In vitro and in vivo evaluation of the comparative thrombogenicity of cellulose acetate hemodialyzers with radiolabeled platelets.

Platelet consumption and platelet kinetics during hemodialysis were quantified in Yorkshire pigs with In-111 labeled platelets. Six anesthetized pigs (20-25 kg) were hemodialyzed at 150 ml/min for 3 hr. All pigs were injected with autologous In-111 labeled platelets (300-420 microCi) 24 hr before dialysis and were systemically heparinized (ACT > 400 sec) before cannulation. Hemodialysis was instituted with a Drake-Willock hemodialysis machine and a hollow fiber dialyzer (Cobe4, 0.6 m2). In vitro sham dialysis was carried out at 150 ml/min for 3 hr with six more dialyzers in a flow-loop with the blood reservoir maintained at 37 degrees C. In vitro thrombogenicity over-estimates (10-fold) in vivo values. In both systems, platelet deposition on dialyzers reached a steady state, suggesting a constant rate of thrombus formation and embolization in the hollow fiber system. The relative thrombus distribution after 3 hr of dialysis was similar in both systems, with adherent thrombi in the entry and exit ports and highest numbers in the midsection of the hemodialyzer. Biodistribution after 3 hr of dialysis indicated that thrombosis of the hemodialyzer and arterial and venous traps as well as embolization reduced the platelet pool in the blood and increased platelet emboli in lung, brain, kidneys, and skeletal muscle, as measured by the In-111 labeled platelets.

Alkaline ribonuclease activity in maternal serum and in serum of newborns from birth up to thirty days of age. A study made with full-term appropriate-, full-term small- and preterm appropriate-for-gestational-age infants.

We have studied the alkaline ribonuclease (RNase) activity in maternal serum and serum of full-term small- (T-SGA), full-term appropriate- (T-AGA) and preterm appropriate-for-gestational age (PT-AGA) newborns. A significantly lower level of RNase was observed in T-AGA and T-SGA newborns on the 30th day of age and in PT-AGA newborns on the 15th and 30th days of age, as compared to other T-AGA, T-SGA and PT-AGA groups of infants at birth. RNase activity was significantly higher in cord blood than in the maternal blood in all categories studied. Moreover, in preterm newborns, RNase activity in cord blood was significantly higher in those presenting a lower gestational age. We did not observe any significant difference in RNase levels in the cord blood of newborns from the 3 categories studied. The same results were observed concerning maternal blood. We, therefore, conclude that RNase activity in cord blood or in maternal blood is not a very satisfactory indicator of fetal malnutrition.

Apgar score and blood coagulation factors.

Blood coagulation tests were performed in 93 newborn infants with different Apgar score at the 1st and 5th minutes of life. The laboratorial determinations were periodically performed at 0, 24 and 48 hours of life. The following tests were performed: bleeding time, whole blood clotting time, prothrombin time, kaolin-cephalin clotting time, thrombin time, dosage of factors I, V, VIII and X, clot retraction, platelet count, englobulin lysis time and the tourniquet test. Immediately after birth, the mean values of the blood coagulation factors were significantly different among the groups, with the exception of the whole blood clotting time and the platelet count. Those differences were due to the presence of the more depressed neonates. Although these results could indicate some degree of hepatic damage, it was apparent that an activation of the blood coagulation mechanisms took place, leading to a consumption coagulopathy. The infants who died (10) presented clinical and laboratorial data suggestive of disseminated intravascular coagulation (DIC). Necroscopic findings of microthrombosis in the liver and in the central nervous system were diagnosed in two infants.