Analysis of the structural and mechanical effects of procoagulant agents on neonatal fibrin networks following cardiopulmonary bypass

Abstract

To cite this article: Nellenbach K, Guzzetta NA, Brown AC. Analysis of the structural and mechanical effects of procoagulant agents on neonatal fibrin networks following cardiopulmonary bypass. J Thromb Haemost 2018; 16: 2159-67. Essentials• The standard of care (SOC) for treating neonatal bleeding is transfusion of adult blood products. • We compared neonatal clots formed with cryoprecipitate (SOC) to two procoagulant therapies. • The current SOC resulted in clots with increased stiffness and decreased fibrinolytic properties. • Procoagulant therapies may be a viable alternative to SOC treatment for neonatal bleeding.Summary. Background: Bleeding is a serious complication of neonates undergoing cardiopulmonary bypass (CPB) and associated with substantial morbidity and mortality. Bleeding is addressed through the transfusion of adult blood products, including platelets and cryoprecipitate. However, significant differences exist between neonatal and adult clotting components, specifically fibrinogen. Our recent ex vivo studies have shown that neonatal fibrinogen does not fully integrate with adult fibrinogen, leading to decreased susceptibility to fibrinolysis. These differences may contribute to ineffective clot formation and/or an increased risk of thrombosis. A need exists to identify more effective and safer methods to promote clotting in neonates. Objectives: Procoagulant agents, such as prothrombin complex concentrates (PCCs) and recombinant activated factor VII (rFVIIa), are being used off-label to treat excessive bleeding in neonates after CPB. Because these agents stimulate endogenous fibrin formation, we hypothesize that their addition to post-CPB neonatal plasma will better recapitulate native clot properties than cryoprecipitate. Methods: We analyze the structural, mechanical and degradation properties of fibrin matrices formed by neonatal plasma collected after CPB in the presence of an activated four-factor (F) PCC (FEIBA), rFVIIa, or cryoprecipitate using confocal microscopy, atomic force microscopy and a fluidics-based degradation assay. Results: The ex vivo addition of FEIBA and rFVIIa to post-CPB neonatal plasma resulted in enhanced clot networks with differences in fibrin alignment, mechanics and degradation properties. Conclusions: Our results suggest that these procoagulant agents could be used as an alternative to the transfusion of adult fibrinogen for the treatment of bleeding after CPB in neonates.

Clot Structure and Implications for Bleeding and Thrombosis

“…These structural characteristics in neonatal clotting were also associated with clot function, such as increased clot degradation post-CPB, and mechanical properties, such as decreased clot stiffness post-CPB. 15,16 These studies also revealed that clot structure of baseline neonatal clots differed significantly from adult clot properties. Neonatal clots were found to have more highly aligned fibers and more porous clot structures than adult clots.…”

“…Clinical outcomes associated with bleeding risks have been examined through direct clot structure analysis. 15 In recent studies using plasma samples collected from neonates younger than 30 days undergoing cardiopulmonary bypass (CPB), analysis of clot structure has provided new information regarding bleeding phenotypes often observed in these patients. The hemostatic system is immature for the first year of life and in neonates, bleeding is a critical issue especially after CPB.…”

“…Sample volume limitations and/or interest in analyzing the influence of pro-/anticoagulant agents with complex absorbance profiles, such as colloidal-based therapeutics, motivate the use of microscopy-based microfluidics techniques to analyze clot degradation. [15][16][17] In these studies, fluorescently labeled fibrin clots are formed in a microfluidics device. After polymerization, plasmin or other profibrinolytic agents are flowed by the clot boundary and migration of the clot boundary is measured over time to determine a degradation rate.…”

Comparison of Neonatal and Adult Fibrin Clot Properties between Porcine and Human Plasma

“…5,15,16 Also, our previous studies demonstrate that the ex vivo addition of procoagulant therapies to post-CPB plasma from human neonates enhances fibrin clot properties. [17][18][19][20] We hypothesize that the in vitro addition of these hemostatic therapies to neonatal porcine samples will similarly augment plasma fibrin clot properties. If confirmed, piglets could serve as a suitable and much needed preclinical model for evaluating neonatal specific hemostatic therapies.…”

Recombinant Activated Factor VII in Children Undergoing Cardiac Surgery: Remember How and Why to Use It

“…Assuming that thrombin generation is decreased significantly post-CPB (and that remains to be proven), 16 the effect of rFVIIa administration on thrombin generation, clot formation, and hemostasis at the local site of injury rather than systemically remains to be determined. Although data obtained from ex vivo studies suggest that rFVIIa and/or activated prothrombin complex concentrates can be used to augment thrombin generation 17 and enhance the neonatal fibrin network, 18 in vivo studies are urgently needed to understand the effect of those procoagulant agents on local and systemic clot formation. Assuming that rFVIIa effectively improves in vivo hemostasis, adequate concentrations of platelets and fibrinogen should be present before its administration is considered.…”