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VALUE OF HYPOTENSIVE DRUGS IN MINIMISING BLOOD-LOSS IN THORACIC SURGERY
150
VALUE OF HYPOTENSIVE DRUGS IN MINIMISING BLOOD-LOSS IN THORACIC SURGERY IVOR LEWIS M.R.C.S., D.A. LIVERPOOL UNITED HOSPITALS, REGIONAL HOSPITALS AND WALES SANATORIUM
ANÆSTHETIST,
(EASTERN GROUP),
LIVERPOOL
If this is not reached, a further dose of the drug is given, the amount depending on the response to the test dose, but this dose should not exceed 30 mg. If after two minutes it is found that the optimal hypotension has not been reached, further doses not exceeding 30 mg. each are given at two-minute intervals, until the desired bloodpressure has been reached. Once this has been reached, the pressure remains unaltered for 25-50 minutes.
NORTH
THE clinical effects of pentamethonium and hexamethonium bromides and iodides in lowering the bloodpressure (Arnold and Rosenheim 1949, Burt and Graham 1950) have led to their use in the treatment of hypertension and, combined with posture, to control hoemor-
rhage during surgical operations (Enderby 1950). Having observed the effects of these drugs combined with posture in general and aural surgery, I decided to try them in all types ofmajor thoracic operations done for pulmonary tuberculosis. Hitherto, despite the use of diathermy, blood-loss has been considerable in this field of surgery owing to oozing from stripped periosteum when several ribs are removed, from cut ends of pleural adhesions when lung is excised, and from minute vessels when extrapleural stripping is done. This type of bloodloss is negligible when the haemorrhage is controlled with these hypotensive drugs. TECHNIQUE
AND MANAGEMENT
The use of hypotensive drugs has not required any change in the usual premedication with morphine and atropine, or withOmnopon ’ and scopolamine given an hour before the operation. The blood-pressure is measured
,
before the induction of anaesthesia with d-tubocurarine chloride and thiopentone given through a combined intravenous needle and cannula (Ellis type), the dosage varying with the age and weight of the patient. Oral intubation with the largest cuffed tube that can be passed is done in all cases, and anaesthesia is maintained through a closed circuit (Waters) with nitrous oxide and oxygen (1:1) supplemented by intermittent doses of pethidine, thiopentone, and d-tubocurarine chloride as required. The patient is placed on the operating-table in the standard lateral position with a moderate down-tilt of the thorax and head and a considerable down-tilt of the pelvis and legs (the so-called jack-knife position) ; the stylet is removed from the Ellis needle and cannula, and a blood drip is instituted. The blood-pressure is then measured. The initial injection, which is a test dose, of the hypotensive drug is next given ; in the present series it has always been 20 mg. After three minutes the bloodpressure is again measured, to assess the effect of this test dose combined with posture.The optimal hypotension for these cases was deemed to be 55-65 mm. Hg systolic. MURRAY, DR. CRAWFORD: REFERENCES Bodger, W. P., Orritt, J. E., Israel, H. L., Flippin, H. F. (1948) Amer. J. med. Sci. 215, 250. Cohlan, S. Q., Lewis, J. M., Seligmann E. (1948) Amer. J. Dis. DR.
Child. 75, 15. Emery, J. L., Rose, L. M., Stewart, S. M., Wayne, E. J. (1949a) Brit. med. J. i, 1110. Stewart, S. M., Stone, D. G. H. (1949b) Ibid, p. 844. Fairbrother, R. W., Daber, K. S. (1950) Ibid, i, 1098. Fleming, A. (1944) Lancet, ii, 620. Herrell, W. E., Nichols, D. R., Heilman, F. R. (1947) Proc. Mayo —
Clin. 22, 567.
Hewitt, W. L.. Whittlesey, P., Keefer, C. S. (1948) New Engl. J. Med. 239, 286. Hoffman, W. S., Hofer, J. W., Gordon. H. (1948) J. Pediat. 32, 1. Levin, B., Neill, C. A. (1949) Arch. Dis. Childh. 24, 171. McDermott, W.. Bunn, P., Benoit, M., Du Bois, R., Reynolds, M. (1946) J. clin. Invest. 25, 190. Moseley, J. M. (1948) Arch. Dis. Childh. 23, 93. Salivar, C. J., Hedger, F. H., Brown, E. V. (1948) J. Amer. chem. Soc. 70, 1287. Sullivan, N. P., Symmes, A. T., Miller, H. C., Rhodehamel, H. W. (1948) Science, 107, 169. Wayne, E. J., Colquhoun, J., Burke, J. (1949) Brit. med. J. ii, 1319. Wilson, W. M., Farquhar, J. W., Lewis, I. C. (1949) Lancet, ii, 866.
Repeated blood-pressure readings, usually at intervals of 6-8 minutes, are taken until the end of the operation, and any rise is countered by a further injection of the hypotensive drug, provided the operation is not within ten minutes of completion. In all the cases the pulse-rate increased and, though the radial pulse often could not be felt, the carotid pulse was always palpable. The state of the pulse and of the capillary circulation was kept under constant observation during the whole operation. Adequate oxygenation was maintained by aided respiration. As the skin is being sutured, the legs and pelvis are gradually brought up to the horizontal position, and a further blood-pressure’ reading is then taken; in the present series it always rose to 80-90 mm. Hg, and this was considered to be the optimal pressure with which the patient should leave the theatre. There was no need for hypertensive drugs, as was sometimes found necessary in a series of non-thoracic cases. The explanation of this seems to be that in thoracic cases the restoration of the blood-pressure to 80-90 mm. Hg is due to the cancellation of the effect of the down-tilt of the pelvis and legs, the latter effect not being possible when the Trendelenburg position has been used. The head-down tilt is next very slowly corrected, and after the application of dressings the patient is gently turned to the supine position and taken to the ward. It must be emphasised that the return of the operating-table to the horizontal position must be gradual to avoid any sudden rise in the blood-pressure ; and this is further ensured on the return of the patient to bed by adoption of the sitting position. This procedure is quite safe with the anaesthetic technique used, because the cough reflex returns before the patient leaves the theatre. When the patient has been propped up in bed, the blood-pressure is again measured ; if it has fallen below the last reading the foot of the bed is raised, and then the blood-pressure usually rises to the desired level of 80—90 mm. Hg systolic. Although the cough reflex has returned, it is essential to see that there is an adequate airway during the recovery period, and that oxygen is immediately available if there is any evidence of anoxia. A clear airway is of fundamental importance in the hypotensive state, and for this reason intubation is an absolute necessity when the technique described here is used. RESULTS
The method described above has been used in 80 3 pneumonectomies, 15 lobectomies, 42 thoracoplasties, and 20 pneumoplasties. In 74 a blood-pressure level of about 60 mm. Hg or less was maintained and the blood-loss was negligible. In the remaining 6 cases the blood-pressure could not be reduced below 90 mm. Hg systolic in spite of repeated injections of the drug, and oozing was much greater. Each of the four drugs-the bromides and iodides of pentamethonium and hexamethonium-was used in 20 cases. Hexamethonium was more constant than was pentamethonium in reducing the blood-pressure, the iodide being more consistent in its action than the bromide. A similar difference was not found- between the pentamethonium iodide and pentamethonium bromide. Comparison of the present series with similar case where the hypotensive technique was not adopted shows less postoperative vomiting. Smaller amounts of ana’acases :
151 thetic agents were required to keep the patients in superintendent, of the North Wales Sanatorium, Denbigh, for their cooperation and helpful suggestions. the desired plane of anaesthesia, and this probably was no their from there in explains why delay recovery REFERENCES anaesthesia. M. Arnold, P., Rosenheim, L. (1949) Lancet, ii, 321. The longest operation, a difficult extrapleural pneumoBurt, C. C., Graham, A. J. P. (1950) Brit. med. J. i, 455. three and a half hours. lasted the nectomy, Although Enderby, G. E. H. (1950) Lancet, i, 1145. optimal low blood-pressure was maintained throughout, the period of recovery did not differ from cases which THE MULTIPLE-PUNCTURE TUBERCULIN had taken a much shorter time ; hence it seems that TEST protracted hypotension has no deleterious effect. The patients were aged 18-40, and in this age-group FREDERICK HEAF any difference in response to the hypotensive drug was not related to age. Dosage was often related to the M.A., M.D. Camb., F.R.C.P. patient’s weight but depended much more on his sensi- DAVID DAVIES PROFESSOR OF TUBERCULOSIS, UNIVERSITY OF WALES tivity to the drug, and this sensitivity varied greatly in different cases. For this reason it is important to give a ONE of the disadvantages common to most methods test dose of only 20 mg., as emphasised above. In one of determining if a person is a non-reactor to tuberculin this test dose alone to the case proved adequate bring the of tuberculin tests that have to be made. is systolic pressure to the optimal 60 mm. Hg. In the present These number been have reduced to two, but even so it is series the largest total amount of hypotensive drug given to make visits to the clinic. If these necessary a an to single patient during operation was 300 mg. of tests are followed threeB.C.G. vaccination, many more by pentamethonium bromide. In 6 cases the response to visits are in the full programme for fact, necessary ; the hypotensive drug was unsatisfactory, the systolic B.C.G. as outlined in the Ministry of Health vaccination, pressure falling only to about 90-95 mm. Hg, and further Memorandum 32/B.C.G.jrevised, requires seven visits doses produced no response. It can therefore be assumed to the clinic. Most people find such a schedule very that, if no satisfactory response is obtained after 150 mg. and it is not improbable that some will refuse trying, has been given, the patient is not sufficiently sensitive to comply with it. If it is possible to determine tuberto the drugs at present available and should not be culin sensitivity by one test, considerable simplification subjected to further doses. of the routine can be effected. The multiple-puncture A blood drip is instituted in each case because in the tuberculin test has been devised with this object. So hypotensive state the loss of even a small quantity of far the results have been encouraging, and the simplicity blood may be dangerous, and by the use of a blood drip of the technique should make it useful in mass surveys. any blood-loss can be immediately replaced. The rate of the drip is kept as low as blood-loss necessitates ; otherAPPARATUS REQUIRED wise the added blood would tend to neutralise the effect The equipment required for the test is as follows : of the hypotensive drug. 1 platinum loop of 2 mm. diameter, 1 spirit lamp, -1 The postoperative rise of the blood-pressure is very gradual and takes 3-8 hours to reach its preoperative multiple-puncture apparatus, some spirit, cotton-wool, and 1 ml. of adrenalised pure Old Tuberculin. It is an level. This slow rise allows adequate time for the sealing of the minute blood-vessels, and this prevents reactionary advantage, but not a necessity, to have a small petri dish to obtain a shallow reservoir of spirit about 5 mm. haemorrhage and excessive postoperative oozing. deep for sterilising the needles of the multiple-puncture CONCLUSIONS apparatus. The- petri dish assures that the needles are not immersed too deeply in spirit and thereby collect The use of hypotensive drugs to produce an optimal low blood-pressure not only minimises blood-loss, thus too great a quantity of the fluid, which when ignited and makes it too diminishing the necessity for extensive blood-transfusion, heatstothe whole of the end apparatus use. This is avoided if the needles are dipped hot but also should shorten the operation by providing a clearer field and reducing time taken in obtaining hsemoonly to a depth of 5 mm. and then flamed. The multiple-puncture apparatus * provides an autostasis. In a case of pneumonectomy the clamp was7 inadvertently taken off the inferior pulmonary vein matic punch mechanism whereby six needles are released to puncture the skin evenly to a depth of 1 or 2 mm. before ligation, but no difficulty was encountered in controlling the haemorrhage, there being no sudden gush as desired. The needles are arranged in a circle of 6 mm. diameter. One set of needles remains sharp for about of blood from the venous stump. The battery of needles is easily 2500 punctures. In the past, one of the fundamental concepts of surgery, a reserve set while the first set is sharpened. for been the of thoracic has exchanged especially surgery, importance The apparatus is simply constructed and easy to use. of maintaining the blood-pressure, but this does not seem to hold with the use of the technique described here. The apparatus may be obtained from Messrs. Allen & Hanburys-, Shock seemed to be much less, compared with similar Wigmore Street, London, W.I. cases where the hypotensive technique was not used, possibly owing to the minimising of loss of blood and tissue .
,
fluid.
It is
problematical why a
smaller amount of anaesthetic
agent is required ; it may be due to lowered cellular metabolism
or
to
a
diminution in
nervous
reflex
irritability. This form of control of the circulation seems to be particularly suitable in thoracic surgery, because the diminution of respiratory movements reduces the venous return to the heart and aids the maintenance of hypotension. Further, the position of the patient that gives the best hypotensive effect is only a modification of the position in common use in thoracic surgery.
My thanks are due to Mr. J. Howell Hughes, surgeon to the thoracic unit, and Dr. J. H. Hawkins, physician-
Multiple-puncture apparatus.
VALUE OF HYPOTENSIVE DRUGS IN MINIMISING BLOOD-LOSS IN THORACIC SURGERY IVOR LEWIS M.R.C.S., D.A. LIVERPOOL UNITED HOSPITALS, REGIONAL HOSPITALS AND WALES SANATORIUM
ANÆSTHETIST,
(EASTERN GROUP),
LIVERPOOL
If this is not reached, a further dose of the drug is given, the amount depending on the response to the test dose, but this dose should not exceed 30 mg. If after two minutes it is found that the optimal hypotension has not been reached, further doses not exceeding 30 mg. each are given at two-minute intervals, until the desired bloodpressure has been reached. Once this has been reached, the pressure remains unaltered for 25-50 minutes.
NORTH
THE clinical effects of pentamethonium and hexamethonium bromides and iodides in lowering the bloodpressure (Arnold and Rosenheim 1949, Burt and Graham 1950) have led to their use in the treatment of hypertension and, combined with posture, to control hoemor-
rhage during surgical operations (Enderby 1950). Having observed the effects of these drugs combined with posture in general and aural surgery, I decided to try them in all types ofmajor thoracic operations done for pulmonary tuberculosis. Hitherto, despite the use of diathermy, blood-loss has been considerable in this field of surgery owing to oozing from stripped periosteum when several ribs are removed, from cut ends of pleural adhesions when lung is excised, and from minute vessels when extrapleural stripping is done. This type of bloodloss is negligible when the haemorrhage is controlled with these hypotensive drugs. TECHNIQUE
AND MANAGEMENT
The use of hypotensive drugs has not required any change in the usual premedication with morphine and atropine, or withOmnopon ’ and scopolamine given an hour before the operation. The blood-pressure is measured
,
before the induction of anaesthesia with d-tubocurarine chloride and thiopentone given through a combined intravenous needle and cannula (Ellis type), the dosage varying with the age and weight of the patient. Oral intubation with the largest cuffed tube that can be passed is done in all cases, and anaesthesia is maintained through a closed circuit (Waters) with nitrous oxide and oxygen (1:1) supplemented by intermittent doses of pethidine, thiopentone, and d-tubocurarine chloride as required. The patient is placed on the operating-table in the standard lateral position with a moderate down-tilt of the thorax and head and a considerable down-tilt of the pelvis and legs (the so-called jack-knife position) ; the stylet is removed from the Ellis needle and cannula, and a blood drip is instituted. The blood-pressure is then measured. The initial injection, which is a test dose, of the hypotensive drug is next given ; in the present series it has always been 20 mg. After three minutes the bloodpressure is again measured, to assess the effect of this test dose combined with posture.The optimal hypotension for these cases was deemed to be 55-65 mm. Hg systolic. MURRAY, DR. CRAWFORD: REFERENCES Bodger, W. P., Orritt, J. E., Israel, H. L., Flippin, H. F. (1948) Amer. J. med. Sci. 215, 250. Cohlan, S. Q., Lewis, J. M., Seligmann E. (1948) Amer. J. Dis. DR.
Child. 75, 15. Emery, J. L., Rose, L. M., Stewart, S. M., Wayne, E. J. (1949a) Brit. med. J. i, 1110. Stewart, S. M., Stone, D. G. H. (1949b) Ibid, p. 844. Fairbrother, R. W., Daber, K. S. (1950) Ibid, i, 1098. Fleming, A. (1944) Lancet, ii, 620. Herrell, W. E., Nichols, D. R., Heilman, F. R. (1947) Proc. Mayo —
Clin. 22, 567.
Hewitt, W. L.. Whittlesey, P., Keefer, C. S. (1948) New Engl. J. Med. 239, 286. Hoffman, W. S., Hofer, J. W., Gordon. H. (1948) J. Pediat. 32, 1. Levin, B., Neill, C. A. (1949) Arch. Dis. Childh. 24, 171. McDermott, W.. Bunn, P., Benoit, M., Du Bois, R., Reynolds, M. (1946) J. clin. Invest. 25, 190. Moseley, J. M. (1948) Arch. Dis. Childh. 23, 93. Salivar, C. J., Hedger, F. H., Brown, E. V. (1948) J. Amer. chem. Soc. 70, 1287. Sullivan, N. P., Symmes, A. T., Miller, H. C., Rhodehamel, H. W. (1948) Science, 107, 169. Wayne, E. J., Colquhoun, J., Burke, J. (1949) Brit. med. J. ii, 1319. Wilson, W. M., Farquhar, J. W., Lewis, I. C. (1949) Lancet, ii, 866.
Repeated blood-pressure readings, usually at intervals of 6-8 minutes, are taken until the end of the operation, and any rise is countered by a further injection of the hypotensive drug, provided the operation is not within ten minutes of completion. In all the cases the pulse-rate increased and, though the radial pulse often could not be felt, the carotid pulse was always palpable. The state of the pulse and of the capillary circulation was kept under constant observation during the whole operation. Adequate oxygenation was maintained by aided respiration. As the skin is being sutured, the legs and pelvis are gradually brought up to the horizontal position, and a further blood-pressure’ reading is then taken; in the present series it always rose to 80-90 mm. Hg, and this was considered to be the optimal pressure with which the patient should leave the theatre. There was no need for hypertensive drugs, as was sometimes found necessary in a series of non-thoracic cases. The explanation of this seems to be that in thoracic cases the restoration of the blood-pressure to 80-90 mm. Hg is due to the cancellation of the effect of the down-tilt of the pelvis and legs, the latter effect not being possible when the Trendelenburg position has been used. The head-down tilt is next very slowly corrected, and after the application of dressings the patient is gently turned to the supine position and taken to the ward. It must be emphasised that the return of the operating-table to the horizontal position must be gradual to avoid any sudden rise in the blood-pressure ; and this is further ensured on the return of the patient to bed by adoption of the sitting position. This procedure is quite safe with the anaesthetic technique used, because the cough reflex returns before the patient leaves the theatre. When the patient has been propped up in bed, the blood-pressure is again measured ; if it has fallen below the last reading the foot of the bed is raised, and then the blood-pressure usually rises to the desired level of 80—90 mm. Hg systolic. Although the cough reflex has returned, it is essential to see that there is an adequate airway during the recovery period, and that oxygen is immediately available if there is any evidence of anoxia. A clear airway is of fundamental importance in the hypotensive state, and for this reason intubation is an absolute necessity when the technique described here is used. RESULTS
The method described above has been used in 80 3 pneumonectomies, 15 lobectomies, 42 thoracoplasties, and 20 pneumoplasties. In 74 a blood-pressure level of about 60 mm. Hg or less was maintained and the blood-loss was negligible. In the remaining 6 cases the blood-pressure could not be reduced below 90 mm. Hg systolic in spite of repeated injections of the drug, and oozing was much greater. Each of the four drugs-the bromides and iodides of pentamethonium and hexamethonium-was used in 20 cases. Hexamethonium was more constant than was pentamethonium in reducing the blood-pressure, the iodide being more consistent in its action than the bromide. A similar difference was not found- between the pentamethonium iodide and pentamethonium bromide. Comparison of the present series with similar case where the hypotensive technique was not adopted shows less postoperative vomiting. Smaller amounts of ana’acases :
151 thetic agents were required to keep the patients in superintendent, of the North Wales Sanatorium, Denbigh, for their cooperation and helpful suggestions. the desired plane of anaesthesia, and this probably was no their from there in explains why delay recovery REFERENCES anaesthesia. M. Arnold, P., Rosenheim, L. (1949) Lancet, ii, 321. The longest operation, a difficult extrapleural pneumoBurt, C. C., Graham, A. J. P. (1950) Brit. med. J. i, 455. three and a half hours. lasted the nectomy, Although Enderby, G. E. H. (1950) Lancet, i, 1145. optimal low blood-pressure was maintained throughout, the period of recovery did not differ from cases which THE MULTIPLE-PUNCTURE TUBERCULIN had taken a much shorter time ; hence it seems that TEST protracted hypotension has no deleterious effect. The patients were aged 18-40, and in this age-group FREDERICK HEAF any difference in response to the hypotensive drug was not related to age. Dosage was often related to the M.A., M.D. Camb., F.R.C.P. patient’s weight but depended much more on his sensi- DAVID DAVIES PROFESSOR OF TUBERCULOSIS, UNIVERSITY OF WALES tivity to the drug, and this sensitivity varied greatly in different cases. For this reason it is important to give a ONE of the disadvantages common to most methods test dose of only 20 mg., as emphasised above. In one of determining if a person is a non-reactor to tuberculin this test dose alone to the case proved adequate bring the of tuberculin tests that have to be made. is systolic pressure to the optimal 60 mm. Hg. In the present These number been have reduced to two, but even so it is series the largest total amount of hypotensive drug given to make visits to the clinic. If these necessary a an to single patient during operation was 300 mg. of tests are followed threeB.C.G. vaccination, many more by pentamethonium bromide. In 6 cases the response to visits are in the full programme for fact, necessary ; the hypotensive drug was unsatisfactory, the systolic B.C.G. as outlined in the Ministry of Health vaccination, pressure falling only to about 90-95 mm. Hg, and further Memorandum 32/B.C.G.jrevised, requires seven visits doses produced no response. It can therefore be assumed to the clinic. Most people find such a schedule very that, if no satisfactory response is obtained after 150 mg. and it is not improbable that some will refuse trying, has been given, the patient is not sufficiently sensitive to comply with it. If it is possible to determine tuberto the drugs at present available and should not be culin sensitivity by one test, considerable simplification subjected to further doses. of the routine can be effected. The multiple-puncture A blood drip is instituted in each case because in the tuberculin test has been devised with this object. So hypotensive state the loss of even a small quantity of far the results have been encouraging, and the simplicity blood may be dangerous, and by the use of a blood drip of the technique should make it useful in mass surveys. any blood-loss can be immediately replaced. The rate of the drip is kept as low as blood-loss necessitates ; otherAPPARATUS REQUIRED wise the added blood would tend to neutralise the effect The equipment required for the test is as follows : of the hypotensive drug. 1 platinum loop of 2 mm. diameter, 1 spirit lamp, -1 The postoperative rise of the blood-pressure is very gradual and takes 3-8 hours to reach its preoperative multiple-puncture apparatus, some spirit, cotton-wool, and 1 ml. of adrenalised pure Old Tuberculin. It is an level. This slow rise allows adequate time for the sealing of the minute blood-vessels, and this prevents reactionary advantage, but not a necessity, to have a small petri dish to obtain a shallow reservoir of spirit about 5 mm. haemorrhage and excessive postoperative oozing. deep for sterilising the needles of the multiple-puncture CONCLUSIONS apparatus. The- petri dish assures that the needles are not immersed too deeply in spirit and thereby collect The use of hypotensive drugs to produce an optimal low blood-pressure not only minimises blood-loss, thus too great a quantity of the fluid, which when ignited and makes it too diminishing the necessity for extensive blood-transfusion, heatstothe whole of the end apparatus use. This is avoided if the needles are dipped hot but also should shorten the operation by providing a clearer field and reducing time taken in obtaining hsemoonly to a depth of 5 mm. and then flamed. The multiple-puncture apparatus * provides an autostasis. In a case of pneumonectomy the clamp was7 inadvertently taken off the inferior pulmonary vein matic punch mechanism whereby six needles are released to puncture the skin evenly to a depth of 1 or 2 mm. before ligation, but no difficulty was encountered in controlling the haemorrhage, there being no sudden gush as desired. The needles are arranged in a circle of 6 mm. diameter. One set of needles remains sharp for about of blood from the venous stump. The battery of needles is easily 2500 punctures. In the past, one of the fundamental concepts of surgery, a reserve set while the first set is sharpened. for been the of thoracic has exchanged especially surgery, importance The apparatus is simply constructed and easy to use. of maintaining the blood-pressure, but this does not seem to hold with the use of the technique described here. The apparatus may be obtained from Messrs. Allen & Hanburys-, Shock seemed to be much less, compared with similar Wigmore Street, London, W.I. cases where the hypotensive technique was not used, possibly owing to the minimising of loss of blood and tissue .
,
fluid.
It is
problematical why a
smaller amount of anaesthetic
agent is required ; it may be due to lowered cellular metabolism
or
to
a
diminution in
nervous
reflex
irritability. This form of control of the circulation seems to be particularly suitable in thoracic surgery, because the diminution of respiratory movements reduces the venous return to the heart and aids the maintenance of hypotension. Further, the position of the patient that gives the best hypotensive effect is only a modification of the position in common use in thoracic surgery.
My thanks are due to Mr. J. Howell Hughes, surgeon to the thoracic unit, and Dr. J. H. Hawkins, physician-
Multiple-puncture apparatus.