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Comparison of Thrombelastography-Derived Fibrinogen Values at Rewarming and Following Cardiopulmonary Bypass in Cardiac Surgery Patients

BACKGROUND

The inflated costs and documented deleterious effects of excess perioperative transfusion have led to the investigation of targeted coagulation factor replacement strategies. One particular coagulation factor of interest is factor I (fibrinogen). Hypofibrinogenemia is typically tested for using time-consuming standard laboratory assays. The thrombelastography (TEG)-based functional fibrinogen level (FLEV) provides an assessment of whole blood clot under platelet inhibition to report calculated fibrinogen levels in significantly less time. If FLEV values obtained on cardiopulmonary bypass (CPB) during rewarming are similar to values obtained immediately after the discontinuation of CPB, then rewarming values could be used for preemptive ordering of appropriate blood product therapy.

METHODS

Fifty-one cardiac surgery patients were enrolled into this prospective nonrandomized study to compare rewarming fibrinogen values with postbypass values using TEG FLEV assays. Baseline, rewarming, and postbypass fibrinogen values were recorded for all patients using both standard laboratory assay (Clauss method) and FLEV. Mixed-effects regression models were used to examine the change in TEG FLEV values over time. Bland-Altman analysis was used to examine bias and the limits of agreement (LOA) between the standard laboratory assay and FLEVs.

RESULTS

Forty-nine patients were included in the analysis. The mean FLEV value during rewarming was 333.9 mg/dL compared with 332.8 mg/dL after protamine, corresponding to an estimated difference of -1.1 mg/dL (95% confidence interval [CI], -25.8 to 23.6; P = 0.917). Rewarming values were available on average 47 minutes before postprotamine values. Bland-Altman analysis showed poor agreement between FLEV and standard assays: mean difference at baseline was 92.5 mg/dL (95% CI, 71.1 to 114.9), with a lower LOA of -56.5 mg/dL (95% CI, -94.4 to -18.6) and upper LOA of 242.4 mg/dL (95% CI, 204.5 to 280.3). The difference between assays increased after CPB and persisted after protamine administration.

CONCLUSIONS

Our results revealed negligible change in FLEV values from the rewarming to postbypass periods, with a CI that does not include clinically meaningful differences. These findings suggest that rewarming samples could be utilized for ordering fibrinogen-specific therapies before discontinuation of CPB. Mean FLEV values were consistently higher than the reference standard at each time point. Moreover, bias was highly heterogeneous among samples, implying a large range of potential differences between assays for any 1 patient.

Perioperatively acquired disorders of coagulation

Purpose of review

To provide an overview of acquired coagulopathies that can occur in various perioperative clinical settings. Also described are coagulation disturbances linked to antithrombotic medications and currently available strategies to reverse their antithrombotic effects in situations of severe hemorrhage.

Recent findings

Recent studies highlight the link between low fibrinogen and decreased fibrin polymerization in the development of acquired coagulopathy. Particularly, fibrin(ogen) deficits are observable after cardiopulmonary bypass in cardiac surgery, on arrival at the emergency room in trauma patients, and with ongoing bleeding after child birth. Regarding antithrombotic therapy, although new oral anticoagulants offer the possibility of efficacy and relative safety compared with vitamin K antagonists, reversal of their anticoagulant effect with nonspecific agents, including prothrombin complex concentrate, has provided conflicting results. Specific antidotes, currently being developed, are not yet licensed for clinical use, but initial results are promising.

Summary

Targeted hemostatic therapy aims to correct coagulopathies in specific clinical settings, and reduce the need for allogeneic transfusions, thus preventing massive transfusion and its deleterious outcomes. Although there are specific guidelines for reversing anticoagulation in patients treated with antiplatelet agents or warfarin, there is currently little evidence to advocate comprehensive recommendations to treat drug-induced coagulopathy associated with new oral anticoagulants.

Impact of fibrinogen concentrate alone or with prothrombin complex concentrate (+/- fresh frozen plasma) on plasma fibrinogen level and fibrin-based clot strength (FIBTEM) in major trauma: a retrospective study

Background

Low plasma fibrinogen concentration is a predictor of poor outcome in major trauma patients. The role of fibrinogen concentrate for rapidly increasing fibrinogen plasma levels in severe trauma is not well defined.

Methods

In this retrospective study we included severe trauma patients treated with fibrinogen concentrate alone (FC group), fibrinogen concentrate with prothrombin complex concentrate (FC–PCC group) or fibrinogen concentrate with PCC and fresh frozen plasma (FC–PCC–FFP group). PCC was generally administered as the second step of intraoperative therapy, while FFP was only administered as a third step. All patients received ≥1 g fibrinogen concentrate within 24 hours. Plasma fibrinogen concentration and ROTEM parameters upon emergency room (ER) admission, intensive care unit (ICU) admission, and after 24 hours were analysed.

Results

Among 157 patients fulfilling the inclusion criteria, 83% were male; mean age was 44 years and median injury severity score (ISS) was 29. Standard coagulation tests reflected increasing severity of coagulopathy with increasing complexity of haemostatic therapy (highest severity in the FC–PCC–FFP group; p < 0.0001). Total 24-hour fibrinogen concentrate dose also increased with complexity of haemostatic therapy. Plasma fibrinogen concentration was maintained, with no significant difference between ER admission and ICU admission in all patient groups. FIBTEM clot firmness at 10 minutes (CA₁₀) was similarly maintained, albeit with a small increase in the FC–PCC group. Fibrinogen concentration and FIBTEM CA₁₀ were within the normal range in all groups at 24 hours. The ratio of fibrinogen concentrate to red blood cells (g:U) ranged between 0.7:1.0 and 1.0:1.0.

Conclusion

Fibrinogen concentrate therapy maintained fibrinogen concentration and FIBTEM CA₁₀ during the initial phase of trauma care until ICU admission. After 24 hours, these parameters were comparable between the three groups and within the normal range for each of them. Further studies are warranted to investigate the effect of fibrinogen concentrate on clinical outcomes.