Fibrinogen supplementation ex vivo increasesclot firmness comparable to platelet transfusion in thrombocytopenia

Supplemental fibrinogen restores thrombus formation in cardiopulmonary bypass-induced platelet dysfunction ex vivo

BACKGROUND

Major cardiac surgery related blood loss is associated with increased postoperative morbidity and mortality. Platelet dysfunction is believed to contribute to post-cardiopulmonary bypass (CPB)-induced microvascular bleeding. We hypothesised that moderately hypothermic CPB induces platelet dysfunction and that supplemental fibrinogen can restore in vitro thrombus formation.

METHODS

Blood from 18 patients, undergoing first-time elective isolated aortic valve surgery was drawn before CPB, 30 min after initiation of CPB, and after CPB and protamine administration, respectively. Platelet aggregation was quantified by optical aggregometry, platelet activation by flow-cytometric detection of platelet surface expression of P-selectin, annexin V, and activated glycoprotein IIb/IIIa, thrombus formation under flow and effect of supplemental fibrinogen (4 mg ml-1) on in vitro thrombogenesis.

RESULTS

Post-CPB adenosine-diphosphate and TRAP-6-induced aggregation decreased by 40% and 10% of pre-CPB levels, respectively (P<0.0001). Although CPB did not change glycoprotein IIb/IIIa receptor expression, it increased the percentage of unstimulated P-selectin (1.2% vs 7%, P<0.01) positive cells and annexin V mean fluorescence intensity (15.5 vs 17.2, P<0.05), but decreased percentage of stimulated P-selectin (52% vs 26%, P<0.01) positive cells and annexin V mean fluorescence intensity (508 vs 325, P<0.05). Thrombus area decreased from 6820 before CPB to 5230 after CPB (P<0.05, arbitrary units [a.u.]). Supplemental fibrinogen increased thrombus formation to 20 324 and 11 367 a.u. before CPB and after CPB, respectively (P<0.001), thereby restoring post-CPB thrombus area to levels comparable with or higher than pre-CPB baseline.

CONCLUSIONS

Single valve surgery using moderately hypothermic CPB induces partial platelet dysfunction. Thrombus formation was restored in an experimental study design by ex vivo supplementation of fibrinogen.

Patient Blood Management in Liver Transplant—A Concise Review

Transfusion of blood products in orthotopic liver transplantation (OLT) significantly increases post-transplant morbidity and mortality and is associated with reduced graft survival. Based on these results, an active effort to prevent and minimize blood transfusion is required. Patient blood management is a revolutionary approach defined as a patient-centered, systematic, evidence-based approach to improve patient outcomes by managing and preserving a patient’s own blood while promoting patient safety and empowerment. This approach is based on three pillars of treatment: (1) detecting and correcting anemia and thrombocytopenia, (2) minimizing iatrogenic blood loss, detecting, and correcting coagulopathy, and (3) harnessing and increasing anemia tolerance. This review emphasizes the importance of the three-pillar nine-field matrix of patient blood management to improve patient outcomes in liver transplant recipients.

Does Intraoperative Fibrinogen Affect Blood Loss or Transfusion Practice After Aortic Arch Surgery: A Prematurely Ended Randomized Trial

Cardiovascular surgery is often complicated by significant bleeding due to perioperative coagulopathy. The effectiveness of treatment with fibrinogen concentrate to reduce the perioperative blood transfusion rate after thoracic aortic replacement surgery in prior studies has shown conflicting results. Therefore, we conducted a double-blind randomized controlled trial to investigate if a single dose of intraoperative fibrinogen administration reduced blood loss and allogeneic transfusion rate after elective surgery for thoracic arch aneurysm with deep hypothermic circulatory arrest. Twenty patients were randomized to fibrinogen concentrate (N = 10) or placebo (N = 10). The recruitment of study patients was prematurely ended due to a low inclusion rate. Perioperative transfusion, 5-minute bleeding mass after study medication and postoperative blood loss were not different between the groups with fibrinogen concentrate or placebo. Due to small volumes of postoperative blood loss and premature study termination, a beneficial effect of fibrinogen concentrate on the number of blood transfusions could not be established. However, treatment with fibrinogen efficiently restored fibrinogen levels and clot strength to preoperative values with a more effective preserved postoperative thrombin generation capacity. This result might serve as a pilot for further multicenter studies to assess the prospective significance of automated and standardized thrombin generation as a routine assay for monitoring perioperative coagulopathy and its impact on short- and long-term operative results.

Cryoprecipitate as an alternative to platelet transfusion in thrombocytopenia

Platelet transfusions are not always available for bleeding in severe thrombocytopenia, as storage outside of major centers is limited by their short shelf-life. Data are lacking to support alternative available blood products; however, additional fibrinogen has been shown to enhance clot formation in vitro. To test the hypothesis that cryoprecipitate supplementation could improve clot formation in severe thrombocytopenia, eight hematological malignancy patients with platelet counts under 10 × 109/L each had 10 units of apheresis cryoprecipitate transfused prior to planned prophylactic platelet transfusions. The primary endpoint of thromboelastometry amplitude at 20 min increased by a mean of 5.1 mm (p < 0.01) following cryoprecipitate transfusion despite persisting thrombocytopenia. Thromboelastometry clotting times reduced by a mean of 7.8 s (p < 0.05) and alpha angle increased by a mean of 10.6⁰ (p < 0.01). These results are consistent with cryoprecipitate enhancing the strength of the fibrin/platelet meshwork within the forming thrombus. While platelet transfusion remains the standard of care, where platelet supplies are limited, these data provide a rationale for the use of cryoprecipitate to obtain hemostasis in bleeding thrombocytopenic patients.

Stability of Reconstituted Fibrinogen Concentrate in Hemostatic Function and Concentration

INTRODUCTION

Canadian Armed Forces adopted fibrinogen concentrate (RiaSTAP) for hemostatic resuscitation in the far-forward combat setting, given its potential benefits of reducing blood loss, blood transfusion and mortality, and its long storage stability and high portability. The current guidance recommends that RiaSTAP should be administered within 8 hours after reconstitution when stored at room temperature. However, little information about its stability is available. There is also a need to investigate the stability and efficacy of RiaSTAP after reconstitution and exposure to extreme temperatures in which our forces may operate.

MATERIALS AND METHODS

RiaSTAP was reconstituted as per manufacturer's instruction and stored at specific temperatures (-20°C, 4°C, 22°C, 35°C, 42°C, or 50°C) for up to 6 months. Reconstituted RiaSTAP was also oscillated on a rocker at 18 rpm under 22°C and 50°C. Its hemostatic function was measured using rotational thromboelastometry performed with RiaSTAP-spiked whole blood. Fibrinogen concentrations were measured by a commercial enzyme-linked immunosorbent assay (ELISA) kit. Gel electrophoresis was also conducted for initial and stored samples.

RESULTS

We found no change to the hemostatic function of reconstituted RiaSTAP after storage at -20°C for 6 months. At 4°C, no obvious changes to the hemostatic effect of reconstituted RiaSTAP relative to 0 hours were seen until 1,680 hours. At 22°C, a remarkable decrease began after storage for 168 hours. Storage at 35°C significantly decreased the hemostatic effect after 144 hours, while the storage at 42°C resulted in decreased hemostatic function after 72 hours. Finally, storage at 50°C for 8 hours resulted in complete loss of hemostatic function. Compared to the hemostatic activity, the fibrinogen concentration for reconstituted RiaSTAP showed less change over time. No apparent decline in fibrinogen concentration was seen after storage at -20°C for 6 months and at 4°C for 1,680 hours. At 22°C, there were no clear alterations until 792 hours. There was a decline in fibrinogen concentration at 35°C and 42°C after 672 and 600 hours of storage, respectively. At 50°C, little amount of fibrinogen was detected by ELISA at 8 hours. Similar changes in the hemostatic effect and fibrinogen concentration over time were observed under the rocking condition in comparison with the static condition at the same temperature. The gel electrophoresis confirmed fibrinogen degradation which increased with storage temperature and time.

CONCLUSIONS

The stability of reconstituted RiaSTAP decreases with increasing storage temperature. The hemostatic function deteriorated before fibrinogen concentration and integrity were significantly altered at all temperatures for the study period except at 50°C where there was a rapid decline in both hemostatic function and fibrinogen concentration. Sample oscillation did not significantly affect its stability. The shelf life of reconstituted RiaSTAP may, therefore, be recommended accordingly when stored at different temperatures and extended to 6 days at room temperature provided that sterility is maintained.

The role of ROTEM variables based on clot elasticity and platelet component in predicting bleeding risk in thrombocytopenic critically ill neonates

BACKGROUND

Our aim was to investigate the role of thromboelastometry (ROTEM) parameters, including maximum clot elasticity (MCE) and platelet component (PLTEM MCE and PLTEM MCF), in early prediction of bleeding events in thrombocytopenic critically ill neonates.

MATERIAL AND METHODS

This single-center, prospective cohort study included 110 consecutive thrombocytopenic neonates with sepsis, suspected sepsis, or hypoxia. On the first day of disease onset, ROTEM EXTEM and FIBTEM assays were performed and the neonatal bleeding assessment tool was used for the evaluation of bleeding events.

RESULTS

Most EXTEM and FIBTEM ROTEM parameters significantly differed between neonates with (n = 77) and without bleeding events (n = 33). Neonates with bleeding events had significantly lower PLTEM MCE and PLTEM MCF values compared to those without bleeding events (P < .001). Platelet count was found to be strongly positively correlated with EXTEM A5 (Spearman's rho = 0.61, P < .001) and A10 (rho = 0.64, P < .001). EXTEM A10 demonstrated the best prognostic performance (AUC = 0.853) with an optimal cutoff value (≤37 mm) (sensitivity = 91%, specificity = 76%) for prediction of bleeding events in thrombocytopenic neonates.

CONCLUSIONS

EXTEM A5 and EXTEM A10 were found to be strong predictors of hemorrhage, compared to most ROTEM variables quantifying clot elasticity and platelet component in thrombocytopenic critically ill neonates.

Endothelial damage and a thin intercellular fibrin network promote haemorrhage in acute promyelocytic leukaemia

Background

The role of vascular endothelium in acute promyelocytic leukaemia (APL) remains unknown. We aimed to investigate the mechanisms by which APL cells interact with endothelial cells (ECs) and to further explore how the endothelium affects bleeding as well as therapeutic interventions.

Method

APL cells and an original APL cell line, NB4 cells, were used for experiments. The effects of leukaemic cells on ECs were analyzed in vitro and in vivo. Moreover, the endothelial barrier function and procoagulant activity were detected. An APL mouse model was established for in vivo studies.

Findings

APL cells interacted with ECs via ICAM-1 and VCAM-1 receptors to disrupt endothelial integrity. This binding activated MLCK signaling, resulting in the trans-endothelial passage of protein and red blood cells (RBCs). Combined treatment with asiatic acid or anti-adhesion receptor antibody inhibited the response of ECs to APL cells, thereby preventing APL-associated haemorrhage in vitro and in vivo. Activated ECs exhibited a procoagulant phenotype after phosphatidylserine exposure. Plasma from APL patients formed a thin fibrin network between procoagulant ECs, and this intercellular fibrin decreased the passage of albumin and RBCs. Ex vivo addition of fibrinogen further enhanced this barrier function in a dose-dependent manner.

Interpretation

Endothelial damage induced by leukaemic cell adherence promotes haemorrhaging in APL. Stabilization of ECs, decreasing adhesion receptor expression, and increasing fibrinogen transfusion levels may be a new therapeutic avenue to alleviate this fatal bleeding complication.

Funding

National Science Foundation of China (81670128, 81873433).

Supplemental Fibrinogen Restores Platelet Inhibitor-Induced Reduction in Thrombus Formation without Altering Platelet Function: An In Vitro Study

BACKGROUND

 For patients treated with dual antiplatelet therapy, standardized drug-specific 3-to-7 day cessation is recommended prior to major surgery to reach sufficient platelet function recovery. Here we investigated the hypothesis that supplemental fibrinogen might mitigate the inhibitory effects of antiplatelet therapy.

METHODS AND RESULTS

 To this end blood from healthy donors was treated in vitro with platelet inhibitors, and in vitro thrombus formation and platelet activation were assessed. Ticagrelor, acetylsalicylic acid, the combination of both, and tirofiban all markedly attenuated the formation of adherent thrombi, when whole blood was perfused through collagen-coated microchannels at physiological shear rates. Addition of fibrinogen restored in vitro thrombus formation in the presence of antiplatelet drugs and heparin. However, platelet activation, as investigated in assays of P-selectin expression and calcium flux, was not altered by fibrinogen supplementation. Most importantly, fibrinogen was able to restore in vitro thrombogenesis in patients on maintenance dual antiplatelet therapy after percutaneous coronary intervention.

CONCLUSION

 Thus, our in vitro data support the notion that supplementation of fibrinogen influences the perioperative hemostasis in patients undergoing surgery during antiplatelet therapy by promoting thrombogenesis without significantly interfering with platelet activation.

Dynamics of Platelet Counts in Major Trauma: The Impact of Haemostatic Resuscitation and Effects of Platelet Transfusion-A Sub-Study of the Randomized Controlled RETIC Trial

Although platelets play a central role in haemostasis, the dynamics of platelet counts during haemostatic resuscitation, the response to platelet transfusion, and effects on clinical outcome are poorly described for trauma patients. As a sub-study of the already published randomized controlled RETIC Study "Reversal of Trauma-induced Coagulopathy using First-line Coagulation Factor Concentrates or Fresh-Frozen Plasma" trial, we here analysed whether the type of first-line haemostatic resuscitation influences the frequency of platelet transfusion and determined the effects of platelet transfusion in coagulopathic patients with major trauma. Patients randomly received first-line plasma (FFP) or coagulation factor concentrates (CFC), mainly fibrinogen concentrate. In both groups, platelets were transfused to maintain platelet counts between 50 and 100 × 10⁹ /L. Transfusion rates were significantly higher in the FFP (n = 44) vs. CFC (n = 50) group (FFP 47.7% vs. CFC 26%); p = 0.0335. Logistic regression analysis adjusted for the stratification variables injury severity score (ISS) and brain injury confirmed that first-line FFP therapy increases the odds for platelet transfusion (odds ratio (OR) 5.79 (1.89 to 20.62), p = 0.0036) and this effect was larger than a 16-point increase in ISS (OR 4.33 (2.17 to 9.74), p =0.0001). In conclusion, early fibrinogen supplementation exerted a platelet-saving effect while platelet transfusions did not substantially improve platelet count and might contribute to poor clinical outcome.

The effect of hematocrit, fibrinogen concentration and temperature on the kinetics of clot formation of whole blood

BACKGROUND

Dynamic mechanical analysis of blood clots can be used to detect the coagulability of blood.

OBJECTIVE

We investigated the kinetics of clot formation by changing several blood components, and we looked into the clot "signature" at its equilibrium state by using viscoelastic and dielectric protocols.

METHODS

Oscillating shear rheometry, ROTEM, and a dielectro-rheological device was used.

RESULTS

In fibrinogen- spiked samples we found the classical high clotting ability: shortened onset, faster rate of clotting, and higher plateau stiffness. Electron microscopy explained the gain of stiffness. Incorporated RBCs weakened the clots. Reduction of temperature during the clotting process supported the development of high moduli by providing more time for fiber assembly. But at low HCT, clot firmness could be increased by elevating the temperature from 32 to 37°C. In contrast, when the fibrinogen concentration was modified, acceleration of clotting via temperature always reduced clot stiffness, whatever the initial fibrinogen concentration. Electrical resistance increased continuously during clotting; loss tangent (D) (relaxation frequency 249 kHz) decreased when clots became denser: fewer dipoles contributed to the relaxation process. The relaxation peak (Dmax) shifted to lower frequencies at higher platelet count.

CONCLUSION

Increasing temperature accelerates clot formation but weakens clots. Rheometry and ROTEM correlate well.

New Hemostatic Agents: Perioperative Anesthetic Considerations

AIM

Pharmacologic agents with procoagulant effects and antidotes against antithrombotic drugs play an important role in the prevention and management of perioperative coagulopathic bleeding. The aim of this narrative review is knowledge transfer from new and renewed hemostatic agents to anesthesiologists and other physicians involved in perioperative medicine.

METHODS

The literature search was performed on PubMed and the Summaries of Product Characteristics of 6 pharmacologic agents of interest: fibrinogen concentrate, vonicog alfa, susoctocog alfa, idarucizumab, andexanet alfa, and argatroban.

RESULTS AND DISCUSSION

This review highlights renewed interest in fibrinogen concentrate, an old prohemostatic drug, in correcting hypofibrinogenemia which is a leading pathomechanism of perioperative bleeding. This review describes clinically relevant aspects for brand new recombinant prohemostatic drugs for their use in critical clinical situations: vonicog alfa for the prevention and correction of bleeding in von Willebrand syndrome, and susoctocog alfa in acquired hemophilia A. Clinical experience and increasing evidence broadened the field of applications of the old antithrombotic drug argatroban to heparin resistance. New antidotes against new antithrombotic agents revolutionized the safety of chronic antithrombotic therapy in the emergency situations of acute and trauma surgery. Information on dosing and handling of new hemostatic drugs is summarized.

CONCLUSION

New and potent hemostatic agents exist for perioperative use and may enrich the armamentarium of anesthesiologists. Implementation into clinical practice requires their availability and user knowledge. Sustainability of these new drugs depends on post-licensing research, cost-effectiveness, and clinical experience.

A Low-dose human fibrinogen is not effective in decreasing postoperative bleeding and transfusion requirements during cardiac surgery in case of concomitant clinical bleeding and low FIBTEM values: A retrospective matched study

Background

Studies evaluating the hemostatic effects of fibrinogen administration in cardiac surgery are not conclusive.

Aims

We investigated whether the use of a low-dose human fibrinogen in case of clinical bleeding after protamine administration and concomitant low FIBTEM values is effective in reducing postoperative bleeding. Secondary end-point was to investigate the consumption of allogeneic blood products.

Setting and Design

This was a retrospective matched study conducted at university hospital.

Materials and Methods

Among 2257 patients undergoing surgery with cardiopulmonary (CPB) bypass, 73 patients received a median dose of 1 g human fibrinogen (ROTEM-Fibri group). This group was matched with 73 patients who had not received human fibrinogen (control group) among 390 patients having undergone surgery at the moment FIBTEM analysis was unavailable.

Statistical Analysis

Matching was performed for the type and the presence of redo surgery. McNemar and Wilcoxon paired tests were used to respectively compare the categorical and quantitative variables.

Results

The CPB bypass time was significantly higher in the ROTEM-Fibri group (P = 0.006). This group showed significantly higher bleeding in the first 12 and 24 h postoperatively (P < 0.001) and required significantly more transfusion of blood products (P < 0.001) and surgical revision (P = 0.007) when compared with the control group. There was no significant difference in the number of thromboembolic complications.

Conclusions

These results show that the administration of 1 g of fibrinogen based on low-FIBTEM values and clinical bleeding after protamine administration does not stop bleeding and the need for transfusion of allogeneic blood products.

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.

Haemotherapy algorithm for the management of trauma-induced coagulopathy: an Australian perspective

PURPOSE OF REVIEW

Recent advances in the understanding of the pathophysiological processes associated with traumatic haemorrhage and trauma-induced coagulopathy have resulted in improved outcomes for seriously injured trauma patients. However, a significant number of trauma patients still die from haemorrhage. This article reviews the various transfusion strategies utilized in the management of traumatic haemorrhage and describes the major haemorrhage protocol (MHP) strategy employed by an Australian trauma centre.

RECENT FINDINGS

Few topics in trauma resuscitation incite as much debate and controversy as to what constitutes the 'ideal' MHP. There is a widespread geographical and institutional variation in clinical practice. Three strategies are commonly utilized; fixed ratio major haemorrhage protocol (FRMHP), viscoelastic haemostatic assay (VHA)-guided MHP and hybrid MHP. The majority of trauma centres utilize an FRMHP and there is high-level evidence to support the use of high blood product ratios. It can be argued that the FRMHP is too simplistic to be applied to all trauma patients and that the use of VHA-guided MHP with predominant factor concentrate transfusion can allow rapid individualized interventions. In between these two strategies is a hybrid MHP, combining early FRMHP with subsequent VHA-guided transfusion.

SUMMARY

There are advantages and disadvantages to each of the various MHP strategies and the evidence base to support one above another with any certainty is lacking at this time. One strategy cannot be considered superior to the other and the choice of MHP is dependent on interpretation of the current literature and local institutional logistical considerations. A number of exciting studies are currently underway that will certainly increase the evidence base and help inform clinical practice.