SummaryEvidence of developmental evolution of coagulation can be seen when the studies of 10 thriving extremely premature (EPT) infants are compared to normal full-term (FT) infants. The prothrombin time, partial thromboplastin time, and thrombin time all became shorter with increasing gestational age. Fibrinogen levels and platelet counts appear to be comparable to term infant and adult levels. Fibrin degradation products (FDP) of 10 pg/ml or less were found in the thriving EPT infants. When compared to healthy fullterm infants, there is a definite gestational dependency of antithrombin 111 levels. Factors 11 and VII appear to be related to intrauterine maturation after the age of viability (24 wk), but factor VII-X complex does not. The contact factors XI, XII, high molecular weight kininogen (Fitzgerald factor), and prekallikrein (Fletcher factor) are all markedly decreased in thriving EPT infants. The mean factor V level is lower than that found in FT infants. This study confirms a gestational age dependency of factor VIlI activity. The ratio of factor VIlI antigen to factor VIlI clotting activity is increased (2.8 vs 1.01 in FT and adults). Thriving small for gestational age (SGA) infants had coagulation studies which were not statistically different from those of thriving EPT infants. The coagulation changes which occurred in severely ill EPT were mainly in the factors which decrease during intravascular coagulation (factors I, V, and VIII). The present study suggests that because of the high antigen to activity ratio seen in thriving EPT infants, a dysfunctional or fetal factor VlIl may have been produced. However, the further elevation of this ratio in the severely ill EPT infants is in keeping with a pathologic proteolysis or increased endothelial release of factor VIII antigen.
SpeculationPrevention of and prompt therapeutic intervention for asphyxia, sepsis, hypovolemia, hypotension, hypothennia, hypoxia, and acidosis may prevent the occurrence of the coagulation changes seen in the severely ill EPT infants. A distinction between abnormal proteolysis versus production of dysfunctional proteins is essential before specific therapies can be designed.