Abstract
Congenital and acquired hemostatic disorders present during childhood. An accurate
diagnosis is critically important in order to implement optimal therapy. Over the
last century, several investigators have measured plasma concentrations of hemostatic
components in newborns and compared the results to adult values. Clinically significant
differences exist for many hemostatic components. Recently, three large studies in
more than 400 healthy children have provided reference ranges for hemostatic components
throughout childhood. Together, these studies provide insight into the regulation
of coagulation and fibrinolysis in children in physiologic and pathologic states.
Some examples of the influence of age on hemostasis are: (1) the diagnosis of some
congenital factor deficiencies, based on plasma levels, can be difficult due to physiologically
low values; (2) despite very low levels of many inhibitors of hemostasis, thrombotic
complications are rare; (3) the interaction of anticoagulants and thrombolytic agents
is profoundly influenced by the relative immaturity of hemostasis at birth; and (4)
in contrast to the risk of thrombosis, healthy infants are at risk for vitamin K deficiency
bleeding due to poor transport of vitamin K across the placenta and plasma concentrations
of the vitamin K dependent proteins of less than 50% of adults values. The following
review discusses the age dependency of hemostasis during childhood and the effect
of the physiologically immature system on the diagnosis and treatment of hemostatic
disorders.
Key words:
Newborn - hemostasis - pediatrics - developmental biology - clotting factors
