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Ann Thorac Surg 2001;71:927-928
© 2001 The Society of Thoracic Surgeons
a Department of Anesthesiology, German Heart Center Munich, Lazarettstrasse 36, D-80636 Munich, Germany
e-mail: dietrich{at}dhu.mhu.de
Codispoti and colleagues described the use of individualized heparin and protamine management in pediatric patients undergoing cardiac surgery. The authors investigated 26 infants and children being operated for repair of congenital cardiac defects with the use of CPB. In half of the patients heparin management was guided by an individualized and integrated management of anticoagulation (Hepcon HMS), in the other 12 patients standard doses of heparin were applied. The heparin dosage was significantly higher in the study group (891 ± 108 vs 311 ± 5 U/kg) while the protamine dosage necessary for complete heparin antagonization could be dramatically reduced by individualized titration (2.9 ± 0.2 vs 8.6 ± 1.4 mg/kg). Patients in the control group received an extremely high dose of protamine. On the other hand, as stated, the ACT never fell below the limit of 480 seconds and heparin was only given when volume was added to the pump prime. The authors found a better preserved coagulation profile in the study group and reduced blood loss and allogeneic blood requirement. This finding was attributed to the individualized anticoagulation. The study confirms that the ACT shows a wide variability also in a young patient group. The message from this study is that the ACT is unreliable, high heparin levels attenuate thrombin formation more effectively than low levels, and precise protamine reversal can reduce the protamine dosage.
There is only limited information in the literature about heparinization in infant or pediatric cardiac surgical patients. Especially, data about heparin levels during cardiac surgery and their correlation to hemostatic activation are lacking for this patient group. Insofar, this manuscript provides interesting new aspects. Particularly, the hypothesis that extremely high dosages of heparin may result in better preserved coagulation profiles is provocative and stimulating, although in contrast to other opinions advocating preferably low heparin dosages during CPB.
The authors investigated pediatric patients with a mean age of 4.4 and 5.2 years, respectively. Only a few infant patients aged less than one year were studied. The hemostatic system has unique features only in neonates and small infants when compared to adults and children: many components of this system are diminished in the postnatal period. The ratio of pro- and anti-coagulatory factors is in favor of anticoagulation in newborns but not in children. For example, despite low antithrombin activity the prothrombotic activity is even more reduced in neonates. Newborns have been reported to be both resistant or excessively sensitive to heparin. However, the coagulation system is essentially complete after one year of age. Thus, from a hemostasiological standpoint, the present study investigated patients with a mature hemostatic system, comparable to adult patients. Insofar, the title of the article is somewhat misleading. The difference to adult patient lies in the smaller circulating blood volume, the higher degree of hemodilution, the type of surgery, and, possibly, in the different heparin metabolism. It would be of great interest to perform a study like the one of Codispoti and associates in an all infant population.
The study design has two independent variables: one is the management and control of anticoagulation during CPB and the other is heparin reversal by protamine. Since there were no measuring points prior to and after protamine administration, the study can not discriminate whether the differences in hemostatic activation were caused by the higher heparin levels or by the lower protamine dosage in the study group. It is well known that the heparin protamine complex acts as a strong activator of hemostasis. Thus, further studies should elucidate the different influence of heparin dosage and protamine on attenuation and activation of the hemostatis system.
The study raises very important questions about heparinization and hemostatic activation in young patients. However, due to the small sample size, and to the mixture of infants and children in the study population, these questions can hardly be answered form the present study. Clinical implications have to be interpreted with caution. This article underscores the importance of deeper insight into hemostasis and anticoagulation during CPB. Despite more than 40 years of clinical use of heparin for anticoagulation during CPB, many questions are still awaiting an answer.
Related Article
Ann. Thorac. Surg. 2001 71: 922-927.
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