- Email: [email protected]
METHOD OF ARTERIAL SAMPLING
40
less disease-centred criterion of therapeutic success. Sickness absence from work, ability to continue housework, or other facility for specific activity may be of value. These factors would take account of the enormous power of human adaptability in adversity. We should also avoid the lesser degrees of " the operation was a success, but the patient died ". J. J. MCMULLAN. London, W.2.
some
internal massage should be used. Donald et al. have not measured cardiac output and coronary flow during internal cardiac massage, and they therefore have no reasons other than purely theoretical ones for assuming that it will be more effective than external massage. Furthermore their suggestion that internal massage may be less damaging to an already ailing myocardium is contrary to the established facts. Thoracic
METHOD OF ARTERIAL SAMPLING SIR,-The frequency with which single arterial samples
required from conscious patients for clinical or research purposes makes a simple, reliable, and painless
are
method of arterial puncture desirable. The usual technique of inserting a medium to large needle into the brachial or femoral arteries after infiltration of a local anxsthetic does not fulfil these requirements, being always uncomfortable, often painful, and sometimes difficult. The following technique has been found to be free from these objections:
Surgical Unit, Papworth Hospital, Cambridge.
B. B. MILSTEIN.
PLASMA-CORTICOTROPHIN SIR,-May I add two comments to the correspondence
about
plasma-corticotrophin estimations ?
Espiner1 suggested that venesection for large blood samples (always 500 ml.) causes pituitary secretion of corticotrophin during the collection period. Naturally, precautions to minimise the possible shock of this procedure were taken in my work, such as using subjects resting in bed to whom a simple prior explanation (and breakfast) was given. The blood was obtained, in the majority of cases, by very experienced The region around the radial artery at the wrist is infiltrated people, including a blood-transfusion officer for the normal with 1 % procaine using a fine no. 20 needle; the same needle subjects. While augmentation of blood-corticotrophin by is used to puncture the artery, and the sample syringe is then venepuncture cannot be ruled out, I think it arguable that, if attached in place of that containing the procaine and the sample venepuncture had a great quantitative effect in the hypertensive obtained. The needle is then withdrawn and the puncture site Cushing’s patients, it would have " blanketed " the variations compressed for 30 seconds. The freedom from discomfort, in blood-corticotrophin that I found between individual cases. haematomas, or inadvertent venepuncture, together with the I am at present using a method, to be published, involving ease of making the actual arterial ’puncture have made 50-100 ml. samples of blood, but this was introduced mainly to the collection of these samples a pleasanter matter for both save the patients parting with so much blood. As I mentioned the patient and the operator. previously, at present perhaps most information can be obtained by comparing corticotrophin values for pathological Department of Anæsthesia, Addenbrooke’s Hospital, BRYAN E. MARSHALL. plasmas with the same worker’s figures for normal plasma. Cambridge. It is a little difficult that the results of the sheep adrenal autotransplant work have been given before a full description HÆMODYNAMIC EFFECTS OF EXTERNAL of the assay has been published, and I look forward to reading CARDIAC COMPRESSION this in the Journal of Physiology. I still think it reasonable to SIR,-Professor Donald and his colleagues must be con- expect that a bioassay be based on an effect measured at its gratulated on their initiative in obtaining measurements peak (or over a short period containing its rise to and fall from of the hxmodynamic changes during external cardiac the maximum); that the test preparation causes its response at same time-interval after injection as the standard hormone; compression in man.1 Several interesting points arise from the and that the assay has a statistical design. their findings: 1. The venous pressure is not necessarily elevated to a very high level during the phase of cardiac compression. I have published an illustration of the consecutively recorded arterial and venous pressures during external cardiac compression in one patient. In this case the venous pressure was elevated only slightly during cardiac compression. Possibly, therefore, the technique of cardiac compression, or the condition of the heart, determines whether venous pressures are high. 2. Donald and his colleagues show that the cardiac output from external cardiac compression is only about half that during normal sinus rhythm. As they point out, the cardiac output was in any event low as a result of myocardial damage in their cases. It has always been apparent, however, from observation of skin pallor or cyanosis during cardiac massage, and subsequent flushing of the skin when the heart starts, that the cardiac output is abnormally low during cardiac massage. This has not prevented resuscitation of the heart or the return of normal cerebral function. Although Donald has produced some evidence that the coronary arteries were inadequately perfused during cardiac massage, no evidence has been adduced concerning the cerebral blood-flow. It seems likely that, as the cardiac output falls, the cerebral blood-flow will come to represent an increasing proportion of the total.
The chief criticism of Donald’s article must be of the last paragraph in which it is suggested that, if cardiac massage is to be continued for more than a brief period, 1.
2.
MacKenzie, G. J., Taylor, S. H., McDonald, A. H., Donald, K. W. Lancet, 1964, i, 1342. Milstein, B. B. Cardiac Arrest and Resuscitation; fig. 14, p. 117. London, 1963.
Dr.
Division of Physiology and Endocrinology, Imperial Cancer Research Fund, Lincoln’s Inn Fields, London, W.C.2.
BERYL M. A. DAVIES.
SCREENING TEST FOR CHLOROQUINE RETINOPATHY
SIR,-Inoted with interest the article by Dr. Copeman and his colleagues.2 First I wish to congratulate the authors on their adaptation of the E.G.G. machine to do electro-oculography (E.O.G.) Unfortunately there are several points in their article with which I must disagree. First, the initials E.o.G. generally stand for electro-oculogram, and there is little reason for calling the test the extraoculogram. The authors’ statement, " Extraoculography is the only reliable method for detecting early retinopathy caused by chloroquine and related antimalarial drugs ", does not appear to be supported by any of the material they provide. Indeed, they mention the paper of Gouras and Gunkel3 which, far from supporting their statement, actually shows that the E.o.G. may be normal in patients with definite early retinopathy. My own experience 4 indicates that there is often visible evidence of chloroquine retinopathy preceding any notable change in the E.o.G. or the E.R.G. (electroretinogram). The early changes usually occur in the macular region and consist of the following: loss of foveal reflex, macular mottling-probably resulting in changes in the underlying pigment epithelium, and the so-called macular bull’s-eye ". Undoubtedly the E.o.G. is a useful "
1. 2. 3. 4.
Espiner, E. A. Lancet, 1964, i, 1327. Copeman, P. W. M., Cowell, T. K., Dallas, M. L. ibid p. 1369. Gouras, P., Gunkel, R. D. Arch. Ophthal. 1963, 70, 629. Henkind, P., Carr, R., Siegel, I. ibid. 1964, 71, 157.
less disease-centred criterion of therapeutic success. Sickness absence from work, ability to continue housework, or other facility for specific activity may be of value. These factors would take account of the enormous power of human adaptability in adversity. We should also avoid the lesser degrees of " the operation was a success, but the patient died ". J. J. MCMULLAN. London, W.2.
some
internal massage should be used. Donald et al. have not measured cardiac output and coronary flow during internal cardiac massage, and they therefore have no reasons other than purely theoretical ones for assuming that it will be more effective than external massage. Furthermore their suggestion that internal massage may be less damaging to an already ailing myocardium is contrary to the established facts. Thoracic
METHOD OF ARTERIAL SAMPLING SIR,-The frequency with which single arterial samples
required from conscious patients for clinical or research purposes makes a simple, reliable, and painless
are
method of arterial puncture desirable. The usual technique of inserting a medium to large needle into the brachial or femoral arteries after infiltration of a local anxsthetic does not fulfil these requirements, being always uncomfortable, often painful, and sometimes difficult. The following technique has been found to be free from these objections:
Surgical Unit, Papworth Hospital, Cambridge.
B. B. MILSTEIN.
PLASMA-CORTICOTROPHIN SIR,-May I add two comments to the correspondence
about
plasma-corticotrophin estimations ?
Espiner1 suggested that venesection for large blood samples (always 500 ml.) causes pituitary secretion of corticotrophin during the collection period. Naturally, precautions to minimise the possible shock of this procedure were taken in my work, such as using subjects resting in bed to whom a simple prior explanation (and breakfast) was given. The blood was obtained, in the majority of cases, by very experienced The region around the radial artery at the wrist is infiltrated people, including a blood-transfusion officer for the normal with 1 % procaine using a fine no. 20 needle; the same needle subjects. While augmentation of blood-corticotrophin by is used to puncture the artery, and the sample syringe is then venepuncture cannot be ruled out, I think it arguable that, if attached in place of that containing the procaine and the sample venepuncture had a great quantitative effect in the hypertensive obtained. The needle is then withdrawn and the puncture site Cushing’s patients, it would have " blanketed " the variations compressed for 30 seconds. The freedom from discomfort, in blood-corticotrophin that I found between individual cases. haematomas, or inadvertent venepuncture, together with the I am at present using a method, to be published, involving ease of making the actual arterial ’puncture have made 50-100 ml. samples of blood, but this was introduced mainly to the collection of these samples a pleasanter matter for both save the patients parting with so much blood. As I mentioned the patient and the operator. previously, at present perhaps most information can be obtained by comparing corticotrophin values for pathological Department of Anæsthesia, Addenbrooke’s Hospital, BRYAN E. MARSHALL. plasmas with the same worker’s figures for normal plasma. Cambridge. It is a little difficult that the results of the sheep adrenal autotransplant work have been given before a full description HÆMODYNAMIC EFFECTS OF EXTERNAL of the assay has been published, and I look forward to reading CARDIAC COMPRESSION this in the Journal of Physiology. I still think it reasonable to SIR,-Professor Donald and his colleagues must be con- expect that a bioassay be based on an effect measured at its gratulated on their initiative in obtaining measurements peak (or over a short period containing its rise to and fall from of the hxmodynamic changes during external cardiac the maximum); that the test preparation causes its response at same time-interval after injection as the standard hormone; compression in man.1 Several interesting points arise from the and that the assay has a statistical design. their findings: 1. The venous pressure is not necessarily elevated to a very high level during the phase of cardiac compression. I have published an illustration of the consecutively recorded arterial and venous pressures during external cardiac compression in one patient. In this case the venous pressure was elevated only slightly during cardiac compression. Possibly, therefore, the technique of cardiac compression, or the condition of the heart, determines whether venous pressures are high. 2. Donald and his colleagues show that the cardiac output from external cardiac compression is only about half that during normal sinus rhythm. As they point out, the cardiac output was in any event low as a result of myocardial damage in their cases. It has always been apparent, however, from observation of skin pallor or cyanosis during cardiac massage, and subsequent flushing of the skin when the heart starts, that the cardiac output is abnormally low during cardiac massage. This has not prevented resuscitation of the heart or the return of normal cerebral function. Although Donald has produced some evidence that the coronary arteries were inadequately perfused during cardiac massage, no evidence has been adduced concerning the cerebral blood-flow. It seems likely that, as the cardiac output falls, the cerebral blood-flow will come to represent an increasing proportion of the total.
The chief criticism of Donald’s article must be of the last paragraph in which it is suggested that, if cardiac massage is to be continued for more than a brief period, 1.
2.
MacKenzie, G. J., Taylor, S. H., McDonald, A. H., Donald, K. W. Lancet, 1964, i, 1342. Milstein, B. B. Cardiac Arrest and Resuscitation; fig. 14, p. 117. London, 1963.
Dr.
Division of Physiology and Endocrinology, Imperial Cancer Research Fund, Lincoln’s Inn Fields, London, W.C.2.
BERYL M. A. DAVIES.
SCREENING TEST FOR CHLOROQUINE RETINOPATHY
SIR,-Inoted with interest the article by Dr. Copeman and his colleagues.2 First I wish to congratulate the authors on their adaptation of the E.G.G. machine to do electro-oculography (E.O.G.) Unfortunately there are several points in their article with which I must disagree. First, the initials E.o.G. generally stand for electro-oculogram, and there is little reason for calling the test the extraoculogram. The authors’ statement, " Extraoculography is the only reliable method for detecting early retinopathy caused by chloroquine and related antimalarial drugs ", does not appear to be supported by any of the material they provide. Indeed, they mention the paper of Gouras and Gunkel3 which, far from supporting their statement, actually shows that the E.o.G. may be normal in patients with definite early retinopathy. My own experience 4 indicates that there is often visible evidence of chloroquine retinopathy preceding any notable change in the E.o.G. or the E.R.G. (electroretinogram). The early changes usually occur in the macular region and consist of the following: loss of foveal reflex, macular mottling-probably resulting in changes in the underlying pigment epithelium, and the so-called macular bull’s-eye ". Undoubtedly the E.o.G. is a useful "
1. 2. 3. 4.
Espiner, E. A. Lancet, 1964, i, 1327. Copeman, P. W. M., Cowell, T. K., Dallas, M. L. ibid p. 1369. Gouras, P., Gunkel, R. D. Arch. Ophthal. 1963, 70, 629. Henkind, P., Carr, R., Siegel, I. ibid. 1964, 71, 157.