Fibrinogen recovery and changes in fibrin-based clot firmness after cryoprecipitate administration in patients undergoing aortic surgery involving deep hypothermic circulatory arrest

Amplitude at 10 min in thromboelastography predicts maximum amplitude: a single-center observational study

Thromboelastography is a quantitative test widely used to measure the efficiency of blood clotting. However, awaiting the results of maximum amplitude (MA) is necessary for determining the need for platelet- and fibrinogen-containing products. A more rapid prediction of MA could facilitate faster preparation and administration of blood transfusion products, thereby resulting in coagulation improvement. In this retrospective study, we hypothesized that early amplitude at 10 min (A10) could be a predictor of MA. Therefore, we investigated whether MA can be rapidly inferred from thromboelastographic 6 s (TEG6s) measurements and evaluated its correlation with A10. We extracted TEG6s measurements obtained in operating rooms and intensive care units of our hospital between January 2018 and December 2022. The correlation of MA with display items of TEG6s results, including reaction time, kinetics, α angle, activated clotting time, and A10, was evaluated. The relationship between citrated rapid TEG (CRT)-A10 and CRT-MA, as well as between citrated functional fibrinogen (CFF)-A10 and CFF-MA, were evaluated if A10 and MA showed a good correlation. The results showed good correlations between CRT-A10 and CRT-MA, as well as between CFF-A10 and CFF-MA. Therefore, evaluating A10 using TEG6s could predict MA.

Coagulation management during liver transplantation: monitoring and decision making for hemostatic interventions

PURPOSE OF REVIEW

Rebalanced hemostasis describes the precarious balance of procoagulant and antithrombotic proteins in patients with severe liver failure. This review is aimed to discuss currently available coagulation monitoring tests and pertinent decision-making process for plasma coagulation factor replacements during liver transplantation (LT).

RECENT FINDINGS

Contemporary viscoelastic coagulation monitoring systems have demonstrated advantages over conventional coagulation tests in assessing the patient's coagulation status and tailoring hemostatic interventions. There is increasing interest in the use of prothrombin complex and fibrinogen concentrates, but it remains to be proven if purified factor concentrates are more efficacious and safer than allogeneic hemostatic components. Furthermore, the decision to use antifibrinolytic therapy necessitates careful considerations given the risks of venous thromboembolism in severe liver failure.

SUMMARY

Perioperative hemostatic management and thromboprophylaxis for LT patients is likely to be more precise and patient-specific through a better understanding and monitoring of rebalanced coagulation. Further research is needed to refine the application of these tools and develop more standardized protocols for coagulation management in LT.

The role of fibrinogen in traumatic brain injury: from molecular pathological mechanisms to clinical management

Fibrinogen is the substrate of plasma coagulation. It plays an important role in the formation of reticular network, which is crucial to the strength and stability of blood clots. In addition to directly participating in coagulation, fibrinogen also participates in the destruction of blood-brain barrier and neuroinflammation. This article reviews the pathophysiological changes of fibrinogen after traumatic brain injury. Considerable efforts have been made to understand the mechanisms by which fibrinogen damages the central nervous system. Combined with the latest research hotspots, potentially promising treatment strategies at the molecular level were discussed. We believe that understanding the role of fibrinogen-mediated damage in nerve and blood-brain barrier function will enable timely intervention in patients with nerve damage, and guide the development of novel targeted therapeutics.

The CRYOSTAT2 trial: The rationale and study protocol for a multi-Centre, randomised, controlled trial evaluating the effects of early high-dose cryoprecipitate in adult patients with major trauma haemorrhage requiring major haemorrhage protocol activation

OBJECTIVES

To describe the protocol for a multinational randomised, parallel, superiority trial, in which patients were randomised to receive early high-dose cryoprecipitate in addition to standard major haemorrhage protocol (MHP), or Standard MHP alone.

BACKGROUND

Blood transfusion support for trauma-related major bleeding includes red cells, plasma and platelets. The role of concentrated sources of fibrinogen is less clear and has not been evaluated in large clinical trials. Fibrinogen is a key pro-coagulant factor that is essential for stable clot formation. A pilot trial had demonstrated that it was feasible to deliver cryoprecipitate as a source of fibrinogen within 90 min of admission.

METHODS

Randomisation was via opaque sealed envelopes held securely in participating Emergency Departments or transfusion laboratories. Early cryoprecipitate, provided as 3 pools (equivalent to 15 single units of cryoprecipitate or 6 g fibrinogen supplementation), was transfused as rapidly as possible, and started within 90 min of admission. Participants in both arms received standard treatment defined in the receiving hospital MHP. The primary outcome measure was all-cause mortality at 28 days. Symptomatic thrombotic events including venous thromboembolism and arterial thrombotic events (myocardial infarction, stroke) were collected from randomisation up to day 28 or discharge from hospital. EQ5D-5Land Glasgow Outcome Score were completed at discharge and 6 months. All analyses will be performed on an intention to treat basis, with per protocol sensitivity analysis.

RESULTS

The trial opened for recruitment in June 2017 and the final patient completed follow-up in May 2022.

DISCUSSION

This trial will provide firmer evidence to evaluate the effectiveness and cost-effectiveness of early high-dose cryoprecipitate alongside the standard MHP in major traumatic haemorrhage.

Management of severe peri-operative bleeding: Guidelines from the European Society of Anaesthesiology and Intensive Care: Second update 2022

BACKGROUND

Management of peri-operative bleeding is complex and involves multiple assessment tools and strategies to ensure optimal patient care with the goal of reducing morbidity and mortality. These updated guidelines from the European Society of Anaesthesiology and Intensive Care (ESAIC) aim to provide an evidence-based set of recommendations for healthcare professionals to help ensure improved clinical management.

DESIGN

A systematic literature search from 2015 to 2021 of several electronic databases was performed without language restrictions. Grading of Recommendations, Assessment, Development and Evaluation (GRADE) was used to assess the methodological quality of the included studies and to formulate recommendations. A Delphi methodology was used to prepare a clinical practice guideline.

RESULTS

These searches identified 137 999 articles. All articles were assessed, and the existing 2017 guidelines were revised to incorporate new evidence. Sixteen recommendations derived from the systematic literature search, and four clinical guidances retained from previous ESAIC guidelines were formulated. Using the Delphi process on 253 sentences of guidance, strong consensus (>90% agreement) was achieved in 97% and consensus (75 to 90% agreement) in 3%.

DISCUSSION

Peri-operative bleeding management encompasses the patient's journey from the pre-operative state through the postoperative period. Along this journey, many features of the patient's pre-operative coagulation status, underlying comorbidities, general health and the procedures that they are undergoing need to be taken into account. Due to the many important aspects in peri-operative nontrauma bleeding management, guidance as to how best approach and treat each individual patient are key. Understanding which therapeutic approaches are most valuable at each timepoint can only enhance patient care, ensuring the best outcomes by reducing blood loss and, therefore, overall morbidity and mortality.

CONCLUSION

All healthcare professionals involved in the management of patients at risk for surgical bleeding should be aware of the current therapeutic options and approaches that are available to them. These guidelines aim to provide specific guidance for bleeding management in a variety of clinical situations.

Cryoprecipitate Transfusion After Cardiac Surgery

OBJECTIVES

The association of cryoprecipitate transfusion with patient outcomes after cardiac surgery is unclear. We aimed to investigate the predictors of, and outcomes associated with, postoperative cryoprecipitate transfusion in cardiac surgery patients.

METHODS

We used the Medical Information Mart for Intensive Care III and IV databases. We included adults undergoing cardiac surgery, and propensity score matched cryoprecipitate-treated patients to controls. Using the matched cohort, we investigated the association of cryoprecipitate use with clinical outcomes. The primary outcome was in-hospital mortality. Secondary outcomes were infection, acute kidney injury, intensive care unit length of stay, hospital length of stay, and chest tube output at 2-hour intervals.

RESULTS

Of 12,043 eligible patients, 283 (2.35%) patients received cryoprecipitate. The median dose was 5.83 units (IQR 4.17-7.24) given at a median first transfusion time of 1.75 hours (IQR 0.73-4.46) after intensive care unit admission. After propensity scoring, we matched 195 cryoprecipitate recipients to 743 controls. Postoperative cryoprecipitate transfusion was not significantly associated with in-hospital mortality (odds ratio [OR] 1.10; 99% confidence interval [CI] 0.43-2.84; p=0.791), infection (OR 0.77; 99% CI 0.45-1.34; p=0.220), acute kidney injury (OR 1.03; 99% CI 0.65-1.62; p=0.876) or cumulative chest tube output (adjusted mean difference 8 hrs post transfusion, 11 mL; 99% CI -104 to 125; p=0.804).

CONCLUSIONS

Although cryoprecipitate was typically given to sicker patients with more bleeding, its administration was not associated with worse outcomes. Large, multicentred studies are warranted to further elucidate cryoprecipitate's safety profile and patterns of use in cardiac surgery.

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.

Fibrinogen and Bleeding in Adult Cardiac Surgery: A Review of the Literature

Background: Fibrinogen is a substrate for blood clots formation. In cardiac surgery, a number of different mechanisms lead to a decrease in fibrinogen levels and consequent impaired haemostasis. Patients undergoing cardiac surgery are therefore frequently exposed to blood loss and allogeneic blood transfusion, which are risk factors associated with morbidity and mortality. Thus, particular efforts in fibrinogen management should be made to decrease bleeding and the need for blood transfusion. Therefore, fibrinogen remains an active focus of investigations from basic science to clinical practice. This review aims to summarise the latest evidence regarding the role of fibrinogen and current practices in fibrinogen management in adult cardiac surgery. Methods: The PubMed database was systematically searched for literature investigating the role and disorders of fibrinogen in cardiac surgery and diagnostic and therapeutic procedures related to fibrinogen deficiency aimed at reducing blood loss and transfusion requirements. Clinical trials and reviews from the last 10 years were included. Results: In total, 146 articles were analysed. Conclusion: The early diagnosis and treatment of fibrinogen deficiency is crucial in maintaining haemostasis in bleeding patients. Further studies are needed to better understand the association between fibrinogen levels, bleeding, and fibrinogen supplementation and their impacts on patient outcomes in different clinical settings.

Cryoprecipitate transfusion in bleeding patients

OBJECTIVES

The management of acquired coagulopathy in multiple clinical settings frequently involves fibrinogen supplementation. Cryoprecipitate, a multidonor product, is widely used for the treatment of acquired hypofibrinogenemia following massive bleeding, but it has been associated with adverse events. We aimed to review the latest evidence on cryoprecipitate for treatment of bleeding.

METHODS

We conducted a narrative review of current literature on cryoprecipitate therapy, describing its history, formulations and preparation, and recommended dosing. We also reviewed guideline recommendations on the use of cryoprecipitate in bleeding situations and recent studies on its efficacy and safety.

RESULTS

Cryoprecipitate has a relatively high fibrinogen content; however, as it is produced by pooling fresh frozen donor plasma, the fibrinogen content per unit can vary considerably. Current guidelines suggest that cryoprecipitate use should be limited to treating hypofibrinogenemia in patients with clinical bleeding. Until recently, cryoprecipitate was deemed unsuitable for pathogen reduction, and potential safety concerns and lack of standardized fibrinogen content have led to some professional bodies recommending that cryoprecipitate is only indicated for the treatment of bleeding and hypofibrinogenemia in perioperative settings where fibrinogen concentrate is not available. While cryoprecipitate is effective in increasing plasma fibrinogen levels, data on its clinical efficacy are limited.

CONCLUSIONS

There is a lack of robust evidence to support the use of cryoprecipitate in bleeding patients, with few prospective, randomized clinical trials performed to date. Clinical trials in bleeding settings are needed to investigate the safety and efficacy of cryoprecipitate and to determine its optimal use and administration.

Pediatric Fibrinogen PART II-Overview of Indications for Fibrinogen Use in Critically Ill Children

Bleeding is frequently seen in critically ill children and is associated with increased morbidity and mortality. Fibrinogen is an essential coagulation factor for hemostasis and hypofibrinogenemia is an important risk factor for bleeding in pediatric and adult settings. Cryoprecipitate and fibrinogen concentrate are often given to critically ill children to prevent bleeding and improve fibrinogen levels, especially in the setting of surgery, trauma, leukemia, disseminated intravascular coagulopathy, and liver failure. The theoretical benefit of fibrinogen supplementation to treat hypofibrinogenemia appears obvious, yet the evidence to support fibrinogen supplementation in children is sparce and clinical indications are poorly defined. In addition, it is unknown what the optimal fibrinogen replacement product is in children and neonates or what the targets of treatment should be. As a result, there is considerable variability in practice. In this article we will review the current pediatric and applicable adult literature with regard to the use of fibrinogen replacement in different pediatric critical care contexts. We will discuss the clinical indications for fibrinogen supplementation in critically ill children and the evidence to support their use. We summarize by highlighting current knowledge gaps and areas for future research.

Pediatric Fibrinogen PART I-Pitfalls in Fibrinogen Evaluation and Use of Fibrinogen Replacement Products in Children

Fibrinogen is a key coagulation protein, playing a critical role in hemostasis. It is the first factor to decrease to critical levels during bleeding. Hypofibrinogenemia is an important risk factor for bleeding in clinical settings, including pediatric surgery. Yet, the optimal measurement of fibrinogen levels is subject to debate, as is the critical threshold for intervention. Fibrinogen replacement may be provided by cryoprecipitate and fibrinogen concentrate. Whilst both products contain fibrinogen, they are not equivalent, each has its own advantages and disadvantages, especially for pediatric use. Unfortunately, medical literature to support fibrinogen replacement in children is limited. In this article we review the current diagnostic tools to measure fibrinogen, with respect to their use in the pediatric critical care setting. Secondly, we evaluate the different fibrinogen replacement therapies, focusing on cryoprecipitate and fibrinogen concentrate and examine their individual product characteristics, associated risks and benefits, different dosing strategies and specific pitfalls for use in children. We summarize by highlighting current knowledge gaps and areas for future research.

Efficacy of fibrinogen concentrate in major abdominal surgery - A prospective, randomized, controlled study in cytoreductive surgery for pseudomyxoma peritonei

BACKGROUND

Cytoreductive surgery (CRS) with hyperthermic intraperitoneal chemotherapy for pseudomyxoma peritonei (PMP) is associated with excessive bleeding and acquired fibrinogen deficiency. Maintaining plasma fibrinogen may support hemostasis.

OBJECTIVES

To compare hemostatic efficacy and safety of human fibrinogen concentrate (HFC) vs cryoprecipitate as fibrinogen sources for bleeding patients with acquired fibrinogen deficiency undergoing PMP CRS.

METHODS

FORMA-05 was an off-label single-center, prospective, randomized, controlled phase 2 study. Patients undergoing PMP surgery with predicted intraoperative blood loss ≥2 L received human fibrinogen concentrate (HFC; 4 g) or cryoprecipitate (two pools of 5 units, containing approximately 4.0-4.6 g fibrinogen), repeated as needed. The primary endpoint was a composite of intraoperative and postoperative efficacy, graded using objective 4-point scales and adjudicated by an independent committee.

RESULTS

One hundred percent of patients receiving HFC (95% confidence interval: 83.9-100.0, n = 21) or cryoprecipitate (84.6-100.0, n = 22) achieved hemostatic success. HFC demonstrated noninferior efficacy (P = .0095; post hoc) and arrived in the operating room 46 minutes faster. There were significantly greater mean increases with HFC vs cryoprecipitate in plasma fibrinogen (0.78 vs 0.35 g/L; P < .0001) and FIBTEM A20 (3.33 vs 0.93 mm; P = .003). Factor XIII, factor VIII, and von Willebrand factor activity were maintained throughout surgery. Only red blood cells were transfused intraoperatively (median units: HFC group, 1.0; cryoprecipitate group, 0.5). Thromboembolic events were detected with cryoprecipitate only. Safety was otherwise comparable between groups.

CONCLUSIONS

Human fibrinogen concentrate was hemostatically efficacious in patients undergoing major abdominal PMP surgery, with a favorable safety profile. These results are relevant to other surgical settings where bleeding and acquired fibrinogen deficiency occur.

Fibrinogen in traumatic haemorrhage: A narrative review

Haemorrhage in the setting of severe trauma is associated with significant morbidity and mortality. There is increasing awareness of the important role fibrinogen plays in traumatic haemorrhage. Fibrinogen levels fall precipitously in severe trauma and the resultant hypofibrinogenaemia is associated with poor outcomes. Hence, it has been postulated that early fibrinogen replacement in severe traumatic haemorrhage may improve outcomes, although, to date there is a paucity of high quality evidence to support this hypothesis. In addition there is controversy regarding the optimal method for fibrinogen supplementation. We review the current evidence regarding the role of fibrinogen in trauma, the rationale behind fibrinogen supplementation and discuss current research.

Crotalus atrox venom preconditioning increases plasma fibrinogen and reduces perioperative hemorrhage in a rat model of surgical brain injury

Perioperative bleeding is a potentially devastating complication in neurosurgical patients, and plasma fibrinogen concentration has been identified as a potential modifiable risk factor for perioperative bleeding. The aim of this study was to evaluate preconditioning with Crotalus atrox venom (Cv-PC) as potential preventive therapy for reducing perioperative hemorrhage in the rodent model of surgical brain injury (SBI). C. atrox venom contains snake venom metalloproteinases that cleave fibrinogen into fibrin split products without inducing clotting. Separately, fibrinogen split products induce fibrinogen production, thereby elevating plasma fibrinogen levels. Thus, the hypothesis was that preconditioning with C. atrox venom will produce fibrinogen spilt products, thereby upregulating fibrinogen levels, ultimately improving perioperative hemostasis during SBI. We observed that Cv-PC SBI animals had significantly reduced intraoperative hemorrhage and postoperative hematoma volumes compared to those of vehicle preconditioned SBI animals. Cv-PC animals were also found to have higher levels of plasma fibrinogen at the time of surgery, with unchanged prothrombin time. Cv-PC studies with fractions of C. atrox venom suggest that snake venom metalloproteinases are largely responsible for the improved hemostasis by Cv-PC. Our findings indicate that Cv-PC increases plasma fibrinogen levels and may provide a promising therapy for reducing perioperative hemorrhage in elective surgeries.

Anesthetic Considerations for Surgery on the Aortic Arch

Aortic arch surgery requires meticulous teamwork in the true perioperative sense. Planning and communication at all phases from preoperative evaluation, through intraoperative management, to postoperative care should be well coordinated between surgical, anesthesia, perfusion, and intensive care unit teams. This review discusses intraoperative management from the anesthesiologist’s perspective, with particular emphasis on transesophageal echo evaluation and coagulation management.

Comparing efficacy and safety of fibrinogen concentrate to cryoprecipitate in bleeding patients: a systematic review

BACKGROUND

Bleeding is associated with the depletion of fibrinogen, thus increasing the risk of coagulopathy, further bleeding and transfusion requirements. Both fibrinogen concentrate and cryoprecipitate replenish low plasma fibrinogen levels. This systematic review aims to identify and evaluate evidence of efficacy and safety of fibrinogen concentrate and cryoprecipitate in bleeding patients.

METHOD

Cochrane Central Register of Controlled Trials (CENTRAL), Medline, EMBASE up to 2nd of March 2015 were among the electronic search strategies of randomized controlled trials and non-randomized studies with meta-analysis employed. Studies for inclusion required bleeding patients being treated with either fibrinogen concentrate or cryoprecipitate. Mortality was the primary endpoint. Secondary outcomes included bleeding, coagulopathy, transfusion requirements and clinical complications related to the intervention. PRISMA methodology, a data-extraction form and the Cochrane risk of bias tool were all employed.

RESULTS

Four studies were eligible for inclusion in this systematic review; one randomized controlled trial (RCT) consisting of 66 patients and three observational studies involving 218 patients in total. No mortality was reported in the published papers. There were no differences in fibrinogen-level increase, bleeding, RBC transfusions or thromboembolic complications. The RCT showed a possible increased functional improvement of haemostasis after cryoprecipitate therapy compared to fibrinogen concentrate.

CONCLUSION

The available evidence directly comparing fibrinogen concentrate to cryoprecipitate is sparse and with high risk of bias. Recommendation of one product over the other for fibrinogen substitution in the bleeding patient with acquired hypofibrinogenaemia is currently not possible. Future research should guide us towards evidence-based decisions of product superiority.

Early cryoprecipitate for major haemorrhage in trauma: a randomised controlled feasibility trial

BACKGROUND

Low fibrinogen (Fg) concentrations in trauma haemorrhage are associated with poorer outcomes. Cryoprecipitate is the standard source for Fg administration in the UK and USA and is often given in the later stages of transfusion therapy. It is not known whether early cryoprecipitate therapy improves clinical outcomes. The primary aim of this feasibility study was to determine whether it was possible to administer cryoprecipitate, within 90 min of admission to hospital. Secondary aims were to evaluate laboratory measures of Fg and clinical outcomes including thrombotic events, organ failure, length of hospital stay and mortality.

METHODS

This was an unblinded RCT, conducted at two civilian UK major trauma centres of adult trauma patients (age ≥16 yrs), with active bleeding and requiring activation of the major haemorrhage protocol. Participants were randomised to standard major haemorrhage therapy (STANDARD) (n=22), or to standard haemorrhage therapy plus two early pools of cryoprecipitate (CRYO) (n=21).

RESULTS

85% (95% CI: 69-100%) CRYO participants received cryoprecipitate within 90 min, median time 60 min (IQR: 57-76) compared with 108 min (67-147), CRYO and STANDARD arms respectively (P=0.002). Fg concentrations were higher in the CRYO arm and were maintained above 1.8 g litre(-1) at all time-points during active haemorrhage. All-cause mortality at 28 days was not significantly different (P=0.14).

CONCLUSIONS

Early Fg supplementation using cryoprecipitate is feasible in trauma patients. This study supports the need for a definitive RCT to determine the effect of early Fg supplementation on mortality and other clinical outcomes.

TRIAL REGISTRY NUMBER

ISRCTN55509212.

[The cryoprecipitate: that old unknown]

Cryoprecipitate is a plasma derivative rich in fibrinogen and other procoagulant factors. It has been successfully used for decades in the treatment of the coagulopathy of trauma patients, cardiovascular surgery, liver failure and disseminated intravascular coagulation. Although cryoprecipitate is routinely used in many western countries, most of the Spanish regional blood banks stopped its production in the late 1990's. Moreover, in recent years there is a movement to replace cryoprecipitate with manufactured fibrinogen concentrate. As a consequence, many of the younger anaesthesiologists did not have any direct experience with cryoprecipitate. This article aims to describe the characteristics of cryoprecipitate since it is a different product from manufactured fibrinogen concentrate, with its own specific indications that deserve to be further studied in clinical trials.

How I use fibrinogen replacement therapy in acquired bleeding

Fibrinogen is a critical protein for hemostasis and clot formation. However, transfusion guidelines have variable recommendations for maintaining fibrinogen levels in bleeding patients. An increasing number of studies support the practice of fibrinogen replacement therapy for acquired coagulopathies, and additional studies are underway. Fibrinogen therapy can be administered with cryoprecipitate or fibrinogen concentrates, and clinical practice varies according to their availability and licensing status. Fibrinogen concentrate therapy has been studied in animal models and clinical trials and supports the critical role of fibrinogen repletion in bleeding patients. Point-of-care testing will have an important role in guiding fibrinogen replacement for hemostatic therapy in clinical settings such as cardiovascular surgery, postpartum hemorrhage, and trauma. Fibrinogen therapy is an important component of a multimodal strategy for the treatment of coagulopathic bleeding.

Cryoprecipitate therapy

Cryoprecipitate, originally developed as a therapy for patients with antihaemophilic factor deficiency, or haemophilia A, has been in use for almost 50 yr. However, cryoprecipitate is no longer administered according to its original purpose, and is now most commonly used to replenish fibrinogen levels in patients with acquired coagulopathy, such as in clinical settings with haemorrhage including cardiac surgery, trauma, liver transplantation (LT), or obstetric haemorrhage. Cryoprecipitate is a pooled product that does not undergo pathogen inactivation, and its administration has been associated with a number of adverse events, particularly transmission of blood-borne pathogens and transfusion-related acute lung injury. As a result of these safety concerns, along with emerging availability of alternative fibrinogen preparations, cryoprecipitate has been withdrawn from use in a number of European countries. Compared with the plasma from which it is prepared, cryoprecipitate contains a high concentration of coagulation factor VIII, coagulation factor XIII, and fibrinogen. Cryoprecipitate is usually licensed by regulatory authorities for the treatment of hypofibrinogenaemia, and recommended for supplementation when plasma fibrinogen levels decrease below 1 g litre(-1); however, this threshold is empiric and is not based on solid clinical evidence. Consequently, there is uncertainty over the appropriate dosing and optimal administration of cryoprecipitate, with some guidelines from professional societies to guide clinical practice. Randomized, controlled trials are needed to determine the clinical efficacy of cryoprecipitate, compared with the efficacy of alternative preparations. These trials will allow the development of evidence-based guidelines in order to inform physicians and guide clinical practice.

Layered wrapping technique combined with oxidized cellulose and vascular prosthesis for effective haemostasis in aortic surgery

Bleeding from anastomotic sites is one of the major complications of aortic surgery. We describe a novel double-layer wrapping technique using a combination of oxidized cellulose and a vascular prosthesis to effectively achieve haemostasis. The anastomotic site is surrounded by a prosthetic graft inlaid with a strip of Nu-Knit. These are fixed by horizontal mattress and over-and-over sutures. Nu-Knit acts as an ideal cushion to achieve haemostasis, because it has a haemostatic effect and fills the space between the anastomotic site and wrapping graft. This technique is simple, and facilitates adequate haemostasis without complications.

Theoretical modelling of fibrinogen supplementation with therapeutic plasma, cryoprecipitate, or fibrinogen concentrate

Background

We aimed to create a theoretical tool to model the effect of three haemostatic agents containing fibrinogen (therapeutic plasma, cryoprecipitate, and fibrinogen concentrate) on the patient's plasma fibrinogen level.

Methods

A mathematical model was developed step-wise. The relationship between the amount of haemostatic agent and plasma fibrinogen level was plotted for each agent. A fibrinogen concentration simulator (FCS_amount) was developed, where the amount of haemostatic agent was calculated from patient characteristics, agent characteristics, and target plasma fibrinogen level. Refinements were introduced so that (i) FCS_amount would account for in vivo fibrinogen recovery, (ii) circulatory volume would not increase ad infinitum with increasing amounts, and (iii) red blood cells would be included in the simulation if haematocrit decreased below a certain level. A second FCS (FCS_level) was created to calculate fibrinogen levels resulting from specified amounts of haemostatic agents.

Results

Fibrinogen concentration in haemostatic agents has a critical impact on their ability to increase patients' fibrinogen levels. If the target plasma fibrinogen level approaches the concentration of the fibrinogen source, the required amounts increase exponentially; it is impossible to achieve a target above the concentration of the fibrinogen source.

Conclusions

We successfully developed two theoretical tools answering the questions: ‘How much therapeutic plasma, cryoprecipitate, or fibrinogen concentrate would be needed to achieve a specified target fibrinogen level?’ and ‘What would be the resultant fibrinogen level for a specified amount of haemostatic agent?’ The current tools are not intended for clinical application, but they are potentially useful for educational purposes.