Is fibrinogen the answer to coagulopathy after massive transfusions?

Hypofibrinogenemia following injury in 186 children and adolescents: identification of the phenotype, current outcomes, and potential for intervention

Objectives

Recent studies evaluating fibrinogen replacement in trauma, along with newly available fibrinogen-based products, has led to an increase in debate on where products such as cryoprecipitate belong in our resuscitation strategies. We set out to define the phenotype and outcomes of those with hypofibrinogenemia and evaluate whether fibrinogen replacement should have a role in the initial administration of massive transfusion.

Methods

All patients <18 years of age presenting to our trauma center 11/17-4/21 were reviewed. We then evaluated all patients who received emergency-release and massive transfusion protocol (MTP) products. Patients were defined as hypofibrinogenemic (HYPOFIB) if admission fibrinogen <150 or rapid thrombelastography (r-TEG) angle <60 degrees. Our analysis sought to define risk factors for presenting with HYPOFIB, the impact on outcomes, and whether early replacement improved mortality.

Results

4169 patients were entered into the trauma registry, with 926 level 1 trauma activations, of which 186 patients received emergency-release blood products during this time; 1%, 3%, and 10% were HYPOFIB, respectively. Of the 186 patients of interest, 18 were HYPOFIB and 168 were non-HYPOFIB. The HYPOFIB patients were significantly younger, had lower field and arrival Glasgow Coma Scale, had higher head Abbreviated Injury Scale, arrived with worse global coagulopathy, and died from brain injury. Non-HYPOFIB patients were more likely to have (+)focused assessment for the sonography of trauma on arrival, sustained severe abdominal injuries, and die from hemorrhage. 12% of patients who received early cryoprecipitate (0-2 hours) had higher mortality by univariate analysis (55% vs 31%, p=0.045), but no difference on multivariate analysis (OR 0.36, 95% CI 0.07 to 1.81, p=0.221). Those receiving early cryoprecipitate who survived after pediatric intensive care unit (PICU) admission had lower PICU fibrinogen and r-TEG alpha-angle values.

Conclusion

In pediatric trauma, patients with hypofibrinogenemia on admission are most likely younger and to have sustained severe brain injury, with an associated mortality of over 80%. Given the absence of bleeding-related deaths in HYPOFIB patients, this study does not provide evidence for the empiric use of cryoprecipitate in the initial administration of a massive transfusion protocol.

Level of Evidence

Level III - Therapeutic/Care Management.

Rapid, hand-held paper diagnostic for measuring Fibrinogen Concentration in blood

Critical bleeding causes over 2 million deaths a year. Early hypofibrinogenemia is a strong predictor of mortality in critically bleeding patients. The early replenishment of fibrinogen can significantly improve outcomes. However, over replenishment can also be dangerous. Furthermore, there is no rapid, cheap, hand-held diagnostic that can aid critically bleeding patients in fibrinogen replacement therapy. In this study, we have developed a hand-held paper diagnostic that measures plasma fibrinogen concentrations. The diagnostic has the potential to be used as a point of care device both inside and outside of hospital settings. It can vastly reduce the time to treatment for fibrinogen replacement therapy. The diagnostic is a two-step process. First, thrombin and plasma are added onto horizontially-orientated paper strips where the fibrinogen is converted into fibrin, drastically increasing the plasma's hydrophobicity. Second, an aqueous blue dye is pipetted onto the strips and allowed to wick through the fibrin. The distance the blue dye wicks through the strip correlates precisely to the fibrinogen concentration. The diagnostic can provide results within a minute. It can distinguish low fibrinogen concentrations (ie. <2 g/L) from normal fibrinogen concentrations. It shows remarkable reproducibility between healthy individuals. It is unaffected by common blood conditions such as acidosis, blood alcohol, severe hypertriglyceridemia, severe haemolysis and warfarin administration. Finally, it is unaffected by humidity and can withstand cold temperatures.

Prevalence, predictors and outcome of hypofibrinogenaemia in trauma: a multicentre observational study

INTRODUCTION

Exsanguination due to trauma-induced coagulopathy is a continuing challenge in emergency trauma care. Fibrinogen is a crucial factor for haemostatic competence, and may be the factor that reaches critically low levels first. Early fibrinogen substitution is advocated by a number of authors. Little evidence exists regarding the indications for fibrinogen supplementation in the acute phase. This study aims to estimate the prevalence of hypofibrinogenaemia in a multi-center trauma population, and to explore how initial fibrinogen concentration relates to outcome. Also, factors contributing to low fibrinogen levels are identified.

METHODS

Patients arriving in hospital less than 180 minutes post-injury requiring full trauma team activation in four different centers were included in the study. Time from injury, patient demographics, injury severity scores (ISS) and 28 days outcome status were recorded. Initial blood samples for coagulation and blood gas were analyzed. Generalized additive regression, piecewise linear regression, and multiple linear regression models were used for data analyses.

RESULTS

Out of 1,133 patients we identified a fibrinogen concentration ≤1.5g/L in 8.2%, and <2 g/L in 19.2%. A non-linear relationship between fibrinogen concentration and mortality was detected in the generalized additive and piecewise linear regression models. In the piecewise linear regression model we identified a breakpoint for optimal fibrinogen concentration at 2.29 g/L (95% confidence interval (CI): 1.93 to 2.64). Below this value the odds of death by 28 days was reduced by a factor of 0.08 (95% CI: 0.03 to 0.20) for every unit increase in fibrinogen concentration. Low age, male gender, lengthened time from injury, low base excess and high ISS were unique contributors to low fibrinogen concentrations on arrival.

CONCLUSIONS

Hypofibrinogenaemia is common in trauma and strongly associated with poor outcome. Below an estimated critical fibrinogen concentration value of 2.29 g/L a dramatic increase in mortality was detected. This finding indicates that the negative impact of low fibrinogen concentrations may have been previously underestimated. A number of clinically identifiable factors are associated with hypofibrinogenaemia. They should be considered in the management of massively bleeding patients. Interventional trials with fibrinogen substitution in high-risk patients need to be undertaken.

Cryoprecipitate transfusion: assessing appropriateness and dosing in trauma

BACKGROUND

Originally developed for patients with congenital factor VIII deficiency, cryoprecipitate is currently largely used for acquired hypofibrinogenemia in the context of bleeding. However, scant evidence supports this indication and cryoprecipitate is commonly used outside guidelines. In trauma, the appropriate cryoprecipitate dose and its impact on plasma fibrinogen levels are unclear.

OBJECTIVES

The aims were to evaluate (i) the appropriateness of cryoprecipitate transfusion in trauma and (ii) the plasma fibrinogen response to cryoprecipitate transfusion during massive transfusion in trauma.

METHODS

Retrospective review (January 1998-June 2008) of indications, dose and plasma fibrinogen response to cryoprecipitate transfusion at a large teaching hospital. A fibrinogen of <1.0 g L(-1) within 2 and 6 h of transfusion was used for evaluating appropriateness.

RESULTS

Ten thousand five hundred and forty cryoprecipitate units were transfused in 1004 patients. Thirty-seven percent and 31% were used in cardiac surgery and trauma, respectively. In 394 events in trauma, 238 (60%) and 259 (66%) were considered appropriate using the 2- and 6-h cut-off criteria, respectively. In patients who did not receive plasma components 2 h prior to cryoprecipitate, a dose of 8.7 (± 1.7) units caused a mean increase in fibrinogen levels of 0.55 (± 0.24) g L(-1), or 0.06 g L(-1) per unit.

CONCLUSIONS

In our hospital, where transfusion guidelines are overseen by transfusion medicine specialists and technologists, and policies for rapid blood component and laboratory turnaround times exist, it is possible to achieve high rates of appropriateness for cryoprecipitate transfusion in trauma. The current recommended dose causes a modest increase in fibrinogen levels (0.55 g L(-1) ).