester, A. C. (1962). Personal communication quoted by Hunter, A. R., in Neurosurgical Anaesthesia, p. 160 (1964). Oxford: Blackwell. Galleti, P. M., and Brecher, G. A. (1962). Heart-lung bypass, p. 287. New York and London: Grune and Stratton. McDowall, D. G. (1971). Current usage of hypothermia in British neurosurgery. Br. J. Anaesth., 43, 1084. Mohri, H., Dillard, D. H., Crawford, E. W., Martin, W. E., and Merendino, K. A. (1969). Method of surface-induced deep hypothermia for open heart surgery in infants. J. Thorac. Cardiovasc. Surg., 58, 262. Mori, A., Muraoka, R., Yokota, Y., Okamoto, Y., Ando, F., Fukumasu, H., Oku, H., Ikeda, M., Shirotani, H., and Hikasa, Y. (1972). Deep hypothermia combined with cardiopulmonary bypass for cardiac surgery in neonates and infants. J. Thorac. Cardiovasc. Surg., 64, 422. Sealy, W. C , Brown, I. W., Young, G. W., Stephen, R. C , Harris, J. S., and Merrit, D. (1957). Hypothermia, low flow extracorporeal circulation and controlled cardiac arrest for open heart surgery. Surg. Gynecol. Obstet., 104, 441. Sellick, B. A. (1957). A method of hypothermia for open heart surgery. Lancet, 1, 443. Subramanian, S. (1974). Early correction of congenital cardiac defects using profound hypothermia and circulatory arrest. Ann. R. Coll. Surg. Engl., 54, 176. Wagner, H., Vlad, P., and Lambert, E. (1971). Surface-induced deep hypothermia in cardiac surgery. J. Pediatr. Surg., 6, 612. Swan, H., Virtue, R. W., Blount, S. G., jr, and Kircher, L. T., jr (1955). Hypothermia in surgery. Ann. Surg., 142, 382. Williams, R. H. (1954). Clinical investigator and his role in teaching, administration and the care of the patient. J.A.M.A., 156, 131.
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