Maternal and fetal platelet activation in normal pregnancy.

OBJECTIVE: To study the platelet activation phase in normal pregnant women and their fetuses, both in vivo under basal conditions and in vitro after stimulation by adenosine diphosphate (ADP), a weak agonist, and U46619, a strong one. METHODS: Platelet function was investigated in 39 normal pregnant women and their fetuses undergoing fetal blood sampling at 18-37 weeks' gestation, using flow cytometry and the anti-GMP140 monoclonal antibody. This combined technique allows platelets to be investigated in small aliquots of whole blood, and it detects platelet secretion regardless of aggregation. In all cases, the percentage of activated platelets was determined under basal conditions and after addition of platelet agonists: ADP at concentrations of 10 and 50 mumol/L, and U46619, a stable analogue of thromboxane A2, at 1 mumol/L. RESULTS: Compared to nonpregnant controls, pregnant women had a significantly lower percentage of activated platelets after addition of U46619 (P = .02). Compared to their mothers, fetuses had significantly inferior platelet activation after addition of both platelet-activating factors at all concentrations used (ADP 10 mumol/L, P < .0001 and ADP 50 mumol/L, P < .0001; U46619, P < .0001). Maternal and fetal platelet activation did not change with duration of gestation. In the fetus, the percentage of activated platelets did not correlate with hematocrit, pH, or oxygen pressure, but it correlated significantly with platelet count after addition of U46619 (r = 0.45, P = .006). CONCLUSIONS: Decreased platelet activation in both pregnant women and fetuses suggests the action of a plasma factor that selectively inhibits prostaglandin-dependent activation. Prostacyclin, which is known to decrease platelet aggregation and release reactions caused by agonists, might have a greater inhibitory effect in the fetus than in the mother, or be present in larger amounts in the fetus.

Leukocyte depletion of red cell units at the bedside by transfusion through a new filter.

Standard packed red cell (PRC) units can be depleted of leukocytes and platelets if they are transfused through a blood administration set in which the usual 170-mu filter has been replaced by a leukocyte removal filter (Sepacell R-500). During a 6-month period, 1550 PRC units were transfused through this filter in 611 transfusions to 80 multitransfused patients with thalassemia who had had a patient reaction rate (PRR) of 63 percent and a transfusion reaction rate (TRR) of 13 percent when given standard PRC or buffy-coat-depleted PRC. When given filtered PRC, PRR and TRR became 3.7 percent and 0.5 percent, respectively. The effectiveness of the filter was also evaluated in vitro. By filtering 2 standard PRC units through the same filter, median values (and ranges) for red cell recovery and for residual leukocytes and platelets were 87 percent (83-92), 6.1 X 10(6) (0-100), and 2.7 X 10(9) (0.6-9.7), respectively. Although refinements are needed to improve standardization of the filter and to increase red cell recovery (which is low when 1 unit is filtered through one filter) and blood administration rate, the ability to provide leukocyte-free red cells prepared at the bedside for virtually all recipients appears to be a realistic goal.

Platelet activation in newborns detected by flow-cytometry.

Platelet function was investigated in full-term infants on the first, the fourth and tenth days of life and compared to normal adult controls. Platelet function was analyzed through a new cytofluorimetric technique with two murine monoclonal antibodies, PAC-1 and anti-GMP-140, directed against two membrane proteins expressed on the activated platelets' surface. The percentage of activated platelets detected with PAC-1 and anti-GMP-140 was evaluated at basal condition and after in vitro stimulation with a weak agonist (ADP) and a strong Txa2 analogue inducer (U 46619). At day 1 platelet activation at basal condition was negligible and similar to adult controls both with PAC-1 (1.2 vs 1.1%) and anti-GMP-140 (2.6 vs. 3.3%). On the contrary, after ADP stimulation the percentage of PAC-1-positive activated platelets was significantly reduced in neonates compared to adults (22 vs. 66%; p < 0.001) and even more after U 46619 (11 vs. 72%; p < 0.001). The percentage of anti-GMP-140-positive activated platelets behaved similarly after adding both ADP (26 vs. 46%; p < 0.01) and U 46619 (37 vs. 67%; p < 0.001). The reduced platelet activation after ADP and U 46619 persisted at day 4 both with PAC-1 and with anti-GMP-140. On the contrary, at day 10 newborn platelets analyzed with anti-GMP-140 behaved similarly to the adult ones both at basal condition and after stimulation with ADP or U 46619 (6 vs. 3% at basal state, 42 vs. 46% after ADP addition, and 55 vs. 67% after U 46619). These data demonstrate that the reduced platelet activation present in newborns is restored by the tenth day after birth.

The fibrinolytic system in the newborn: role of histidine-rich glycoprotein.

The fibrinolytic system controls fibrin deposition and its clearance. The efficacy of this system can be evaluated by plasminogen concentration determinations and by the behavior of factors such as histidine-rich glycoprotein (HRG) which controls plasminogen activation and alpha 2-antiplasmin which controls plasmin activity. Circulating plasminogen levels are decreased in the neonatal period. We studied factors affecting fibrinolysis in neonates and observed that an important reduction in HRG accompanied the reduced circulating plasminogen levels, with the result that 85% of circulating plasminogen was not bound to HRG and was thus free for binding to fibrin and for activation to plasmin. This condition is consistent with the increased fibrinolytic activity secondary to the "clotting activation' observed in the neonatal period particularly on the 1st day of life.

Hemostatic parameters and platelet activation by flow-cytometry in normal pregnancy: a longitudinal study.

Nineteen pregnant women with uncomplicated pregnancies were studied during the first, second, and third trimesters. We measured the following hemostatic parameters: prothrombin time, activated partial thromboplastin time, fibrinogen, antithrombin III, protein C, protein S, platelet number and volume. Platelet function was examined by a cytofluorimetric method, using an anti-GPM-140 antibody which is directed against a platelet alpha granule membrane protein. Activated platelets were expressed as a percentage of the GMP-140-positive platelets over total platelets. Fibrinogen levels showed a steady increase during pregnancy; conversely prothrombin time, activated partial thromboplastin time, protein C, and antithrombin III showed no significant modifications and remained within the reference range. There was a decrease of protein S activity throughout pregnancy, although protein S antigen did not follow this trend. The decrease occurred early in pregnancy and persisted during the second and third trimesters, reaching a stable plateau. We observed no platelet volume change or activation: the percentage of activated platelets was within the normal reference range, even in late pregnancy.

[Fetal hemolytic disease in a patient immunized by six antibodies: diagnosis and treatment]. / Malattia emolitica fetale in una paziente immunizzata da sei anticorpi: diagnosi e trattamento.

A case of severe haemolytic disease of the fetus due to six rare alloantibodies is described. In a pregnant women at 23 weeks gestation after the finding of a positive indirect Coombs test maternal antibodies have been precisely identified and titrated: anti-I: 1/23, anti-c: 1/64, anti-S: 1/16, anti-Fya: 1/128, anti-M: 1/64, anti-Jka: 1/32000. Fetal blood group, free and red blood cell adherent antibodies have been investigated on fetal blood samples obtained by means of cord centesis. A compatible donor has been found. Severe fetal anemia has been corrected by ultrasound guided intrauterine transfusions (one abdominal and two intravascular transfusions) with positive outcome of the pregnancy.

Platelet function and anesthetics in cardiac surgery: an in vitro and ex vivo study.

UNLABELLED: We studied the effects of the anesthetics commonly used in cardiac surgery on platelet function. Fentanyl, droperidol, succinylcholine, pancuronium, thiopental, and diazepam at therapeutic concentrations were tested for their in vitro effects on the expression of platelet membrane glycoproteins Ib and IIbIIIa (GpIb, GpIIb-IIIa) and of P-selectin in anticoagulated whole blood by flow cytometry. The expression of P-selectin was determined under basal conditions, after the incubation of blood with adenosine diphosphate (ADP) 10 micromol/L, and the stable prostaglandin endoperoxide analog U46619 1 micromol/L. No drug affected the expression of P-selectin in unstimulated and ADP- or U46619-stimulated platelets, with the exception of thiopental, which markedly decreased the U46619-induced expression of P-selectin. Thiopental concentration-dependently inhibited U46619-induced and ADP-induced platelet aggregation, with effects on U46619-induced aggregation at therapeutic concentrations. To assess ex vivo effects, the same platelet markers were also assessed in blood obtained from 10 patients undergoing elective coronary surgery. Compared with basal values, platelet response to U46619 was significantly reduced just after the administration of anesthetic drugs, and the effect persisted for 48 h after surgery. Our study suggests that, at therapeutic concentrations, thiopental inhibits U46619-induced platelet activation both in vitro and ex vivo. The mechanisms responsible of this effect, together with its clinical significance, require further investigation. IMPLICATIONS: Thiopental inhibited prostaglandin-induced platelet activation at therapeutic concentrations both in vitro and ex vivo in cardiac surgical patients whereas adenosine diphosphate-induced activation was affected only at supratherapeutic drug concentrations. Thus, administration of sodium thiopental may contribute to the in vivo impairment of platelet function in patients undergoing elective cardiac surgery.