Fibrinolysis in newborns.

Abstract

SummaryThe fibrinolytic system was studied in 207 normal fullterm newborns during the first 5 days of life. A high, but rapidly decreasing plasminogen activator activity was found during the first 4 hours in umbilical vein blood in all of the children studied. The activity in the cord blood was lower and cannot be regarded as representative of the child. Fibrinolytic split products were demonstrated in large and rapidly decreasing amounts in serum samples without the addition of EACA but in at most small amounts in serum when EACA was added at sampling. These findings confirm the high plasminogen activator activity at birth which rapidly falls and furthermore show that there are no significant amounts of split products in vivo in the newborn. The plasminogen level was decreased in accordance with previous investigations. The high activator activity is counterbalanced by adequate inhibitory protection with an increase of the α2‐macroglobulin and inhibitors of plasminogen activation and the adult content of antiplasmin. The mean fibrinogen values in the first 48 hours of life are in the lower part of the normal range, but increase on the third day to a significantly higher level.