217 enzymes which play a part in active transport. Dichlorphenamide lowers intraocular pressure, probably by acting against carbonic anhydrase in the ciliary body as well as by its diuretic effect. Cytostatics also deserve consideration as agents directed

against the activity of cyst-wall epithelium. Polycystic disease of the kidneys usually

means a long and inconstant course, so assessment of the proposed therapeutic approach will be difficult. Unfortunately, we know of no animal model with which to study the effects of enzyme inhibitors and cytostatic drugs on the growth of kidney cysts.

Department of Urology, University of Zagreb, YU-41000, Zagreb, Yugoslavia

Severity of cicatricial R.L.F. in

two time

McGill

University-Montreal Children’s Hospital, Montreal, Quebec, Canada

TANIA R. GUNN JACOB V. ARANDA JOHN LITTLE

POSSIBLE ROLE FOR ENZYME INHIBITION IN CONTROLLING KIDNEY CYSTS

SIR,-Multiple cysts in patients with cystic disease of the kidney are usually associated with the destruction of functional parenchyma, and they can lead to renal insufficiency. Growth of cysts is a major hazard for surrounding parenchyma. Microscopy suggests that cysts enlarge mainly because of increased hydrostatic pressure. Active transport of solutes, and the resulting osmotic imbalance, might increase the pressure of fluid in the cavity against the tension of the cyst wall and surrounding structures. Enzyme inhibitors and cytostatic drugs as potential inhibitors of biological activity of the cyst wall might suppress growth. We have measured the hydrostatic pressure of cyst fluid in sixteen patients with multiple or solitary cystic lesions of the kidney. Pressure was determined by needle puncture in the lumbar region and measurement of the height of the fluid column. Pressures were on average 22 cm H2O (range 16-31). The pressure seemed greater in patients with multiple cysts than in those with solitary ones. There seemed to be no correlation between cyst volume and fluid pressure. The osmolarity of cystic fluid was 315-321 mosmol/1. Unusually high concentrations of urate, creatinine, and potassium in some fluids suggest active transport in the cyst wall. Such an active transport mechanism might be an inheritance of cystic-wall epithelium originating from parts of the nephron during cyst formation.’ Nevertheless we could not attribute the pressure of cyst fluid to its osmotic activity. One approach to suppression of cyst growth might be to decrease the active transport of cyst-wall epithelium and its "pumping" effect-for example, by inhibiting the activity of 1. Ostanondh, V., Potter, E. Archs Path.

1964, 77, 510.

LJUBOMIR CECUK

PULSATILE PUMPS FOR OPEN-HEART SURGERY

periods.

Surveillance of the results of intensive care and a search for additional factors leading to R.L.F. are possible, when all infants affected are recognised. In the time period studied increased survival of very small preterm infants did not seem to play a role in the greater incidence of R.L.F. However, in the last year of the study (1976) the survival-rate of such infants rose to 44%. Our findings strongly support the recommendation that, for all infants at risk of R.L.F., ophthalmological examination with indirect fundoscopy with or without scleral depression should be done both in the neonatal intensive-care unit and within three months of discharge.

DANIEL DEREŻIĆ

SIR,-Following recent meetings of the American, Scandinavian, and British Thoracic Surgeons and Extracorporeal

Technologists, it is apparent that there is considerable interest use of pulsatile pumps in open-heart surgery. This is a highly commendable development since the experimental and clinical evidence favouring pulsatile blood-flow over non-pulsain the

tile blood-flow is substantial. The many advantages of pulsatile flow include more uniform tissue perfusion, 1.2 more efficient use of energy,3 greater movement of tissue fluids and higher rates of tissue metabolism.5 These factors are probably responsible for lower peripheral vascular resistancehigher rates of oxygen use,’ improved kidney function,8 and better preservation of the brain9,lO and heart" during pulsatile perfusions than during non-pulsatile perfusions. These advantages can be obtained if the pump produces arterial pressure and flow waveforms similar to those produced by the natural heart. An accurate description of these waveforms requires harmonic analysis of records made with measuring systems which have linear highfrequency responses.12 Coupling the pressure transducer to the patient’s artery with a long catheter reduces the frequency response below that necessary to record the highest frequency components. Also, simultaneous recording of blood-flow is rarely possible, so that the ideal recording situation is difficult to achieve in human subjects. However, a normal range of values can be established very crudely by measuring the ejection phase, rise time, and peak values on the systemic arterial pressure and flow records.13 It is not known which of these features is responsible for the proven advantages of pulsatile flow. More accurate records can be obtained in laboratory animals or with a model circulation in vitro. If the measured values are used to define pulsatile flow, it can be seen that the modified roller pumps currently being offered as pulsatile pumps produce pressure and flow waveforms that are far from normal (fig. 1). We have measured the flow waveforms produced by the Stockert pulsatile pump and found that, compared with normal flow waveforms, the rise times are close to the normal range but their peak flow is very low and the ejec1. Nonoyama, A. Archs jap. Chir. 1960, 29, 1381. 2. Ogata, T., Ida, Y., Nonoyama, A., Sasaki, H. ibid. 59. 3. Shepard, R. B., Simpson, D. C., Sharp, J. F. Archs Surg. 1966, 93, 730. 4. McMaster, P. D., Parsons, R. J. J. exp. Med. 1938, 68, 377. 5. Trinkle, J. K., Helton, N. E., Wood, R. E., Bryant, L. R. J. thorac. cardio-

6.

vasc. Surg. 1969, 58, 562. Nakayama, K., Tamiya, T., Yamanoto, K., Izumi, T., Akimoto, S.,

zumi,

Hashi-

S., Iimori, T., Odaka, M., Yazawa, C. Surgery, St. Louis, 1963, 54,

694. 7. Shepard, R. B., Kirklin, J. W. J. thorac. cardiovasc. Surg. 1969, 58, 694. 8. Many, M., Soroff, H. S., Birtwell, W. C., Giron, F., Wise, H., Deterling, R. A. Archs Surg. 1967, 95, 762. 9. Sanderson, J. M., Wright, G., Sims, F. W. Thorax, 1972, 27, 275. 10. Wright, G., Sanderson, J. M. ibid. 1972, 27, 738. 11. Habal, S. M., Weiss, M. B., Spotnitz, H. M., Parodi, E. N., Wolff, M., Cannon, P. J., Hoffman, B. F., Malm, J. R. J. thorac. cardiovasc Surg. 1976,

72, 742. 12. McDonald, D. A., Blood Flow in Arteries; p. 162. London, 1974. 13. Sanderson, J. M., Morton, P. G., Tolloczko, T. S., Vennart, T., Med. Biol. Eng. 1973, 182.

Wright,

G.

218 Similar potentially confusing situations are liable to occur whenever engineering and scientific principles are ignored in the development of medical equipment. The proper procedure should be to draw up a list of priority needs before designing any equipment in accordance with fundamental design methods. The best solution is then sought and tested before production. This approach leads to the optimal solution and is far superior to the methods of modifying existing equipment to approach an ill-defined objective. W. E. Dunn Unit of Cardiology,

University of Keele, and North Staffordshire Stoke-on-Trent ST4 7JN

Royal Infirmary,

G. WRIGHT J. M. SANDERSON A. FURNESS

BETAMETHASONE-INDUCED LEUKÆMOID REACTION IN PRE-TERM INFANT

Fig.

I-In-vitro flow waveforms

generated by roller pumps com-

pared with the flow waveform in the The

mean

flow

rates were

Fig. 2-Normalised in Fig. 1.

aorta of a

3.8 I min-’ in all three

normal

dog.16

cases.

SIR,-The induction of fetal lung maturation by giving betamethasone to the mother is gaining acceptance in perinatal medicine. Because of its increasing use and questions regarding possible short and long term side-effects this drug is under close scrutiny. There is little evidence that the postnatal clinical course is altered by betamethasone, but we have seen a case of betamethasone-induced leukmmoid reaction in a premature infant. This female was born to a 21-year-old woman at approximately 30 weeks’ gestation with a weight of 880 g. The preg-

power spectra of the flow waveforms shown

....=aortic waveform 8=roIler pump pulsatile mode O=roller pump non-pulsatile mode

tion phase very prolonged under modal operating conditions with flow rates above 3.11 min-’. Harmonic analysis of the flow waveforms reveals that the high-frequency components are similar in the pulsatile and non-pulsatile modes and that they both carry much less energy than normal pulsatile flow in the dog aorta (fig. 2). The purely non-pulsatile component is much higher during pulsatile than during non-pulsatile operation of the pump (70-9 ml spulsatile; 58-4 ml s1 non-pulsatile ; 34-5 ml S-1 dog aorta). The shapes of the waveforms, are bizarre compared with the normal arterial waveforms, due to multiple roller revolutions in each pulse. Since it has not been demonstrated that the established advantages of pulsatile flow can be obtained with these bizarre waveforms, the pulsatile flow evidence should not be used to justify the use of modified roller pumps for extracorporeal circulation during open-heart surgery. Of course, modified roller pumps may have advantages of their own14,1S or it may be that the rise times on the waveforms are the only important features of pulsatile flow.

Serial W.B.C. counts.

nancy was uncomplicated except for recurrent tonsillitis. Leakage of amniotic fluid was noted approximately 72 h before delivery, but, because of possible amnionitis, no attempt was made to suppress labour. Spontaneous labour began 6 h before delivery. The mother was given betamethasone 12 mg 4 h before birth. Spontaneous vaginal delivery resulted in a depressed infant with Apgar scores of 1 and 5 who responded to resusci-

tation. 14. Moores, W.

Y., Gago, O., Morris, J. D., Peck, C. C. J. thorac. cardiovasc. Surg. 1977, 74, 73. 15. Taylor, K. M., Wright, G. S., Bain, W. H., Caves, P. K., Reid, J. S., Walker, M. S., McNab, W., Hutton, M. M. in Abstracts of the Annual Meeting of the Society of Thoracic and Cardiovascular Surgeons of Great Britain and Ireland; p. 26, 1977. 16. Noble, M I. M., Gabe, I. T., Guy, A. Cardiovasc. Res. 1967, 1, 9.

Pulsatile pumps for open-heart surgery.

217 enzymes which play a part in active transport. Dichlorphenamide lowers intraocular pressure, probably by acting against carbonic anhydrase in the...
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