The effects of in vitro hemodilution and fibrinogen concentrate substitution on thromboelastometry analysis in patients qualified for liver transplantation - preliminary results

Preoperative fibrinogen level and blood transfusions in liver transplantation: A systematic review

BACKGROUND

Orthotopic liver transplantation (OLT) is a major surgery often associated with significant bleeding. We conducted a systematic review to explore the association between preoperative fibrinogen level and intraoperative blood products transfusion, blood loss and clinical outcomes in patients undergoing OLT.

METHODS

We included observational studies conducted in patients undergoing an OLT mostly for end-stage liver disease that reported an association between the preoperative fibrinogen level and our outcomes of interest. Our primary outcome was the intraoperative red blood cell (RBC) transfusion requirements. Our secondary outcomes were intraoperative blood loss, intraoperative transfusion of any blood product, postoperative RBC transfusion, postoperative thrombotic or hemorrhagic complications, and mortality. We used a standardized search strategy. We reported our results mostly descriptively but conducted meta-analyses using random-effect models when judged feasible.

RESULTS

We selected 24 cohort studies reporting at least one of our outcomes. We found that a high preoperative fibrinogen level was associated with fewer intraoperative RBC and other blood products transfusions, and lower blood loss. We also found a lower overall survival in patients with a higher fibrinogen level (pooled hazard ratio [95% CI] of 1.50 [1.23 to 1.84]; 5 studies, n = 1012, I2 = 48%). Only one study formally explored a fibrinogen level threshold effect. Overall, reporting was heterogeneous, and risk of bias was variable mostly because of uncontrolled confounding.

CONCLUSION

A higher preoperative fibrinogen level was associated with fewer intraoperative RBC and other blood products transfusions, lower blood loss, and higher mortality. Further studies may help clarify observed associations and inform guidelines.

How Much Is the Inevitable Loss of Different Coagulation Factors During Blood Product-Free Liver Transplantations?

BACKGROUND

Bloodless liver transplantations (LT) have already been reported, but special characteristics of hemostatic changes remain less defined. The aim of this study was to evaluate the "inevitable" loss of coagulation factors (CF) in blood product-free LT.

METHODS

Blood product and CF concentrate-free LT patient data were analyzed in terms of the first 2 days of perioperative hemostasis kinetics (N = 59). CF levels (FI, II, V, VII, X, and XIII), platelet (PLT) levels, and hemoglobin levels were measured before LT (T1), on arrival at the intensive care unit (T2), and 12, 24, and 48 hours after LT (T3, T4, and T5, respectively). Thromboelastographic (TEG) parameters were determined before and at the end of LT (T1-T2).

RESULTS

Fibrinogen levels decreased by 1.2 ± 0.6 g/L, prothrombin levels by 26% ± 14%, factor V levels by 40% ± 23%, VII levels by 29% ± 19%, and X levels by 39% ± 22% (P < .001). From T2 to T4 fibrinogen increased by 0.9 ± 0.6g/L for 24 hours (P < .001). Factor II, V, and VII levels increased by 20% ± 16%, 31% ± 32%, and 12% ± 27%, respectively, between T3 and T5 (P < .001). However, factor X reached only half of the T1 level (T3-T5, P < .001). Platelet count increased in 34 (58%) patients at T2 (P < .001). The TEG parameters remained in the normal range during LT (T1-T2).

CONCLUSION

The major findings of this study advocate that "inevitable" levels of CF decrease during LT by an average of 1.2 g/L in terms of fibrinogen and 23% to 40% regarding factors II, V, VII, and X. The authors suggest that knowing the "magic numbers" and comparing them against baseline laboratory results might predict the possibility of blood product-free transplant, providing confidence and safety to the surgeon and the anesthetist.

Reducing transfusion requirements in liver transplantation

Liver transplantation (LT) was historically associated with massive blood loss and transfusion. Over the past two decades transfusion requirements have reduced dramatically and increasingly transfusion-free transplantation is a reality. Both bleeding and transfusion are associated with adverse outcomes in LT. Minimising bleeding and reducing unnecessary transfusions are therefore key goals in the perioperative period. As the understanding of the causes of bleeding has evolved so too have techniques to minimize or reduce the impact of blood loss. Surgical “piggyback” techniques, anaesthetic low central venous pressure and haemodilution strategies and the use of autologous cell salvage, point of care monitoring and targeted correction of coagulopathy, particularly through use of factor concentrates, have all contributed to declining reliance on allogenic blood products. Pre-emptive management of preoperative anaemia and adoption of more restrictive transfusion thresholds is increasingly common as patient blood management (PBM) gains momentum. Despite progress, increasing use of marginal grafts and transplantation of sicker recipients will continue to present new challenges in bleeding and transfusion management. Variation in practice across different centres and within the literature demonstrates the current lack of clear transfusion guidance. In this article we summarise the causes and predictors of bleeding and present the evidence for a variety of PBM strategies in LT.