Collagen/endogenous thrombin-induced platelet aggregation in cord versus adult whole blood.

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 Omega; p = 0.94), slope (5.8 +/- 1.8 vs. 6.2 +/- 2.6 Omega/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.