Collagen/Endogenous Thrombin-Induced Platelet Aggregation in Cord versus Adult Whole Blood

Abstract

Background: In previous studies, neonatal platelets have been shown to be hypoaggregable to various agonists when compared with adult platelets. Objectives: It was the aim of this study to investigate the aggregability of neonatal versus adult platelets when the physiological relevant agonist collagen/endogenous thrombin is used. Methods and Results: Whole blood (WB) aggregation experiments employing the impedance method revealed the same responsiveness of neonatal and adult platelets to collagen/endogenous thrombin. Maximum aggregation (13.5 ± 3.2 vs. 13.6 ± 3.2 Ω; p = 0.94), slope (5.8 ± 1.8 vs. 6.2 ± 2.6 Ω/min; p = 0.79) and lag time until the onset of platelet aggregation (38.7 ± 8.9 vs. 42.6 ± 16.5 s; p = 0.59) were similar in cord and adult WB. However, the rise in serotonin plasma levels due to platelet activation was significantly lower in neonates versus adults (227.57 ± 57.65 vs. 473.34 ± 155.75 ng/ml; p = 0.0001). Furthermore, we found a fast capability of cord plasma to generate (the efficient platelet agonist) endogenous thrombin: thrombin generation started significantly earlier in cord compared with adult plasma (215 ± 19 vs. 247 ± 21 s; p = 0.01). Moreover, thrombelastometry revealed significantly shorter coagulation times in cord versus adult WB activated with collagen/endogenous thrombin (229.8 ± 12.5 vs. 256.3 ± 25.3 s; p = 0.003). Conclusions: The efficient platelet aggregation in cord WB provoked by collagen/endogenous thrombin might help to explain the clinically observed well-functioning primary hemostasis of neonates.

Effects of Nadroparin, Enoxaparin, and Unfractionated Heparin on Endogenous Formation of Factor Xa and IIa and on Thrombelastometry Profiles in Cord versus Adult Blood

“…Platelet counts were approximately the same, hematocrit and white blood cell count were higher in cord versus adult WB, as shown previously [22] .…”

Comparative evaluation of PAR1, GPIb-IX-V, and integrin αIIbβ3 levels in cord and adult platelets

“…Finally, there could be other patterns of platelet receptors as well as platelet binding proteins supporting hemostasis differently on newborn platelets than on adult platelets. Additionally different signal transduction pathways in newborn platelets may compensate for the observed impaired ones, such as reduced GTPase activity of G q coupled receptors and lower serotonin excretion upon collagen/endogenous thrombin stimulation (15,16).…”

Closure Times Measured by the Platelet Function Analyzer PFA-100® Are Longer in Neonatal Blood Compared to Cord Blood Samples

“…tor plus collagen [7] . In contrast to these in vitro studies, bleeding times in healthy term neonates have been shown to be shorter than in adults [8][9][10][11][12] .…”