Anticoagulant therapy by continuous heparinization in newborn and older infants.

In order to evaluate the metabolism and anticoagulant effect of heparin in the newborn infant and young child, 15 babies were monitored during continuous intravenous heparinization for documented large vessel thromboses. Infants with the most significant thromboses had the highest clearance rates for heparin. Plasma heparin levels in the therapeutic range (0.3 to 0.5 U/ml) and clinical resolution of the thrombi were associated with heparin doses of 16 to 35 U/kg/hour (mean = 27 U/kg/hour). A micro whole blood clotting time was evaluated and shown to be a useful guide to heparin effect in these infants. With the exception of excessive oozing from puncture sites in one infant, no complications of heparin therapy were noted. The newborn infant appears to require a larger amount of heparin than adults in order to achieve adequate heparinization.