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DETECTION OF SMALL AMOUNTS OF HEPARIN BY THE THROMBIN CLOTTING-TIME
376 health-but both deal with medical problems at base. The practitioner does not consider treating " poverty "-but those factors that eliminate poverty (or the ignorance that may accompany poverty) thereby help treat the avitaminoses or other diseases that may stem from poverty. Whether, as Dr. Szasz implies, alcoholism is a bad habit rather than a medically treatable disease, I hold open to question. The legalistic approach to controlling alcoholism has failed: let us take the hypothesis that it is amenable to medical control, and scientifically prove or disprove it. The existence of a biochemical lesion in the alcoholic is not beyond possibility, and may explain areas now un-
explained. More specifically, the judgment of the alcoholic may be sufficiently impaired that the illness may need to be descried by proxy for the individual, even as in some of the foregoing examples. And this may be so despite alcoholism being a bad habit, and even despite the alcoholic’s claim that he is in need of no medical attention, or despite the willingness of the alcoholic to accept the legal consequences devolving from his state of insobriety. I take it that alcoholism is a medical problem, and that a more viable, more sophisticated concept of illness and medical treatment is needed-the one proposed seems unduly rigid and restrictive. That institution of treatment should preferably be done with the informed consent of the recipient goes without saying. But circumstances are known where a guardian or proxy is the one who in fact is informed and gives the
consent.
3014 Hallowell
Court, Neshaminy Valley, Cornwells Heights, Pa. 19020, U.S.A.
PEACE PAUBIONSKY.
DETECTION OF SMALL AMOUNTS OF HEPARIN BY THE THROMBIN CLOTTING-TIME
SIR,-Kakkar et al. 1,stated that subcutaneous administration of 5000 units of heparin every 12 hours did not affect the thrombin clotting-time of citrated plasma, even in normal subjects. By a new assay method, however, based on inactivation of factor xa, they invariably detected heparin activity in plasma.2II This heparin assay, effected by 0-02 units of heparin per ml. of plasma, is therefore 1. 2.
Kakkar, V. V., Field, E. S., Nicolaides, A. N., Flute, P. T., Wessler, S., Yin, E. T. Lancet, 1971, ii, 669. Kakkar, V. V., Corriga, T., Spindler, J., Fossard, D. P., Flute, P. T., Crelin, R. Q., Wessler, S., Yin, E. T. ibid. July 15, 1972, p. 101.
recommended to control subcutaneous administration of small doses of heparin. As is evident from the accompanying figure, the thrombin clotting-time system3 used by Kakkar et al. is not sensitive to small amounts of heparin, mainly because of dilution of the test sample and the presence of calcium ions. In our laboratory, 0-2 ml. of fresh, platelet-poor, citrated plasma (centrifuged 1500 g for 30 min.) is clotted with 01 ml. bovine thrombin (3 N.I.H. units per ml.), giving control values of 20-22 sec. By this procedure, as little as 0-0030.01 units of heparin can be detected (see fig.). After subcutaneous administration of 5000 units of heparin to healthy subjects, the thrombin-time becomes greatly prolonged. For example, in one healthy subject the times were: Time (hours) Thrombin clotting-time (sec.) ....
0 20
>
2 180
4
110
6 29
It is very important to avoid liberation of anti-heparin activity from the platelets. Thus, if plasma cannot be tested shortly after centrifugation, the plasma should be rendered nearly platelet-free by high-speed centrifugation (20,000 g for 30 min.). Such high-speed-centrifuged plasma may be tested even after having been frozen. We find the thrombin clotting-time a simple and reliable way of detecting small amounts of heparin. As this test is even more sensitive than the rather complicated technique proposed by Kakkar et al., we recommend it for routine purposes. Hæmatological Research Laboratory, Ullevål Hospital, University Clinic, Oslo, Norway.
C. EIKA H. C. GODAL P. KIERULF.
EFFECT OF HEPARIN ON PLATELETS Sin,—The letters of Dr. Eika4 and of Dr. O’Brien and his co-workers (July 29, p. 233) emphasise the complex effect of heparin on platelet function. We have found that the primary aggregation induced by A.D.P. in physiological citrated (31 mg. per ml. trisodium citrate final concentration) platelet-rich plasma (P.R.P.) does not differ from that obtained in heparinised (10 units per ml. heparin final concentration) P.R.P.; but disaggregation was more often observed in citrated than in heparinised P.R.P., using rather low (final) concentrations of A.D.P. (10-s-10-’
M). The primary aggregation by adrenaline (5-10 Vg. per ml. final concentration) was also comparable in citrated and heparinised P.R.P.; the second wave of aggregation was not inhibited by heparin, and it seemed to be even potentiated on occasions. Phenol, at the concentrations used in most heparin preparations, did not influence any parameter of
aggregation. We do not think that the somewhat better aggregation observed in heparinised P.R.P. is due to a greater availability of calcium ions; indeed, by comparing the aggregation response in heparinised or citrated-heparinised P.R.P., no difference could be found; this would suggest a potentiating effect of heparin by itself. As pointed out by O’Brien et al., heparin is a highly charged molecule, which could well modify the platelet membrane and, consequently, some platelet functions. Bang et al.5 and Weiss and Rogershave reported that, whereas the response of platelets to A.D.P. in citrated P.R.P. from afibrinogensemic subjects was impaired, it was nearly normal in both heparinised and heparinised-citrated 3.
Influence of heparin on thrombin clotting-time, measured as Kakkar et al.1,2 (O—O) and as described in text (•—•).
by
R. M., Ingram, G. I. C. Bleeding Disorders; p. 285. Oxford, 1965. 4. Eika, C. Lancet, 1972, i, 1343. 5. Bang, N. U., Heidenreich, R. O., Matsuda, M. Thromb. Diath. hæmorrh. 1970, suppl. 42, p. 37. 6. Weiss, H. J., Rogers, J. New Engl. J. Med. 1971, 285, 369.
Hardisty,
explained. More specifically, the judgment of the alcoholic may be sufficiently impaired that the illness may need to be descried by proxy for the individual, even as in some of the foregoing examples. And this may be so despite alcoholism being a bad habit, and even despite the alcoholic’s claim that he is in need of no medical attention, or despite the willingness of the alcoholic to accept the legal consequences devolving from his state of insobriety. I take it that alcoholism is a medical problem, and that a more viable, more sophisticated concept of illness and medical treatment is needed-the one proposed seems unduly rigid and restrictive. That institution of treatment should preferably be done with the informed consent of the recipient goes without saying. But circumstances are known where a guardian or proxy is the one who in fact is informed and gives the
consent.
3014 Hallowell
Court, Neshaminy Valley, Cornwells Heights, Pa. 19020, U.S.A.
PEACE PAUBIONSKY.
DETECTION OF SMALL AMOUNTS OF HEPARIN BY THE THROMBIN CLOTTING-TIME
SIR,-Kakkar et al. 1,stated that subcutaneous administration of 5000 units of heparin every 12 hours did not affect the thrombin clotting-time of citrated plasma, even in normal subjects. By a new assay method, however, based on inactivation of factor xa, they invariably detected heparin activity in plasma.2II This heparin assay, effected by 0-02 units of heparin per ml. of plasma, is therefore 1. 2.
Kakkar, V. V., Field, E. S., Nicolaides, A. N., Flute, P. T., Wessler, S., Yin, E. T. Lancet, 1971, ii, 669. Kakkar, V. V., Corriga, T., Spindler, J., Fossard, D. P., Flute, P. T., Crelin, R. Q., Wessler, S., Yin, E. T. ibid. July 15, 1972, p. 101.
recommended to control subcutaneous administration of small doses of heparin. As is evident from the accompanying figure, the thrombin clotting-time system3 used by Kakkar et al. is not sensitive to small amounts of heparin, mainly because of dilution of the test sample and the presence of calcium ions. In our laboratory, 0-2 ml. of fresh, platelet-poor, citrated plasma (centrifuged 1500 g for 30 min.) is clotted with 01 ml. bovine thrombin (3 N.I.H. units per ml.), giving control values of 20-22 sec. By this procedure, as little as 0-0030.01 units of heparin can be detected (see fig.). After subcutaneous administration of 5000 units of heparin to healthy subjects, the thrombin-time becomes greatly prolonged. For example, in one healthy subject the times were: Time (hours) Thrombin clotting-time (sec.) ....
0 20
>
2 180
4
110
6 29
It is very important to avoid liberation of anti-heparin activity from the platelets. Thus, if plasma cannot be tested shortly after centrifugation, the plasma should be rendered nearly platelet-free by high-speed centrifugation (20,000 g for 30 min.). Such high-speed-centrifuged plasma may be tested even after having been frozen. We find the thrombin clotting-time a simple and reliable way of detecting small amounts of heparin. As this test is even more sensitive than the rather complicated technique proposed by Kakkar et al., we recommend it for routine purposes. Hæmatological Research Laboratory, Ullevål Hospital, University Clinic, Oslo, Norway.
C. EIKA H. C. GODAL P. KIERULF.
EFFECT OF HEPARIN ON PLATELETS Sin,—The letters of Dr. Eika4 and of Dr. O’Brien and his co-workers (July 29, p. 233) emphasise the complex effect of heparin on platelet function. We have found that the primary aggregation induced by A.D.P. in physiological citrated (31 mg. per ml. trisodium citrate final concentration) platelet-rich plasma (P.R.P.) does not differ from that obtained in heparinised (10 units per ml. heparin final concentration) P.R.P.; but disaggregation was more often observed in citrated than in heparinised P.R.P., using rather low (final) concentrations of A.D.P. (10-s-10-’
M). The primary aggregation by adrenaline (5-10 Vg. per ml. final concentration) was also comparable in citrated and heparinised P.R.P.; the second wave of aggregation was not inhibited by heparin, and it seemed to be even potentiated on occasions. Phenol, at the concentrations used in most heparin preparations, did not influence any parameter of
aggregation. We do not think that the somewhat better aggregation observed in heparinised P.R.P. is due to a greater availability of calcium ions; indeed, by comparing the aggregation response in heparinised or citrated-heparinised P.R.P., no difference could be found; this would suggest a potentiating effect of heparin by itself. As pointed out by O’Brien et al., heparin is a highly charged molecule, which could well modify the platelet membrane and, consequently, some platelet functions. Bang et al.5 and Weiss and Rogershave reported that, whereas the response of platelets to A.D.P. in citrated P.R.P. from afibrinogensemic subjects was impaired, it was nearly normal in both heparinised and heparinised-citrated 3.
Influence of heparin on thrombin clotting-time, measured as Kakkar et al.1,2 (O—O) and as described in text (•—•).
by
R. M., Ingram, G. I. C. Bleeding Disorders; p. 285. Oxford, 1965. 4. Eika, C. Lancet, 1972, i, 1343. 5. Bang, N. U., Heidenreich, R. O., Matsuda, M. Thromb. Diath. hæmorrh. 1970, suppl. 42, p. 37. 6. Weiss, H. J., Rogers, J. New Engl. J. Med. 1971, 285, 369.
Hardisty,