Developmental hemostasis: recommendations for laboratories reporting pediatric samples

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.

Thrombophilia Screening: Not So Straightforward

Although inherited thrombophilias are lifelong risk factors for a first thrombotic episode, progression to thrombosis is multifactorial and not all individuals with inherited thrombophilia develop thrombosis in their lifetimes. Consequently, indiscriminate screening in patients with idiopathic thrombosis is not recommended, since presence of a thrombophilia does not necessarily predict recurrence or influence management, and testing should be selective. It follows that a decision to undertake laboratory detection of thrombophilia should be aligned with a concerted effort to identify any significant abnormalities, because it will inform patient management. Deficiencies of antithrombin and protein C are rare and usually determined using phenotypic assays assessing biological activities, whereas protein S deficiency (also rare) is commonly detected with antigenic assays for the free form of protein S since available activity assays are considered to lack specificity. In each case, no single phenotypic assay is capable of detecting every deficiency, because the various mutations express different molecular characteristics, rendering thrombophilia screening repertoires employing one assay per potential deficiency, of limited effectiveness. Activated protein C resistance (APCR) is more common than discrete deficiencies of antithrombin, protein C, and protein S and also often detected initially with phenotypic assays; however, some centres perform only genetic analysis for factor V Leiden, as this is responsible for most cases of hereditary APCR, accepting that acquired APCR and rare F5 mutations conferring APCR will go undetected if only factor V Leiden is evaluated. All phenotypic assays have interferences and limitations, which must be factored into decisions about if, and when, to test, and be given consideration in the laboratory during assay performance and interpretation. This review looks in detail at performance and limitations of routine phenotypic thrombophilia assays.

Contemporary tools for evaluation of hemostasis in neonates. Where are we and where are we headed?

The assessment of hemostatic disorders in neonates is crucial, but remains challenging for clinicians. Although the concept of developmental hemostasis is widely accepted among hemostasis specialists globally, it is probably under-recognized by clinicians and laboratory practitioners. In parallel with age-dependent hemostatic status maturation, comprehension of the differences between normal values is crucial for the accurate diagnosis of potential hemorrhagic and thrombotic disorders of the vulnerable neonatal population. This review outlines the basics of developmental hemostasis and the features of the available coagulation testing methods, with a focus on novel tools for evaluating the neonatal hemostatic profile. Common errors, issues, and pitfalls during the assessment of neonatal hemostasis are discussed, along with their impact on patient management. Current knowledge gaps and research areas are addressed. Further studying to improve our understanding of developmental hemostasis and its reflection on everyday clinical practice is warranted.

Thrombin, protein C, and protein S values in mother-infant dyads in the postpartum period

INTRODUCTION

The objective of the study was to establish the normal range for the levels of antithrombin (AT), protein C (PC), and protein S (PS) in the first week post birth in mother-infant pairings, adjusting for obstetric and perinatal factors, based on 2 different laboratory methods.

METHODS

Determinations were carried out in 83 healthy term neonates and their mothers, establishing 3 postpartum age groups: 1-2 days, 3 days, and 4-7 days.

RESULTS

There were no differences in the levels of any of the proteins between the different age groups in neonates or mothers in the first week post birth. The adjusted analysis found no association with obstetric or perinatal factors. The AT and PC levels were higher in mothers compared to infants (P < .001), while the PS levels were similar in both. Overall, the correlation of maternal and infant protein values was poor, except for the levels of free PS in the first 2 days after delivery. Although we found no differences based on which of the 2 laboratory methods was applied, the absolute values did differ.

Reference Intervals for Coagulation Parameters in Developmental Hemostasis from Infancy to Adolescence

Background: The objective of this study was to establish the age and sex-dependent reference intervals for coagulation assays evaluated in healthy children, ranging from 0 days to 16 years old. Methods: PT, aPTT, Fibrinogen (functional), Antithrombin activity, Protein C anticoagulant activity, Protein S free antigen, Thrombin time, D-Dimer, Von Willebrand Factor antigen, Lupus anticoagulant (screening), extrinsic and intrinsic pathway factors, and activated Protein C resistance were evaluated using STA-R Max². Results: A total of 1280 subjects (671 males and 609 females) were divided into five groups, according to their age: 0–15 days (n = 280, 174 M and 106 F), 15–30 days (n = 208, 101 M and 107 F), 1–6 months (n = 369, 178 M and 191 F), 6–12 months (n = 214, 110 M and 104 F), and 1–16 years (n = 209, 108 M and 101 F). The 95% reference intervals and the 90% CI were established using the Harrell–Davis bootstrap method and the bootstrap percentile method, respectively. Conclusions: The present study supports the concept that adult and pediatric subjects should be evaluated using different reference intervals, at least for some coagulation tests, to avoid misdiagnosis, which can potentially lead to serious consequences for patients and their families, and ultimately the healthcare system.

Developmental Hemostasis: The Evolution of our Coagulation System

Developmental hemostasis describes the evolution of the coagulation system from the neonatal period through adulthood. Neonates have lower levels of coagulation factors and elevated screening levels at birth. These levels can be influenced by various circumstances including gestational age, labor effects, and clinical status. The most commonly used screening tests for coagulopathy are the prothrombin time, partial thromboplastin time, and fibrinogen level. These values can be difficult to interpret as every laboratory has its own age-specific reference ranges. An understanding of developmental hemostasis is important when evaluating, diagnosing, and treating clinical manifestations, including vitamin K deficiency, surgical needs, infections, inherited thrombophilias, and inherited bleeding disorders. The mainstay of treatment for bleeding or hemorrhage is platelet and fresh frozen plasma transfusions. For the treatment of thrombosis, unfractionated heparin and low-molecular-weight heparin are the 2 most commonly used anticoagulants in the neonatal setting.

The use of thromboelastography (TEG) and rotational thromboelastometry (ROTEM) in neonates: a systematic review

"Developmental hemostasis" refers to the dynamic process of gradual hemostatic maturation. Conventional coagulation tests seem to fail to accurately depict the in vivo hemostasis, while viscoelastic tests, thromboelastography (TEG), and rotational thromboelastometry (ROTEM) appear very promising as they provide insight more rapidly and accurately into the hemostatic potential. We systematically reviewed the literature in PubMed to examine the use of TEG and ROTEM in neonates. Our search yielded 34 studies, of which 18 concerned healthy neonates and 16 sick neonates. These viscoelastic tests have shown accelerated initiation of coagulation, increased clot strength, and increased fibrinolysis in healthy neonates compared to children and adults. Cord blood leads to a hypercoagulable state as compared to whole blood when testing is performed with TEG. Pre-term neonates have a more hypocoagulable profile, but balanced hemostasis, related to term neonates, that evolves to a more procoagulant phenotype over the first month of life. Critically ill neonates exhibit a more hypocoagulable profile as compared to healthy neonates. TEG and ROTEM have shown predictive value for bleeding events in critically ill neonates and neonates undergoing cardiopulmonary bypass or therapeutic hypothermia.Conclusion: TEG and ROTEM need to become part of the standard coagulation assessment in clinical settings in which hemostatic abnormalities are involved, as they seem to provide more rapid and accurate information regarding the hemostatic profile of the neonates. Their predictive value for bleeding events in critically ill neonates could lead to a more targeted therapy optimizing utilization of blood products. What is Known: • Conventional coagulation tests seem to fail to accurately depict the in vivo hemostasis. • TEG and ROTEM delineate more rapidly and accurately the hemostatic potential. What is New: • TEG and ROTEM have shown predictive value for bleeding events. • TEG and ROTEM may lead to a more targeted transfusion therapy optimizing utilization of blood products.

Pediatric Thromboelastograph 6s and Laboratory Coagulation Reference Values

CONTEXT.—

Specific reference intervals (RIs) facilitate accurate interpretation of results. Coagulation assay results may vary by demographics and also between reagents and analyzers used. Current Thromboelastograph 6s (TEG 6s) Hemostasis Analyzer RIs were generated from adult samples.

OBJECTIVE.—

To generate reagent analyzer-specific pediatric RIs for TEG 6s and coagulation parameters.

DESIGN.—

A prospective, observational, single-center study of healthy children undergoing general anesthesia (January 3, 2017 to January 3, 2019). Venous blood samples were obtained for TEG 6s (Kaolin, Kaolin-Heparinase, Rapid and Functional Fibrinogen assays) and coagulation parameters (activated partial thromboplastin time, prothrombin time, thrombin clotting time, Echis time, antithrombin activity, and fibrinogen concentration using Instrumentation Laboratory ACL-TOP analyzers). Differences between activated partial thromboplastin time and prothrombin time reagents were investigated using mixed-effects regression, comparing maximum coefficients-of-variation with assay-specific allowable variation. RIs (lower/upper limits 2.5th of 97.5th percentiles) were generated using the following 2 methods: within discrete age-groups (neonates [<1 month], infants [1 month-1 year], young children [1-5 years], older children [6-10 years], and adolescents [11-16 years]), and modeled as functions of age and/or sex using quantile regression, including significant fractional polynomial and interaction terms.

RESULTS.—

Variation between prothrombin time and activated partial thromboplastin time assays using different reagents was clinically significant. Reagent-analyzer specific pediatric RIs were generated using data from 254 children. Discrete and model-based RIs varied by age for all coagulation parameters and TEG 6s variables in all assays.

CONCLUSIONS.—

We report reagent-analyzer specific pediatric RIs for TEG 6s and coagulation parameters. Observed variation reinforces recommendations for laboratory-specific RIs. These findings improve accuracy of interpretation of clinical results, provide a foundation for comparison and validation of tests in pathology and illustrate feasibility and advantages of model-based RI approaches.

Hot topics in coagulation testing: Important considerations for testing children for bleeding/thrombotic disorders

The accurate use and interpretation of diagnostic investigations are essential for safe and effective patient care. Appropriate application and interpretation of coagulation testing can be challenging, and many controversies exist relating to the standardization of testing procedures, the application of relevant tests to different patient populations and the interpretation of test results. We present a list of the most prominent controversies in coagulation testing and have selected three specific examples (age-appropriate reference ranges, therapeutic anticoagulation monitoring and tests of thrombin generation) for closer discussion, highlighting examples with a paediatric framework. We discuss the limitations of discrete age-partitioned reference intervals, given the established principle of developmental haemostasis; the difficulties in establishing normative data across different laboratories; important pre-analytical variables affecting coagulation testing; the challenges in interpreting APTT and anti-Xa assays for monitoring unfractionated heparin therapy in different clinical situations; and the limitations in interpreting tests of thrombin generation due to current available thrombin-specific substrates and the complicating factor of variable alpha2-macroglobulin levels. These controversies are demonstrated using paediatric examples, but raise important implications for coagulation testing in patients of all ages and highlight the pressing need for further research in these areas.

Recommendations for clinical laboratory testing for protein S deficiency: Communication from the SSC committee plasma coagulation inhibitors of the ISTH

Hereditary deficiencies of protein S (PS) increase the risk of venous thrombosis; however, assessing the plasma levels of PS can be difficult because of its complex physiological interactions in plasma, sample-related preanalytical variables, and numerous acquired disease processes. Reliable laboratory assays are essential for accurate evaluation of PS when diagnosing a congenital deficiency based on the plasma phenotype alone. This report presents the current evidence-based recommendations for clinical PS assays as well as when to test for PS abnormalities.

Coagulation standards in healthy newborns and infants

BACKGROUND

The range of normal values for coagulation factors in the healthy newborn was described 30 years ago but since then the reagents, automated systems, and dosing techniques have changed considerably. For 30 years, several authors have tried to update the standards and references in children using updated reagents but the newborn and infant population in these studies has been quite small, limiting the findings. The aim of this study was to establish the normal coagulation standards in healthy newborns.

METHODS

We included all consecutive healthy newborns with pyloric stenosis presenting to our reference center over a period of 5 years. We calculated the reference ranges defined as mean±2 SD. Normality of distribution was checked graphically and by using the Shapiro-Wilk test. Correlations between two continuous variables were assessed using Spearman's rank coefficient correlation. Statistical testing was done at the two-tailed α-level of 0.05. Data were analyzed using the SAS software package, release 9.4 (SAS Institute, Cary, NC).

RESULTS

We included 112 healthy newborns and infants. The median age was 35.5 days (15.0-88.0), median weight was 4062g (2855-6040), and 90.2% were boys. Activated partial thromboplastin time (aPTT) and prothrombin time (PT) were not correlated with age (P=0.92 and P=0.21, respectively) or with weight (P=0.16 and P=0.90, respectively). The reference range was 28.6-46.2 s for aPTT, 0.91-1.49 for aPTT ratio, and 71.3-110.6 s for PT. Regarding fibrinogen (n=24), the median was 2.2g/L (1.2-3.2); the median for factor II was 67.0U/dL (51.0-130.0; n=20), and 101.5U/dL for factor V (68.0-233.0; n=20). Regarding factor VIII, the median was 75.0U/dL (45.0-152.0; n=25), 49.0U/dL for factor IX (32.0-96.0; n=25) and 53.0U/dL (29.0-112.0) for factor XI (n=23).

CONCLUSION

This study can help to establish standards for coagulation testing in this very specific population. Indeed, our study represents the largest newborn population in a recent investigation of PT and aPTT using updated reagents.

A Risk Score for Predicting the Incidence of Hemorrhage in Critically Ill Neonates: Development and Validation Study

The aim of the study was to develop and validate a prediction model for hemorrhage in critically ill neonates which combines rotational thromboelastometry (ROTEM) parameters and clinical variables. This cohort study included 332 consecutive full-term and preterm critically ill neonates. We performed ROTEM and used the neonatal bleeding assessment tool (NeoBAT) to record bleeding events. We fitted double selection least absolute shrinkage and selection operator logit regression to build our prediction model. Bleeding within 24 hours of the ROTEM testing was the outcome variable, while patient characteristics, biochemical, hematological, and thromboelastometry parameters were the candidate predictors of bleeding. We used both cross-validation and bootstrap as internal validation techniques. Then, we built a prognostic index of bleeding by converting the coefficients from the final multivariable model of relevant prognostic variables into a risk score. A receiver operating characteristic analysis was used to calculate the area under curve (AUC) of our prediction index. EXTEM A10 and LI60, platelet counts, and creatinine levels were identified as the most robust predictors of bleeding and included them into a Neonatal Bleeding Risk (NeoBRis) index. The NeoBRis index demonstrated excellent model performance with an AUC of 0.908 (95% confidence interval [CI]: 0.870-0.946). Calibration plot displayed optimal calibration and discrimination of the index, while bootstrap resampling ensured internal validity by showing an AUC of 0.907 (95% CI: 0.868-0.947). We developed and internally validated an easy-to-apply prediction model of hemorrhage in critically ill neonates. After external validation, this model will enable clinicians to quantify the 24-hour bleeding risk.

Thromboelastographic profiles of healthy very low birthweight infants serially during their first month

OBJECTIVE

We determined thromboelastographic (TEG) profiles of healthy very low birthweight infants (VLBWIs) of the day of birth and at set intervals during their first month.

DESIGN

Prospective observational study with blinded clinical and laboratory follow-up.

SETTING

Level III neonatal intensive care unit (June 2015 to June 2018).

PATIENTS

Consecutive qualifying VLBWIs were enrolled at birth and followed up for 30 days.

INTERVENTIONS AND MAIN OUTCOMES MEASURES

Laboratory (citrated-native TEG, prothrombin time (PT), activated partial thromboplastin time (APTT), fibrinogen, blood count) and clinical variables were retrieved at birth, 3rd-5th, 10th and 30th day of life. Blood samples temporally related to events with a potential hemostatic impact (sepsis, bleeding, platelets/plasma transfusions, ibuprofen/indomethacin administration) were excluded from analysis.

RESULTS

We enrolled 201 VLBWIs and 72 full-term neonates. Sixty-seven of the healthy VLBWIs completed the 30-day follow-up. 541 TEG traces were analysed.On day 1, the median (minimum-maximum) TEG values were as follows: reaction time (R), 8.2 min (1-21.8); kinetics (K), 2.8 min (0.8-16); α angle, 51° (14.2-80.6); maximum amplitude (MA), 54.9 mm (23.9-76.8). PT and APTT were 15.9 s (11.7-51.2) and 59 s (37.8-97.5), respectively. The above parameters suggest minor hypocoagulability compared with term infants. On day 30, the median (minimum-maximum) R was 5 (1-16.9), K 1 (0.8-4.1), α 74.7 (41.1-86.7) and MA 70.2 (35.8-79.7). PT and APTT were 12.1 (10.4-16.6) and 38.8 (29.6-51.4), respectively. Those parameters are consistent with a relatively hypercoagulable phenotype, compared with term infants.

CONCLUSIONS

Healthy VLBWIs have a prolonged PT and APTT, but their TEG profiles suggest a relatively balanced hemostatic system, with slight hypocoagulability initially (compared with term neonates), gradually evolving to a somewhat more procoagulant phenotype over the first month.

Procoagulant imbalance in preterm neonates detected by thrombin generation procedures

Preterm newborns are considered at risk of acquired coagulopathy and are often prophylactically infused with fresh frozen plasma (FFP) even in the absence of bleeding. To assess the coagulation asset of preterm neonates and the biological plausibility of such infusions, we investigated at birth 87 very low birth weight (≤1500 g) preterm (gestational age <35 weeks) newborns and 64 full-term newborns. Preterm neonates were also investigated at different time-points up to 30 days after birth. Plasma from preterm and full-term neonates were subjected to the measurement of prothrombin and activated partial thromboplastin time (PT, APTT), pro- and anticoagulant factors as well as to thrombin-generation procedures both with and without thrombomodulin. PT and APTT of preterm newborns were longer than those of full-term neonates [PT: 15.9 s (11.7-51.2)-vs-13.8 (11.0-25.4), p < 0.001. APTT: 59.0 (37.8-97.5)-vs- 47.3 (28.1-71.9), p < 0.001] and tended to shortening after 30 days from birth. Thrombin-generation defined as endogenous thrombin potential (ETP) was increased in preterm as compared to full-term neonates at birth [1322 nM·min (474-2384)-vs-1006 (697-1612), p < 0.001] and did not change appreciably over time up to 30 days from birth. In conclusion, plasma from preterm neonates displays a procoagulant imbalance at birth as shown by increasing ETP, despite the prolongation of PT and APTT. The results define preterm newborns as having hyper- rather than hypo-coagulability and argue against the infusion of FFP when given prophylactically and/or based solely on prolongation of PT or APTT.

Croatian Society of Medical Biochemistry and Laboratory Medicine: National recommendations for blood collection, processing, performance and reporting of results for coagulation screening assays prothrombin time, activated partial thromboplastin time, thrombin time, fibrinogen and D-dimer

A modern diagnostic laboratory offers wide spectrum of coagulation assays utilized in the diagnosis and management of patients with haemostatic disorders, preoperative screening and anticoagulation therapy monitoring. The recent survey conducted among Croatian medical biochemistry and transfusion laboratories showed the existence of different practice policies in particular phases of laboratory process during coagulation testing and highlighted areas that need improvement. Lack of assay standardization together with non-harmonized test results between different measurement methods, can potentially lead to incorrect decisions in patient’s treatment. Consequently, patient safety could be compromised. Therefore, recommended procedures related to preanalytical, analytical and postanalytical phases of prothrombin time, activated partial thromboplastin time, thrombin time, fibrinogen and D-dimer testing are provided in this review, aiming to help laboratories to generate accurate and reliable test results.

Paediatric reference intervals for common coagulation assays in Chinese children as performed on the STA-R coagulation analyzer

INTRODUCTION

In order to correctly manage the paediatric patients affected with haemostatic disorders, age-appropriate reference intervals should be used. The purpose of this study was to establish age-specific reference intervals for prothrombin time (PT), thrombin time (TT), activated partial thromboplastin time (aPTT) and fibrinogen (Fg).

METHODS

In this study, a total of 34 234 apparently healthy children and adolescents aged 0-15 years were chosen as reference individuals. PT, TT, aPTT and Fg were performed on the STA-R coagulation analyzer. Outliers were eliminated using the Dixon D/R ratio rule. Partitioning by age was achieved using Harris and Boyd's standard normal deviate test. The lower (2.5th percentiles) and upper (97.5 percentiles) reference intervals were established using the nonparametric method.

RESULTS

Compared with the adult group, the median time of PT was significantly different in the groups consisting of children aged 0-15 days, 15 days-1 month, 1-6 months and 11-15 years. The median time of APTT and TT was significantly prolonged in all paediatric age groups than in the adult group (P < .05). Compared with the adult group, the median values of Fg were significantly different in the groups consisting of children aged 0-15 days and 2-15 years. Our results showed that all coagulation assays required partitioning by age.

CONCLUSION

Our results suggest that results of coagulation assays are highly dependent on age, and that age-specific reference intervals must be used to ensure proper evaluation of paediatric coagulation assays.

Establishing a reference range for thromboelastograph parameters in the neonatal period

Introduction

Acquired coagulation disorders are a common cause of neonatal bleeding. The thromboelastograph (TEG) comprehensively assesses haemostatic processes in the body. Unfortunately, the reference range of TEG parameters in the neonatal period has not yet been evaluated, which limits the use of the TEG in neonates. In this study, we aimed to establish the reference range of TEG parameters for the neonatal period.

Methods

This study included 371 full‐term infants (≥37 weeks of gestation), and we divided these infants into three groups according to age as follows: 1, 2‐7 and 8‐28 days. We measured their peripheral blood using TEG, coagulation routine and platelet count tests. We analysed differences among the groups.

Results

The reference ranges for TEG parameters are presented as medians and reference ranges (2.5th and 97.5th percentiles) as follows: R (clot reaction time, seconds) 4.80 (2.80‐7.17), Angle (fibrin production rate) 69.90 (44.91‐78.89), K (clot kinetics, min) 1.40 (0.80‐4.50), MA (maximum amplitude, mm) 63.50(44.34‐74.66) and LY30 (lysis at 30 minutes, %) 0.10 (0.10‐6.95). There were significant differences in Angle, K, MA and LY30 values between the different neonatal day age groups.

Conclusion

This study preliminarily establishes a reference range for TEG parameters during the neonatal period. The age of a newborn had a large influence on TEG parameters. Additionally, we demonstrated a correlation between laboratory tests and TEG parameters for this age period. The reference values provided herein are meaningful for future studies.

Antithrombotic therapy management of adult and pediatric cardiac surgery patients

Despite the development of catheter-based interventions for ischemic and valvular heart disease, hundreds of thousands of people undergo open heart surgery annually for coronary artery bypass graft (CABG), valve replacement or cardiac assist device implantation. Cardiac surgery patients are unique because therapeutic anticoagulation is required during cardiopulmonary bypass. Developmental hemostasis and altered drug metabolism affect management in children. This narrative review summarizes the current evidence-based and consensus guidelines regarding perioperative, intraoperative and postoperative antithrombotic therapy in patients undergoing cardiac surgery. Anticoagulation preoperatively is required in the setting of cardiac arrhythmias, prior valve replacement or history of venous thromboembolism. In patients with ischemic heart disease, aspirin is continued in the perioperative period, whereas oral P2Y12 antagonists are withheld for 5-7 days to reduce the risk of perioperative bleeding. Intraoperative management of cardiopulmonary bypass in adults and children includes anticoagulation with unfractionated heparin. Variability in dose-response to heparin and influence of other medical conditions on dosing and reversal of heparin make intraoperative anticoagulation challenging. Vitamin K antagonist therapy is the standard anticoagulant after mechanical heart valve or left ventricular assist device (LVAD) implantation. Longer duration of dual antiplatelet therapy is recommended after CABG if patients undergo surgery because of acute coronary syndrome. Antiplatelet therapy after LVAD implantation includes aspirin, dipyridamole and/or clopidogrel in children and aspirin in adults. A coordinated approach between hematology, cardiology, anesthesiology, critical care and cardiothoracic surgery can assist to balance the risk of thrombosis and bleeding in patients undergoing cardiac surgery.

Dynamic reference intervals for coagulation parameters from infancy to adolescence

INTRODUCTION

Practical and ethical challenges as well as time and costs have restricted the generation of pediatric reference intervals. Therefore, pediatric reference intervals on coagulation parameters based on solid evidence are still scarce. Furthermore, reference intervals by age-group cannot reflect the dynamics of age and sex specific coagulation values during childhood. This study is the first to close this gap and provide continuous age and sex dependent reference intervals during childhood in hemostasis.

METHODS

We used an innovative indirect method for providing continuous reference intervals for five common coagulation parameters: Activated partial thromboplastin time (aPTT), prothrombin time (PT), thrombin clotting time (TT), fibrinogen (FIB) and antithrombin (AT). Calculations were performed using retrospective laboratory data from pediatric patients between 2005 and 2015 of two major Austrian hospitals, resulting in a total of 195.360 measurements (aPTT: 55,100; PT: 35,492; TT: 35,295; FIB: 49,789; AT: 19,684).

RESULTS

This multicenter study provides calculations of continuous reference intervals for five common coagulation parameters in a large pediatric cohort, accounting for age and gender.

CONCLUSION

To the best of our knowledge, this is the first multicenter study, determining continuous pediatric coagulation reference intervals based on a large retrospective dataset.

Patient blood management, what does this actually mean for neonates and infants?

Patient blood management (PBM) refers to an evidence-based package of care that aims to improve patient outcomes by optimal use of transfusion therapy, including managing anaemia, preventing blood loss and improving anaemia tolerance in surgical and other patients who may need transfusion. In adults, PBM programmes are well established, yet the definition and implementation of PBM in neonates and children lags behind. Neonates and infants are frequently transfused, yet they are often under-represented in transfusion trials. Adult PBM programmes may not be directly applicable to these populations. We review the literature in neonatal (and applicable paediatric) transfusion medicine and propose specific neonatal PBM definitions and elements.

Neonatal haemostasis

The maturation and postnatal development of the human coagulation system results in significant and important differences in the coagulation and fibrinolysis of neonates and young children compared to older children and adults. Importantly, these differences, which mostly reflect the immaturity of the neonatal haemostasis system, are functionally balanced. Healthy neonates show no signs of easy bruising or other bleeding diathesis and no increased tendency to thrombosis for any given stimulus compared to adults.

Systemic diseases may affect haemostasis, thus predisposing ill neonates to increased risk for haemorrhagic or thrombotic complications. In hospitalized children, neonates have increased risk of developing thrombosis compared to infants and children, mostly associated with the presence of central venous catheter. For diagnosis of haemostasis disorders, diagnostic laboratories processing pediatric samples should use age, analyzer and reagent appropriate reference ranges. Age specific guidelines should be followed for the management of neonates with hemostatic disorders.

Age dependency for coagulation parameters in paediatric populations

Understanding of developmental haemostasis is critical to ensure optimal prevention, diagnosis, and treatment of haemorrhagic and thrombotic diseases in children. As coagulation test results are known to be dependent on the reagents/analysers used, it is recommended for each laboratory to define the age-dependent reference ranges by using its own technical condition. That study was carried out in seven centers to establish age-specific reference ranges using the same reagents and analyser. Plasma samples were obtained from 1437 paediatric patients from the following age groups: 15 days-4 weeks (n=36), 1–5 months (n=320), 6–12 months (n=176), 1–5 years (n=507), 6–10 years (n=132) and 11–17 years (n=262). Indication of coagulation testing was pre-operative screening for non-acute diseases in most cases. PT values were similar in the different age groups to those in adults, whereas longer aPTTs were demonstrated in the younger children. Plasma levels of all clotting factors, except for FV, were significantly decreased (p<0.0001) in the youngest children, adult values being usually reached before the end of the first year. The same applied to antithrombin, protein C/S, and plasminogen. In contrast, FVIII and VWF levels were elevated in the youngest children and returned to adult values within six months. The same applied to D-dimer levels, which were found elevated, particularly until six months of life, until puberty. These data suggest that most coagulation test results are highly dependent on age, mainly during the first year of life, and that age-specific reference ranges must be used to ensure proper evaluation of coagulation in children.

Thrombo-hemorrhagic liability in children with congenital heart diseases

BACKGROUND

The precise mechanisms of the increased incidence of hemostatic abnormalities in congenital heart disease (CHD) have not been determined. The aim of the study was to evaluate some indicators of activation of platelets and vascular endothelial cells in patients with CHD, evaluation of bleeding liability of these patients, and correlation with the clinical presentation of these patients.

METHODS

This work was carried out on 20 patients with cyanotic congenital heart diseases (CCHD), 20 patients with acyanotic congenital heart diseases (ACHD), and 20 healthy children who served as the control group, aged between 1 and 10years. All were subjected to full clinical examination, complete blood count, oxygen saturation, echocardiography, bleeding and coagulation times, PT, PTT, FDPs, plasma soluble P-selectin, E-selectin, and platelet factor 4 (PF4).

RESULTS

There was significant prolongation of PT and PTT, and there was a significant lowering of platelet counts. These results were obtained in CCHD and ACHD, but were more significant in CCHD patients. There was a significant elevation in PF4 (55.0±25.5ng/mL), P-selectin (128.9±42.44ng/dL), and E-selectin (9461.5±1701.24pg/mL) levels in children with CCHD as compared to those with ACHD (PF4, 21±7.94ng/mL; P-selectin, 80.1±13.2ng/mL; E-selectin, 7969.6±2127.5pg/mL), and significant increase in both groups when compared to the control group (PF4, 8.1±4.7ng/mL; P-selectin, 27.83±9.73ng/mL; E-selectin, 6750.00±3204.00pg/mL). There was a significant negative correlation between oxygen saturation, plasma P-selectin (r=-0.865), E-selectin (r=-0.401), and PF4 (r=-0.792) in patients with CCHD.

CONCLUSION

Patients with CHD-both cyanotic and acyanotic-have variable degrees of increased liability for both thrombosis and hemorrhage that represents some sort of adaptation to preserve hemostasis and to protect these patients against the clinical presentation of both thrombosis and bleeding. This is to say that CHD patients have their own point of balance between thrombogenicity and bleeding liability. Wide-scale studies are needed to detect the normal levels of different thrombohemorrhagic parameters of these patients.

Does whole blood coagulation analysis reflect developmental haemostasis?

: Developmental haemostasis has been well documented over the last 3 decades and age-dependent reference ranges have been reported for a number of plasmatic coagulation parameters. With the increasing use of whole blood point-of-care tests like rotational thromboelastometry (ROTEM) and platelet function tests, an evaluation of age-dependent changes is warranted for these tests as well. We obtained blood samples from 149 children, aged 1 day to 5.9 years, and analysed conventional plasmatic coagulation tests, including activated partial prothrombin time, prothrombin time, and fibrinogen (functional). Whole blood samples were analysed using ROTEM to assess overall coagulation capacity and Multiplate analyzer to evaluate platelet aggregation. Age-dependent changes were analysed for all variables. We found age-dependent differences in all conventional coagulation tests (all P values < 0.05), but there was no sign of developmental changes in whole blood coagulation assessment when applying ROTEM, apart from clotting time in the EXTEM assay (P < 0.03). Despite marked differences in mean platelet aggregation between age groups, data did not reach statistical significance. Citrate-anticoagulated blood showed significantly reduced platelet aggregation compared with blood anticoagulated with heparin or hirudin (all P values < 0.003). We confirmed previous developmental changes in conventional plasmatic coagulation test. However, these age-dependent changes were not displayed in whole blood monitoring using ROTEM or Multiplate analyzer. Type of anticoagulant had a significant influence on platelet aggregation across all age groups.

Reference ranges of thromboelastometry in healthy full-term and pre-term neonates

Background:

Rotational thromboelastometry (ROTEM) is an attractive method for rapid evaluation of hemostasis in neonates. Currently, no reference values exist for ROTEM assays in full-term and pre-term neonates. Our aim was to establish reference ranges for standard extrinsically activated ROTEM assay (EXTEM) in arterial blood samples of healthy full-term and pre-term neonates.

Methods:

In the present study, EXTEM assay was performed in 198 full-term (≥37 weeks’ gestation) and 84 pre-term infants (<37 weeks’ gestation) using peripheral arterial whole blood samples.

Results:

Median values and reference ranges (2.5th and 97.5th percentiles) for the following main parameters of EXTEM assay were determined in full-term infants: clotting time (seconds), 41 (range, 25.9–78); clot formation time (seconds), 70 (range, 40–165.2); maximum clot firmness (mm), 66 (range, 41–84.1); lysis index at 60 min (LI60, %), 97 (range, 85–100). The only parameter with a statistically significant difference between full-term and pre-term neonates was LI60 (p=0.006). Furthermore, it was inversely correlated with gestational age (p=0.002) and birth weight (p=0.016) in pre-term neonates.

Conclusions:

In conclusion, an enhanced fibrinolytic activity in pre-term neonates was noted. For most EXTEM assay parameters, reference ranges obtained from arterial newborn blood samples were comparable with the respective values from studies using cord blood. Modified reagents, small size samples, timing of sampling, and different kind of samples might account for any discrepancies among similar studies. Reference values hereby provided can be used in future studies.

Determination of Age-Dependent Reference Ranges for Coagulation Tests Performed Using Destiny Plus

BACKGROUND

In order to apply the right treatment for hemostatic disorders in pediatric patients, laboratory data should be interpreted with age-appropriate reference ranges.

OBJECTIVES

The purpose of this study was to determining age-dependent reference range values for prothrombin time (PT), activated partial thromboplastin time (aPTT), fibrinogen tests, and D-dimer tests.

MATERIALS AND METHODS

A total of 320 volunteers were included in the study with the following ages: 1 month - 1 year (n = 52), 2 - 5 years (n = 50), 6 - 10 years (n = 48), 11 - 17 years (n = 38), and 18 - 65 years (n = 132). Each volunteer completed a survey to exclude hemostatic system disorder. Using a nonparametric method, the lower and upper limits, including 95% distribution and 90% confidence intervals, were calculated.

RESULTS

No statistically significant differences were found between PT and aPTT values in the groups consisting of children. Thus, the reference ranges were separated into child and adult age groups. PT and aPTT values were significantly higher in the children than in the adults. Fibrinogen values in the 6 - 10 age group and the adult age group were significantly higher than in the other groups. D-dimer levels were significantly lower in those aged 2 - 17; thus, a separate reference range was established.

CONCLUSIONS

These results support other findings related to developmental hemostasis, confirming that adult and pediatric age groups should be evaluated using different reference ranges.

The bleeding newborn: A review of presentation, diagnosis, and management

The neonatal hemostatic system is continuously developing with rapidly changing concentrations of many coagulation proteins. Thus, determining the etiology of bleeding in a newborn has additional challenges beyond those seen in older children or adults. Bleeding can be seen in both well and sick newborns due to congenital causes, such as hemophilia or von Willebrand disease, and acquired causes, such as liver failure or disseminated intravascular coagulation. Traditional coagulation testing should be interpreted with caution and with the help of a hematologist, if possible, due to the greatly different normal ranges between neonates as compared with older children and adults. However, despite these challenges, both clinical and laboratory clues can guide physicians appropriately to diagnose and treat the bleeding newborn.

Fresh Frozen Plasma Administration in the Neonatal Intensive Care Unit: Evidence-Based Guidelines

Neonates receiving fresh frozen plasma (FFP) should do so according to evidence-based guidelines so as to reduce inappropriate use of this life-saving and costly blood product and to minimize associated adverse effects. The consensus-based uses of FFP in neonatology involve neonates with active bleeding and associated coagulopathy. However, because of limited and poor-quality evidence, considerable FFP utilization occurs outside these recommendations. In this review, we describe what we conclude are currently the best practices for the use of FFP in neonates, including interpreting neonatal coagulation tests and strategies for reducing unnecessary FFP transfusions.

A retrospective analysis of outcomes of dalteparin use in pediatric patients: a single institution experience

BACKGROUND

Dalteparin is a commonly used low molecular weight heparin (LMWH) with extensive safety data in adults. With distinct advantages of once daily dosing and relative safety in renal impairment, it has been used off-label in pediatric practice; however, age-based dosing guidelines, safety and efficacy data in children are evolving.

OBJECTIVES

To report our institutional experience with the use of dalteparin in the treatment and prophylaxis of venous thromboembolism (VTE) in pediatric patients.

PATIENTS/METHODS

Retrospective chart review of all children (0-18years) that received dalteparin from December 1, 2000 through December 31, 2011. Doses per unit body weight per day (units/kg/day) were calculated for age-based group comparisons.

RESULTS

Of 166 patients identified, 116 (70%) received prophylactic doses while 50 (30%) received therapeutic doses of dalteparin. Infants (<1year) required significantly higher weight-based dosing to achieve therapeutic anti-Xa levels compared to children (1-10years) or adolescents (>10-18years) (mean dose units/kg/day; 396.6 versus 236.7 and 178.8 respectively, p<0.0001). Overall response rate, including complete and partial thrombus resolution, was 83%. Bleeding complications were minor and the rates were similar in therapeutic and prophylaxis patients. No significant differences in dosing or bleeding events were noted based on obesity or malignancy.

CONCLUSIONS

In our experience, dalteparin is effective for prophylaxis and therapy of VTE in pediatric patients. Dosing should be customized in an age-based manner with close monitoring of anti-Xa activity in order to achieve optimal levels, prevent bleeding complications, and to allow full benefit of prevention or therapy of thrombotic complications.

Reducing the risk in neonatal anesthesia

Neonatal anesthesia is fraught with potential risk for the patient and stress for the anesthesiologist. Where possible, recognition of these risks, avoidance of, and being able to manage them appropriately, must impact positively on perioperative outcomes in this vulnerable group of patients. Good communication with the parents, as well as with other healthcare providers, is crucial to safe and successful anesthetic care.

Developmental hemostasis: age-specific differences in the levels of hemostatic proteins

INTRODUCTION

Developmental hemostasis recognizes the physiologic differences between the hemostatic system of neonates and children and that of adults. As compared with the knowledge of hemostatic system physiology in adults, our understanding in neonates and children remains inadequate. Routine clinical coagulation testing most commonly measures functional parameters of the hemostatic system. Very few studies have measured age-specific levels of hemostatic proteins. An understanding of the normal fluctuations in the levels of hemostatic proteins is vital in the prevention, diagnosis and treatment of hemostatic problems during infancy and childhood. This study was designed as the first comprehensive study of the age-specific changes in the levels of important hemostatic proteins in healthy neonates, children, and adults.

METHODS

Plasma samples were obtained from 120 healthy individuals from the following age groups: neonates (day 1 and day 3), 28 days to 1 year, 1-5 years, 6-10 years, 11-16 years, and adults. Factor II, FV, FVII, FVIII, FIX, FX, FXI, FXII, FXIII, plasminogen, protein C and total and free protein S were quantified with commercially available ELISA kits.

RESULTS

The levels of 10 proteins were significantly different between neonates and adults, and these differences persisted throughout childhood for most of these proteins.

CONCLUSION

The results of this study confirm that the levels of the majority of coagulation proteins vary significantly with age. Future studies should investigate how hemostatic protein level relates to functional changes with age.

Thromboelastography: might work in neonatology too?

AIM

To review the working principles of thromboelastography and evaluate the current knowledge about the possibility of its implementation in the neonatal intensive care unit setting.

METHOD

Thorough search of the literature in the PubMed database (until May 31, 2012) concerning Thromboelastography (TEG) and/or Thromboelastometry (ROTEM) use in the newborn infant.

RESULTS

Neonatal data are limited to a small number of healthy subjects and virtually absent in the extreme premature infant. Healthy newborns exhibit age dependent accelerated initiation and propagation of coagulation despite prolonged standard plasma coagulation test results, whereas clot firmness and fibrinolysis are similar to adult values. Several neonatal pathological conditions (e.g. sepsis; hypothermia) are linked with substantial changes in the thromboelastographic parameters.

CONCLUSIONS

The current knowledge is too limited to express a definitive indication on the reliability of the use of viscoelastic point of care analyzer in the neonatal intensive care unit setting. However, their potential use not only as a diagnostic tool, but also to guide the transfusion therapy requires careful consideration.

The conundrum of neonatal coagulopathy

The maturation and postnatal development of the human coagulation system was first studied and described more than 20 years ago. These older studies, supported by more recent data, confirm the significant and important differences in the physiology of coagulation and fibrinolysis in neonates and young children compared with older children and adults. Subsequently, significant differences were also described in the physiology of primary hemostasis and in global in vitro tests for hemostasis. These differences, which mostly reflect the immaturity of the neonatal hemostasis system, are functionally balanced. Healthy neonates show no signs of easy bruising or other bleeding diathesis and no increased tendency to thrombosis for any given stimulus compared with adults. Systemic diseases may affect hemostasis, predisposing ill neonates to increased hemorrhagic or thrombotic complications. The immaturity of the hemostasis system in preterm and very-low-birth-weight neonates may contribute to a higher risk for intraventricular hemorrhage. Therapies targeting the hemostasis system can be effective for preventing and treating these events. The concept of “neonatal coagulopathy” has an important impact on both the diagnosis and management of hemorrhagic or thrombotic events in neonates. For diagnosis of hemostasis disorders, diagnostic laboratories processing pediatric samples should use age-, analyzer-, and reagent-appropriate reference ranges. Age-specific guidelines should be followed for the management of neonates with hemostatic disorders.