163
products, they conclude that " no protein deficiency due to an inadequate protein energy (P.E.) ratio could occur in Ethiopia ". Furthermore, they state that in the Harerghe region of Ethiopia " no amount of maldistribution of food within the family can give rise These statements stem from to a protein deficiency ". misunderstanding of the purpose of supplementary foods such as Faffa " and the fact that safe levels of protein intake calculated in healthy individuals living under ideal conditions are not meant to be applied to sick and malnourished populations.1 In situations of internationally recognised catastrophes many benevolent organisations act quickly by sending food and other supplies. Sometimes " bizarre " food items turn up, although they account only for the smaller part of emergency foods which are sent by more experienced aid organisations. Mr Rivers and his colleagues should not have concluded that they were requested by E.N.I. The provision of baby foods from external donors has probably been no different in Ethiopia than in other famine-stricken countries. Once such foods have arrived it is only natural to hand them out. Where there is food shortage, bizarre items, high protein or not, are better than no food at all. It seems to us that in the correspondence which followed McLaren’s article, insufficient attention has been given to the age factor, particularly the special needs and functional peculiarities of the infant and the young child. In certain areas of Ethiopia the food consumed may be even
some
bizarre
PRODUCTION FIGURES AND TARGETS FOR E.N.I. SUPPLEMENTARY FOOD PROGRAMME I
"
very deficient in energy in children below the age of 3.2-3 However, it does not follow that this deficiency can be corrected just by providing more of the ordinary food. The physical bulk of such a diet cannot be accommodated by a young child, even if divided into several meals. Even in
normal times, most Ethiopian families live under adverse environmental conditions with infections and parasitoses which cause repeated diarrhoeas and malabsorption-levels of protein intake recommended for healthy individuals do not apply to them. The optimum protein intake in severely malnourished and sick children is not known. In kwashiorkor Whitehead found that a protein intake of 4-2 g. per kg. body-weight per day raised the serum-albumin concentration faster than 2-3 g.4 He recommended 4 g. of milk protein per kg. per day for the treatment of kwashiorkor. Such protein allowances require food with a P.E. ratio greater than 0-08. It seems logical to supply a food supplement which will provide energy and protein in reasonable density and preferably with a protein quality and a P.E. ratio above that Faffa is such a food and has been of the ordinary diet. produced and marketed through E.N.I. since 1967. Faffa is a low-cost supplementary food which consists mainly of locally produced cereals and legumes. It is meant for use as a supplementary weaning food during the critical period from 6 months to 4 years, particularly in urban areas. The protein content, 20% of the dry substance and other additives accord with Protein Advisory Group guidelines for protein-rich mixtures for use as weaning foods.5 Although Faffa is sold through the ordinary market, its promotion is always combined with nutrition and health
education, with particular emphasis on home-made weaning foods and
hygiene. This is done because we know that industrially produced supplementary foods reach only a fraction of the needy child population and the rest should 1. Tech.
Rep. Ser. Wld Hlth Org. 1973, no. 522, p. 99 (F.A.O. Nutr. Mtg Rep. Ser. no. 52). 2. Selinus, R., Gobezie, A., Knutsson, K. E., Vahlquist, B. Am. J. clin. Nutr. 1971, 24, 365. 3. Selinus, R., Awalom, G., Gobezie, A. Acta Soc. Med. upsal. 1971, 76, 17. 4. Whitehead, R. C. in Proteins in Human Nutrition (edited by J. W. G. Porter and B. A. Rolls); p. 103. London, 1973. 5. P.A.G. Guidelines, No. 8 Supplementary Foods, Oct. 13, 1973.
.. S.W.F.=soy wheat flour-wheat 90%, additives 1 %.
soy
4,0, non-fat milk 5
receive widespread information concerning the proper use of available staples. During the past few years, E.N.I. has expanded its nutrition and health-education activities and has been instrumental in large-scale production of teaching kits and training of various cadres of field workers. In answer to the comments by Mr Rivers and his colleagues on the production and request of excessive amounts of high-protein foods and other bizarre products, we give the actual production figures and targets for the E.N.I. Supplementary Food Programme in the accompanying table. Faffa, which is available both in bulk and in 250 g. plastic bags is a 1/5-1/3 of the cost of imported products of comparable nutritional value. The s.w.F. is intended for use both by children and adults (especially mothers), and provides a wheat flour that is fortified with protein, minerals, and vitamins for only a modest price increase. The total sales of Faffa and s.w.F. for famine relief purposes for 1974 are expected to reach 2400 tons. Ethiopian Nutrition Institute, P.O. Box 5654, Addis Ababa, Ethiopia.
MEHARI GEBRE-MEDHIN GUNNAR MEEUWISSE ERWIN KOPP.
URINARY REFLUX AND CHRONIC PYELONEPHRITIS
SIR,-Unfortunately, I have only just read Dr Evans’s interesting invocation of the law of Laplace to explain the damaging effect of intrarenal reflux (Nov. 23, p. 1259), but may I make some belated comments on his ingenious suggestions ? It is true that the renal tubule contains neither muscle nor elastic tissue (although intracellular filaments which are probably contractile are present in proximal tubule cells), but Dr Evans has not mentioned the basement membrane. Welling et al.l showed that the Young’s modulus of this structure had a value close to that of pure collagen. They also found that by perfusion of isolated tubules at different pressures, an opening phenomenon could, in fact, be demonstrated, since the lumen opened suddenly at pressures of about 5 cm. H2O, but with further increases in pressure there was a progressive decrease in the slope of the tubular diameter. The relative rigidity of the intact tubule is also demonstrated by the work of Brenner et al.,2 who found that the wall of the proximal tubule was able to sustain a pressure difference of 30 cm. of water between the lumen and the peritubular capillaries. Certainly in micropuncture experiments I have never been able to produce a blow-out " of a tubule by increasing intratubular pressure and it seems likely, therefore, that the basement membrane performs the same function as the collagen in the wall of blood-vessels in providing the main elastic resistance to overstretching. "
1. 2.
Welling, L. W., Grantham, J. J., Qualizza, P. J. clin. Invest. 1972, 51, 1063. Brenner, B. M., Troy, J. L., Daugharty, T. M. Am. J. Physiol. 1972, 222, 246.
164 It is quite likely that the damage in intrarenal reflux is due to pyelotubular reflux at all but rather to damage to the pelvic wall, and evidence for this will shortly be presented by myself and my colleagues.
not
University College, Cardiff, P.O. Box 78, Cardiff CF1 XL.
D. B. MOFFAT.
PROSPECTIVE DIAGNOSIS OF SPINA BIFIDA SIR,-Dr Leek and his colleagues (Dec. 21, p. 1511) described another antenatal diagnosis of a neural-tube defect. Their patient, aged 41, and with a previous child with spina bifida, is reported as being from an " unselected population. This is alarming, since her risk of having a child with a neural-tube defect was 5% and a child with mongolism between 1% and 2%. In most hospitals such patients would be regarded as special high-risk cases and offered amniocentesis for amniotic-fluid oc-fetoprotein (A.F.P.) and cytogenetic analysis. There can be no justifiable reason for using the less reliable plasma-A.F.P. measurement1 in such a situation, except to gain experimental data or claim an apparent " first ". In point of fact, the first prospective diagnoses of anencephaly2 and spina bifida3 based on maternal blood-A.F.P. were reported some time ago. Both patients were selected in the same sense as Dr Leek’s patient, in that they had already delivered children with neural-tube defects. Neither, however, was over the age of 35. Perhaps more serious than a dispute as to what constitutes " selected " is the report that in St. Bartholomew’s Hospital maternal serum-A.F.p. levels are being used as the basis for an intervention study. If two successive A.F.P. values lie more than two standard deviations above the mean appropriate to the gestation, amniocentesis is suggested and confirmatory amniotic-fluid A.F.P. determination performed. Since amniocentesis carries an imprecisely defined risk, we wonder how this definition of the abnormal Is it based on a large experience of the was arrived at. diagnosis of neural-tube defects in retrospective studies ? If screening of a truly unselected population were carried out, how many unnecessary amniocenteses (caused by false positives in the maternal serum assay) would be involved ? It would be a pity if a promising diagnostic method were discredited by a premature application to the clinical scene. "
Departments of Human Genetics and Obstetrics and Gynæcology, Western General Hospital, Edinburgh 4.
D. J. H. BROCK J. B. SCRIMGEOUR.
SIR,—We are grateful to Dr Brock and Dr Scrimgeour for the points they raise about our letter. The first concerns the use of the term " unselected ", which we believe to be completely justified in the context used. Contrary to their statement, the majority of pregnant women in the U.K., regardless of their past history, are not at present screened for neural-tube defects by oc-fetoprotein (A.F.P.) determination. In order to ascertain the clinical value of a screening programme based on simple and risk-free determinations of A.F.P. in maternal blood,4,5 we have mounted a prospective survey in a general population, and it was in this population that the case occurred. It is easy in retrospect to say that this woman was " selected " because of her clinical history. In practice, however, she 1. 2. 3. 4.
Lancet, 1974, i, 907. Brock, D. J. H., Bolton, A. E., Monaghan, J. M. ibid. 1973, ii, 923. Brock, D. J. H., Bolton, A. E., Scrimgeour, J. B. ibid. 1974, i, 767. Leek, A. E., Ruoss, C. F., Kitau, M. J., Chard, T. ibid., 1973, ii,
5.
Leek, A. E., Leighton, P. C., Kitau, M. J., Chard, T. ibid. 1974, ii,
385. 1511.
not, and had she been in a unit without access to A.F.P. determinations the diagnosis would not have been made. We stated before, and would further emphasise here, that the only way to assess the real value of such a test is by its prospective application to a complete population. The limited and non-prospective studies referred to by the Edinburgh workers 6,7 in no sense meet these criteria. The second point is whether such investigations should be " intervention " studies (i.e., action is taken on the basis of the results). This question is more difficult, and the points raised by Dr Brock and Dr Scrimgeour are well taken both by ourselves and others conducting studies of this type. However, we would value his suggestions for an alternative method. Given high circulating levels of A.F.P., should we at present stand aside and do nothing ? If we do not perform an amniocentesis, we will never know whether the answer would have been definitive, and the study would, in practical terms, be valueless. If an amniocentesis is done and reveals a high level, should we again stand aside, or should we take cognisance of Dr Brock’s own pioneering work in this area and act ? It is accepted that amniocentesis carries a risk, the major problem being an incidence of abortion of around 2%; but the present proposals would involve applying the procedure to less than 2-5 % of all pregnancies, a group no greater than that selected by clinical history and probably, on present information, yielding a larger harvest of defects. The Dr Brock’s argument must be that logical conclusion amniocentesis on any grounds is unjustified, in which case all clinical work on A.F.P. should cease forthwith. Many will join us in our reaction that this would be a disappointing end to one of the most promising new techniques in obstetric practice. was
of
I
Departments of Obstetrics and Gynæcology and Reproductive
Physiology, St. Bartholomew’s Hospital Medical College, London EC1, and the London Hospital Medical School.
T. CHARD A. E. LEEK M. J. KITAU P. C. LEIGHTON.
ASSESSMENT OF THE APGAR SCORE
SIR,-It was gratifying to read the paper by Mr Chamberlain and Mr Banks (Nov. 23, p. 1225) and find that so much work and thought had gone into an idea Mr Chamberlain and I discussed together some four years ago. It has been obvious for some time that whatever the merits of the Apgar scoring system as a prognostic index it is a poor guide to treatment, and I only regret that the authors did not link their new scoring system to management. It may be that its direction towards midwives prohibited this. The introduction of a score of 0, 1, or 2 for new parameters such as " time to first breath " or " time to cry " also complicates the picture as a new learning task is introduced, whereas most practitioners are already familiar with the Apgar score. Respiration is the one parameter which we can actively
modify by treatment. My own score,8,9 therefore, simply totals the Apgar ratings of heart-rate and respiration, giving similar 0 to 4 range. In a series of 300 infants assessed, 65% with a B/R score of 4 had a mean Apgar of 8-5 (range 6-10); 17% with a B/R score of 3 had a mean Apgar of 7-3 (range 5-9); 12% with a B/R score of 2 had a mean Apgar of 4-8 (range 2-7); and 5 % witha B/R score of 1 had a mean Apgar of 2-6 (range 1-3). One infant in the series (the only mortality) had a B/R score of 0 and an Apgar of 0.
a
6. 7. 8. 9.
Brock, D. J. H., Bolton, A. E., Monaghan, J. M. ibid. 1973, ii, 923. Brock, D. J. H., Bolton, A. E., Scrimgeour, J. B. ibid. 1974, i, 767. Roberts, R. B. Br. med. J. 1969, iii, 532. Stark, D. C. C., Roberts, R. B. Practical Points in Anesthesiology; chap. 14, p. 126. New York, 1974.
products, they conclude that " no protein deficiency due to an inadequate protein energy (P.E.) ratio could occur in Ethiopia ". Furthermore, they state that in the Harerghe region of Ethiopia " no amount of maldistribution of food within the family can give rise These statements stem from to a protein deficiency ". misunderstanding of the purpose of supplementary foods such as Faffa " and the fact that safe levels of protein intake calculated in healthy individuals living under ideal conditions are not meant to be applied to sick and malnourished populations.1 In situations of internationally recognised catastrophes many benevolent organisations act quickly by sending food and other supplies. Sometimes " bizarre " food items turn up, although they account only for the smaller part of emergency foods which are sent by more experienced aid organisations. Mr Rivers and his colleagues should not have concluded that they were requested by E.N.I. The provision of baby foods from external donors has probably been no different in Ethiopia than in other famine-stricken countries. Once such foods have arrived it is only natural to hand them out. Where there is food shortage, bizarre items, high protein or not, are better than no food at all. It seems to us that in the correspondence which followed McLaren’s article, insufficient attention has been given to the age factor, particularly the special needs and functional peculiarities of the infant and the young child. In certain areas of Ethiopia the food consumed may be even
some
bizarre
PRODUCTION FIGURES AND TARGETS FOR E.N.I. SUPPLEMENTARY FOOD PROGRAMME I
"
very deficient in energy in children below the age of 3.2-3 However, it does not follow that this deficiency can be corrected just by providing more of the ordinary food. The physical bulk of such a diet cannot be accommodated by a young child, even if divided into several meals. Even in
normal times, most Ethiopian families live under adverse environmental conditions with infections and parasitoses which cause repeated diarrhoeas and malabsorption-levels of protein intake recommended for healthy individuals do not apply to them. The optimum protein intake in severely malnourished and sick children is not known. In kwashiorkor Whitehead found that a protein intake of 4-2 g. per kg. body-weight per day raised the serum-albumin concentration faster than 2-3 g.4 He recommended 4 g. of milk protein per kg. per day for the treatment of kwashiorkor. Such protein allowances require food with a P.E. ratio greater than 0-08. It seems logical to supply a food supplement which will provide energy and protein in reasonable density and preferably with a protein quality and a P.E. ratio above that Faffa is such a food and has been of the ordinary diet. produced and marketed through E.N.I. since 1967. Faffa is a low-cost supplementary food which consists mainly of locally produced cereals and legumes. It is meant for use as a supplementary weaning food during the critical period from 6 months to 4 years, particularly in urban areas. The protein content, 20% of the dry substance and other additives accord with Protein Advisory Group guidelines for protein-rich mixtures for use as weaning foods.5 Although Faffa is sold through the ordinary market, its promotion is always combined with nutrition and health
education, with particular emphasis on home-made weaning foods and
hygiene. This is done because we know that industrially produced supplementary foods reach only a fraction of the needy child population and the rest should 1. Tech.
Rep. Ser. Wld Hlth Org. 1973, no. 522, p. 99 (F.A.O. Nutr. Mtg Rep. Ser. no. 52). 2. Selinus, R., Gobezie, A., Knutsson, K. E., Vahlquist, B. Am. J. clin. Nutr. 1971, 24, 365. 3. Selinus, R., Awalom, G., Gobezie, A. Acta Soc. Med. upsal. 1971, 76, 17. 4. Whitehead, R. C. in Proteins in Human Nutrition (edited by J. W. G. Porter and B. A. Rolls); p. 103. London, 1973. 5. P.A.G. Guidelines, No. 8 Supplementary Foods, Oct. 13, 1973.
.. S.W.F.=soy wheat flour-wheat 90%, additives 1 %.
soy
4,0, non-fat milk 5
receive widespread information concerning the proper use of available staples. During the past few years, E.N.I. has expanded its nutrition and health-education activities and has been instrumental in large-scale production of teaching kits and training of various cadres of field workers. In answer to the comments by Mr Rivers and his colleagues on the production and request of excessive amounts of high-protein foods and other bizarre products, we give the actual production figures and targets for the E.N.I. Supplementary Food Programme in the accompanying table. Faffa, which is available both in bulk and in 250 g. plastic bags is a 1/5-1/3 of the cost of imported products of comparable nutritional value. The s.w.F. is intended for use both by children and adults (especially mothers), and provides a wheat flour that is fortified with protein, minerals, and vitamins for only a modest price increase. The total sales of Faffa and s.w.F. for famine relief purposes for 1974 are expected to reach 2400 tons. Ethiopian Nutrition Institute, P.O. Box 5654, Addis Ababa, Ethiopia.
MEHARI GEBRE-MEDHIN GUNNAR MEEUWISSE ERWIN KOPP.
URINARY REFLUX AND CHRONIC PYELONEPHRITIS
SIR,-Unfortunately, I have only just read Dr Evans’s interesting invocation of the law of Laplace to explain the damaging effect of intrarenal reflux (Nov. 23, p. 1259), but may I make some belated comments on his ingenious suggestions ? It is true that the renal tubule contains neither muscle nor elastic tissue (although intracellular filaments which are probably contractile are present in proximal tubule cells), but Dr Evans has not mentioned the basement membrane. Welling et al.l showed that the Young’s modulus of this structure had a value close to that of pure collagen. They also found that by perfusion of isolated tubules at different pressures, an opening phenomenon could, in fact, be demonstrated, since the lumen opened suddenly at pressures of about 5 cm. H2O, but with further increases in pressure there was a progressive decrease in the slope of the tubular diameter. The relative rigidity of the intact tubule is also demonstrated by the work of Brenner et al.,2 who found that the wall of the proximal tubule was able to sustain a pressure difference of 30 cm. of water between the lumen and the peritubular capillaries. Certainly in micropuncture experiments I have never been able to produce a blow-out " of a tubule by increasing intratubular pressure and it seems likely, therefore, that the basement membrane performs the same function as the collagen in the wall of blood-vessels in providing the main elastic resistance to overstretching. "
1. 2.
Welling, L. W., Grantham, J. J., Qualizza, P. J. clin. Invest. 1972, 51, 1063. Brenner, B. M., Troy, J. L., Daugharty, T. M. Am. J. Physiol. 1972, 222, 246.
164 It is quite likely that the damage in intrarenal reflux is due to pyelotubular reflux at all but rather to damage to the pelvic wall, and evidence for this will shortly be presented by myself and my colleagues.
not
University College, Cardiff, P.O. Box 78, Cardiff CF1 XL.
D. B. MOFFAT.
PROSPECTIVE DIAGNOSIS OF SPINA BIFIDA SIR,-Dr Leek and his colleagues (Dec. 21, p. 1511) described another antenatal diagnosis of a neural-tube defect. Their patient, aged 41, and with a previous child with spina bifida, is reported as being from an " unselected population. This is alarming, since her risk of having a child with a neural-tube defect was 5% and a child with mongolism between 1% and 2%. In most hospitals such patients would be regarded as special high-risk cases and offered amniocentesis for amniotic-fluid oc-fetoprotein (A.F.P.) and cytogenetic analysis. There can be no justifiable reason for using the less reliable plasma-A.F.P. measurement1 in such a situation, except to gain experimental data or claim an apparent " first ". In point of fact, the first prospective diagnoses of anencephaly2 and spina bifida3 based on maternal blood-A.F.P. were reported some time ago. Both patients were selected in the same sense as Dr Leek’s patient, in that they had already delivered children with neural-tube defects. Neither, however, was over the age of 35. Perhaps more serious than a dispute as to what constitutes " selected " is the report that in St. Bartholomew’s Hospital maternal serum-A.F.p. levels are being used as the basis for an intervention study. If two successive A.F.P. values lie more than two standard deviations above the mean appropriate to the gestation, amniocentesis is suggested and confirmatory amniotic-fluid A.F.P. determination performed. Since amniocentesis carries an imprecisely defined risk, we wonder how this definition of the abnormal Is it based on a large experience of the was arrived at. diagnosis of neural-tube defects in retrospective studies ? If screening of a truly unselected population were carried out, how many unnecessary amniocenteses (caused by false positives in the maternal serum assay) would be involved ? It would be a pity if a promising diagnostic method were discredited by a premature application to the clinical scene. "
Departments of Human Genetics and Obstetrics and Gynæcology, Western General Hospital, Edinburgh 4.
D. J. H. BROCK J. B. SCRIMGEOUR.
SIR,—We are grateful to Dr Brock and Dr Scrimgeour for the points they raise about our letter. The first concerns the use of the term " unselected ", which we believe to be completely justified in the context used. Contrary to their statement, the majority of pregnant women in the U.K., regardless of their past history, are not at present screened for neural-tube defects by oc-fetoprotein (A.F.P.) determination. In order to ascertain the clinical value of a screening programme based on simple and risk-free determinations of A.F.P. in maternal blood,4,5 we have mounted a prospective survey in a general population, and it was in this population that the case occurred. It is easy in retrospect to say that this woman was " selected " because of her clinical history. In practice, however, she 1. 2. 3. 4.
Lancet, 1974, i, 907. Brock, D. J. H., Bolton, A. E., Monaghan, J. M. ibid. 1973, ii, 923. Brock, D. J. H., Bolton, A. E., Scrimgeour, J. B. ibid. 1974, i, 767. Leek, A. E., Ruoss, C. F., Kitau, M. J., Chard, T. ibid., 1973, ii,
5.
Leek, A. E., Leighton, P. C., Kitau, M. J., Chard, T. ibid. 1974, ii,
385. 1511.
not, and had she been in a unit without access to A.F.P. determinations the diagnosis would not have been made. We stated before, and would further emphasise here, that the only way to assess the real value of such a test is by its prospective application to a complete population. The limited and non-prospective studies referred to by the Edinburgh workers 6,7 in no sense meet these criteria. The second point is whether such investigations should be " intervention " studies (i.e., action is taken on the basis of the results). This question is more difficult, and the points raised by Dr Brock and Dr Scrimgeour are well taken both by ourselves and others conducting studies of this type. However, we would value his suggestions for an alternative method. Given high circulating levels of A.F.P., should we at present stand aside and do nothing ? If we do not perform an amniocentesis, we will never know whether the answer would have been definitive, and the study would, in practical terms, be valueless. If an amniocentesis is done and reveals a high level, should we again stand aside, or should we take cognisance of Dr Brock’s own pioneering work in this area and act ? It is accepted that amniocentesis carries a risk, the major problem being an incidence of abortion of around 2%; but the present proposals would involve applying the procedure to less than 2-5 % of all pregnancies, a group no greater than that selected by clinical history and probably, on present information, yielding a larger harvest of defects. The Dr Brock’s argument must be that logical conclusion amniocentesis on any grounds is unjustified, in which case all clinical work on A.F.P. should cease forthwith. Many will join us in our reaction that this would be a disappointing end to one of the most promising new techniques in obstetric practice. was
of
I
Departments of Obstetrics and Gynæcology and Reproductive
Physiology, St. Bartholomew’s Hospital Medical College, London EC1, and the London Hospital Medical School.
T. CHARD A. E. LEEK M. J. KITAU P. C. LEIGHTON.
ASSESSMENT OF THE APGAR SCORE
SIR,-It was gratifying to read the paper by Mr Chamberlain and Mr Banks (Nov. 23, p. 1225) and find that so much work and thought had gone into an idea Mr Chamberlain and I discussed together some four years ago. It has been obvious for some time that whatever the merits of the Apgar scoring system as a prognostic index it is a poor guide to treatment, and I only regret that the authors did not link their new scoring system to management. It may be that its direction towards midwives prohibited this. The introduction of a score of 0, 1, or 2 for new parameters such as " time to first breath " or " time to cry " also complicates the picture as a new learning task is introduced, whereas most practitioners are already familiar with the Apgar score. Respiration is the one parameter which we can actively
modify by treatment. My own score,8,9 therefore, simply totals the Apgar ratings of heart-rate and respiration, giving similar 0 to 4 range. In a series of 300 infants assessed, 65% with a B/R score of 4 had a mean Apgar of 8-5 (range 6-10); 17% with a B/R score of 3 had a mean Apgar of 7-3 (range 5-9); 12% with a B/R score of 2 had a mean Apgar of 4-8 (range 2-7); and 5 % witha B/R score of 1 had a mean Apgar of 2-6 (range 1-3). One infant in the series (the only mortality) had a B/R score of 0 and an Apgar of 0.
a
6. 7. 8. 9.
Brock, D. J. H., Bolton, A. E., Monaghan, J. M. ibid. 1973, ii, 923. Brock, D. J. H., Bolton, A. E., Scrimgeour, J. B. ibid. 1974, i, 767. Roberts, R. B. Br. med. J. 1969, iii, 532. Stark, D. C. C., Roberts, R. B. Practical Points in Anesthesiology; chap. 14, p. 126. New York, 1974.
