Published online Nov 28, 2020. doi: 10.5500/wjt.v10.i11.345
Peer-review started: June 17, 2020
First decision: July 25, 2020
Revised: July 28, 2020
Accepted: September 2, 2020
Article in press: September 2, 2020
Published online: November 28, 2020
End-stage liver disease has been generally perceived as a hypocoagulable condition, related to an increase in bleeding risk in the case of invasive procedures. In cirrhotic patients, coagulopathy is a composite condition in which rebalanced hemostasis is realized by the simultaneous reduction in pro- and antihemostatic factors, responsible for a new hemostatic balance which can tip toward thrombosis or bleeding. In cirrhotic patients, the rebalanced coagulation, together with the reduction in hemorrhagic complications during liver transplantation have made surgeons and anesthetists more conscious and frightened of possible venous or arterial thrombotic events.
Thrombotic events associated with liver transplantation (LT) may be more frequent than believed in the past, sometimes representing a potential risk to patients' lives and organ survival. Changes in the hemostatic system, intra- and postoperative blood products transfusion and surgical causes may contribute to the development of vessel thrombosis. Independent of the real cause of the prothrombotic status, more efforts on the rapid detection and prevention of such complications are necessary.
Due to the limits of conventional coagulation tests in recognizing alterations in the hemostatic balance, in recent years viscoelastic tests, such as thromboelastography (TEG), have gained increasing importance. The use of TEG in identifying hypercoagulation status during LT has been shown to be useful in better guiding blood product transfusion or, theoretically, prophylactic therapy. If its usefulness in identifying coagulopathy has already been shown in LT, its ability to recognize hypercoagulation has yet to be demonstrated.
Encouraging results suggest that hypercoagulability detected by TEG can increase the probability of venous or arterial thrombotic complications in certain patients. The presence of hypercoagulability, represented by TEG variables, can be predictive of thromboembolic complications in patients following surgery. In the present study, we aimed to verify if patients who developed hepatic artery or portal vein thrombotic complications showed predictive thromboelastographic indices which can be used for early detection of these complications in patients at greater risk.
To achieve our objective, we adopted a retrospective case-control study. The goal was to determine if there was an association between the risk factor (specific TEG variables) and the outcome of interest [hepatic artery thrombosis (HAT) and portal vein thrombosis (PVT)]. We hypothesized that TEG performed 120’ postreperfusion is more comprehensive and clinically reliable than at basal for evaluating the coagulative status of the patients.
A comparison between the case and control groups showed some statistically significant differences in the duration of surgery (longer in the case group; P = 0.032) and in two thromboelastographic parameters (G value measured at basal and 120’ postreperfusion time and LY60 measured at 120’ postreperfusion time). G value, a mathematical conversion of the MA value, was higher, although within the reference range, in the case group than in the control group (P = 0.001 and P < 0.001, respectively). In addition, LY60 measured at 120’ postreperfusion time was lower in the case group than in the control group (P = 0.035). This parameter is representative of a fibrinolysis shutdown in 85% of patients who experienced a thrombotic complication, resulting in a statistical correlation with HAT and PVT. Given the retrospective nature of our study, further research is needed in this area, but postoperative TEG seems to be a more accurate surrogate marker for the "real" hemostatic balance in recipients, possibly identifying those patients with a postoperative condition that increases the risk of HAT or PVT.
Our study suggests that TEG can be used to identify patients at an increased risk of thromboembolic events due to postoperative normal clot strength or fibrinolysis reduction, directing appropriate and more intense investigations to detect early HAT and PVT. Thromboelastography identification of an increased thrombotic risk, may also suggest the more frequent use of thromboprophylaxis.
Our findings suggest that a reduction in fibrinolytic activity and a normal clot strength (G value) detected by viscoelastic tests, identify some patients at risk of both PVT and HAT. This causal relationship requires further research to prove a conclusive link. Large randomized controlled trials could help in the stratification of patients with a higher postoperative thrombotic tendency eventually directing postoperative thromboprophylaxis and more intense surveillance to maximize the likelihood of early diagnosis.