Brazilian Journal of Anesthesiology
https://bjan-sba.org/article/doi/10.1590/S0034-70942010000400003
Brazilian Journal of Anesthesiology
Scientific Article

Efeito da hemodiluição normovolêmica aguda na coagulação sanguínea: comparação entre os testes colhidos de um modelo in vivo e de um modelo in vitro

Effects of acute normovolemic hemodilution on blood coagulation: comparison between tests of an in vivo and an in vitro model

Marco Aurélio Beloto de Souza; Jyrson Guilherme Klamt; Luís Vicente Garcia

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Resumo

JUSTIFICATIVA E OBJETIVOS: A hemodiluição normovolêmica produz resultados conflitantes na hemostasia, pois os trabalhos diferem quanto a tipo de líquido utilizado, profundidade da hemodiluição, método utilizado para avaliar a hemostasia e forma de se produzir hemodiluição. O efeito da hemodiluição na hemostasia pode depender da forma como ela é feita, se no modelo in vivo ou no modelo in vitro. O objetivo deste estudo foi avaliar e comparar a hemostasia em ambos os modelos, em dois diferentes graus de profundidade. MÉTODO: Treze pacientes foram submetidos à hemodiluição normovolêmica aguda e o hematócrito foi reduzido para 30% e 20%. A volemia foi mantida com lactato de Ringer. Foram colhidas amostras de sangue para avaliação da hemostasia nos momentos M1 antes da hemodiluição, M2 20 minutos após a obtenção do hematócrito de 30% e M3 20 minutos após a obtenção do hematócrito de 20%. Antes da hemodiluição, amostras de sangue foram colhidas para a realização da hemodiluição em um tubo de ensaio. Os graus de hemodiluição no tubo de ensaio (in vitro) foram os mesmos que os produzidos nos pacientes (in vivo). A hemostasia foi avaliada por meio dos tempos de protrombina, tromboplastina parcial ativado e de trombina e da quantificação do fibrinogênio. RESULTADOS: O comportamento dos testes que avaliaram a hemostasia foi idêntico nos dois modelos utilizados. Houve aumento do TP, do TTPA e do TT e diminuição da concentração de fibrinogênio. Quanto maior o grau de hemodiluição, maior o comprometimento da coagulação. CONCLUSÕES: O modelo in vitro pode substituir o modelo in vivo na avaliação da hemostasia durante hemodiluição normovolêmica aguda.

Palavras-chave

SANGUE, hemodiluição normovolêmica

Abstract

BACKGROUND AND OBJECTIVES: Normovolemic hemodilution produces conflicting results on hemostasis, since works differ according to the fluids used, degree of hemodilution, method used to evaluate hemostasis, and the way used to produce hemodilution. The effects of hemodilution on hemostasis can depend on how it is done and whether an in vivo or an in vitro model is used. The objective of this study was to evaluate and compare hemostasis in two different degrees of hemodilution in both models. METHODS: Thirteen patients underwent acute normovolemic hemodilution with a reduction in hematocrit to 30% and 20%. Volemia was maintained with Ringer's lactate. Blood samples for evaluation of hemostasis were collected at moments M1 before hemodilution, M2 20 minutes after obtaining a hematocrit of 30%, and M3 20 minutes after obtaining a hematocrit of 20%. Before hemodilution, blood samples were collected to perform hemodilution in a test tube. The degree of hemodilution in the test tube (in vitro) was the same as that produced in the patients (in vivo). Hemostasis was evaluated by the prothrombin time, partial activated thromboplastin time, and thrombin time, and by quantifying fibrinogen. RESULTS: The behavior of the tests that evaluated hemostasis was identical in both models. An increase in PT, aPTT, and TT, as well as a reduction in the concentration of fibrinogen was observed. The higher degree of hemodilution was associated with greater compromise of coagulation. CONCLUSIONS: The in vitro model can substitute the in vivo mode in the evaluation of hemostasis during acute normovolemic hemodilution.

Keywords

BLOOD, normovolemic hemodilution

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