Performance of functional fibrinogen thromboelastography in children undergoing congenital heart surgery

Effects of Fibrinogen Concentrate Supplementation on Postoperative Bleeding in Infants Undergoing Complex Cardiac Surgery

The use of allogeneic blood products to restore hemostasis during pediatric cardiac surgery is associated with major risks. Consequently, there has been a growing interest in new patient blood management strategies, such as those based on the use of fibrinogen concentrate (FC). Accumulating evidence has shown FC supplementation to be safe and effective. Nevertheless, no guidelines are available on using FC in the pediatric setting, and few objective evaluations have been provided in clinical practice. The endpoint of this monocenter retrospective study was the hemostatic effect of additional FC in infants undergoing complex cardiac surgery with cardiopulmonary bypass to manage persistent clinically relevant bleeding. After weaning from cardiopulmonary bypass and after protamine administration, patients were transfused with conventional allogeneic products such as packed red blood cells, fresh frozen plasma (FFP), and platelets. In the case of redo surgery, according to the institutional protocol, patients also received tranexamic acid. In case of clinically persistent relevant bleeding, according to the anesthesiologist's judgment and thromboelastography, patients received FC supplementation (group with FC) or further FFP transfusions without receiving FC supplementation (group without FC). The primary endpoint was the hemostatic effects of FC. Secondary endpoints were the functional hypofibrinogenemia threshold value (expressed as maximum amplitude fibrinogen, MA-Fib) and postoperative MA-Fib, fibrinogenemia, intraoperative transfusions, and adverse events (AEs). In total, 139 patients who underwent cardiac surgery with CPB and aged less than 2 years were enrolled: 70 patients received allogeneic blood products and FC supplementation (group FC); 69 patients received allogeneic products without FC supplementation (group without FC). Patients that received FC supplementation were characterized by a significantly longer time of extracorporeal circulation (p < 0.001) and aortic cross-clamping (p < 0.001), a significantly lower minimum temperature (p = 0.011), increased use of concentrated prothrombin complex (p = 0.016) and tranexamic acid (p = 0.010), and a significantly higher amount of packed red blood cells, platelets (p < 0.001) and fresh frozen plasma (p = 0.03). Postoperative bleeding and severe bleeding were not statistically different between patients treated with FC and those not treated with FC supplementation (p = 0.786 and p = 0.695, respectively); after adjustment, a trend toward reduced bleeding can be observed with FC (p = 0.064). Overall, 88% of patients with severe bleeding had MA-Fib < 10 mm; a moderate association between severe bleeding and MA-Fib (odds ratio 1.7, 95% CI 0.5-6.5, p = 0.425) was found. Increased MA-Fib and postoperative fibrinogen were higher in the FC group (p = 0.003 and p < 0.001, respectively) than in FFP. AEs in the FC group were comparable to those observed in less complicated surgeries. Our results suggest a potential role of FC in complex surgery in maintaining postoperative bleeding at a level comparable to less complicated surgical procedures and favoring the increase in postoperative MA-Fib and fibrinogen.

A single-center, retrospective analysis to compare measurement of fibrinogen using the TEG6 analyzer to the Clauss measurement in children undergoing heart surgery

BACKGROUND

Newer generation viscoelastic tests, TEG6s, offer point-of-care hemostatic therapy in adult patients. However, their efficacy in estimating fibrinogen levels in pediatric patients undergoing cardiac surgery is not well established.

AIMS

This study evaluates TEG6s for estimating fibrinogen levels in pediatric cardiac surgery patients and its predictive capability for post-bypass hypofibrinogenemia.

METHODS

A single-center, retrospective study on pediatric patients (under 18 years) who underwent cardiac surgery with cardiopulmonary bypass from August 2020 and November 2022. Blood samples for estimated whole blood functional fibrinogen level via TEG6s (Haemonetics Inc.) and concurrent laboratory-measured plasma fibrinogen via von Clauss assay were collected at pre- and post-cardiopulmonary bypass.

RESULTS

Paired data for TEG6s estimated functional fibrinogen levels and plasma fibrinogen were analyzed for 432 pediatric patients pre-bypass. It was observed that functional fibrinogen consistently overestimated plasma fibrinogen across all age groups with a mean difference of 138 mg/dL (95% confidence interval [CI]: 128-149 mg/dL). This positive bias in the pre-bypass data was confirmed by Bland-Altman analysis. Post-bypass, functional fibrinogen estimates were comparable to plasma fibrinogen in all patient groups with a mean difference of -6 mg/dL (95% CI: -20-8 mg/dL) except for neonates, where functional fibrinogen levels underestimated plasma fibrinogen with a mean difference of -38 mg/dL (95% CI: -64 to -12 mg/dL). The predictive accuracy of functional fibrinogen for detecting post-bypass hypofibrinogenemia (plasma fibrinogen ≤250 mg/dL) demonstrated overall fair accuracy in all patients, indicated by an area under the curve of 0.73 (95% CI: 0.65-0.80) and good accuracy among infants, with an area under the curve of 0.80 (95% CI: 0.70-0.90). Similar performance was observed in predicting critical post-bypass hypofibrinogenemia (plasma fibrinogen ≤200 mg/dL). Based on these analyses, optimal cutoffs for predicting post-bypass hypofibrinogenemia were established as a functional fibrinogen level ≤270 mg/dL and MAFF ≤15 mm.

CONCLUSION

This study demonstrates that whole blood functional fibrinogen, as estimated by TEG6s, tends to overestimate baseline plasma fibrinogen levels in pediatric age groups but aligns more accurately post-cardiopulmonary bypass, particularly in neonates and infants, suggesting its potential as a point-of-care tool in pediatric cardiac surgery. However, the variability in TEG6s performance before and after bypass highlights the need for careful interpretation of its results in clinical decision-making. Despite its contributions to understanding TEG6s in pediatric cardiac surgery, the study's design and inherent biases warrant cautious application of these findings in clinical settings.

Empiric Cryoprecipitate Transfusion in Patients with Severe Hemorrhage: Results from the US Experience in the International CRYOSTAT-2 Trial

BACKGROUND

Hypofibrinogenemia has been shown to predict massive transfusion and is associated with higher mortality in severely injured patients. However, the role of empiric fibrinogen replacement in bleeding trauma patients remains controversial. We sought to determine the effect of empiric cryoprecipitate as an adjunct to a balanced transfusion strategy (1:1:1).

STUDY DESIGN

This study is a subanalysis of patients treated at the single US trauma center in a multicenter randomized controlled trial. Trauma patients (more than 15 years) were eligible if they had evidence of active hemorrhage requiring emergent surgery or interventional radiology, massive transfusion protocol (MTP) activation, and received at least 1 unit of blood. Transfer patients, those with injuries incompatible with life, or those injured more than 3 hours earlier were excluded. Patients were randomized to standard MTP (STANDARD) or MTP plus 3 pools of cryoprecipitate (CRYO). Primary outcomes included all-cause mortality at 28 days. Secondary outcomes were transfusion requirements, intraoperative and postoperative coagulation laboratory values, and quality-of-life measures (Glasgow outcome score-extended).

RESULTS

Forty-nine patients (23 in the CRYO group and 26 in the STANDARD group) were enrolled between May 2021 and October 2021. Time to randomization was similar between groups (14 vs 24 minutes, p = 0.676). Median time to cryoprecipitate was 41 minutes (interquartile range 37 to 48). There were no differences in demographics, arrival physiology, laboratory values, or injury severity. Intraoperative and ICU thrombelastography values, including functional fibrinogen, were similar between groups. There was no benefit to CRYO with respect to post-emergency department transfusions (intraoperative and ICU through 24 hours), complications, Glasgow outcome score, or mortality.

CONCLUSIONS

In this study of severely injured, bleeding trauma patients, empiric cryoprecipitate did not improve survival or reduce transfusion requirements. Cryoprecipitate should continue as an "on-demand" addition to a balanced transfusion strategy, guided by laboratory values and should not be given empirically.

Thromboelastography in the Perioperative Period: A Literature Review

Assessing coagulation status is essential for prompt intervention to reduce morbidity and mortality related to bleeding and thrombotic complications during the perioperative period. Traditional coagulation tests such as platelet count, activated partial thromboplastin time (aPTT), prothrombin time (PT), international normalized ratio (INR), and activated clotting time (ACT) provide only static evaluation. These tests are not designed for assessment of dynamically changing coagulation conditions during the perioperative time. However, viscoelastic coagulation testing such as thromboelastography (TEG) produces a rapid numerical and graphical representation that helps to detect and direct targeted hemostatic therapy. Searching the literature through PubMed, Medline, Ovid, CINAHL, and ClinicalTrials.gov we retrieved 210 studies, which represent the use of TEG in the perioperative period. The included studies were categorized under various settings such as trauma, obstetrics, orthopedics, intensive care unit (ICU), cardiovascular, transplant, and miscellaneous scenarios. TEG showed promising results in trauma surgeries in predicting mortality, hypercoagulability, and bleeding even when it was compared to conventional methods. TEG was also useful in monitoring anticoagulant therapy in orthopedic and obstetric surgeries; however, its role in predicting thrombotic events, hypercoagulability, or complications was questionable. In ICU patients, it showed promising results, especially in the prediction or improvement of sepsis, coagulopathy, thrombotic events, ICU duration, hospital stay, and ventilator duration. TEG parameters effectively predicted hypercoagulation in transplant surgeries. Regarding cardiovascular surgeries, they were effective in the prediction of the need for blood products, coagulopathy, thrombotic events, and monitoring anticoagulation therapy. More randomized clinical trials comparing TEG parameters with standardized tools are needed to produce robust results to standardize its use in different perioperative settings.

Viscoelastic testing in pediatric patients

A tailored transfusion algorithm based on viscoelastic testing in the perioperative period or in trauma patients is recommended by guidelines for bleeding management. Bleeding management strategies in neonates and children are mostly extrapolated from the adult experience, as published evidence in the youngest age group is scarce. This manuscript is intended to give a structured overview of what has been published on the use of viscoelastic testing to guide bleeding management in neonates and children. Several devices that use either the traditional viscoelastic method or resonance viscoelastography technology are on the market. Reference ranges for children have been evaluated in only some of them. As most of the hemostasis maturation processes can be observed during the first year of life, adult reference ranges for viscoelastic testing could be applied over the age of 1 year. The majority of the published trials in children are based on retrospective analyses describing the correlation between viscoelastic testing and standard laboratory testing or focusing on the prediction of bleeding. Clinically more relevant studies in pediatric patients undergoing cardiac surgery have demonstrated that the implementation of a transfusion algorithm based on viscoelastic testing has significantly reduced transfusion requirements and that this approach has enabled a rapid detection of coagulation disorders in the presence of excessive bleeding. Although further studies are urgently needed, experts have reviewed the use of a transfusion algorithm based on viscoelastic testing in children as a feasible approach, as it has been shown to improve bleeding management and rationalize blood product transfusion.

Prevention of postoperative bleeding after complex pediatric cardiac surgery by early administration of fibrinogen, prothrombin complex and platelets: a prospective observational study

Background

Postoperative bleeding is a major problem in children undergoing complex pediatric cardiac surgery. The primary aim of this prospective observational study was to evaluate the effect of an institutional approach consisting of early preventive fibrinogen, prothrombin complex and platelets administration on coagulation parameters and postoperative bleeding in children. The secondary aim was to study the rate of re-intervention and postoperative transfusion, the occurrence of thrombosis, length of mechanical ventilation, ICU stay and mortality.

Methods

In fifty children (age 0–6 years) with one or more predefined risk factors for bleeding after cardiopulmonary bypass (CPB), thrombelastography (TEG) and standard coagulation parameters were measured at baseline (T1), after CPB and reversal of heparin (T2), at sternal closure (T3) and after 12 h in the ICU (T4). Clinical bleeding was evaluated by the surgeon at T2 and T3 using a numeric rating scale (NRS, 0–10).

Results

After CPB and early administration of fibrinogen, prothrombin complex and platelets, the clinical bleeding evaluation score decreased from a mean value of 6.2 ± 1.9 (NRS) at T2 to a mean value of 2.1 ± 0.8 at T3 (NRS; P <  0.001). Reaction time (R), kinetic time (K), maximum amplitude (MA) and maximum amplitude of fibrinogen (MA-fib) improved significantly (P <  0.001 for all), and MA-fib correlated significantly with the clinical bleeding evaluation (r = 0.70, P <  0.001). The administered total amount of fibrinogen (mg kg^− 1) correlated significantly with weight (r = − 0.42, P = 0.002), priming volume as percentage of estimated blood volume (r = 0.30, P = 0.034), minimum CPB temperature (r = − 0.30, P = 0.033) and the change in clinical bleeding evaluation from T2 to T3 (r = 0.71, P <  0.001). The incidence of postoperative bleeding (> 10% of estimated blood volume) was 8%. No child required a surgical re-intervention, and no cases of thrombosis were observed. Hospital mortality was 0%.

Conclusion

In this observational study of children with an increased risk of bleeding after CPB, an early preventive therapy with fibrinogen, prothrombin complex and platelets guided by clinical bleeding evaluation and TEG reduced bleeding and improved TEG and standard coagulation parameters significantly, with no occurrence of thrombosis or need for re-operation.

Trial registration

German Clinical Trials Register DRKS00018109 (retrospectively registered 27th August 2019).

Diagnostic accuracy of viscoelastic point-of-care identification of hypofibrinogenaemia in cardiac surgical patients: A systematic review

Hypofibrinogenaemia during cardiac surgery may increase blood loss and bleeding complications. Viscoelastic point-of-care tests provide more rapid diagnosis than laboratory measurement, allowing earlier treatment. However, their diagnostic test accuracy for hypofibrinogenaemia has never been reviewed systematically. We aimed to systematically review their diagnostic test accuracy for the identification of hypofibrinogenaemia during cardiac surgery. Two reviewers assessed relevant articles from seven electronic databases, extracted data from eligible articles and assessed quality. The primary outcomes were sensitivity, specificity and positive and negative predictive values. A total of 576 articles were screened and 81 full texts were assessed, most of which were clinical agreement or outcome studies. Only 10 diagnostic test accuracy studies were identified and only nine were eligible (ROTEM delta 7; TEG5000 1; TEG6S 1, n = 1820 patients) (ROTEM, TEM International GmbH, Munich, Germany; TEG, Haemonetics, Braintree, MA, USA). None had a low risk of bias. Four ROTEM studies with a fibrinogen threshold less than 1.5–1.6 g/l and FIBTEM threshold A10 less than 7.5–8 mm had point estimates for sensitivity of 0.61–0.88; specificity 0.54–0.94; positive predictive value 0.42–0.70; and negative predictive value 0.74–0.98 (i.e. false positive rate 30%–58%; false negative rate 2%–26%). Two ROTEM studies with higher thresholds for both fibrinogen (<2 g/l) and FIBTEM A10 (<9.5 mm) had similar false positive rates (25%–46%), as did the two TEG studies (15%–48%). This review demonstrates that there have been few diagnostic test accuracy studies of viscoelastic point-of-care identification of hypofibrinogenaemia in cardiac surgical patients. The studies performed so far report false positive rates of up to 58%, but low false negative rates. Further diagnostic test accuracy studies of viscoelastic point-of-care identification of hypofibrinogenaemia are required to guide their better use during cardiac surgery.

Comparison between the new fully automated viscoelastic coagulation analysers TEG 6s and ROTEM Sigma in trauma patients: A prospective observational study

BACKGROUND

Viscoelastic coagulation testing is increasingly used to diagnose trauma-induced coagulopathy. Two fully automated analysers, TEG 6s and ROTEM Sigma, were launched recently. No previous studies have compared these devices in trauma paients.

OBJECTIVE

The aim of this study was to evaluate whether both fully automatic devices deliver comparable results.

DESIGN

Prospective observational study.

SETTING

Level one trauma centre from August 2017 to September 2018.

PATIENTS

A total of 105 blood samples from 67 trauma patients were analysed simultaneously on TEG 6s and ROTEM Sigma.

MAIN OUTCOME MEASURES

TEG 6s assays kaolin (CK), RapidTEG (CRT), kaolin with heparinase (CKH) and functional fibrinogen were compared with ROTEM Sigma assays INTEM, EXTEM, HEPTEM and FIBTEM. TEG 6s functional fibrinogen level was compared with plasma fibrinogen concentration, measured using the Clauss method. Correlations were classified as weak (Spearman correlation coefficient 0.20 to 0.39), moderate (0.40 to 0.59), strong (0.60 to 0.79) or very strong (≥0.80).

RESULTS

The TEG 6s parameters reaction time, kinetic time and α-angle (CK, CRT and CKH assays) mostly showed strong correlations with the corresponding ROTEM parameters clotting time, clot formation time and α-angle (INTEM, EXTEM and HEPTEM assays). The exceptions were CRT reaction time vs. EXTEM clotting time, and CK α-angle vs. INTEM α-angle, which correlated moderately. Absolute values for many of these parameters showed significant differences between the two devices. Very strong correlations and similar absolute values were observed between TEG 6s maximum amplitude (CRT, CK and CKH assays) and ROTEM maximum clot firmness (EXTEM, INTEM and HEPTEM assays). Correlations were also very strong for functional fibrinogen maximum amplitude vs. FIBTEM maximum clot firmness and functional fibrinogen level vs. Clauss fibrinogen concentration, but absolute values were significantly different.

CONCLUSION

Strong to very strong correlations were observed between corresponding TEG 6s and ROTEM Sigma parameters. However, absolute values showed significant differences for most of the measurements.

Use of Coagulation Point-of-Care Tests in the Management of Anticoagulation and Bleeding in Pediatric Cardiac Surgery: A Systematic Review

Bleeding and coagulation management are essential aspects in the management of neonates and children undergoing cardiac surgery. The use of point-of-care tests (POCTs) in a pediatric setting is not as widely used as in the adult setting. This systematic review aims to summarize the evidence showed by the literature regarding the use of POCTs in children undergoing cardiac surgery. We included all studies examining the pediatric population (<18 years old) undergoing cardiac surgery in which the coagulation profile was assessed with POCTs. Three electronic databases (PubMed, Embase, and the Cochrane Controlled Clinical Trials register) were searched. Tests involved were heparin effect tests, viscoelastic tests, and platelet function tests. Due to the wide heterogeneity of the patients and tests studied, a formal meta-analysis was impossible, and the results are therefore presented through a systematic review. Eighty articles were found, of which 47 are presented in this review. At present, literature data are too weak to define POCTs as a "gold standard" for the treatment of perioperative bleeding in pediatric cardiac surgery. Nevertheless, introduction of POCTs into postoperative algorithms has shown to improve bleeding management, patient outcome, and cost efficiency.

A comparative study of fibrinogen measurement using TEG® functional fibrinogen and Clauss in adolescents undergoing scoliosis surgery

INTRODUCTION

Thromboelastography (TEG®) functional fibrinogen (FF) test is a point-of-care test for fibrinogen measurement and is preferred for its rapid turnaround time. This study was designed to compare TEG® functional fibrinogen level (FLEV) with classic Clauss fibrinogen in patients undergoing scoliosis surgery and to evaluate the concordance between the two methods.

METHODS

Patients in this study were part of a larger study evaluating the effect of fibrinogen concentrate (FC) supplementation on perioperative blood loss in scoliosis surgery. Paired samples for TEG® FF and Clauss fibrinogen assays were taken from 40 patients at three different timepoints perioperatively. The agreement between FLEV and Clauss was assessed, and the possibility of using FLEV measurements to predict Clauss fibrinogen was explored.

RESULTS

One hundred and seventeen paired samples from 39 patients were finally analyzed. Pearson correlation test confirmed positive linear correlations between FLEV and Clauss at all three timepoints (r = .70, .67, and .66 at baseline, before FC administration, and after FC administration, respectively; P < .001 for all) and together for all measures (r = .76, P < .001), while Bland-Altman plots showed FLEV significantly overestimated Clauss constantly. Optimum diagnostic values of FLEV at 4.27 and 3.77 g/L were generated to predict normal fibrinogen as Clauss ≥ 3.0 g/L (AUROC 0.941, 95% CI: 0.891-0.991) and critical intraoperative hypofibrinogenemia as Clauss ≤ 2.0g/L (AUROC 0.894, 95% CI: 0.838-0.950), respectively.

CONCLUSIONS

In adolescents undergoing scoliosis surgery, FLEV correlated linearly with Clauss fibrinogen. Though FLEV overestimates Clauss constantly, FLEV values are able to predict hypofibrinogenemia and normal fibrinogen with both AUROC > 0.85.

Thromboelastography and Thromboelastometry in Assessment of Fibrinogen Deficiency and Prediction for Transfusion Requirement: A Descriptive Review

Fibrinogen is crucial for the formation of blood clot and clinical outcomes in major bleeding. Both Thromboelastography (TEG) and Rotational Thromboelastometry (ROTEM) have been increasingly used to diagnose fibrinogen deficiency and guide fibrinogen transfusion in trauma and surgical bleeding patients. We conducted a comprehensive and comparative review on the technologies and clinical applications of two typical functional fibrinogen assays using TEG (FF TEG) and ROTEM (FIBTEM) for assessment of fibrinogen level and deficiency, and prediction of transfusion requirement. Clot strength and firmness of FF TEG and ROTEM FIBTEM were the most used parameters, and their associations with fibrinogen levels as measured by Clauss method ranged from 0 to 0.9 for FF TEG and 0.27 to 0.94 for FIBTEM. A comparison of the interchangeability and clinical performance of the functional fibrinogen assays using the two systems showed that the results were correlated, but are not interchangeable between the two systems. It appears that ROTEM FIBTEM showed better associations with the Clauss method and more clinical use for monitoring fibrinogen deficiency and predicting transfusion requirements including fibrinogen replacement than FF TEG. TEG and ROTEM functional fibrinogen tests play important roles in the diagnosis of fibrinogen-related coagulopathy and guidance of transfusion requirements. Despite the fact that high-quality evidence is still needed, the two systems are likely to remain popular for the hemostatic management of bleeding patients.

Noteworthy Literature published in 2017 for Congenital Cardiac Anesthesiologists

This review focuses on the literature published during the 13 months from December 2016 to December 2017 that is of interest to anesthesiologists taking care of children and adults with congenital heart disease. Five themes are addressed during this time period and 100 peer-reviewed articles are discussed.