Activated thrombelastogram in neonates and infants with complex congenital heart disease in comparison with healthy children

Hemostatic Profile of Intrauterine Growth-Restricted Neonates: Assessment with the Use of NATEM Assay in Cord Blood Samples

BACKGROUND

Intrauterine growth restriction (IUGR) is associated with hemorrhagic and thrombotic complications during the perinatal period. Thrombocytopenia, platelet dysfunction, and prolonged standard coagulation tests are observed in this population. The aim of this study is to examine the hemostatic profile of IUGR neonates with the use of a non-activated assay (NATEM) in cord blood samples.

METHODS

During an 18 month period, a NATEM ROTEM assay was performed on cord blood samples of 101 IUGR neonates. A total of 189 appropriate for gestational age (AGA) neonates were used as a control group. The NATEM variables recorded include the following: clotting time (CT); clot formation time (CFT); clot amplitude at 5, 10, and 20 min (A5, A10, A20); α-angle (a°); maximum clot firmness (MCF); lysis index at 30 and 60 min (LI30, LI60); and maximum clot elasticity (MCE).

RESULTS

IUGR neonates demonstrate a hypocoagulable state, with lower A5, A10, A2, MCF, and MCE values when compared to AGA. Using multiple linear regression, we determined IUGR as an independent factor influencing all NATEM parameters (except CT and LI30) exhibiting a hypocoagulable and hypofibrinolytic profile. Platelet count was positively correlated with A5, A10, A20, MCF, alpha angle, and MCE, and negatively correlated with CFT.

CONCLUSION

IUGR neonates appear with lower clot strength and elasticity and prolonged clot kinetics, as illustrated by ROTEM variables.

Comparison of the predictive value of thromboelastography and Sonoclot analysis for postoperative bleeding in children undergoing corrective surgery for cyanotic congenital heart disease

Background

The aim of the study was to compare the predictive value of Sonoclot analysis and thromboelastography (TEG) for postoperative bleeding in children younger than 12 years coming for cardiac surgery for congenital cyanotic heart disease.

Methods

This is a prospective, observational study carried out in a single tertiary care military hospital. Ninety patients of the paediatric age group undergoing bypass cardiac surgery for correction of congenital cyanotic heart defect were included in the study. Laboratory-derived values to assess coagulation status (prothrombin time, international normalisation ratio, activated partial thromboplastin time) and point-of-care Sonoclot- and TEG-derived parameters were noted at the start of surgery and postoperatively in all patients. Bleeders were predefined on the basis of chest tube drainage.

Results

The incidence of bleeders was 42.2% (38/90 patients), whereas 57.8% (52/90 patients) were non-bleeders. The postoperative R value and preoperative gbPF test were predictive for postoperative bleeders on multivariate analysis. Postoperative gbPF had the highest area under the curve (0.72), with a cut-off value of 1.75, and gbPF had 82% sensitivity and 71% specificity in predicting significant postoperative bleeding in paediatric cyanotic congenital heart surgeries. Transfusion requirements and mechanical ventilation duration were higher in bleeders; however; length of intensive care unit stay, incidence of sepsis and mortality were similar in both the groups.

Conclusion

Bleeding in patients undergoing corrective surgery for cyanotic congenital heart disease could be predicted by the preoperative gbPF and postoperative R value. Among these, preoperative gbPF has the maximum predictive value.

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.

Outcomes and factors associated with early mortality in pediatric postcardiotomy veno-arterial extracorporeal membrane oxygenation

Mortality and morbidity of children received veno-arterial extracorporeal membrane oxygenation (VA-ECMO) support after cardiac surgery remain high despite remarkable advances in medical management and devices. The purpose of this study was to describe outcomes and risk factors of applying VA-ECMO in the surgical pediatric population. We retrospectively analyzed 85 consecutive pediatric patients (aged <18 years) who received postcardiotomy VA-ECMO from January 2010 to December 2018. Median (IQR) age at ECMO implantation in this cohort was 12.7 (6.4, 43.2) months, median weight was 8.5 (6.0, 12.8) kg, mean ECMO duration was 143.2 ± 81.6 hours and mean hospital length of stay was 48.4 ± 32.4 days. Seventy-five patients (88.2%) were indicated for postcardiotomy cardiogenic shock. The successful ECMO weaning rate was 70.6% and in-hospital mortality was 52.9%. The most common diagnosis was transposition of great arteries (n = 18, 21.2%), while acute kidney injury occurred most often (n = 64, 75.3%). Multivariate logistic regression analysis showed that thrombocytopenia, hemolysis, and nosocomial infection were positively correlated with in-hospital mortality. Multivariate Cox proportional hazard regression analysis presented that thrombocytopenia significantly increased the 180-day mortality in patients with successful weaning. Therefore, multiple factors had adverse effects on prognosis. Patient selection and procedures from ECMO implantation to weaning need to be closely monitored and performed in a timely manner to improve outcome.

Point-of-care hemostasis in children with congenital heart disease, the POCHEMO study: baseline reference values of thromboelastometry and impedance aggregometry

: Viscoelastic tests and impedance aggregometry allow coagulation evaluation at the bedside, but reference values are scarce in pediatrics. The aim of this study was to establish reference values of thromboelastometry and impedance aggregometry for this population and compare it between age groups. This prospective, single-center, observational study evaluates viscoelastic tests and impedance aggregometry in children with congenital heart disease. A total of 204 children were included with a median age of 3.6 years old. We provide references values for this population with median, percentile 2.5 and percentile 97.5. Infants demonstrate for extrinsic activity a shorter coagulation time (52 [49-55] vs. 56 [51-62] s, P = 0.007) and clot formation time (90 [71-118] vs. 113 [93-146] s, P < 0.0001) so as for intrinsic activity a shorter clot formation time (53 [44-69] vs. 75 [59-92] s, P < 0.0001). The maximal clot firmness was significantly stronger in infants for extrinsic (65 [61-69] vs. 59 [54-63] mm, P < 0.0001), intrinsic (68 [64-70] vs. 61 [57-65] mm, P < 0.0001), and fibrinogen (12 [9-16] vs. 10 [8-13] mm, P = 0.02) activities. Platelet aggregation was significantly higher in infants with an amplitude at 6 min of 28 [23-34] vs. 22 [15-27] Ω, P less than 0.0001, a maximum speed of 11 [9-13] vs. 7 [5-10] Ω/min, P less than 0.0001, and an area under the curve of 120 [92-135] vs. 86 [59-112] Ω min, P less than 0.0001. We provided the first reference values for impedance aggregometry and thromboelastometry in children with congenital heart disease. We showed that these infants tend to have accelerated coagulation and stronger clot firmness compared with older children, but this finding may have only minimal relevance when treating a bleeding child. Trial registration number: ClinicalTrials.gov (clinicaltrials.gov/ct2/show/NCT02387944).

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.

Comparison of the Effects of Albumin 5% versus Ringer's Lactate on Blood Loss and Coagulation after Vascular Surgery Using Thromboelastography

AIM

Comparing the effects of Albumin 5% versus Ringer's lactate on blood loss and coagulation after vascular surgery using.

METHODS

In this randomised study, 60 patients, aged (18-60 years) ASA physical status (I-III) undergoing vascular surgery were included in the study and randomly allocated into two groups using a random number generator, to receive either Human albumin or Ringer lactate after obtaining written informed consent. Group A received 1-2 ml per minute of human albumin 5% combined with normal saline (0.9%). Group B received Ringer's lactate only as of the main solution. Variables were measured after administration of fluids as postoperative measures. The amount of blood needed for testing was 4 ml drawn before the operation and at the end of surgery with a citrate tube (blue tube) from the venous line or using a regular needle. The standard time of 15 minutes was considered to begin processing.

RESULTS

There was no statistically significant difference observed between both groups regarding demographic data, surgical wound drainage, haemoglobin level, hematocrit level and coagulation profile. Regarding ROTEM thermoelectrometry variables showed that there was no statistically significant difference was found between the two groups In-TEM variables (Ex-TEM Clotting time, TEM Clot Formation Time) but In-TEM Alpha Angel measured in degrees showed a Statistically significant difference between the two groups. P < 0.001 and Ex-TEM Maximum Clotting Firmness MCF values measured in mm, there was a statistically significant difference between the two groups P = 0.045.

CONCLUSION

This study concluded that the use of human albumin (5%) in vascular surgeries before reaching the trigger point for blood transfusion didn't improve blood loss or coagulation profile compared to the use of ringer lactate only. Therefore, ringer lactate can be used as a good replacement for human albumin. Ringer lactate is readily available and inexpensive while human albumin may be costly.

Position of the French Working Group on Perioperative Haemostasis (GIHP) on viscoelastic tests: What role for which indication in bleeding situations?

PURPOSE

Viscoelastic tests (VETs), thromboelastography (TEG^®) and thromboelastometry (ROTEM^®) are global tests of coagulation performed on whole blood. They evaluate the mechanical strength of a clot as it builds and develops after coagulation itself. The time required to obtain haemostasis results remains a major problem for clinicians dealing with bleeding, although some teams have developed a rapid laboratory response strategy. Indeed, the value of rapid point-of-care diagnostic devices such as VETs has increased over the years. However, VETs are not standardised and there are few recommendations from the learned societies regarding their use. In 2014, the recommendations of the International Society of Thrombosis and Haemostasis (ISTH) only concerned haemophilia. The French Working Group on Perioperative haemostasis (GIHP) therefore proposes to summarise knowledge on the clinical use of these techniques in the setting of emergency and perioperative medicine.

METHODS

A review of the literature.

PRINCIPAL FINDINGS

The role of the VETs seems established in the management of severe trauma and in cardiac surgery, both adult and paediatric. In other situations, their role remains to be defined: hepatic transplantation, postpartum haemorrhage, and non-cardiac surgery. They must be part of the global management of haemostasis based on algorithms defined in each centre and for each population of patients. Their position at the bedside or in the laboratory is a matter of discussion between clinicians and biologists.

CONCLUSION

VETs must be included in algorithms. In consultation with the biology laboratory, these devices should be situated according to the way each centre functions.

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.

Mathematical modelling of blood-brain barrier failure and oedema

Injuries such as traumatic brain injury and stroke can result in increased blood-brain barrier (BBB) permeability. This increase may lead to water accumulation in the brain tissue resulting in vasogenic oedema. Although the initial injury may be localized, the resulting oedema causes mechanical damage and compression of the vasculature beyond the original injury site. We employ a biphasic mixture model to investigate the consequences of BBB permeability changes within a region of brain tissue and the onset of vasogenic oedema. We find that such localized changes can indeed result in brain tissue swelling and suggest that the type of damage that results (stress damage or strain damage) depends on the ability of the brain to clear oedema fluid.

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.

Reference Intervals of Thromboelastometric Evaluation of Coagulation in Pediatric Patients with Congenital Heart Diseases: A Retrospective Investigation

Background

Rotational thromboelastometry (ROTEM^®) is a point-of-care test for coagulation, enabling physicians to make a swift decision. The aim of this investigation was to establish reference intervals of thromboelastometric evaluation for coagulation in pediatric patients with congenital heart diseases (CHD).

Material/Methods

As baseline data, 3 assays of ROTEM^® (INTEM, EXTEM, and FIBTEM) were measured after anesthesia induction. ROTEM^® parameters were clotting time (CT), amplitude at 10 min (A10), clot formation time (CFT), α angle, maximal clot firmness (MCF), clot lysis index at 60 min (LI60), and maximal clot elasticity (MCE). As age is a well-known factor for maturation, age groups were determined as follows; 1) <1 month, 2) 1–3 months, 3) 4–12 months, 4) 1–3 years, 5) 4–6 years, 6) 7–12 years, and 7) 13–16 years. Reference limits representing 95% of distribution of ROTEM^® parameters and 90% confidence intervals of upper and lower reference limits were calculated.

Results

The data of 413 patients were analyzed. Although INTEM CT was prolonged, significantly shorter CT and CFT, steeper α, and greater A10, MCF, and MCE were shown in patients age <3 months compared to older children.

Conclusions

Reference intervals of thromboelastometric evaluation for coagulation from pediatric patients with CHD were shown to have similar pattern to those obtained from healthy pediatric patients. Pediatric patients with CHD, even with cyanosis, were demonstrated to have functionally intact coagulation profile before surgery.

Assessment of Functional Fibrinolysis in Cord Blood Using Modified Thromboelastography

BACKGROUND

The fibrinolytic system in newborns is immature and probably impaired. The aim of this study was to prospectively evaluate functional fibrinolytic capacity of newborn's cord blood using a new thromboelastometry (rotational thromboelastogram, ROTEM®) test.

METHODS

Infants born at Sheba Medical Center were studied prospectively. Cord blood was obtained immediately after clumping, and ROTEM parameters were assessed applying non-activated TEM (NATEM) assay with increasing concentration of tissue plasminogen activator (tPA, 0-200 U/ml). Baseline clotting time (CT), clot formation time (CFT), alpha angle, and maximum clot firmness (MCF) were compared among infants versus adults. Each infant's demographic information was prospectively followed up until discharge.

RESULTS

One hundred one newborns were tested. CT and CFT values were lower and alpha angles were higher among neonate's cord blood compared to adults (n = 23; P = 0.001, 0.03, and 0.02, respectively). The addition of tPA significantly shortened CT and CFT, and reduced alpha angles and MCF in both groups. The lysis index at 30 min (LI30) and lysis onset time (LOT) decreased significantly, and fibrinolysis was more rapid in the newborns. Hematocrit and platelet counts in neonates correlated with LI30 (P = 0.035 and 0.037, respectively) and LOT (P = 0.02) when higher tPA concentrations were used. ROTEM values were unrelated to the occurrence of postnatal complications.

CONCLUSIONS

This first report of functional fibrinolysis in cord blood demonstrated that neonatal fibrinolysis may be augmented as compared to adult values. Further studies are required to validate this test and assess its predictive value and clinical relevance.

Coagulopathy and transfusion therapy in pediatric liver transplantation

Bleeding and coagulopathy are critical issues complicating pediatric liver transplantation and contributing to morbidity and mortality in the cirrhotic child. The complexity of coagulopathy in the pediatric patient is illustrated by the interaction between three basic models. The first model, "developmental hemostasis", demonstrates how a different balance between pro- and anticoagulation factors leads to a normal hemostatic capacity in the pediatric patient at various ages. The second, the "cell based model of coagulation", takes into account the interaction between plasma proteins and cells. In the last, the concept of "rebalanced coagulation" highlights how the reduction of both pro- and anticoagulation factors leads to a normal, although unstable, coagulation profile. This new concept has led to the development of novel techniques used to analyze the coagulation capacity of whole blood for all patients. For example, viscoelastic methodologies are increasingly used on adult patients to test hemostatic capacity and to guide transfusion protocols. However, results are often confounding or have limited impact on morbidity and mortality. Moreover, data from pediatric patients remain inadequate. In addition, several interventions have been proposed to limit blood loss during transplantation, including the use of antifibrinolytic drugs and surgical techniques, such as the piggyback and lowering the central venous pressure during the hepatic dissection phase. The rationale for the use of these interventions is quite solid and has led to their incorporation into clinical practice; yet few of them have been rigorously tested in adults, let alone in children. Finally, the postoperative period in pediatric cohorts of patients has been characterized by an enhanced risk of hepatic vessel thrombosis. Thrombosis in fact remains the primary cause of early graft failure and re-transplantation within the first 30 d following surgery, and it occurs despite prolongation of standard coagulation assays. Data, however, are currently lacking regarding the use of anti-aggregation/anticoagulation therapies and how to best monitor for thrombosis in the early postoperative period in pediatric patients. Therefore, further studies are necessary to elucidate the interaction between the development of the coagulation system and cirrhosis in children. Moreover, strategies to optimize blood transfusion and anticoagulation must be tested specifically in pediatric patients. In conclusion, data from the adult world can be translated with difficulty into the pediatric field as indication for transplantation, baseline pathologies and levels of pro- and anticoagulation factors are not comparable between the two populations.

Assessing the Methodology for Calculating Platelet Contribution to Clot Strength (Platelet Component) in Thromboelastometry and Thrombelastography

The viscoelastic properties of blood clot have been studied most commonly using thrombelastography (TEG) and thromboelastometry (ROTEM). ROTEM-based bleeding treatment algorithms recommend administering platelets to patients with low EXTEM clot strength (e.g., clot amplitude at 10 minutes [A10] <40 mm) once clot strength of the ROTEM® fibrin-based test (FIBTEM) is corrected. Algorithms based on TEG typically use a low value of maximum amplitude (e.g., <50 mm) as a trigger for administering platelets. However, this parameter reflects the contributions of various blood components to the clot, including platelets and fibrin/fibrinogen. The platelet component of clot strength may provide a more sensitive indication of platelet deficiency than clot amplitude from a whole blood TEG or ROTEM® assay. The platelet component of the formed clot is derived from the results of TEG/ROTEM® tests performed with and without platelet inhibition. In this article, we review the basis for why this calculation should be based on clot elasticity (e.g., the E parameter with TEG and the CE parameter with ROTEM®) as opposed to clot amplitude (e.g., the A parameter with TEG or ROTEM®). This is because clot elasticity, unlike clot amplitude, reflects the force with which the blood clot resists rotation within the device, and the relationship between clot amplitude (variable X) and clot elasticity (variable Y) is nonlinear. A specific increment of X (ΔX) will be associated with different increments of Y (ΔY), depending on the initial value of X. When calculated correctly, using clot elasticity data, the platelet component of the clot can provide a valuable insight into platelet deficiency in emergency bleeding.

Cyanotic congenital heart disease (CCHD): focus on hypoxemia, secondary erythrocytosis, and coagulation alterations

Children with cyanotic congenital heart disease (CCHD) have complex alterations in their whole blood composition and coagulation profile due to long-standing hypoxemia. Secondary erythrocytosis is an associated physiological response intended to increase circulating red blood cells and oxygen carrying capacity. However, this response is frequently offset by an increase in whole blood viscosity that paradoxically reduces blood flow and tissue perfusion. In addition, the accompanying reduction in plasma volume leads to significant deficiencies in multiple coagulation proteins including platelets, fibrinogen and other clotting factors. On the one hand, these patients may suffer from severe hyperviscosity and subclinical 'sludging' in the peripheral vasculature with an increased risk of thrombosis. On the other hand, they are at an increased risk for postoperative hemorrhage due to a complex derangement in their hemostatic profile. Anesthesiologists caring for children with CCHD and secondary erythrocytosis need to understand the pathophysiology of these alterations and be aware of available strategies that lessen the risk of bleeding and/or thrombosis. The aim of this review is to provide an updated analysis of the systemic effects of long-standing hypoxemia in children with primary congenital heart disease with a specific focus on secondary erythrocytosis and hemostasis.

Effect of temperature on thromboelastography and implications for clinical use in newborns undergoing therapeutic hypothermia

BACKGROUND

Encephalopathic neonates undergoing therapeutic hypothermia have increased risk for coagulopathy secondary to perinatal asphyxia and effects of cooling on the coagulation enzyme cascade. Thromboelastography (TEG) allows for a comprehensive assessment of coagulation that can be regulated for temperature. TEG has not been previously evaluated in newborns undergoing hypothermia treatment.

METHODS

Encephalopathic neonates treated with systemic hypothermia were enrolled in this prospective observational study. Daily blood specimens were collected for standard coagulation tests and platelet counts during hypothermia and after rewarming. Concurrent TEG assays were performed at 33.5 and 37.0 °C for comparison.

RESULTS

A total of 48 paired TEGs from 24 subjects were performed. Forty percent of the subjects were males, the mean (± SD) birth weight was 3.2 ± 0.7 kg, and the mean gestational age was 38.4 ± 1.4 wk. TEG results differed significantly between assays performed at 37.0 vs. 33.5 °C, indicating more impaired coagulation at 33.5 °C. TEG parameters clot kinetics, angle, maximum amplitude (MA), and coagulation index were significantly associated with clinical bleeding (P < 0.05). These remained significant (except for MA) after controlling for transfusion therapy.

CONCLUSION

TEG results are affected by temperature, consistent with the known association of hypothermia with coagulopathy. Several TEG parameters are predictive of clinical bleeding in newborns undergoing hypothermia. Selected cutpoints to predict bleeding risk are temperature dependent.

Earlier detection of coagulopathy with thromboelastometry during pediatric cardiac surgery: a prospective observational study

OBJECTIVE

Earlier detection of coagulopathy in pediatric cardiac surgery patients.

AIM

To determine whether thromboelastometry (TEM) analysis before weaning from cardiopulmonary bypass (CPB) and hemoconcentration is predictive of post-CPB results and whether analysis of clot firmness already after 10 min yields reliable results.

BACKGROUND

Cardiac surgery with CPB induces a coagulopathy that may contribute to postoperative complications. Earlier detection increases the possibility of initiating countermeasures. METHODS/MATERIAL: Fifty-six pediatric cardiac surgery patients were included in a prospective observational study. HEPTEM and FIBTEM clotting time (CT), clot formation time (CFT), and clot firmness after 10 min (A10) and at maximum (MCF) were analyzed during CPB and after CPB and ultrafiltration with modified rotational thromboelastometry (ROTEM). The analyses were compared, and correlations and differences were calculated.

RESULTS

Hemoconcentration with modified ultrafiltration increased hematocrit from 28 ± 3 to 37 ± 4% (P < 0.001). Correlation coefficients of the TEM variables during and after CPB ranged from 0.61 to 0.82 (all P < 0.001). HEPTEM-CT and HEPTEM-MCF differed significantly but the differences were marginal. Both HEPTEM and FIBTEM A10 measurements during CPB were significantly less than MCF (P < 0.001 for both), but the correlations were highly significant (HEPTEM: r = 0.95, P < 0.001; FIBTEM: r = 0.96, P < 0.001), and the differences were predictable, with narrow confidence intervals (HEPTEM: -8.2 mm (-8.9 to -7.5); FIBTEM: -0.5 mm (-0.7 to -0.3).

CONCLUSION

The results suggest that intraoperative TEM analyses can be accelerated by analyzing HEPTEM/FIBTEM on CPB before hemoconcentration and by analyzing clot firmness already after 10 min.

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.

Effect of haematocrit on fibrin-based clot firmness in the FIBTEM test

BACKGROUND

Point-of-care thromboelastometry (ROTEM(®)) can be used to assess coagulation in whole blood. In the ROTEM(®) FIBTEM test, cytochalasin D eliminates the contribution of platelets to the whole blood clot; hence, only the remaining elements, including fibrinogen/fibrin, red blood cells and factor XIII, contribute to clot strength. We investigated the relationships between FIBTEM maximum clot firmness (MCF), whole blood fibrinogen concentration and plasma fibrinogen concentration to determine the impact of haematocrit on these parameters during cardiac surgery.

MATERIALS AND METHODS

The relationships between FIBTEM MCF and both whole blood fibrinogen concentration and plasma fibrinogen concentration (Clauss assay) were evaluated pre-operatively and after cardiopulmonary bypass/protamine administration in haematocrit-based subgroups.

RESULTS

The study included 157 patients. The correlation coefficient rho between FIBTEM MCF and plasma fibrinogen concentration was 0.68 at baseline and 0.70 after protamine, while that between FIBTEM MCF and whole blood fibrinogen concentration was 0.74 at baseline and 0.72 after protamine (all P <0.001). In subgroup analyses based on haematocrit levels, pre-operative FIBTEM MCF and whole blood fibrinogen concentration were both significantly higher (P <0.05) for the lowest haematocrit subgroup, but plasma fibrinogen concentration was similar in all groups. After protamine, no significant differences were observed between the lowest haematocrit group and the other groups for any of the three parameters.

CONCLUSIONS

The effect of haematocrit on blood clotting is not reflected by plasma fibrinogen concentration, in contrast to FIBTEM MCF which incorporates the contribution of haematocrit to whole blood clot firmness. This effect does, however, appear to be negligible in haemodiluted patients.

Comparison of thromboelastometry (ROTEM®) with standard plasmatic coagulation testing in paediatric surgery

BACKGROUND

Thromboelastometry (ROTEM(®)) might be useful to detect intraoperative coagulation disorders early in major paediatric surgery. This observational trial compares this technique to standard coagulation tests.

METHODS

Intraoperative blood sampling was obtained in children undergoing elective major surgery. At each time point, standard coagulation tests [activated partial thromboplastin time (aPTT), prothrombin time (PT), and fibrinogen level] and ROTEM(®) analyses (InTEM, ExTEM, and FibTEM) were performed simultaneously by trained hospital laboratory staff.

RESULTS

A total of 288 blood samples from 50 subjects were analysed. While there was a poor correlation between PT and aPTT to ExTEM clotting time (CT) and InTEM CT, respectively, a good correlation was detected between PT and aPTT to clot formation time, and a very good correlation between fibrinogen level and FibTEM assay (r=0.882, P<0.001). Notably, 64% of PT and 94% of aPTT measurements were outside the reference range, while impaired CT was observed in 13% and 6.3%, respectively. Standard coagulation test results were available after a median of 53 min [inter-quartile range (IQR): 45-63 min], whereas 10 min values of ROTEM(®) results were available online after 23 min (IQR: 21-24 min).

CONCLUSIONS

PT and aPTT cannot be interchangeably used with ROTEM(®) CT. Based on the results of ROTEM(®), recommended thresholds for PT and aPTT might overestimate the need for coagulation therapy. A good correlation was found between the fibrinogen level and the FibTEM assay. In addition, ROTEM(®) offered faster turnaround times.

Correlations between global clotting function tests, duration of operation, and postoperative chest tube drainage in pediatric cardiac surgery

BACKGROUND

Systemic coagulation disorders after cardiac surgery represent serious postoperative complications. There have been few reports, however, identifying preoperative coagulation tests that predict postoperative bleeding. The aim of the present study was to investigate the relationship between postoperative hemorrhage and coagulation parameters determined by global coagulation assays, to define potential predictive markers.

METHODS

Twenty-one pediatric patients were enrolled. Blood samples were collected before and 24 h after cardiac surgery. Laboratory investigations included platelet count, hematocrit, classical coagulation tests [prothrombin time, activated partial thromboplastin time, thrombin-antithrombin complex (TAT)], rotation thromboelastometry (ROTEM), and the thrombin generation test (TGT). The duration of the surgical procedure was recorded. Chest tube drainage was monitored for 24 h after operation as an index of postoperative hemorrhage.

RESULTS

Comparisons between preoperative and postoperative results indicated that TAT increased significantly after operation, whereas ROTEM parameters did not show a hypercoagulable pattern. Preoperative endogenous thrombin potential (ETP) measured in the TGT and clot formation time (CFT) in the ROTEM correlated with chest tube drainage. The classical coagulation tests were not informative. Postoperatively, peak height and ETP in TGT, all ROTEM parameters, and duration of surgery were correlated with chest tube drainage. Duration of surgery was correlated with postoperative ROTEM parameters but not with TGT. Postoperative maximum clot firmness and AUC were correlated with platelet count decrease ratio.

CONCLUSIONS

The preoperative CFT and ETP provide useful indices for predicting postoperative chest tube drainage volume. In addition, the duration of surgery also correlated with chest tube drainage and affected ROTEM parameters.

Point-of-care assessment of platelet aggregation in paediatric open heart surgery

BACKGROUND

Congenital heart disease (CHD) is associated with complex coagulation abnormalities. Platelet aggregability has not been investigated in detail in children with acyanotic and cyanotic malformations undergoing open heart surgery. The method of whole-blood multiple electrode aggregometry (MEA) appears suitable for rapid platelet analysis in children, for example, because of small sample volumes. We investigated perioperative evolution of platelet aggregation by means of MEA in children with CHD.

METHODS

Fifty children with acyanotic or cyanotic malformations were included in a prospective observational study. Laboratory testing was assessed before anaesthesia, and during and after surgery until the fifth postoperative day. MEA was performed in hirudin-anticoagulated blood using adenosine diphosphate (ADP), arachidonic acid, and thrombin receptor-activating peptide for platelet activation. Surgical variables, bleeding volumes, and transfusion requirements were documented during hospital stay.

RESULTS

Mean platelet count was within the normal range in all patients with no intergroup differences. Before surgery, aggregation to all agonists was within the age-adjusted normal range in cyanotic children and was statistically significantly higher compared with acyanotic children. Platelet aggregation decreased significantly during surgery in both groups followed by a slow recovery not reaching baseline levels. Bleeding and platelet transfusions were higher in the cyanotic group. Transfusion requirements correlated with ADP-induced platelet aggregation.

CONCLUSIONS

These results indicate higher blood loss, despite better platelet aggregation in cyanotic patients compared with acyanotic patients. MEA alone might not be suitable for predicting increased perioperative blood loss.

Treatment and monitoring of coagulation abnormalities in children undergoing heart surgery

Bleeding is a considerable clinical problem during and after pediatric heart surgery. While the primary cause of bleeding is surgical trauma, its treatment is often complicated by the presence of coagulopathy. The principle causes of coagulopathy are discussed to provide a context for treatment. The role of laboratory and point of care tests, which aim to identify the cause of bleeding in the individual patient, is also discussed. An attempt is made to examine the current evidence for available therapies, including use of blood products and, more recently proposed, approaches based on human or recombinant factor concentrates.

Intraoperative thromboelastometry is associated with reduced transfusion prevalence in pediatric cardiac surgery

BACKGROUND

The majority of pediatric cardiac surgery patients receive blood transfusions. We hypothesized that the routine use of intraoperative thromboelastometry to guide transfusion decisions would reduce the overall proportion of patients receiving transfusions in pediatric cardiac surgery.

METHODS

One hundred pediatric cardiac surgery patients were included in the study. Fifty patients (study group) were prospectively included and compared with 50 procedure- and age-matched control patients (control group). In the study group, thromboelastometry, performed during cardiopulmonary bypass, guided intraoperative transfusions. Intraoperative and postoperative transfusions of packed red blood cells, fresh frozen plasma, platelets, and fibrinogen concentrates, and postoperative blood loss and hemoglobin levels were compared between the 2 groups.

RESULTS

The proportion of patients receiving any intraoperative or postoperative transfusion of packed red blood cells, fresh frozen plasma, platelets, or fibrinogen concentrates was significantly lower in the study group than in the control group (32 of 50 [64%] vs 46 of 50 [92%], respectively; P < 0.001). Significantly fewer patients in the study group received transfusions of packed red blood cells (58% vs 78%, P = 0.032) and plasma (14% vs 78%, P < 0.001), whereas more patients in the study group received transfusions of platelets (38% vs 12%, P = 0.002) and fibrinogen concentrates (16% vs 2%, P = 0.015). Neither postoperative blood loss nor postoperative hemoglobin levels differed significantly between the study group and the control group.

CONCLUSIONS

The results suggest that routine use of intraoperative thromboelastometry in pediatric cardiac surgery to guide transfusions is associated with a reduced proportion of patients receiving transfusions and an altered transfusion pattern.

Thromboelastometry (ROTEM) in children: age-related reference ranges and correlations with standard coagulation tests

BACKGROUND

The small sample volume needed and the prompt availability of results make viscoelastic methods like rotational thromboelastometry (ROTEM) attractive for monitoring coagulation in small children. However, data on reference ranges for ROTEM parameters in children are scarce.

METHODS

Four hundred and seven children (ASA I and II) undergoing elective surgery were recruited for this prospective, two-centre, observational study. Subjects were grouped as follows: 0-3, 4-12, 13-24 months, 2-5, 6-10, and 11-16 yr. Study objectives were to establish age-dependent reference ranges for ROTEM assays, analyse age dependence of parameters, and compare ROTEM data with standard coagulation tests.

RESULTS

Data from 359 subjects remained for final analysis. Except for extrinsically activated clot strength and lysis, parameters for ROTEM assays were significantly different among all age groups. The most striking finding was that subjects aged 0-3 months exhibited accelerated initiation (ExTEM coagulation time: median 48 s, Q1-Q3 38-65 s; P=0.001) and propagation of coagulation (α angle: median 78(o), Q1-Q3 69-84(o); P<0.001) and maximum clot firmness (median 62 mm, Q1-Q3 54-74 mm), although standard plasma coagulation test results were prolonged (prothrombin time: median 13.2 s, Q1-Q3 12.6-13.6 s; activated partial thromboplastin time: median 42 s, Q1-Q3 40-46 s). Lysis indices of <85% were observed in nearly one-third of all children without increased bleeding tendency. Platelet count and fibrinogen levels correlated significantly with clot strength, and fibrinogen levels correlated with fibrin polymerization.

CONCLUSIONS

Reference ranges for ROTEM assays were determined for all paediatric age groups. These values will be helpful when monitoring paediatric patients and in studies of perioperative coagulation in children.

Thromboelastography of patients after fontan compared with healthy children

Patients who have undergone a Fontan procedure face an increased risk for thromboembolic complications. This study aimed to evaluate whether thromboelastography, a global whole-blood assay of coagulation, can be used to detect hypercoagulability in pediatric Fontan patients compared with healthy children. This prospective, cross-sectional study investigated 25 Fontan patients and 51 healthy children in three age groups: 1-5 years, 6-10 years, and 11-16 years. Kaolin-activated thromboelastography was performed on citrated samples. No statistically significant differences in thromboelastography parameters were found among the different age groups of the 51 healthy children. None of the 25 Fontan patients demonstrated evidence of hypercoagulability on thromboelastography (95% confidence interval, 0-7%), as defined by two standard deviations above or below the normal mean. The findings suggest that the percentage of Fontan patients demonstrating hypercoagulability on thromboelastography is substantially lower than the reported incidence of thromboembolic complications. Whether thromboelastography could be helpful in predicting patients at increased risk for thromboembolic complications or not still is not known. Further studies comparing the thromboelastography of Fontan patients with the thromboembolic complications of those without Fontan are needed to delineate these issues.

Whole blood coagulation measured by modified thrombelastography (ROTEM) is impaired in infants with congenital heart diseases

Patients with congenital heart disease (CHD) often do have a variety of coagulation abnormalities that results in bleeding diathesis. Our study aimed to determine the impact of cyanosis and CHD on modified thrombelastography parameters, compared with children without CHD. Preoperative blood samples were taken for TEM analyses from a total of 51 infants scheduled for surgery. The following groups were examined: normal patients without CHD, acyanotic patients with acyanotic CHD, and cyanotic patients with CHD and with preoperative hemoglobin values higher than 15 g dl(-1). Mean values of all patient groups as well as all individual values of normal patients were within their normal ranges. Within these limits, however, clots were significantly inferior in cyanotic patients (worse mean values of eight out of 10 measured TEM parameters representing the intrinsic, extrinsic, and plasmatic pathways of coagulation) and in acyanotic patients (two out of 10 TEM parameters). Individually, pathological TEM parameters were found in seven (41%) cyanotic patients (P=0.003; vs. normal patients) and in three (17%) acyanotic patients (P=0.01). More than one abnormal TEM coagulation parameter was found in four patients, all of them cyanotic patients. Hyperfibrinolysis was detected in one patient, a cyanotic patient. The present investigation confirms previous findings that in patients with CHD the heart defect itself compromises coagulation monitored with TEM, but in addition, we demonstrate that cyanosis and/or polycythemia exert the essential negative impact on hemostasis. Preoperative hyperfibrinolysis detected with TEM seems to play no important role.

Effects of albumin 5% and artificial colloids on clot formation in small infants

Albumin is often cited in textbooks as the gold standard for fluid replacement in paediatrics, but in practice artificial colloids are more frequently used. Although one concern with the use of artificial colloids is their intrinsic action on haemostasis, the available data in children are inconclusive for 6% hydroxyethyl starch 130/0.4 (HES) and no data exist for gelatine solution with respect to coagulation. A total of 42 children (3-15 kg) undergoing surgery and needing colloid replacement were randomly assigned to receive 15 mlxkg(-1) of either albumin 5%, 4% modified gelatine solution or 6% hydroxyethyl starch 130/0.4 solution. Standard coagulation tests and modified thrombelastography (ROTEM) were performed. After colloid administration, routine coagulation test results changed significantly and comparably in all groups, although activated partial thromboplastin time values increased more with gelatine and HES. Coagulation time was unchanged in the children who received albumin or gelatine but other activated modified thrombelastography values were significantly impaired in all groups. After gelatine and after albumin the median clot firmness decreased significantly but remained within the normal range. Following HES, coagulation time increased significantly, and clot formation time, alpha angle, clot firmness, and fibrinogen/fibrin polymerisation were significantly more impaired than for albumin or gelatine, reaching median values below the normal range. From a haemostatic point of view it might be preferable to use gelatine solution as an alternative to albumin; HES showed the greatest effects on the overall coagulation process.