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ORIGINAL ARTICLE

Measurement of heparin in cardiac surgery with extracorporeal circulation

Fernando MoraesI; Helena NaderI; Carlos P DietrichI; Ênio BuffoloI

DOI: 10.1590/S0102-76381996000300010

ABSTRACT

In order to quantify seric levels of heparin, its attenuation as a time function and its residual value after neutralization with protamine sulfate, blood samples were collected, at pre-set intervals, from 27 patients undergoing myocardial revascularization surgery under extracorporeal circulation. After heparinization (400 Ul/Kg), blood samples were collected at 5, 10, 30 and 60 minutes and subsequently every 30 minutes depending upon the extracorporeal circulation lenght. At each hour after heparinization, a new heparin dose (200 Ul/Kg) was administered. The samples were kept at 4ºC prior to the heparin extract process, which was performed by physical/chemical method. The dosages showed that 5 minutes after heparinization the patients show maximal blood concentration of heparin and after 60 minutes it is aproximately 68% of the concentration at 5 minutes. At 90 minutes time, that is, after re-heparinization, the concentration of heparin is 96% of the one showed on the fifth minute and after the protamine sulfate neutralization (1.5:1), a residual value corresponding to 4% of the one initially observed is still found. It was observed that older patients have a tendency to keep longer seric heparin level, and heparin concentration at a given time could be estimated by the Equation Heparin - Concentration = 104.7 + (-12.85 x minutes (In) + 0.25 x age).

RESUMO

Com o objetivo de quantificar o nível sérico de heparina, sua atenuação em função do tempo e o valor residual após a neutralização com sulfato de protamina, foram coletadas amostras de sangue em tempos pré-estabelecidos em 27 pacientes submetidos a revascularização do miocárdio com circulação extracorpórea. Após a heparinização (400 Ul/kg) as amostras de sangue foram coletadas nos tempos de 5, 10,30 e 60 minutos e subseqüentemente a cada 30 minutos, dependendo do tempo da circulação extracorpórea. A cada hora, após a heparinização, administrava-se nova dose de heparina (200 Ul/kg). As amostras eram armazenadas à temperatura de 4ºC antes do processo de extração da heparina que foi realizado por métodos físico-químicos. As dosagens mostraram que 5 minutos após a heparinização os pacientes apresentaram concentração sangüínea máxima de heparina e, ao tempo de 60 minutos, a sua concentração é de aproximadamente 68% da encontrada aos 5 minutos. Ao tempo de 90 minutos, ou seja, após a reheparinização a concentração de heparina é 96% da evidenciada aos cinco minutos e, após a neutralização com sulfato de protamina (1,5:1), ainda se encontra um valor residual de heparina que corresponde a 4% do observado inicialmente. Observou-se que os pacientes mais idosos têm uma tendência a manter um nível sérico mais prolongado e através da equação (Cone. de heparina = 104,7 + (- 12,85 x minutos (In)) + 0,25 x idade) podemos estimar a concentração de heparina em determinado tempo.
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