Abnormal proteolysis in sick newborns.

87 newborn infants were studied on their first day of life for defects in the coagulation and fibrinolytic systems. The infants were divided into two diagnostic groups, one with IRDS, the other with mixed neonatal disorders. Factor V, fibrinogen and fibrin/fibrinogen degradation products (FDP) were abnormal more often than any of the other factors examined. The presence or absence of "multiple defects" appeared to depend on the severity of the illness and its ultimate course. Thus 28% of the surviving infants or 85% of those who died had "multiple defects". The pattern of abnormalities did not differ between the infants with IRDS and those with mixed disorders. The "multiple defects" are ascribed to the following mechanisms: (1) impaired synthesis due to vitamin K deficiency and/or liver damage, (2) abnormal proteolytic activity stimulated by tissue damage and causing (a) an activation of the coagulation process (b) activation of the fibrinolytic system, or (c) of both the coagulation and the fibrinolytic systems. Differentiation between these pathways to defective haemostasis are important when deciding upon therapeutic measures in addition to the basic treatment.