Developmental hemostasis in the neonatal period

Anticoagulant effects of protein C, protein S, and antithrombin levels on the protein C pathway in young children

The protein C (PC) pathway involves physiological anticoagulant factors (PC, protein S [PS], and factor V) and performs major anticoagulant functions in adults. Variations in overall PC pathway function due to dynamic changes in PC and PS in early childhood are poorly understood. We aimed to evaluate the contributions of PC pathway function during early childhood by measuring changes in plasma thrombin generation (TG) after administration of the PC activator protac. We evaluated correlations between anticoagulant factors and percentage of protac-induced coagulation inhibition (PiCi%). Before protac addition, TG in newborns (n = 35), infants (n = 42), young children (n = 35), and adults (n = 20) were 525 ± 74, 720 ± 96, 785 ± 53, and 802 ± 64 mOD/min, and PiCi% were 42.1 ± 9.9, 69.8 ± 11.0, 82.9 ± 4.4, and 86.9 ± 3.4%, respectively. The distribution of PiCi% on the two axes of TG (with or without protac) changed continuously with age and differed from that of warfarin-treated plasma and adult PC- or PS-deficient plasma. PiCi% increased dynamically during infancy and correlated with PS levels in newborns and PC levels in young children. Addition of PC or fresh frozen plasma equivalent to approximately 25% PC to PC-deficient plasma improved PiCi%. This automatic measurement requires only a small sample volume and is useful for analysis of developmental hemostasis.

The History of Extracorporeal Membrane Oxygenation and the Development of Extracorporeal Membrane Oxygenation Anticoagulation

Extracorporeal membrane oxygenation (ECMO) was first started for humans in early 1970s by Robert Bartlett. Since its inception, there have been numerous challenges with extracorporeal circulation, such as coagulation and platelet activation, followed by consumption of coagulation factors and platelets, and biocompatibility of tubing, pump, and oxygenator. Unfractionated heparin (heparin hereafter) has historically been the defacto anticoagulant until recently. Also, coagulation monitoring was mainly based on bedside activated clotting time and activated partial thromboplastin time. In the past 50 years, the technology of ECMO has advanced tremendously, and thus, the survival rate has improved significantly. The indication for ECMO has also expanded. Among these are clinical conditions such as postcardiopulmonary bypass, sepsis, ECMO cardiopulmonary resuscitation, and even severe coronavirus disease 2019 (COVID-19). Not surprisingly, the number of ECMO cases has increased according to the Extracorporeal Life Support Organization Registry and prolonged ECMO support has become more prevalent. It is not uncommon for patients with COVID-19 to be on ECMO support for more than 1 year until recovery or lung transplant. With that being said, complications of bleeding, thrombosis, clot formation in the circuit, and intravascular hemolysis still remain and continue to be major challenges. Here, several clinical ECMO experts, including the "Father of ECMO"-Dr. Robert Bartlett, describe the history and advances of ECMO.

Prevalence of hematologic complications on extracorporeal membranous oxygenation in critically ill pediatric patients: A systematic review and meta-analysis

OBJECTIVES

Despite advances in Extracorporeal Membranous Oxygenation (ECMO) equipment, hematologic complications remain significant in critically ill children. The aim of this study is to summarize prevalence of hematologic complications for children and neonates.

METHODS

MEDLINE, PubMed and Scopus databases were searched focusing on the period from January 01, 2017 to October 01, 2022. The population included critically ill children and neonates with hematologic complications. The review included all aspects of related complications including hemorrhage, thrombosis, and hemolysis. We performed random effects meta-analyses. The primary outcome measure was overall hematologic complications. Secondary outcomes are changes in the prevalence of hemorrhagic complications. Risk of bias of included studies was assessed using the Joanna Briggs Institute checklist.

RESULTS

The systematic search identified 37 studies totaling 10,659 critically ill pediatric patients receiving ECMO. The pooled prevalence of hemorrhagic complications, thrombotic complications and hemolysis among pediatric patients requiring ECMO was 43.7 % (95 % CI: 28.6 % to 58.9 %, P < 0.001), 27.6 % (95 % CI: 20.4 % to 34.8 %, P < 0.001), 34.3 % (95 % CI: 22.9 % to 45.7 %, P < 0.001). The prevalence of hemorrhagic complications was represented in descending order: surgical site (21.6 %, 95 % CI: 10.3 % to 32.9 %); cannulation site (20.6 %, 95 % CI: 11.8 % to 29.3 %); intracranial (12.2 %, 95 % CI: 9.5 % to 15.0 %); pulmonary (7.7 %, 95 % CI: 5.9 % to 9.6 %); gastrointestinal (6.0 %, 3.7 % to 8.4 %). For the assessment of thrombotic complications, thrombosis in cannulation site had a higher prevalence (28.5 %, 95 % CI: 22.1 % to 34.9 %), followed by DIC (13.5 %, 95 % CI: 8.7 % to 18.3 %) and intracranial thrombosis (4.5 %, 95 % CI: 1.4 % to 7.6 %). Predictors of increased prevalence of hemorrhagic complications included age (P = 0.017) and VV-ECMO support mode (P = 0.029).

CONCLUSIONS

Among critically ill pediatric patients, there was a series of hematologic complications can occur during ECMO support. Physicians should pay special attention to the management and establish appropriate treatment programs to reduce the occurrence of hematologic complications.

The Vascular Endothelium and Coagulation: Homeostasis, Disease, and Treatment, with a Focus on the Von Willebrand Factor and Factors VIII and V

The vascular endothelium has several important functions, including hemostasis. The homeostasis of hemostasis is based on a fine balance between procoagulant and anticoagulant proteins and between fibrinolytic and antifibrinolytic ones. Coagulopathies are characterized by a mutation-induced alteration of the function of certain coagulation factors or by a disturbed balance between the mechanisms responsible for regulating coagulation. Homeostatic therapies consist in replacement and nonreplacement treatments or in the administration of antifibrinolytic agents. Rebalancing products reestablish hemostasis by inhibiting natural anticoagulant pathways. These agents include monoclonal antibodies, such as concizumab and marstacimab, which target the tissue factor pathway inhibitor; interfering RNA therapies, such as fitusiran, which targets antithrombin III; and protease inhibitors, such as serpinPC, which targets active protein C. In cases of thrombophilia (deficiency of protein C, protein S, or factor V Leiden), treatment may consist in direct oral anticoagulants, replacement therapy (plasma or recombinant ADAMTS13) in cases of a congenital deficiency of ADAMTS13, or immunomodulators (prednisone) if the thrombophilia is autoimmune. Monoclonal-antibody-based anti-vWF immunotherapy (caplacizumab) is used in the context of severe thrombophilia, regardless of the cause of the disorder. In cases of disseminated intravascular coagulation, the treatment of choice consists in administration of antifibrinolytics, all-trans-retinoic acid, and recombinant soluble human thrombomodulin.