Neonatal Hemostasis Research Articles

Judicious Transfusion of Platelets Among Neonates: A Systematic Review.

In newborns, especially premature babies, there is a high association between thrombocytopenia and bleeding, particularly intraventricular hemorrhage, which may be due to immaturity. It was usual clinical practice that neonates should be transfused with higher platelet counts than older children or adults to reduce their risk of bleeding. However, after keen observations, we noticed that bleeding and mortality were more common in newborns who received more platelet transfusions. The mechanisms underlying the adverse effects of platelet transfusions in neonates may be due to higher antigenicity and immunological factors. We know that neonatal platelets are hyporeactive; this hyporeactivity is balanced by factors in the neonatal blood that promote coagulation, such as increased hematocrit, von Willebrand factor, and fibrinogen, which, on balance, leads to normal primary neonatal hemostasis. Platelets are very similar to adults in number, but functional capabilities were less, and for the reasons mentioned above, particularly bleeding time was short. Theologically, neonatal platelet lifespan was high to compensate for less production. We started this review because we observed that many babies were not having bleeding symptoms in some instances of severe thrombocytopenia. Many well-active babies are receiving unnecessary transfusions, as human blood is precious, and many young neonatologists are going on protocol-based excessive transfusions. This stimulated us to write a review.

Short term outcome of neonatal venous thromboembolism in anticoagulated versus observed patients

BackgroundAdvancements in the medical field and increased survival of premature infants have led to a rise of venous thromboembolism (VTE) in neonates. Neonatal hemostasis exists in a delicate balance with a propensity towards pro-coagulation. Current recommendations include careful observation, therapeutic anti-coagulation and in some cases thrombolysis. We hypothesize that a sub-group of neonates may not require anti-coagulation and could be safely observed thus reducing their risk of bleeding complications. MethodsWe conducted a retrospective chart review of patients with VTE admitted to the neonatal intensive care unit at the Oklahoma University Children's Hospital from October 2009–October 2019. Patients were selected if they had an ICD-9 or ICD-10 code specific for a VTE or if screening with CPT codes for diagnostic imaging including echocardiogram, venous dopplers and computed topographic/magnetic resonance venogram revealed the word ‘thrombus’, ‘clot’ or ‘venous thromboembolism’. Data were collected about demographics, medical history, co-morbidities, thrombosis characteristics, treatment and outcome. ResultsA total of 211 patients were screened and 119 patients were eligible and included in the study. The majority of patients (85 %) had a central venous catheter (CVC) associated VTE. Two-thirds of patients (n = 81, 68 %) received therapeutic anti-coagulation while one-third (n = 38, 32 %) were observed. The group that received anticoagulation had a significantly older age at diagnosis and had a higher frequency of bacteremia, congenital heart disease and presence of symptoms. There was no difference in the odds of complete resolution between patients who were treated with therapeutic anti-coagulation and those that were observed (OR: 1.37, 95 % CI: 0.59–3.20, p-value: 0.47). Univariate analysis revealed maternal preeclampsia (OR: 0.2, 95 % CI: 0.05–0.82, p-value = 0.025), maternal history of chronic hypertension (OR: 0.17, 95 % CI: 0.04–0.68, p-value = 0.01), and presence of complete occlusion (OR = 0.37, 95 % CI: 0.15–0.91, p-value = 0.03) significantly reduced the odds of complete resolution. Furthermore, having a VTE related to a CVC in an extremity versus an ECMO cannula or cardiac catheterization significantly improved the odds of VTE resolution (OR = 5.94, 95 % CI: 1.30–27.20, p-value = 0.022). Using a stepwise regression model, maternal history of chronic hypertension remained significant for a reduced odds of VTE resolution (OR: 0.14, 95 % CI 0.025–0.73, p-value: 0.02). ConclusionsThe short-term outcome of neonatal VTE does not seem to differ between those that were anticoagulated and those that were observed with serial imaging.

Abstract 123: Hemostatic Fibrin Knob Triggered Microgel To Promote Clotting With Reduced Thrombotic Risks In Neonates

Introduction: Effective neonatal hemostatic therapies are vital for complex surgery-related life-threatening bleeding [1]. Neonatal hemostatic systems differ significantly from adults [2, 3]; however, current treatments for bleeding include adult blood products (ABP). Neonatal ABP use poses an elevated thrombotic risk [4, 5], necessitating alternative approaches. We propose hemostatic therapies leveraging age-dependent clotting differences. In adults, clot formation relies on fibrin(ogen) A:a knob-hole binding, while B:b binding dominates in neonates. Targeting B:b interactions with synthetic Bknob conjugated platelet-like particles (BK-PLP) could crosslink neonatal fibrinogen, catalyze clot formation, and enhance clot strength with lower thrombotic risk than ABP. To test this, we synthesized pNIPAm microgels and conjugated them to B-knob (AHRPYAAK), A-knob (GPRPFPAK), and non-binding control peptides (GPSPFPAK) to prepare BK-PLP, AK-PLP, and NB-PLP. Materials and Methods: We prepared BK-PLP, AK-PLP, and NB-PLP by conjugating microgels with mimetic peptides using EDC-Sulfo-NHS chemistry (Fig. 1A); Fibrin clot polymerization, stability, density, and stiffness, were analyzed via plate-based assays, confocal microscopy, and AFM. Results and Discussion: BK-PLPs significantly increased clot stability compared to AK-PLP, NB-PLP, or fibrin-only clots (Fig. 1B). Fiber density also increased with BK-PLPs, indicating a role in promoting denser fibrin clot structures (Fig. 1C). Clot mechanical properties assessment suggested that AKnob and NB-PLPs may disrupt clot networks, decreasing stiffness (Fig. 1D). Conclusion: Our study explored the effects of peptide conjugate particles on neonatal fibrin clots. BK-PLP incorporation increased clot stability, while AK-PLP and NB-PLP decreased clot stiffness, supporting further BK-PLP development for neonatal hemostasis.

Особенности неонатального гемостаза в норме и при патологии

Система гемостаза новорожденных детей отличается от взрослых. Значительные количественные и качественные различия факторов свертывания крови, особенности строения и функции тромбоцитов предопределяют свой, особый характер гемостаза. При этом в норме система сбалансирована и функционирует хорошо. При нарушениях свертываемости крови у врачей нередко возникают затруднения при интерпретации показателей гемостаза у новорожденных. Кроме того, при необходимости заместительная терапия проводится препаратами крови взрослых доноров, что имеет свои особенности. Статья посвящена обзору современных знаний по данной проблеме. The hemostatic system of newborn children differs from that of adults. Significant quantitative and qualitative differences in blood coagulation factors, structural features and function of platelets predetermine their own special nature of hemostasis. At the same time, the system is normally balanced and functions well. In cases of bleeding disorders, doctors often have difficulty interpreting hemostasis indicators in newborns. In addition, if necessary, replacement therapy is carried out with blood products from adult donors, which has its own characteristics. The article is devoted to a review of modern knowledge on this issue.

Hemostasis in Pre-Eclamptic Women and Their Offspring: Current Knowledge and Hemostasis Assessment with Viscoelastic Tests

Pre-eclampsia (PE) is a placenta-mediated disease and remains a major cause of maternal and neonatal mortality and morbidity. As PE develops, normal pregnancy’s hypercoagulable balance is disrupted, leading to platelet hyperactivation, excessive pathological hypercoagulability, and perturbed fibrinolysis. This narrative review aims to summarize the current knowledge regarding hemostasis in PE compared with healthy gestation and the potential effects of maternal PE on neonatal hemostasis. Finally, it aims to discuss hemostasis assessments for normal pregnancies and PE, emphasizing the role of viscoelastic tests, namely, thromboelastography (TEG) and thromboelastometry (ROTEM), for monitoring PE-associated hemostatic alterations. The use of TEG/ROTEM for assessing the hemostatic profile of PE women has been little considered, even though conventional coagulation tests (CCTs) have not helped to monitor hemostasis in this population. Compared with normal pregnancy, TEG/ROTEM in PE reveals an excessive hypercoagulability analogous with the severity of the disease, characterized by higher-stability fibrin clots. The TEG/ROTEM parameters can reflect PE severity and may be used for monitoring and as predictive markers for the disease.

The Hemostatic System in Newborns and the Risk of Neonatal Thrombosis.

Newborns are the most vulnerable patients for thrombosis development among all children, with critically ill and premature infants being in the highest risk group. The upward trend in the rate of neonatal thrombosis could be attributed to progress in the treatment of severe neonatal conditions and the increased survival in premature babies. There are physiological differences in the hemostatic system between neonates and adults. Neonates differ in concentrations and rate of synthesis of most coagulation factors, turnover rates, the ability to regulate thrombin and plasmin, and in greater variability compared to adults. Natural inhibitors of coagulation (protein C, protein S, antithrombin, heparin cofactor II) and vitamin K-dependent coagulation factors (factors II, VII, IX, X) are low, but factor VIII and von Willebrand factor are elevated. Newborns have decreased fibrinolytic activity. In the healthy neonate, the balance is maintained but appears more easily converted into thrombosis. Neonatal hemostasis has less buffer capacity, and almost 95% of thrombosis is provoked. Different triggering risk factors are responsible for thrombosis in neonates, but the most important risk factors for thrombosis are central catheters, fluid fluctuations, liver dysfunction, and septic and inflammatory conditions. Low-molecular-weight heparins are the agents of choice for anticoagulation.

Neonatal hemostasis and the use of thromboelastography/rotational thromboelastometry in the neonatal period.

Developmental hemostasis refers to age-related alterations related to the progressive maturation of the hemostatic system. Although the conventional coagulation tests, such as prothrombin time (PT) and activated partial thromboplastin time (aPTT), are indeed helpful in coagulation workup, they do not accurately delineate the hemostasis in vivo. The viscoelastic tests, namely thromboelastography (TEG) and rotational thromboelastometry (ROTEM), seem to reflect hemostasis more accurately since they measure various clot parameters without excluding the cellular coagulation components. TEG and ROTEM have shown redaction in blood product administration when used in therapeutic algorithms in older children and adults, but their use in neonates is limited. This review summarizes the current literature regarding using these tests in the neonatal population. Several studies tried to resolve the lack of neonatal reference values of the TEG/ROTEM parameters by publishing neonatal reference ranges for various gestational age groups. Moreover, few studies concerning therapeutic hypothermia, neonates undergoing surgery, and critically ill neonates have shown some predictive value of these tests regarding bleeding events. Even though their results seem promising, larger studies of higher quality are needed to clarify any discrepancies and point out whether these tests have significant predictive value. In conclusion, viscoelastic tests need to be increasingly part of the NICUs' clinical routine and should be used along with conventional coagulation tests in transfusion therapy.

Maternal and Neonatal Hemostasis.

Hemostasis is a dynamic process that begins at early stages of fetal development. The hemostatic system comprises procoagulant, natural anticoagulant, and fibrinolytic proteins that interact with each other, as well as with the endothelial wall and blood cells in a complex, yet balanced manner, aiming to avoid either bleeding or thrombosis. Pregnancy is a unique physiological state in which natural biologic alterations predispose both mothers and their offspring to higher risk of hypercoagulability and bleeding. This special issue of Seminars in Thrombosis and Hemostasis is dedicated to maternal and neonatal hemostasis.

Hemostasis in Neonates with Perinatal Hypoxia-Laboratory Approach: A Systematic Review.

Birth asphyxia, with an estimated prevalence of 1 to 6 per 1,000 live births, may lead to multiorgan dysfunction due to impaired oxygen and/or blood supply to various organ systems, including the hemostatic system. Coagulopathy, a common complication of perinatal asphyxia, has been described since the 1960s. The aim of this study was to systematically review the literature for records on the use of hemostasis tests in the evaluation of coagulation disorders, in neonates who had suffered from perinatal hypoxia or asphyxia. We identified published studies by searching PubMed and Scopus, up until April 2022. The literature search retrieved 37 articles fulfilling the inclusion criteria of the review. According to the bibliography, thrombocytopenia is commonly associated with perinatal hypoxia/asphyxia. The thrombocytopenia is usually described as mild and platelets return to normal levels by the 10th day of life. Additionally, hypoxic neonates usually present with a hypocoagulable profile, as reflected by the prolongation of standard coagulation tests, including prothrombin time, activated partial thromboplastin time, and international normalized ratio, findings commonly associated with disseminated intravascular coagulation, and by the reduction of the levels of the physiologic inhibition of coagulation system. A few studies thus far using ROTEM/TEG in hypoxic neonates have come to the same conclusion as well; hypoxic newborns seem to be characterized by a hypocoagulable profile compared with healthy neonates. It should be emphasized, however, that standard coagulation tests provide only a rough estimation of the true bleeding or thrombotic risk of hypoxic neonates. On the contrary, viscoelastic methods seem to be more precise in the early detection of hemostasis disorders in the neonatal population. However, until now, there was uncertainty as to the most appropriate coagulation assays for diagnosis and management of coagulation derangement in neonates with perinatal hypoxia indicating the need for further research on this field.

Primary hemostasis in fetal growth restricted neonates studied via PFA-100 in cord blood samples.

BackgroundPlatelet function of fetal growth restricted (FGR) neonates remains a field of debate. Platelet function analyzer (PFA-100) offers a quantitative in vitro assessment of primary, platelet-related hemostasis. Our aim was to examine platelet function using PFA-100 in FGR neonates and associate our results with perinatal parameters.MethodsPFA-100 was applied on 74 FGR neonates, 48 full-term (>37 weeks' gestation) and 26 preterm neonates (<37 weeks). The control group consisted of 118 healthy neonates. Two closure times (CTs) with COL/EPI and COL/ADP cartridges were determined on cord blood samples for each subject. Statistical analysis was performed by SAS 9.4. The statistical significance level was set at 0.05 and all tests were two-tailed.ResultsCOL/EPI CTs were prolonged in FGR (median 132 s, IQR 95–181 s) compared with control neonates (median 112.5 s, IQR 93–145 s), p = 0.04. Median COL/EPI CT for term and preterm FGR neonates was 126 s (IQR 90–157 s) and 137 s (IQR 104–203), respectively (p = 0.001), and COL/ADP CT was 70 s (IQR 62–80 s) for term and 75 s (IQR 68–82 s) for preterm FGR neonates (p = 0.08). Among FGR neonates, COL/EPI CT was related with delivery time (with preterm neonates exhibiting prolonged COL/EPI CTs), p = 0.05. No correlation was proved between both CTs and hematological parameters in FGR neonates.ConclusionFGR neonates showed impaired platelet function via PFA-100, with preterm FGR neonates confronting the greatest risk. Prolonged COL/EPI CTs in FGR neonates seemed to be independent of hematological parameters and could warn for closer evaluation during the first days of their lives.

Optimizing fresh-frozen plasma transfusion in surgical neonates through thromboelastography: a quality improvement study

Fresh frozen plasma (FFP) is largely misused in the neonatal setting. The aim of the study is to evaluate the impact of a Thromboelastography (TEG)-based Quality Improvement (QI) project on perioperative FFP use and neonatal outcomes. Retrospective pre-post implementation study in a level-III NICU including all neonates undergoing major non-cardiac surgery before (01–12/2017) and after (01–12/2019) the intervention. In 2018, the intervention included the following: (1) Training on TEG, (2) Implementation of TEG, and (3) Algorithm for TEG-directed FFP administration in surgical neonates. We compared pre- vs post-intervention patient characteristics, hemostasis, and clinical management. Linear and logistic regression models were used to evaluate the impact of the project on main outcomes. We analyzed 139 neonates (pre-intervention: 72/post-intervention: 67) with a mean (± SD) gestational age (GA) 34.9 (± 5) weeks and birthweight 2265 (± 980) grams which were exposed to 184 surgical procedures (pre-intervention: 91/post-intervention: 93). Baseline characteristics were similar between periods. In 2019, prothrombin time (PT) was longer (14.3 vs 13.2 s; p < 0.05) and fibrinogen was lower (229 vs 265 mg/dl; p < 0.05), if compared to 2017. In 2019, the intraoperative exposure to FFP decreased (31% vs 60%, p < 0.001), while the pre-operative FFP use did not change. The reduction of intraoperative FFP did not impact on mortality and morbidity. Intraoperative FFP use was lower in the post-intervention even after controlling for GA, American Society of Anesthesiologists score, PT, and fibrinogen (Odds ratio: 0.167; 95% CI: 0.070, 0.371). Conclusion: The TEG-based QI project for the management of FFP during neonatal surgery reduced intraoperative FFP exposure.What is Known:• PT and aPTT are poor predictors of bleeding risk in acquired neonatal coagulopathy, leading to likely unnecessary fresh frozen plasma (FFP) transfusion in the Neonatal Intensive Care Setting. • As neonatal hemostasis is a delicate balance between the concomitant reduction of pro- and anti-coagulants drivers, thromboelastography (TEG) is a promising alternative for coagulation monitoring.What is New:• The implementation of TEG, training, and shared protocols contributed to reduced intraoperative FFP use, which was not associated with increased mortality or bleeding events.• These findings inform future research showing that there is clinical equipoise to allow for larger studies to confirm the use of TEG in NICUs and to identify TEG cut-offs for transfusion practice.

The Effect of Platelets on Thrombin Generation in Cord Blood and Peripheral Neonatal Blood in the Premature Infant; The Event Study

IntroductionInfants born very preterm (<32 weeks) are at increased risk of haemorrhage, particularly intraventricular haemorrhage which can result in short and long term morbidity. Routine clinical laboratory tests such as the prothrombin time and activated partial thromboplastin time are frequently abnormal in this patient group but do not appear to correlate with clinical outcomes. Moreover, while reduced levels of circulating coagulation factors and platelet hypo-reactivity have been reported, plasma thrombin generation (TG), has been reported to be similar or even enhanced in very preterm infants when compared to term infants.Extracellular vesicles, comprising of lipid-bound nanoparticles released from cells (including platelets), may potentially play a role in modulating neonatal haemostasis. We aimed to characterize phospholipid (PL)-dependent plasma thrombin generation in platelet-rich (PRP) and platelet-poor plasma (PPP) in premature infants in both umbilical cord blood & peripheral neonatal blood using calibrated automated thrombography (CAT).MethodsIn this prospective observational study, PRP and PPP was prepared by centrifugation from citrated umbilical cord blood and peripheral neonatal blood collected from premature infants (24 - 31 weeks) and healthy term controls (>37 weeks). No samples were collected from heparinised lines. Parameters of plasma thrombin generation in PRP were assessed using CAT, with thrombin generation stimulated by tissue factor only (TF; final concentration 1pM). CAT was also repeated in PPP using only TF and no exogenous PL (rendering the assay dependent upon the endogenous PL content of plasma).ResultsIn the analysis of umbilical cord blood PRP, plasma thrombin generation was accelerated in the preterm infant group with a significantly shorter time to peak TG observed. The other parameters of TG were similar in both groups (Table 1).In the subset of infants from whom peripheral blood samples were available, there was further evidence of enhanced plasma TG in preterm PRP relative to term infants (Table 2). In this subgroup, the lag time and time to peak thrombin were significantly shorter in the preterm group and peak thrombin was significantly higher.TG was also assessed in both PPP and PRP prepared from umbilical cord blood samples in a subgroup of infants (n=10 term, n=6 preterm) using 1pM TF only, rendering the assay dependent on the phospholipid content of plasma. No difference was observed in any CAT parameters, suggesting that neonatal PPP phospholipid content (potentially from circulating extracellular vesicles) is sufficient to support thrombin generation in the absence of exogenous phospholipid.ConclusionThese preliminary data suggest that neonatal PRP, measured in both umbilical cord blood and peripheral neonatal blood, has similar thrombin generation or may even be hypercoagulable, compared with healthy term controls. Moreover, neonatal plasma phospholipid appears to support thrombin generation in the absence of exogenous phospholipid. This ongoing prospective study aims to further characterize the platelet-dependency of neonatal thrombin generation and evaluate the potential role of extracellular vesicles in neonatal haemostasis. [Display omitted] DisclosuresMaguire: Actelion: Research Funding; Bayer Pharma: Research Funding. Ni Ainle: Leo Pharma: Research Funding; Actelion: Research Funding; Daiichi-Sankyo: Research Funding; Bayer Pharma: Research Funding.

Evolution of Hemostasis in Neonates and Children

Children cannot be considered as miniature adults regarding to hemostatic balance. There is a great difference between neonatal, pediatric, and adult hemostatic systems. The concept of developmental hemostasis is now accepted on a wide range. It ensures accurate prevention, diagnosis, and treatment of thrombotic and hemorrhagic diseases in neonates and children. Developmental hemostasis could affect multiple physiological processes within the body other than hemostasis, such as angiogenesis, inflammation, and wound repair, as well as the interaction between different drugs and the coagulation system. “The Perinatal and Pediatric Hemostasis Subcommittee of the Scientific and Standardization Committee of the International Society on Thrombosis and Hemostasis (ISTH)” recommended for each laboratory to define reference ranges which are age-adjusted using its own technical conditions. Adding to that, accurate sampling techniques are mandatory for correct interpretation of laboratory results. New assays should be developed putting into consideration the fundamentals of developmental hemostasis.

A review of the role of extracellular vesicles in neonatal physiology and pathology.

Extracellular vesicles (EVs) are cell-derived membrane-bound particles, extensively investigated across many fields to improve the understanding of pathophysiological processes, as biomarkers of disease and as therapeutic targets for pharmacological intervention. We aim to describe the current knowledge of EVs detected in the body fluids of human neonates, both term and preterm, from birth to 4 weeks of age. To date, EVs have been described in several neonatal body fluids, including cerebrospinal fluid, umbilical cord blood, neonatal blood, tracheal aspirates and urine. These studies demonstrate some important roles of EVs in the neonatal population, particularly in haemostasis. Moreover, some studies have demonstrated the pathophysiological mechanisms and the identification of potential biomarkers of neonatal disease. We must continue to build on this knowledge, evaluating the role of EVs in neonatal pathology, particularly in prematurity and during the perinatal adaption period. Future studies should use larger numbers, robust EV characterisation techniques and always correlate the findings to clinical outcomes. IMPACT: This article summarises the current knowledge of the effect of EVs in neonates. It describes the potential compensatory role of EVs in neonatal haemostasis. It also describes the role of EVs as mediators of pathology and as potential biomarkers of perinatal and neonatal disease.

Is placental blood a reliable source for the evaluation of neonatal hemostasis at birth?

Phlebotomy is among the main determinants of anemia of prematurity. Blood sparing policies endorsed umbilical cord blood (here called placental) as an alternative source for laboratory testing. Little is known on the suitability of placental blood to evaluate neonatal hemostasis of newborn infants. We aimed to compare the hemostatic profile of paired placental and infant venous blood, by means of prothrombin time (PT), activated partial thromboplastin time (APTT), fibrinogen, antithrombin, protein C, thromboelastography (TEG) and thrombin generation assay (TGA). This was an observational single-center study. We collected at birth venous citrated blood from both placental and infant venous source and performed PT, APTT, fibrinogen, antithrombin, protein C, TEG (reaction time-R; kinetics-K alpha angle-α, maximum amplitude-MA and lysis at 30 minutes-LY30), and TGA (endogenous thrombin potential-ETP). We enrolled 60 neonates with a median gestational age (range) of 37 weeks (28+1 -41) and birth-weight 2417 g (950-4170). Based on TEG and TGA, placental blood showed a procoagulant imbalance as indicated by lower median R (4.0 vs. 6.1 min; p < 0.001) and K (1.3 vs. 2.2 min; p < 0.001); higher α-angle (69.7 vs. 57.4°; p < 0.001) and ETP (1260 vs. 1078; p = 0.002) than those observed for infant venous blood. PT and APTT did not differ significantly between the two groups. While placental and neonatal blood samples are equally suitable to measure the standard coagulation tests PT and APTT, placental blood leads to a procoagulant imbalance when testing is performed with TEG or TGA. These effects should be considered when interpreting results stemming from investigation of neonatal hemostasis.

New insights into neonatal coagulation: normal clot formation despite lower intra-clot thrombin levels

Healthy neonates exhibit no bleeding tendencies, but exhibit longer partial thromboplastin times than adults. Lower clotting factor levels may be balanced by lower inhibitor levels, which is not reflected in routine coagulation assays, but could result in normal clot formation in vivo. The novel thrombodynamics assay simulates a damaged vessel with tissue factor immobilized to a surface. We hypothesized that intra-clot thrombin levels and spatial fibrin clot formation with this assay are comparable in neonates and adults. Coagulation was tested in plasma from venous neonatal blood (N = 12), cord blood (N = 30), and adult blood (N = 20) using thrombodynamics and calibrated automated thrombography. Neonates exhibited a higher initial rate of clot formation than adults (adult: 60.7 ± 3.9 µm/min; neonatal: 66.8 ± 3.9 µm/min; cord: 68.1 ± 3.3 µm/min; P < 0.001) and a comparable stationary rate of clot formation (adult: 35.8 ± 8.5 µm/min; neonatal: 37.0 ± 4.6 µm/min; cord: 36.0 ± 5.2 µm/min; P = 0.834). Intra-clot thrombin levels were lower in neonates (adult: 41.9 ± 11.2 AU/l; neonatal: 22.6 ± 10.2 AU/l; cord: 23.6 ± 9.7 AU/l; P < 0.001), but the longitudinal rate of thrombin propagation was comparable (adult: 27.2 ± 4.2 µm/min neonatal; 27.9 ± 2.9 µm/min; cord: 27.6 ± 3.4 µm/min; P = 0.862). Despite lower intra-clot thrombin levels, neonates exhibit normal spatial fibrin clot growth, which concurs with clinically well-functioning hemostasis in healthy neonates.

Assessment of neonatal, cord, and adult platelet granule trafficking and secretion

Despite the transient hyporeactivity of neonatal platelets, full-term neonates do not display a bleeding tendency, suggesting potential compensatory mechanisms which allow for balanced and efficient neonatal hemostasis. This study aimed to utilize small-volume, whole blood platelet functional assays to assess the neonatal platelet response downstream of the hemostatic platelet agonists thrombin and adenosine diphosphate (ADP). Thrombin activates platelets via the protease-activated receptors (PARs) 1 and 4, whereas ADP signals via the receptors P2Y1 and P2Y12 as a positive feedback mediator of platelet activation. We observed that neonatal and cord blood-derived platelets exhibited diminished PAR1-mediated granule secretion and integrin activation relative to adult platelets, correlating to reduced PAR1 expression by neonatal platelets. PAR4-mediated granule secretion was blunted in neonatal platelets, correlating to lower PAR4 expression as compared to adult platelets, while PAR4 mediated GPIIb/IIIa activation was similar between neonatal and adult platelets. Under high shear stress, cord blood-derived platelets yielded similar thrombin generation rates but reduced phosphatidylserine expression as compared to adult platelets. Interestingly, we observed enhanced P2Y1/P2Y12-mediated dense granule trafficking in neonatal platelets relative to adults, although P2Y1/P2Y12 expression in neonatal, cord, and adult platelets were similar, suggesting that neonatal platelets may employ an ADP-mediated positive feedback loop as a potential compensatory mechanism for neonatal platelet hyporeactivity.

Thromboelastometry: studying hemostatic profile in small for gestational age neonates-a pilot observational study.

Scarce data exists about the hemostatic status of small for gestational age (SGA) neonates. We aimed at evaluating the hemostatic profile of SGA neonates, using thromboelastometry (TEM). This is an observational study performed in a Greek tertiary General Hospital during an 18-month period. Ninety-three neonates were included in the study: 48 appropriate for gestational age weight (AGA) neonates and 45 SGA neonates Extrinsically activated TEM (ex-TEM) parameters, such as clotting time, clot formation time, amplitude recorded at 5 and 10min, a angle, maximum clot firmness, lysis index at 60min, and also platelet count, were used for the evaluation of the hemostatic profile in all neonates. No statistically significant differences were noticed regarding all ex-TEM parameters between AGA and SGA neonates, while no event of hemorrhage or thrombosis was noticed in the study population.Conclusions: The coagulation system of SGA neonates seems to be fully functional, with no evident tendency toward coagulopathy or thrombosis, when compared with AGA neonates. TEM seems to provide a promising and valid assessment of coagulation and fibrinolysis systems and may be used as a valuable biomarker, in the future. Further studies, with large samples, are necessary to confirm our results. What is Known: • SGA neonates may present coagulation disorders mainly due to hepatic dysfunction, polycythemia, and thrombocytopenia owing to long-term intrauterine hypoxia. • In the literature, despite the statistically significant differences in laboratory results between SGA and AGA neonates, no clinical manifestations of significantly altered hemostasis were recorded. Data of TEM interpretation of hemostasis in SGA neonates are not available. What is New: • TEM seems to interpret coagulation mechanism of preterm and full-term SGA neonates and confirm previous relevant literature findings regarding hemostasis in these neonates.

Laboratory aspects of hemostasis in neonates

Newborns have high risks of thrombotic and hemorrhagic complications. Despite the fact that the overall frequency of thrombosis and bleeding in the general population of neonates is low, the risks of both thrombosis and hemorrhage are significantly increased when a newborn has some complications, including prematurity. The mechanisms underlying the onset of thrombotic and hemorrhagic complications in newborns are not fully understood and remain controversial. The hemostasis in newborns drastically differs from adult hemostasis and even from hemostasis in children older than a year. Nevertheless, despite the presence of quantitative and qualitative differences of almost all parameters of the hemostasis system from the parameters of adults, healthy newborns as a whole have clinically normal functional hemostasis without a tendency to coagulopathy or thrombosis. Apparently, the neonatal hemostasis system is in some alternative "balance", which differs from the "balance" of hemostasis in adults. The issue regarding the stability of this balance is still open. Due to the peculiarities of the newborn's hemostasis, clinical laboratory diagnostics of the coagulation disorders is very difficult, and the attending physician is forced to focus exclusively on the clinical picture. This review provides basic information on the neonatal hemostasis system, as well as an attempt to critically evaluate existing laboratory tests in terms of applicability for this group of patients.

In-vitro assessment of the effect of dabigatran on thrombosis of adult and neonatal plasma: comparisons using thromboelastography and microscopic visualization of fibrin clot structure.

: Thromboelastography (TEG) is a global assay used for evaluating features of clot formation in vitro. Dabigatran is a reversible direct inhibitor of thrombin that has not been studied in neonates using a sophisticated global assay, such as TEG. Neonatal hemostasis differs from adult hemostasis in both quantitative and qualitative characteristics. Our aim was to compare the TEG clotting profile of neonatal and adult platelet-poor plasma when exposed to different concentrations of dabigatran. We used commercially collected adult pooled plasma and neonatal cord blood collected from placentas of healthy full term newborns. Platelet-poor plasma was isolated, pooled, and frozen. Prior to experiment, plasma was thawed and filtered. A reaction mixture of CaCl2, corn trypsin inhibitor, tissue factor, and dabigatran in imidazole buffer was mixed with plasma in a TEG cup. Time to clot initiation (R-time), speed of clot strengthening (α-angle), and maximum clot strength (maximal amplitude) were measured. Scanning electron microscopy was performed to evaluate fibrin clot structure. Without dabigatran, there was no significant difference in TEG measurements between neonatal and adult samples. However, neonatal plasma clotting with dabigatran had slower onset, slower speed, and weaker clots that were more porous with thicker fibers, compared with adult plasma clotting. Thus, neonatal plasma may be more sensitive to dabigatran as assessed by our in-vitro TEG study.