Objectives: Orthotopic liver transplant can be accompanied by an obscure bleeding pattern in patients with severe hepatic malfunction. In the present study, coagulation conditions of patients with cirrhosis of the liver due to primary sclerosing cholangitis and nonbiliary causes of cirrhosis were compared using rotational thromboelastometry assays obtained before orthotopic liver transplant.
Materials and Methods: This case control study analyzed patients who were candidates for orthotopic liver transplant from 2010 to 2016. Eighty patients with cirrhosis of the liver (40 patients with primary sclerosing cholangitis and 40 with nonbiliary causes of cirrhosis) were randomly selected and enrolled into the study. Patients received rotational thromboelastometry assays under anesthesia just before the start of the operation, and results were compared between the 2 patient groups.
Results: Of 80 patients, 52 were men and 28 were women. In the assays, we found that maximum amplitudes in 10 and in 20 minutes and maximum clot firmness parameters were higher in patients with primary sclerosing cholangitis. The alpha angle and clot formation time were different in the intrinsic and extrinsic assay panels. In the intrinsic assay, we found clotting time to be shorter (P < .05). The average of all parameters in all 3 assays (intrinsic, extrinsic, and fibrinogen contribution) was lower in patients with nonbiliary causes of cirrhosis than in those with primary sclerosing cholangitis.
Conclusions: In contrast with previous studies that found that patients with primary sclerosing cholangitis are hypercoagulable, our study observed that they have normal coagulable results. Furthermore, we found that, although mean coagulation indexes in patients with primary sclerosing cholangitis were within normal ranges, in patients with nonbiliary causes of cirrhosis, these indexes were generally lower.
Key words : Clotting time, Hypercoagulopathy, Rotational thromboelastometry
Liver damage is usually accompanied by coagulation disorders. The hepatocyte system could be defined as a precise and sensitive balancing system between prothrombotic and antithrombotic processes to prevent heavy bleeding.1 Liver failure is associated with multiple modifications in the hemostatic system because of decreased plasma levels of procoagulants and anticoagulants. Accordingly, thrombosis or bleeding depends on the type of imbalance in this complex mechanism.
Primary sclerosing cholangitis (PSC) is a known progressive cholestatic liver disorder.2,3 Orthotopic liver transplant is the only definitive therapy for advanced liver failure, including for patients with PSC.4 Compared with other chronic liver diseases, cholestatic disorders such as PSC have lower rates of variceal bleeding and blood loss during orthotopic liver transplant. Although clinical symptoms alone cannot depict a proper picture of coagulation conditions, the higher probability of thrombosis of the hepatic artery and portal vein in PSC patients can indicate a hypercoagulable state.5
Intraoperative bleeding is a common complication of orthotopic liver transplant.6 Preoperative coagulation tests cannot effectively predict the amount of intraoperative bleeding and cannot be used to property plan on-time and adequate blood transfusion to the patient.7,8
Rotational thromboelastometry (ROTEM) is an effective tool to assess blood viscoelastic properties, clot initiation, formation, and stability.8-10 Previous studies have shown that regular monitoring of the blood coagulation process with ROTEM has led to a reduction in transfusion volume and a reduction in the number of patients who need blood transfusions.11,12 Rotational thromboelastometry tests include FIBTEM, APTEM, INTEM, EXTEM, HEPTEM, and NATEM assays. In the FIBTEM assay, platelet function in the coagulation process is inhibited with cytochalasin D; in the APTEM assay, the fibrinolysis process is inhibited with aprotinin.13 In the INTEM assay, the coagulation activation occurs through ellagic acid. The INTEM assay mildly activates the hemostasis contact phase and is affected by coagulation factors (fibrinogen, platelets, and heparin). In the EXTEM assay, the coagulation process includes rabbit brain tissue factor as the reagent. The EXTEM assay mildly activates hemostasis through the physiologic tissue factor activator and is influenced by extrinsic coagulation factors (fibrinogen and platelets) but not by heparin. Results obtained from these 2 tests have been used to determine administration of fresh frozen plasma, fibrinogen, platelets, and coagulation factors.14,15 In the present study, we assessed the coagulation conditions of patients with PSC and patients with nonbiliary causes of cirrhosis (non-PSC) before orthotopic liver transplant using EXTEM, INTEM, and FIBTEM tests to compare coagulation processes between these 2 patient groups.
Materials and Methods
In this case-control study, we analyzed orthotopic liver transplant candidates who were referred to Imam-Khomeini Hospital, Tehran University of Medical Sciences (Tehran, Iran) between 2010 and 2016. All livers for transplant were from deceased donors who were medically and legally dead. Convenience sampling was used to select 40 patients, between 18 and 60 years old, who were orthotopic liver transplant candidates due to PSC-associated liver failure and 40 orthotopic liver transplant candidates with nonbiliary cirrhosis (non-PSC group).
Patients who did not consent and those who had gallbladder disease were excluded. The surgical team had information about the cause of cirrhosis. Before the surgical procedure, all patients underwent testing with a ROTEM delta machine (Tem International GmbH, Munich, Germany). Data obtained included maximum amplitude in 10 minutes (A10), maximum amplitude in 20 minutes (A20), maximum clot firmness (MCF), alpha angle, clot formation time (CFT), and clotting time (CT). Furthermore, the ratio of MCF FIBTEM to EXTEM (as a ratio of platelet function) was assessed and compared between the 2 groups. The surgical team monitored coagulation throughout surgery with ROTEM.
We compared clinical findings and Doppler ultrasonography results at 1-month follow-up to assess surgical complications and thrombosis in the 2 groups. The Kolmogorov-Smirnov test was performed to evaluate data normality. For statistical analyses, parametric independent t tests and nonparametric Mann-Whitney U tests and chi-square tests were used. All tests were 2-sided, and P values < .05 were considered significant.
Our study included 52 male and 28 female patients; the PSC group was composed of 67.5% male and 32.5% female patients. Patients ranged between 22 and 62 years old in the PSC group and between 11 and 62 years old in the non-PSC groups. Demographic characteristics and several subsidiary statistics, including Model for End-Stage Liver Disease (MELD) score, platelet counts, and causes of liver disease, are summarized in Table 1 and Table 2.
Table 3 compares the differences between averages of A10, A20, MCF, alpha angle, CFT, and CT parameters measured with EXTEM. All parameters except CFT and CT were significantly lower in the non-PSC group than in the PSC group (P < .05).
We also compared differences in A10, A20, MCF, and alpha angle measured with INTEM between patients with PSC and non-PSC patients. Our results showed that averages for each of these parameters were significantly less in the non-PSC group than in the PSC group (P < .05). There were significant differences between CT and CFT averages in non-PSC and PSC patients (P < .05), with averages of these parameters greater in the non-PSC group (Table 4).
With the FIBTEM assays, differences between groups with regard to CFT, MCF, A10, A20, alpha angle, and CT showed that the averages of these parameters were less in the non-PSC group than in the PSC group. Of note, there were significant differences shown in A10, A20, and MCF (P < .05; Table 5).
We also analyzed conditions of patients after surgery in terms of thrombosis. Evaluations revealed that thrombosis occurred in 7 patients in the PSC group and in 2 patients in the non-PSC group (no significant difference at P > .05). When we analyzed the ratio of MCF FIBTEM to EXTEM (as a ratio of platelet function) in the PSC and non-PSC groups, the average in the PSC group (0.28 ± 0.10) was significantly higher than in the non-PSC group (0.19 ± 0.05) (P = .001), which consequently identified that samples in the PSC group showed normal amounts of fibrinogen and coagulation factors. The mean platelet count in the PSC group was higher than in the non-PSC group (P < .05).
The liver plays a vital role in blood coagulation and in the primary and secondary hemostasis processes. Coagulopathy in cirrhosis occurs as a result of a variety of factors, such as a defect in quantity and quality of platelets, reduction in coagulation factor, or hyperfibrinolysis.16
Merely relying on clinical symptoms in patients with hepatic diseases does not depict an appropriate picture of the patient’s coagulative condition. However, findings from extensive studies and results of clinical evidence, including coagulation tests, can lead to a better understanding of the patient’s coagulative condition. Some researchers have reported that, in patients with PSC, there is a probability of hypercoagulopathy.17,18
Previous studies have shown that, after orthotopic liver transplant in patients with PSC, thrombosis in the hepatic artery and portal vein are increased compared with that shown in non-PSC patients. Therefore, there is a higher probability of occurrence of hypercoagulopathy in PSC patients because blood hypocoagulation is a particular symptom of cirrhosis.19 Compared with other approaches used to monitor coagulation processes,20 ROTEM has been shown to be a safer device in the operating room. This device can provide precious information about viscoelastic properties of the blood coagulation process and also clot lysis.21
We found that average measurements of INTEM and EXTEM in the PSC group were different from those shown in the non-PSC group. In both tests (INTEM and EXTEM), A10, A20, MCF, and alpha angle were higher in the PSC group, although still within normal ranges. However, CT and CFT results in the PSC group were lower than those shown in the non-PSC group. The observed differences in A10, A20, MCF, alpha angle and CFT were significant with both the INTEM and EXTEM test. With the FIBTEM test, A10, A20, MCF, and alpha angle averages were higher in the PSC group, although the CFT average was shorter.
In EXTEM, MCF allows results to show platelet and coagulation factor function; however, in FIBTEM, MCF only allows the function of coagulation factors but not platelets to be shown because of the addition of cytochalasin D, which inhibits platelet function. In our study, we calculated the FIBTEM-to-EXTEM MCF ratio (MCF FIBTEM over MCF EXTEM), which allowed us to observe the function of coagulation factors over the function of platelets plus coagulation factors (that is, the ratio of the coagulation factors’ function to the whole coagulation process). We found the ratio in the PSC group to be significantly higher than in the non-PSC group, showing that PSC patients had normal coagulation processes. Although the platelet count was higher in the PSC group than in the non-PSC group, it was still within the normal range. As a result, we can hypothesize that fibrinogen is the causal factor for the differences seen in the PSC group; however, this hypothesis requires follow-up studies.
In EXTEM, CT is a function of external pathway coagulation factors like tissue factor and factor XIII; therefore, the almost similar CT results in EXTEM in PSC and non-PSC patients demonstrated that both groups had near normal levels of factor XIII and tissue factor due to normal synthesis.
Our findings are in line with studies done from Ben-Ari17 and Pihusch5 and associates. In 1997, Ben-Ari and colleagues used thrombelastography to evaluate blood coagulation conditions, with results showing a 2 times larger standard deviation difference compared with the control group. Among 47 patients with primary biliary cirrhosis (PBC), 21 patients with PSC, 40 patients without cholestatic cirrhosis, and 40 healthy people (control group), hypercoagulability existed in 13 patients (28%) with PBC, 9 patients (43%) with PSC, 2 patients (5%) with noncholestatic cirrhosis, and 0 patients in the control group. Their results also demonstrated that there was no correlation between the concentration of fibrinogen and number of platelets with thrombelastography parameters.17 Conversely, our study demonstrated that, with ROTEM, most patients with PSC were within the normal coagulation range.
In Pihusch and associates,5 plasma coagulation process and function of platelets were estimated in patients with cholestatic liver diseases and noncholestatic liver diseases using thrombelastography. In 37 patients with cholestatic liver diseases (including PBC and PSC), 53 patients with hepatitis C virus and alcoholic cirrhosis, and 62 healthy participants, hypercoagulable conditions were shown in patients with PSC and PBC but not among patients with hepatitis C virus. The researchers concluded that this condition might be a result of high levels of fibrinogen in patients with PBC and PSC compared with the other groups.
By quantitative evaluation of coagulation in patients with PSC and non-PSC cirrhosis, we observed no differences in clinical thrombosis formation in the hepatic artery and portal vein and no deep vein thrombosis during year 1 after liver transplant (P > .05). In addition, no clinical hypercoagulopathy state was found in these patients. Previous studies have shown that PSC patients are hypercoagulable; however, our study showed that PSC patients had normal coagulable parameters. This difference is probably due to the greater precision of ROTEM and the number of factors it is able to analyze compared with that shown with instruments used in previous studies. The contrast of a hypercoagulable state in PSC patients previously shown versus the normal coagulable state that we found may reveal the more exact and complete spectrum of data measured with ROTEM analyses.
In our study, we observed no significant differences in MELD score between the PSC and non-PSC group (P < .05). The evaluation of blood coagulation in these 2 groups revealed that non-PSC patients showed slight hypocoagulopathy, presumably due to the defective function of hepatocytes as a result of cirrhosis, whereas in the PSC group a normal balanced blood coagulation condition was observed.
Blood coagulation disorders may occur after surgical procedures. The use of precise and rapid tests such as ROTEM and knowledge of the properties of the underlying disease, like PSC, may play important roles in the prevention of bleeding and consequent complications.
We observed normal coagulation status in PSC patients in our study and did not see an increased rate of clinical thrombosis in the hepatic artery and portal vein of PSC patients compared with patients with non-biliary cirrhosis. These results suggest that, in PSC patients, the synthesis and function of coagulation factors and platelet count and function are within normal ranges. Therefore, PSC did not seem to affect coagulation function of liver in PSC-induced cirrhosis.
DOI : 10.6002/ect.2018.0374
From the 1Liver Transplantation Research Center, Imam Khomeini Hospital Complex,
Tehran University of Medical Sciences, Tehran, Iran; the 2Department of
Anesthesiology and Critical Care, Tehran University of Medical Sciences, Sina
Hospital, Tehran, Iran; the 3Department of General Surgery, School of Medicine,
TUMS; the 4Department of Anesthesiology and Critical Care, Tehran University of
Medical Sciences, Tehran, Iran; the 5Department of General Surgery, Tehran
University of Medical Sciences, Sina Hospital, Tehran, Iran; and the 6Department
of Internal Medicine, Tehran University of Medicial Sciences, Tehran, Iran
Acknowledgements: This research was supported by the Tehran University of Medical Sciences and Health Services (Grant Number 95-04-205-33802). The authors have no conflicts of interest.
Corresponding author: Reza Shariat Moharari, Department of Anesthesiology and Critical Care, Tehran University of Medical Sciences, Imam Khomeini Street, Hasan-Abad square, Sina Hospital, Tehran, Iran
Phone: +98 9125963486
Table 1. Demographic and Several Subsidiary Statistics in Patients With Primary Sclerosing Cholangitis and Patients With Nonbiliary Causes of Cirrhosis
Table 2. Causes of Disease in Patient Groups
Table 3. Differences Between Parameter Values Calculated With EXTEM Approach in Patient Groups
Table 4. Differences Between Parameter Values Calculated With INTEM Approach in Patient Groups
Table 5. Differences Between Parameter Values Calculated With FIBTEM Approach in Patient Groups