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PROFOUND HYPOTHERMIA IN CARDIAC SURGERY
771
Annotations PROFOUND HYPOTHERMIA IN CARDIAC SURGERY IN two papers which we publish this week Mr. Drew and his colleagues describe a method for operating on the empty heart while maintaining the viability of other organs. The combination of hypothermia with extracorporeal circulation has interested many workers in the past few years.1-4 The main attraction is that reduction, by means of hypothermia, of the organism’s total oxygen requirements reduces the need for a heart-lung machine capable of delivering high outputs of oxygenated blood. Accordingly the design of the machine can be simplified, and much less donor blood is needed to prime the extracorporeal circulation. Drew et al. have employed this method, but have taken a step forward by’ reducing the temperature much further and using the patient’s own lungs for their normal function of oxygenation. The simplified circuit omits the artificial oxygenator and comprises two blood pumps (one pump to bypass each ventricle), a heat exchanger, tubing, and reservoirs. Once the temperature has been reduced to about 15°C, the pump circulations can be stopped and the surgeon has forty-five minutes to operate on the empty heart without any serious risk. Provided that the circulation through the lungs can be maintained at normal pressures, the theoretical advantage is considerable. Drew’s findings in laboratory animals and in patients of relative freedom from postoperative lung troubles is encouraging; but his experimental and clinical series so far are small, and it would be interesting to have data on the pulmonary arterial and venous pressures. Drew and his fellow-workers have shown that in their hands this technique is successful; but it must be emphasised that they are a highly skilled team, and at present it would be unrealistic to compare their technique with established techniques of heart-lung bypass under normothermic conditions. The pumps in these experiments contribute greatly to the cooling, and even more to the rewarming, as well as maintaining the circulation when the heart fails; but, as Drew et al. point out, the optimum flow of blood per kilogramme body-weight required at low temperatures is still unknown. Their technique, by requiring the pump only during the period of cooling and rewarming and not during the period of cardiotomy, keeps the time for using the heart bypass down to a reasonable period; and so there has been no hsemolysis. The operation itself seems to be fairly straightforward provided that the left atrium can be successfully drained; but the method has not yet been tried in some circumstances, such as the complete correction of the tetrad of Fallot with a hypoplastic pulmonary artery and infundibular or pulmonary valvular stenosis. Because the circulation ceases completely during the period of intracardiac surgery, a cannula that is in the way during this time can be withdrawn; and in one case a pulmonary-artery cannula was in fact withdrawn. Owing to the relative simplicity of the extracorporeal circuit combined with the hypothermia, the dose of heparin does 1.
not
1958.
be
as
great
as
that normally used in heartThis should help to lessen
does it make surgery any easier; and the need for a highly skilled team, both for the operation and for postoperative care, is probably no less great than it is with a normothermic heart-lung bypass. On the other hand, we are still far from finality in the techniques of cardiac surgery; and we hope that the theoretical advantages of the Westminster method will be fully realised in practice. Mr. Drew and his colleagues can be congratulated on an original approach, and we look forward to further news of its application. HÆMADSORPTION VIRUSES
developments in cultivating viruses are being reported at present. Eighteen months ago Vogel and Shelokovdescribed a rapid method for isolating and identifying influenza viruses. The virus was isolated in monkey-kidney-tissue cultures, and after an incubation period red blood-cells were added to the culture tubes. The red blood-cells adhered to the infected monkey-kidney cells, and this hsemadsorption (as it is now called) was used to identify the virus. Chanock et al.,9 experimenting with this method, isolated from children with acute respiratory disease two new viruses which had not been recognised before. On first isolation, these haemadsorption viruses types 1 and 2 showed no cytopathic effect on the monkeykidney cells, so their recognition depended entirely on The the isolation technique which had been used. affinities viruses share many haemadsorption biological with the influenza viruses, and the type-2 virus was found to be related antigenically to the Sendai virus (at one time known as influenza D). Now Chanock et al.10 describe a systematic attempt to isolate haemadsorption viruses from 1738 infants and children in three Washington, D.C., hospitals. The study population was made up of infants and children brought to outpatient clinics or for admission to hospital, with various respiratory illnesses, while a control group consisted of a similar number of children without respiratory illness and matched with the study group according to age, sex, and socioeconomic background. The respiratory illnesses studied-croup, bronchiolitis, pharyngitis, or pneumonia-did not seem to be caused primarily by MANY
new
bacteria. From each child a throat swab was taken on admission to hospital or at the first clinic visit, and virus isolation was attempted by the technique of Vogel and Shelokov.11a 5. 6. 7.
Andjus, R. K. J. Physiol. 1955, 128, 547. Smith, A. Proc. roy. Soc. B, 1957, 147, 533. Lewis, F. J. Physiology of Induced Hypothermia; p. 143. Washington,
8. 9.
Vogel, J., Shelokov, A. Science, 1957, 126, 358. Chanock, R. M., Parrott, R. H., Cook, K., Andrews, B. E., Bell, J. A., Reichelderfer, T., Kapikian, A. Z., Mastrota, F. M., Huebner, R. J. New Engl. J. Med. 1958, 258, 207. Chanock, R. M., Vargosko, A., Luckey, A., Cook, M. K., Kapikian, A. Z., Reichelderfer, T., Parrott, R. H. J. Amer. med. Ass. 1959, 169, 548.
1956.
2.
Sealy, W. C., Brown, I. W., Young, G. W., Stephen, R. C., Harris, J. S., Merritt, D. Surg. Gynec. Obstet. 1957, 104, 441. 3. Sealy, W. C., Brown, I. W., Young, W. G. Ann. Surg. 1958, 147, 603. 4. Gollan, F., Hamilton, E. C., Meneely, G. R. Surgery, 1954, 35, 88.
to
lung bypass procedures. postoperative bleeding. With the present rapid increase of centres starting to use extracorporeal circulation for intracardiac surgery, the demands on regional blood-banks are rising alarmingly; and the method of Drew et al., with its relatively small requirement of 2-3 pints of blood for priming the apparatus, may help to resolve this difficulty. Hypothermia at still lower temperatures is, as Drew et al. suggest, an attractive idea whose practicability is supported by some experimental evidence.5-7 But it would be premature to suggest that the technique that has now been developed will replace others. Nor at the moment
King, H.,
Chien Sheng Su, Bounos, G., Hardin, R., Derin, F., Shumacher, H. B. Extracorporeal Circulation; p. 193. Springfield, Ill.,
need
10.
Annotations PROFOUND HYPOTHERMIA IN CARDIAC SURGERY IN two papers which we publish this week Mr. Drew and his colleagues describe a method for operating on the empty heart while maintaining the viability of other organs. The combination of hypothermia with extracorporeal circulation has interested many workers in the past few years.1-4 The main attraction is that reduction, by means of hypothermia, of the organism’s total oxygen requirements reduces the need for a heart-lung machine capable of delivering high outputs of oxygenated blood. Accordingly the design of the machine can be simplified, and much less donor blood is needed to prime the extracorporeal circulation. Drew et al. have employed this method, but have taken a step forward by’ reducing the temperature much further and using the patient’s own lungs for their normal function of oxygenation. The simplified circuit omits the artificial oxygenator and comprises two blood pumps (one pump to bypass each ventricle), a heat exchanger, tubing, and reservoirs. Once the temperature has been reduced to about 15°C, the pump circulations can be stopped and the surgeon has forty-five minutes to operate on the empty heart without any serious risk. Provided that the circulation through the lungs can be maintained at normal pressures, the theoretical advantage is considerable. Drew’s findings in laboratory animals and in patients of relative freedom from postoperative lung troubles is encouraging; but his experimental and clinical series so far are small, and it would be interesting to have data on the pulmonary arterial and venous pressures. Drew and his fellow-workers have shown that in their hands this technique is successful; but it must be emphasised that they are a highly skilled team, and at present it would be unrealistic to compare their technique with established techniques of heart-lung bypass under normothermic conditions. The pumps in these experiments contribute greatly to the cooling, and even more to the rewarming, as well as maintaining the circulation when the heart fails; but, as Drew et al. point out, the optimum flow of blood per kilogramme body-weight required at low temperatures is still unknown. Their technique, by requiring the pump only during the period of cooling and rewarming and not during the period of cardiotomy, keeps the time for using the heart bypass down to a reasonable period; and so there has been no hsemolysis. The operation itself seems to be fairly straightforward provided that the left atrium can be successfully drained; but the method has not yet been tried in some circumstances, such as the complete correction of the tetrad of Fallot with a hypoplastic pulmonary artery and infundibular or pulmonary valvular stenosis. Because the circulation ceases completely during the period of intracardiac surgery, a cannula that is in the way during this time can be withdrawn; and in one case a pulmonary-artery cannula was in fact withdrawn. Owing to the relative simplicity of the extracorporeal circuit combined with the hypothermia, the dose of heparin does 1.
not
1958.
be
as
great
as
that normally used in heartThis should help to lessen
does it make surgery any easier; and the need for a highly skilled team, both for the operation and for postoperative care, is probably no less great than it is with a normothermic heart-lung bypass. On the other hand, we are still far from finality in the techniques of cardiac surgery; and we hope that the theoretical advantages of the Westminster method will be fully realised in practice. Mr. Drew and his colleagues can be congratulated on an original approach, and we look forward to further news of its application. HÆMADSORPTION VIRUSES
developments in cultivating viruses are being reported at present. Eighteen months ago Vogel and Shelokovdescribed a rapid method for isolating and identifying influenza viruses. The virus was isolated in monkey-kidney-tissue cultures, and after an incubation period red blood-cells were added to the culture tubes. The red blood-cells adhered to the infected monkey-kidney cells, and this hsemadsorption (as it is now called) was used to identify the virus. Chanock et al.,9 experimenting with this method, isolated from children with acute respiratory disease two new viruses which had not been recognised before. On first isolation, these haemadsorption viruses types 1 and 2 showed no cytopathic effect on the monkeykidney cells, so their recognition depended entirely on The the isolation technique which had been used. affinities viruses share many haemadsorption biological with the influenza viruses, and the type-2 virus was found to be related antigenically to the Sendai virus (at one time known as influenza D). Now Chanock et al.10 describe a systematic attempt to isolate haemadsorption viruses from 1738 infants and children in three Washington, D.C., hospitals. The study population was made up of infants and children brought to outpatient clinics or for admission to hospital, with various respiratory illnesses, while a control group consisted of a similar number of children without respiratory illness and matched with the study group according to age, sex, and socioeconomic background. The respiratory illnesses studied-croup, bronchiolitis, pharyngitis, or pneumonia-did not seem to be caused primarily by MANY
new
bacteria. From each child a throat swab was taken on admission to hospital or at the first clinic visit, and virus isolation was attempted by the technique of Vogel and Shelokov.11a 5. 6. 7.
Andjus, R. K. J. Physiol. 1955, 128, 547. Smith, A. Proc. roy. Soc. B, 1957, 147, 533. Lewis, F. J. Physiology of Induced Hypothermia; p. 143. Washington,
8. 9.
Vogel, J., Shelokov, A. Science, 1957, 126, 358. Chanock, R. M., Parrott, R. H., Cook, K., Andrews, B. E., Bell, J. A., Reichelderfer, T., Kapikian, A. Z., Mastrota, F. M., Huebner, R. J. New Engl. J. Med. 1958, 258, 207. Chanock, R. M., Vargosko, A., Luckey, A., Cook, M. K., Kapikian, A. Z., Reichelderfer, T., Parrott, R. H. J. Amer. med. Ass. 1959, 169, 548.
1956.
2.
Sealy, W. C., Brown, I. W., Young, G. W., Stephen, R. C., Harris, J. S., Merritt, D. Surg. Gynec. Obstet. 1957, 104, 441. 3. Sealy, W. C., Brown, I. W., Young, W. G. Ann. Surg. 1958, 147, 603. 4. Gollan, F., Hamilton, E. C., Meneely, G. R. Surgery, 1954, 35, 88.
to
lung bypass procedures. postoperative bleeding. With the present rapid increase of centres starting to use extracorporeal circulation for intracardiac surgery, the demands on regional blood-banks are rising alarmingly; and the method of Drew et al., with its relatively small requirement of 2-3 pints of blood for priming the apparatus, may help to resolve this difficulty. Hypothermia at still lower temperatures is, as Drew et al. suggest, an attractive idea whose practicability is supported by some experimental evidence.5-7 But it would be premature to suggest that the technique that has now been developed will replace others. Nor at the moment
King, H.,
Chien Sheng Su, Bounos, G., Hardin, R., Derin, F., Shumacher, H. B. Extracorporeal Circulation; p. 193. Springfield, Ill.,
need
10.