FIBRINOGEN TURNOVER IN THE PREMATURE INFANT WITH AND WITHOUT IDIOPATHIC RESPIRATORY DISTRESS SYNDROME

Summary Measurement of the elimination of small quantities of 125I-fibrinogen (5–15 μCi) demonstrates shortened half-life and higher catabolic rates in premature infants, and particularly in those infants suffering from IRDS compared with adults. Turnover in the adult is 15%, in the premature 25 % and in the premature with IRDS 33 % per day. Equilibrium between intravascular and extravascular fibrinogen is not achieved before the third day of life. Later, elimination is linear. There is a highly significant difference between 32rT-fibrinogen catabolism in the adult and the premature infant with and without the IRDS between the third and twelfth day. Measurement of activity over various organs demonstrates that slow efiux of 125I-fibrinogen into the extravascular compartment causes a continuous fall in plasma activity during the first 2–3 days. In premature infants with IRDS the activity over the lungs rises during the first day of life. These results allow the conclusion that accelerated fibrinogen synthesis in infants with IRDS compensates for losses into the hyaline membranes and intravascular clots and even allows the physiological rise in plasma fibrinogen level during the first three days to take place.