Document karaoKvL2bG9zrQoKnMKBnDOE

ANCET \ whether .-pilcptic .1 ar irriti ,, due to .quently i inent by v ises was sulphate cnis during n table i; 5 ml. 1-4 depression fifty-eight s;emia arc isticallv in been arbiheir age. total and ntly lower seems to . the percantly dc! the ultratsc 1005: ignificantly jt't.v 6, 1968 ORIGINAL ARTICLES THE LAN M-atf &jJj Discussion We infer that hypcrexcitability of the nervous system can be associated with hypomagnestemia without con comitant hypocalctemia. This observation aecords with the findings of Vallee et al. (I960) but not with those of other workers (Hanna et al. 1960, Zimmet et al. 1968) tt ho have claimed that a low serum-calcium arising from the hypomagnesemia is necessary to produce the signs seen in the hypomagnesatmic syndrome. One should not conclude from this association that the hypomagnestemia caused the tremors or convulsions, although this seems likely in view of the fact that mag nesium levels returned to normal on recovery. Further more, (he dose of magnesium in six of the eases was not large enough u> cause drowsiness yet the tremors were quickly controlled. The cause ol the low serum-magnesium is unknown. Since some of the cases recovered spontaneously within a day or tsvo, it is possible, at least in some of the patients, (hat the hypomagnesemia was due to a transient shift of the mineral from the extracellular to the intracellular compartment. The feasibility of such shifts has been mentioned by Martin et al. (1952), and Hasselmart and Van Kampen (1958). It is possible that because of metabolic alterations in the neonatal period and in children who are ill, the magnesium homoeostatic mechanism might not be functioning efficiently. A decreased serum-magnesium could, in turn, stimulate the parathyroids to release parathormone in an attempt to conserve magnesium (MacIntyre et al. 1963). At the same lime the excess parathormone would raise blood-calcium, thus accounting lor the elevated ultrafiltrable calcium level. The combination of hvpomagnesremia and hyper calcemia is not incompatible with the production of hypcrexcitability of the nervous system. In magnesium- deprivation studies in rats, the animals demonstrate hyperirritability, hypomagnesemia, and hypercalcemia 'V hang and Welt 1963). Furthermore, there is evidence to suggest that calcium specifically facilitates the release uf acetylcholine by a nerve impulse (Fact 1959) and that the action of excess magnesium is to cause a block in neuromuscular transmission by decreasing the amount of transmitter substance released at nerve terminals ''del Castillo and Engback 1954). Hence a combination of hypomagnestemia and an elevated calcium concentra tion may act synergisticallv in facilitating acetylcholine release, thus accounting for the neuromuscular irri tability seen in our patients. This antagonistic action of magnesium and calcium at nerve-endings contrasts with their common action-in raising the threshold depolarisa tion for the initiation of an action potential in a nerve or muscle fibre (Fact 1959). Wc thjnk Prof. J. L. Gardiner for help in rhe preparation of the paper. REFERENCES del Castillo, J., Enjxbaek, L. <1954)7. Phynol., Loud. 124, 370. 1 jtt, !\ [ in } LmJhouk of Physiology, section i: Neurophysiology vol. I eJiteJ bv J. field ; p. 20S. Washington, blink, !:. B.. \LlVlliocr. R., Prasad, A. S., Mclby, J. C, Hoe, R. l\ (1957) Ann. intern. M, J 47. 956. Hanna, S., !Lirrton. M., MacIntyre, L, Eraser, R. - i960* f.uncet, ii, 172. Jid'st'rr.tn. J. J. I:., V.n Kamp.in. U. J. '195K) LVifi. ehitmea Acta, 3, 305. Math/vrc. 1 . Ih'-is. S . Trouehton, V. A. 1963' S'jturc, f.omi. 198, 1058. Martin. li. I;... MehK 1.. Wert man, .M. A/..L < .Y. Ant. 36, 1157. K. ,\.. M.<bv, B W. 1961 t chtmtij Aitu. 10, 144. u'l'.r, ' !'>! !>'<: i..ihor.itory Manual 'f Pediatric Micro* and I ,n:. .TeshniiiucN. New York. VMk,. (t |... w .ukvr. \M. I\. l! , IJllJKT. I>. 1). 19641, ,\Vni [\ng(. J. All'll. l5v 'i'ek, 1. t i., t 'jit el nun. H. J. I !96y) lUs. Mjv, p. 1. Whjr.c. K , Welt. L. <L <1963)7- clin. hnc*t. 42. "305. Xitnria '. IV, BrdKl .lt). JJ. |>., N'.tyler, \V. (*,. i Hr. mcJ.J. i, 622. AN ADVERSE EFFECT OF i POLYVINYLCHLORIDE TUBING USED IN EXTRACORPOREAL CIRCULATION Helen N.IDuke M.H., Ph.DNSUin. SENIOR LECTURER IN IM IY.SIOI.OG Y, MIDDLESEX HOSPITAL MEDICAL SCHOOL, LONDON' W. 1 J. R. Vane It.Sc. liirm., H.Sc., D.Bhil. Oxon. PROFESSOR OF' EXPERIMENTAL PHARMACOLOGY, INSTITUTE OF BASIC MF.UICAI. SCIENCES, ROYAL COLLEGE OF SURGEONS OF ENGLAND, LONDON W.C.2 Sttimnary The pulmonary vascular resistance is increased by ventilation hypoxia both in isolated perfused lungs from cats and in anaesthetised cats under conditions of circulatory control. This effect of hypoxia also occurs in man and dogjTihe pulmonary blood-vessels of isolated perfused cats'" lungs do not respond to hypoxia when the perfusion circuit is partly made from polyvinylchloride (e.v.c.) tubing./ Normal pulmonary vascular responses to noradrenaline, 5-hydroxytryptaminc, and prostaglandin FA-, are still obtainable when the response to hypoxia is abolished. It is suggested that a new British Standard should be devised to cover the acute effects produced by injection into the body of fluids which have been in contact with I'.v.c. tubing. Introduction Adverse effects have been shown to follow the use of polyvinylchloride (tw.c.) tubing in normal laboratory procedures. Stewart and Sturridge (1959) found, for instance, that some types of tubing caused haemolysis of the blood perfused through them. Meigler and Durrer (1959) and Meyler et al. (1960) found that isolated rats' hearts were killed within 15 minutes when perfused with fluid delivered through some types ofp.v.c. tubing, where as when the same fluid traversed glass tubing the isolated heart preparations survived many hours; they ascribed the toxicity to the presence of organic tin compounds in certain kinds of t'.v.c. tubing. Haberman et ai. (1968) described harmful effects of plastics and their component materials on reactions involving human and rabbit antibodies, guineapig complement, and serum-proteins. Few, if any, of the commonly used components of plastic tubing were without effect on their test systems. Bowery and Lewis (1968) found that substances were leached out of P.v.c. tubing which contracted guineapig isolated ileum and inhibited the contractions of the rat uterus induced by many substances. Considerable amounts of activity were added to plasma after 10 minutes' contact and these reached a maximum after 60 minutes. The leaching process occurred again and again each time fresh plasma was added. The amount of activity leached out was directly dependent on the protein concentration in the plasma, and this dependence was also demonstrated with purified bovine albumin solutions. Methods ^Isolated lungs of cats anaesthetised with chloralose (80 mg. per kg. intraperitoncallv.i were perfused by the method of Duke (1951k A Dulc-Shustcr pump was used to perfuse the lungs through the pulmonary artery nig. 1 The tvrlusiun was maintained at constant minute volume.............m:in:il s own heparinised blood (10 l.u. heparin pci mi.; at a tctupctaiurc of 37-39 c. The volume of blood in tile apparatus was approximately 120 ml. The venous outflow from the lungs was led through a left-atrial cannula into a venous reservoir which TOO9S0Z 'i I Po^a9- 22 JULY 6, 1968 OUIGINM. AKTICUS Till: l.ASOKT JL. l:ig. 1--l'crfusion circuit for isolated tunes. I* Dak-Shustcr pump. I'.K. venous reservoir. Single lines tubing containing blood. Double lines tubing containing air. Arrows show direction of air or blood How. p.a. pulmonary artery, L.A. left atrium. fed the pump, thus completing the external circuit. Pulmonary arterial pressure (PAp) was measured with a manometer and a tambour filled with 0-9",, sodium-chloride solution attached to a sidearm on the pulmonary-arterial inflow tubing. The lungs were ventilated with a Starling ` Ideal ' pump (6 cycles per minute), and an overflow valve ensured that the peak positive pressure remained constant at a predetermined value of between 6 and 12 cm. H.O in each experiment. The resis tance of the lungs to inflation was measured by the method of Konzctt and Roaster (1940). The time taken to set up the preparation was 4-8 minutes, but ventilation of the lungs was continued throughout collection of the blood from the carotid artery and cannulation of the pulmonary artery and left atrium. The pulmonary arterial pressure was 20-25 cm. H-O at the start of perfusion; this was achieved at a minute-inflow rate of 65 ml. or more per kg. body-weight. The glass parts of the apparatus were cleaned by boiling in chromic-acid solution, rinsed thoroughly, and dried in an oven. The rest of the extra corporeal circuit consisted of approximately 160 cm. of flexible tubing. When red-rubber or silicone-rubber tubing was used it was boiled in l-2",, sodium-bicarbonate solution before being thoroughly washed and oven dried. Results Since the lungs were perfused* at a constant minute rate of blood-flow and the left atrial and peak ventilating pressures were both fixed, the recorded changes in PAp were due to changes of pulmonary vascular resistance. The results of the experiments now reported confirmed others (see Duke and Lee 1963) in that ventilation of the lungs with nitrogen instead of air produced an increase of PAp. The PAp rapidly returned to normal when the lungs were ventilated with air. This increase of vascular resistance occurred in all 12 experiments in which redrubber or silicone-rubber tubing was used in the circuit. The pressor response could be elicited at intervals of 10-15 minutes for 5 or more hours. When r.v.c. tubing (10 or 12 h.f.., Portex Limited) was used as part of the perfusion circuit instead of rubber tubing, no pressor response lo anoxia could he demon strated (12 experiments). I'W ihese experiments new r.v.c. tubing, previously rinsed in 0-9sodium-chloride solution, was used. Washing the l'.v.c. tubing in a strong detergent (`Pyroncg', Divcrsey U.K, Ltd.) followed by thorough washing in distilled water and 0-9",, sodiumchloride solution did not enable anoxic pressor responses from the lungs to be shown. Pulmonary pressor responses to anoxia could only he regularly obtained when the l'.v.c. tubing had been boiled 2-3 times in chromic acid solution and thoroughly rinsed and dried. These experiments showed that the pressor response to anoxia could not he obtained when l'.v.c. tubing was used as part of the perfusion circuit. The effect of l'.v.c. tubing was also demonstrated in another way. In 12 experiments in which the extracorporeal circuit had been made with silicone or red-rubber tubing, the pulmonary pressor response to anoxia was demonstrated. Dilferent amounts and types of l'.v.c. tubing w ere cut into lengths of approximately 1 cm., washed in saline solution, and added to the venous reservoir. Similar results were obtained in all these experiments, one of which is shown in fig. 2. The pulmonary vasoconstrictor response to 5-hydroxy-tryptatninc (5-11.T.), noradrenaline, and anoxia is shown first. The addition of 30 cm. ill. tubing to the venous reservoir by itself changed neither the PAp, nor the resistance of lungs to air inflow, nor did it affect the response to 5-ii.t. or noradrenaline. However, the response to anoxia was completely absent. In other experiments the addition to the venous reservoir of longer lengths (60 cm.) of 10 lt.tt. l'.v.c. tubing caused by itself a rise of PAp and abolished the pulmonary pressor response to anoxia within 5 minutes. The rise in PAp induced by 5-H.T., noradrena line, and prostaglandin IT-, was unchanged when the response to anoxia was abolished. When the tubing was removed from the venous reservoir no recovery of the pressor response to anoxia took place within 30 minutes. Fig. 2--Experiment in cat weighing: 3 kp. Perfusion started 11.24 a.m. Blood-How 300 nil. per minute and ventilation with air. Records, from above down: PAp, signal, and time marker (30 seconds). Drugs injected into the pulmonary arterial tubing. A shows three effects: 1.09 r.M., 20 jxg. 5-hydroxytryptarmne (5-h.t.); 1.13 p.m., 20 jig. noradrenaline (n.a.); 1.20 p.m., ventilation with nitrogen (N5) instead of air during signal. At 1.28 r.M., 30 cm. 10 H.E. tubing (previously rinsed with saline solution) was added to venous reservoir. B shows three effects: 1.47 r.M., 20 gg.. 5-H.T.; 1.52 r.M., N,; 1.57 P.M., 20 ug. n.a. The l!k' t IW snl,p v frt repv. said In . pul n CXpO expe presfrom It' pLljl liulci a me in icons, of p1 ships pros in iv (i)ullQovastv press. im o; i ox\ von.:or iv. pres iii ti. res tlk onh venu. in m hypo cat-, and i Th pros' It iof p! unsu cxiniw trans; In wore I a cl u: The soya- N oct\! O a oak 2 a less Th & that cpov O Drue also > used quire. BFG04330 I MJLY 6, 1968 ORIGINAL ARTICLES THE LANCET 23 I '_______________ __________________________________________________________________________________________ I The pressor response to anoxia was also abolished when permitted weight changes when a plastic disc is immersed the p.v.c. (10 ile.) tubing added to the venous reservoir in distilled water for 48 hours. The tubing also con ^ had been previously boiled in 2",, sodium-bicarbonate forms with the rabbit implantation test laid down in solution. M1L-C-36145A (BuMcd.) Oct. 16, 1963. In addition, ' Some P.v.c. tubing contains different chemical additives the NT tubing complies with n.s. 2463 (specification for i from those in 10 ill. The experiments were therefore transfusion equipment) appendix F which uses a toxicity repeated using one ol these--N.T. 14 SH 80, which is test in mice injected with eluates from tubing heated at said to be more suitable lor perfusion work (Vincent 1968). 85 C for I hour. Mouse fibroblast and 10-day chickIn one experiment 60 cm. of this tubing abolished the embryo tests are performed by the factory. These tests pulmonary pressor response to anoxia, and in another of biocompatibility are designed to establish the safety experiment the pressor response was reduced. In both of P.v.c. either as a chronic implant or in a simple trans ' experiments there was a partial recovery of the anoxic fusion apparatus and may be completely unsuitable for pressor response 5 minutes after the tubing was withdrawn testing the potential toxicity of the large amounts of from the venous reservoir. plastic tubing used acutely in an extracorporeal circula Discussion tion. British Standard'2571 : 1963 allows a loss in weight in 48 hours of 20 mg. from a disc weighing about 4-4 g. In Hypoxia causes an almost immediate increase of uur apparatus, which might be regarded as a small-scale pulmonary arterial pressure in anatsthetised eats (von cardiac bypass circuit, 60-120 g. of p.v.c. tubing was used; liuler and Liljcstrand FUo, Logaras 1947) and also in anatsthetised cats with left-lung perfusion (Duke 1957). the British Standard would have allowed the leaching out of between 1 and 3 g. of material into the circuit, to , In isolated lungs from cats perfused with blood at a reach a concentration of 20 mg. per ml. (2'\,) in 48 hours. constant minute volume, hypoxia causes a similar increase Assuming steady leaching over 48 hours, the allowable of pulmonary vascular resistance with similar time relation concentration of material in the circulating blood could ships to that in the anatsthetised animal. The pulmonary attain at least 0-4 mg. per ml. in 1 hour. pressor response to hypoxia is not accompanied by changes Our results suggest that the toxicity of substances in bronchial resistance to airflow or left atrial pressure associated with the manufacture of p.v.c. tubing should be 1 (Duke 1951, see also Duke and Lee 1963, Daly and Hebb further investigated. They also suggest that a new 1966) and is therefore probably due to pulmonary British Standard should be devised to cover the use of vasoconstriction. In isolated perfused lungs from cats the such tubing in extracorporeal circulations. , pressor response to hypoxia of 3-15 minutes' duration is inversely related to the tension of oxygen in the ventilating Requests fur reprints should be addressed to J, R. V., Department of Pharmacology, Royal College of Surgeons, Lincoln's Inn Fields, ' gas mixture for gas mixtures containing less than 15",, London W'.C.d. oxygen in nitrogen; equivalent effects are produced by ventilation of isolated perfused lungs with neoti, hydrogen, REFERENCES Bowery, N. G., Lewis, C. 1*. (1968') Hr. J. 'Phurmac. (in the press). or nitrogen (Duke 1951). It appears therefore that the Ilaly, I. de B., Hebb, C. O. 0 966) Pulmonary and Bronchial Vascular pressor effect of ventilation hypoxia that has been studied Systems. London. Duke, H. N. (1951) Q. Jl exp. Physiol. 36, 75. ^ in the present series of experiments is a physiological -- (1957) J. Physiol., LonJ. 13S, 45. response in the cat, and rhac the response obtained when the gas mixture is changed from air to nitrogen varies -- Lee, G. de J. (1963.) Hr. tmd. Bid/. 19, 71. Haberman, H., Guess, VT. L., Rowan, D. Bowman, R. O., Bower, R. K. (1968) S.P.UJf, 24, 62. only in degree to the effects produced by changing the ventilating gas mixture from air to I5",, or less oxygen Konzett, H-, Rossler, R. (1940) Arch. exp. Path. Pharmak. 195, 71. Logaras, G. (1947) Acta physiol, scand. 14, 120. Mcigler, F. L., Durrcr, D. (1959) Vox. sang. 5, 239. in nitrogen. Evidence that pulmonary vasoconstriction to Meyler, F. L. Willebrands, A. F., Durrer, D. (1960) Circulation Res. 8, 44. hypoxia is found in man and other species as well as Srewari, J. \V., Sturridce, M. F. (1959) Lancet, i, 340. Vincent, W. VC\ (196K) Personal communication. cats was discussed by Duke and Lee (1963) and Daly von liuler, U. S., Liljcstrand, Cj. ` 1916) Acta physiol. scanJ. 12, 301. and Hebb (19oo). The present experiments show that the pulmonary pressor response to hypoxia is abolished by-p.v.c. tubing. It is therefore possible that procedures involving the use of plastic tubing in man may be attended by hithertounsuspecrcd harmful effects. Such procedures include extracorporeal circulation, renal dialysis, and even blood- OXIDIZED GLUTATHIONE LEVELS IN ERYTHROCYTES OF GLUCOSE-6-PHOSPHATE- DEHYDROGENASE-DEFICIENT SUBJECTS transfusion. In the present experiments two different types of tubes were used, both of which are listed in the current manu facturer's catalogues as of " surgical non-toxic quality The plasticiser was aceivl-tri-n-butyl citrate in epoxy soya-bean oil. The stabiliser in the h.e. tubing was of an octyltin type, whereas the stabiliser in NT 14 SH 80 was Satish K. Srivastava Ph.D. Lucknow RESEARCH SCIENTIST Ernest Beutler M.D. Chicago CHAIRMAN DIVISION OF MEDICINE, CITY tit HOPE MEDICAL CENTER, Dt'ARTE. CALIFORNIA 91010 a calcium-zinc compound. The latter type of tubing had a less harmful effect in our preparation. The manufacturers of the tubing stare (Vincent 1968) Oxidised glutathione (g.s.s.g.) was estiunintary ma[ccj jn normal erythrocytes and in that acctyl-tri-n-butvl citrate and small amounts of erythrocytes deficient in glucosc-6-phosphate dehydro epoxy soya-bean oil are listed under the US. Food and genase (g.-6-p.i>.) using an improved method in which the Drug regulations as suitable for food packaging, as is oxidation of glutathione was prevented by prior alkylation ako the calcium-zinc stabiliser. Both types of tubing with N'-ethyl-maleimidc. The content of g.s.s.g. in the used in the pre'sem experiments comply with the re erythrocytes deficient in G.-6-P.D. was about 3 times that quirements of r.s. 2571: 1963 which specifies maximum in normal erythrocytes. iI ( -S'.