Heparina de alto peso molecular. Uma alternativa nas operações com circulação extracorpórea: estudo experimental

Abstract

Introduction: In surgical procedures, with cardiopulmonary bypass, hemorrhagic syndromes during and after pump constitute a major concern and a great number of cases they are heparin-related, a substance still without substitute. Most authors point out the anticoagulant action of heparin as the main problem bleeding situations and research is developing on antifibrinolytic or platelet-like- drugs to try to substitute for usual heparin. Experience with low-molecular weight heparin, without anticoagulant properties, cardiopulmonary bypass, was disastrous. High dosage was accompanied by high tube drainage suggesting that postoperative bleeding does not happen just because of the anticoagulant effect of heparin. Material and Methods: Believing the vascular component of hemostasis and that low-molecular weight heparin non-neutralized by protamin is responsible for the paralysis of small vessels during and after cardiopulmonary bypass surgery, we isolated a high-molecular weight heparin ( modal weight of 25.000 Daltons) to be tested in vitro and in vivo. Results: Its specific anticoagulant activity, by mass, was superior to usual heparin ( modal weight of 15.000 Daltons) in vitro (273 ui/mg against 181 ui/mg, respectively) as in vivo, dogs, utilizing cardiopulmonary bypass and measuring its activity by activated clotting time, APTT and heparin blood levels. In the experimental laboratory the half-life of usual heparin was of 60 minutes, while for high-molecular weight heparin was above 90 minutes. Conclusion: We believe that this unprecedented experience will lead to its future use anima nobile to further test its neutralization by protamin as well as to confirm the decreased prevalence of bleeding phenomena with its use.