Hypercoagulability following major partial liver resection - detected by thrombomodulin-modified thrombin generation testing

The link between high factor VIII to protein C ratio values and poor liver function after major hepatectomy

Our goal was to assess the coagulation profile in the immediate postoperative time after major liver surgery and its association with the liver function. Our hypothesis is that a decreased synthesis of the coagulation factor levels reflects an impaired liver synthesis following hepatic resection and will be associated with poor outcomes. This is a prospective, observational study recruiting consecutive patients scheduled for major liver resection in a tertiary hospital. Coagulation profile was assessed by conventional assays, viscoelastic assays and coagulation factor levels preoperatively and, on postoperative days 1, 2 and 6. Factor VIII to protein C (FVIII/PC) ratio has been used as a surrogate marker of hemostatic imbalance. Liver function was measured with conventional and indocyanine green (ICG) clearance tests, which were obtained preoperatively and on postoperative days 1 and 2. Sixty patients were recruited and 51 were included in the study. There is a clear increase in FVIII/PC ratio after surgery, which was significantly associated with low liver function, being more pronounced beyond postoperative day 2 and in patients with poorer liver function ( P  < 0.001). High FVIII/PC ratio values were significantly associated with higher postoperative morbidity, prolonged ICU and hospital stay and less survival ( P  < 0.05). High FVIII/PC ratio on postoperative day 2 was found to be predictor of posthepatectomy liver failure (PHLF; area under the ROC curve = 0.8129). Early postoperative high FVIII/PC ratio values are associated with low liver function, PHLF and poorer outcomes in patients undergoing major hepatic resection.

Safety and efficacy of extended thrombophilia screening directed venous thromboembolic events (VTE) prophylaxis in live liver donors: do we really need extended thrombophilia screening routinely?

Background and aims

The study aimed to determine the prevalence of hereditary thrombophilia, and stratify its severity among live liver donors in Pakistan. Also, the authors evaluated the safety and efficacy of thrombophilia profile testing directed venous thromboembolic events (VTE) prophylaxis while balancing bleeding risk and the need for routine thrombophilia testing before live liver donation among living donor candidates.

Materials and methods

Protein S (PS), protein C (PC), anti-thrombin (AT) III, and anti-phospholipid antibody panel (APLA) levels were measured in 567 potential donor candidates. Donors were divided into normal, borderline and high-risk groups based on Caprini score. The safety endpoints were VTE occurrence, bleeding complications or mortality.

Results

Among 567 donors, 21 (3.7%) were deficient in protein C, and 14 (2.5%) were deficient in anti-thrombin-III. IgM and IgG. Anti-phospholipids antibodies were positive in 2/567 (0.4%) and 2/567 (0.4%), respectively. IgM and IgG lupus anticoagulant antibodies were positive in 3/567 (0.5%) and 3/567 (0.5%), respectively. VTE events, bleeding complications and postoperative living donors liver transplantation-related complications were comparable among the three donor groups (P>0.05). One donor in the normal donor group developed pulmonary embolism, but none of the donors in either borderline or high-risk group developed VTE. The mean length of ICU and total hospital stay were comparable. No donor mortality was observed in all donor groups.

Conclusions

Due to thrombophilia testing directed VTE prophylaxis, VTE events were comparable in normal, borderline and high-risk thrombophilia donor groups, but more evaluations are required to determine the lower safe levels for various thrombophilia parameters including PC, PS and AT-III before surgery among living donor candidates.

The Role of Neutrophils as a Driver in Hepatic Ischemia-Reperfusion Injury and Cancer Growth

The innate immune system plays an essential role in the response to sterile inflammation and its association with liver ischemia and reperfusion injury (IRI). Liver IRI often manifests during times of surgical stress such as cancer surgery or liver transplantation. Following the initiation of liver IRI, stressed hepatocytes release damage-associated molecular patterns (DAMPs) which promote the infiltration of innate immune cells which then initiate an inflammatory cascade and cytokine storm. Upon reperfusion, neutrophils are among the first cells that infiltrate the liver. Within the liver, neutrophils play an important role in fueling tissue damage and tumor progression by promoting the metastatic cascade through the formation of Neutrophil Extracellular Traps (NETs). NETs are composed of web-like DNA structures containing proteins that are released in response to inflammatory stimuli in the environment. Additionally, NETs can aid in mediating liver IRI, promoting tumor progression, and most recently, in mediating early graft rejection in liver transplantation. In this review we aim to summarize the current knowledge of innate immune cells, with a focus on neutrophils, and their role in mediating IRI in mouse and human diseases, including cancer and transplantation. Moreover, we will investigate the interaction of Neutrophils with varying subtypes of other cells. Furthermore, we will discuss the role and different treatment modalities in targeting Neutrophils and NETs to prevent IRI.

Haemostatic alterations in patients with cirrhosis and hepatocellular carcinoma: laboratory evidence and clinical implications

Venous thrombosis is a frequent complication in cancer and is associated with high morbidity and mortality. Hepatocellular carcinoma (HCC) is the most common primary liver cancer and a leading cause of cancer-related death worldwide, and it is associated with preexisting cirrhosis in 90% of cases. Patients with cirrhosis acquire complex alterations in their haemostatic system that may predispose them to bleed or thrombotic complications. There is growing evidence that HCC may tilt the haemostatic equilibrium in cirrhosis towards hypercoagulability, thus increasing the risk of venous thrombosis. Previously described mechanisms of HCC-driven thrombophilia include thrombocytosis and increased platelet activation/function, increased fibrinogen concentration/polymerization, enhanced thrombin generation, hypofibrinolysis, and release of tissue factor-expressing microvesicles. Nevertheless, there are currently no specific guidelines on risk stratification and management of thromboprophylaxis in patients with cirrhosis and HCC. Our review endeavours to summarize the latest findings on epidemiology, risk factors and pathogenesis of non-malignant venous thrombosis in patients with cirrhosis and HCC, and provide evidence in support of tailored management of thrombotic risk in these patients.

Perioperative coagulation profile in major liver resection for cancer: a prospective observational study

Hepatectomy induced coagulation disturbances have been well studied over the past decade. Cumulative evidence supports the superiority of global coagulation analysis compared to conventional coagulation tests (i.e. PT or aPTT) for clinical decision making. Cancer, however, represents an acquired prothrombotic state and liver resection for cancer deserves a more thorough investigation. This prospective observational study was conducted to assess the perioperative coagulation status of patients undergoing major hepatectomies for primary or metastatic hepatic malignancy. Patients were followed up to the 10th postoperative day by serial measurements of conventional coagulation tests, plasma levels of coagulation factors and thrombin generation assay parameters. An abnormal coagulation profile was detected at presentation and included elevated FVIII levels, decreased levels of antithrombin and lag time prolongation in thrombin generation. Serial hematological data demonstrated increased vWF, FVIII, D-dimer, fibrinogen and decreased levels of natural anticoagulant proteins in the early postoperative period predisposing to a hypercoagulable state. The ratio of the anticoagulant protein C to the procoagulant FVIII was low at baseline and further declined postoperatively, indicating a prothrombotic state. Though no bleeding complications were reported, one patient experienced pulmonary embolism while under thromboprophylaxis. Overall, patients with hepatic carcinoma presenting for elective major hepatectomy may have baseline malignancy associated coagulation disturbances, aggravating the hypercoagulable state documented in the early postoperative period.

Pre- vs. postoperative initiation of thromboprophylaxis in liver surgery

BACKGROUND

Thromboprophylaxis protocols in liver surgery vary greatly worldwide. Due to limited research, there is no consensus whether the administration of thromboprophylaxis should be initiated pre- or postoperatively.

METHODS

Patients undergoing liver resection in Helsinki University Hospital between 2014 and 2017 were reviewed retrospectively. Initiation of thromboprophylaxis was changed in the institution in the beginning of 2016 from postoperative to preoperative. Patients were classified into two groups for analyses: thromboprophylaxis initiated preoperatively (Preop-group) or postoperatively (Postop-group). The incidences of VTE and haemorrhage within 30 days of surgery were compared between these groups. Patients with permanent anticoagulation were excluded.

RESULTS

A total of 512 patients were included to the study (Preop, n = 253, Postop, n = 259). The incidence of VTE was significantly lower in the Preop-group compared to the Postop-group (3 (1.2%) vs. 25 (9.7%), P = <.0001), mainly due to a lower incidence of pulmonary embolisms in the Preop-group (3 (1.2%) vs. 24 (9.3%), P < .0001). The rates of posthepatectomy haemorrhage within 30 days of surgery were similar (Preop 38 (15.0%) vs. Postop 36 (13.9%), p = .719).

CONCLUSION

Initiating thromboprophylaxis preoperatively may reduce the incidence of postoperative VTE without affecting the incidence of posthepatectomy haemorrhage in patients undergoing liver resection.

Risk of venous thromboembolism in patients with elevated INR undergoing hepatectomy: an analysis of the American college of surgeons national surgical quality improvement program registry

BACKGROUND

Patients undergoing hepatectomy can have elevated INR and may have venous thromboembolism (VTE) prophylaxis withheld as a result. We sought to examine the association between preoperative INR elevation and VTE following hepatectomy.

METHODS

Hepatectomies captured in the American College of Surgeons National Surgical Quality Improvement Program registry between 2007 and 2016 were analyzed. Univariable and multivariable models examined the effect of incremental increases in preoperative INR on 30-day VTE, perioperative transfusion, serious morbidity, and mortality, adjusting for potential confounders.

RESULTS

We included 25,220 elective hepatectomies (62.4% partial lobectomies, 10.1% left hepatectomies, 18.6% right hepatectomies, 9.2% trisegmentectomies). The median age of the patients was 60 years and 49% were male. INR was elevated in 3089 patients (12.2%): 1.1-1.2 in 8.1%, 1.2-1.4 in 3.3%, and 1.4-2.0 in 0.9%. Incremental elevations in INR were independently associated with increasing risk for postoperative VTE [odds ratio (OR) 1.15, 95% confidence intervals 1.01-1.31], perioperative transfusion [OR 1.35 (1.28-1.43)], serious morbidity [OR 1.35 (1.28-1.43)], and mortality [OR 1.76 (1.56-1.98)].

CONCLUSION

Elevation in preoperative INR was counter-intuitively associated with increased risk of both VTE and perioperative transfusion following hepatectomy. The role of perioperative thromboprophylaxis warrants further investigation to determine optimal care in patients with elevated preoperative INR.

Hypercoagulability on thromboelastography after living donor hepatectomy-The true side of the coin

Background and Aims:

Coagulation dynamics after donor hepatectomy are complex. Having complete knowledge of the actual changes in the coagulation status during donor hepatectomy is important to prevent complications such as pulmonary embolism, deep vein thrombosis, and bleeding. Hence, the present study aimed to study the coagulation dynamics following open donor hepatectomy both by thromboelastography (TEG) and conventional coagulation tests (CCT).

Methods:

A total of 50 prospective liver donors were included. TEG and CCT [activated partial thromboplastin time (aPTT), prothrombin time (PT), international normalised ratio (INR), fibrinogen, and platelet counts] were performed for each patient before surgery (baseline), on postoperative day (POD) 0, 1, 2, 3, 5, and 10.

Results:

TEG showed hypercoagulability in 28%, 38%, 30%, 46%, 42%, and 48% patients; in contrast INR showed hypocoagulability in 58%, 63%, 73%, 74%, 20%, and 0% patients on POD 0,1,2,3,5, and 10, respectively. Patients demonstrating hypercoagulability on TEG had significantly decreased reaction time (P = 0.004), significantly increased maximum amplitude (P < 0.001), and alpha angle value (P < 0.001). Postoperatively, INR, PT, and aPTT values increased significantly, while platelets and fibrinogen levels decreased significantly when compared to their baseline values. There was no coagulation-related postoperative complication in any of the patients.

Conclusion:

Hypercoagulability after donor hepatectomy is common. TEG showed hypercoagulability and did not show any hypocoagulability as suggested by the CCT. In patients undergoing donor hepatectomy, CCT may not reflect the actual changes incoagulation status and tests such as TEG should be performed to know the correct nature of changes in coagulation following donor hepatectomy.

Efficacy of pro- and anticoagulant strategies in plasma of patients undergoing hepatobiliary surgery

BACKGROUND

In vitro efficacy of pro- and antihemostatic drugs is profoundly different in patients with compensated cirrhosis and in those who have cirrhosis and are critically ill.

OBJECTIVES

Here we assessed the efficacy of pro- and anticoagulant drugs in plasma of patients undergoing hepato-pancreato-biliary (HPB) surgery, which is associated with unique hemostatic changes.

METHODS

We performed in vitro analyses on blood samples of 60 patients undergoing HPB surgery and liver transplantation: 20 orthotopic liver transplantations, 20 partial hepatectomies, and 20 pylorus-preserving pancreaticoduodenectomies. We performed thrombin generation experiments before and after in vitro addition of fresh frozen plasma (FFP), prothrombin complex concentrate (PCC), recombinant factor VIIa (rFVIIa), low molecular weight heparin (LMWH), unfractionated heparin, dabigatran, and rivaroxaban.

RESULTS

We showed that patients undergoing HPB surgery are in a hypercoagulable state by thrombin generation testing. FFP and rFVIIa had minimal effects on thrombin generation, whereas PCC had a more pronounced procoagulant effect in patients compared with controls. Dabigatran showed a more pronounced anticoagulant effect in patients compared with controls, whereas rivaroxaban and LMWH had a decreased anticoagulant effect in patients.

CONCLUSION

We demonstrate profoundly altered in vitro efficacy of commonly used anticoagulants, in patients undergoing HPB surgery compared with healthy controls, which may have implications for anticoagulant dosing in the early postoperative period. In the correction of perioperative bleeding complications, PCCs appear much more potent than FFP or rFVIIa, and PCCs may require conservative dosing and caution in use in patients undergoing HPB surgery.

Coagulation in liver surgery: an observational haemostatic profile and thromboelastography study

BACKGROUND

International normalized ratio (INR) is used as a marker of the haemostatic status following liver resection. However, the impact of liver resection on haemostasis is complex and beyond what can be measured by INR. This study aimed to prospectively assess haemostatic profile following liver resection and determine if INR measurement can safely guide post-operative thromboprophylaxis.

METHODS

In this prospective cohort study, patients undergoing liver resection had coagulation parameters (International normalised ratio (INR), prothrombin time (PT), activated partial thromboplastin time, fibrinogen, d-dimer, von Willebrand factor antigen, procoagulant activity of phospholipids and clotting factors II, VII, VIIIc, IX and X) and thromboelastogram parameters assessed perioperatively. Clinical follow-up assessed for thromboembolism and haemorrhage.

RESULTS

In the 41 patients included, INR was significantly (P < 0.0001) elevated post-operatively, and INR >1.5 was observed in seven of 41 (17.1%) on post-operative day 1 and one of 41 (2.4%) patients on post-operative day 3, respectively. Factor VII levels showed transient reduction but other factors, especially factors II and X, remained within normal range following liver resection. Thromboelastogram parameters remained normal or supranormal for all patients at all time points. One incident of post-hepatectomy haemorrhage occurred, despite a normal coagulation profile. Two patients suffered late pulmonary embolic episodes.

CONCLUSION

Post liver resection haemostasis is complex and poorly reflected by INR, which should not guide initiation of chemical thromboprophylaxis in the immediate post-operative period.

Hepatic Surgical Stress Promotes Systemic Immunothrombosis That Results in Distant Organ Injury

Innate immunity can initiate platelet activation during the development of thrombosis through a process, termed immunothrombosis. Neutrophils form neutrophil extracellular traps (NETs) that have been shown to interact directly with platelets and play pro-coagulant roles in a variety of infectious and sterile inflammatory settings. Hepatic surgical stress initiated by ischemia/reperfusion (I/R) injury has wide systemic consequences on distant organs. However, the mechanisms of this remote injury phenomenon are not well-understood. Here, we sought to determine the role of NETs in causing systemic immunothrombosis and distant organ injury following a local inflammatory insult with liver I/R. Postoperative thromboelastographic revealed that the speed of clot formation (alpha-angle) was significantly increased whereas time to clot formation (R-time) were decreased by in patients undergoing liver resection, indicating a hypercoagulable state after surgery. In mice subjected to liver I/R, circulating platelet activation and platelet-neutrophil aggregates were significantly increased. Injured distant organs such as the lung and kidney displayed NETs and platelet-rich micro-thrombi in the microvasculature following liver I/R. The immune-thrombi and organ damage were dramatically decreased when NETs were inhibited by DNase treatment. Depletion of Tlr4 on platelets limited NET-induced activation of platelets but had no effect on NET formation. Furthermore, platelet-specific TLR4 KO mice had significantly reduced distant organ injury with decreased circulating platelet activation, platelet-neutrophil aggregates following liver I/R in comparison to their control counterparts. These data establish that after an acute local inflammatory process, NET-activated platelets can lead to a systemic pro-coagulant state with resultant remote organ injury by immunothrombosis.

Incidence and Risk Factors of Coagulation Profile Derangement After Liver Surgery: Implications for the Use of Epidural Analgesia-A Retrospective Cohort Study

BACKGROUND

Hepatic surgery is a major abdominal surgery. Epidural analgesia may decrease the incidence of postoperative morbidities. Hemostatic disorders frequently occur after hepatic resection. Insertion or withdrawal (whether accidental or not) of an epidural catheter during coagulopathic state may cause an epidural hematoma. The aim of the study is to determine the incidence of coagulopathy after hepatectomy, interfering with epidural catheter removal, and to identify the risk factors related to coagulopathy.

METHODS

We performed a retrospective review of a prospective, multicenter, observational database including patients over 18 years old with a history of liver resection. Main collected data were the following: age, preexisting cirrhosis, Child-Pugh class, preoperative and postoperative coagulation profiles, extent of liver resection, blood loss, blood products transfused during surgery. International normalized ratio (INR) ≥1.5 and/or platelet count <80,000/mm defined coagulopathy according to the neuraxial anesthesia guidelines. A logistic regression analysis was performed to assess the association between selected factors and a coagulopathic state after hepatic resection.

RESULTS

One thousand three hundred seventy-one patients were assessed. Seven hundred fifty-nine patients had data available about postoperative coagulopathy, which was observed in 53.5% [95% confidence interval, 50.0-57.1]. Maximum derangement in INR occurred on the first postoperative day, and platelet count reached a trough peak on postoperative days 2 and 3. In the multivariable analysis, preexisting hepatic cirrhosis (odds ratio [OR] = 2.49 [1.38-4.51]; P = .003), preoperative INR ≥1.3 (OR = 2.39 [1.10-5.17]; P = .027), preoperative platelet count <150 G/L (OR = 3.03 [1.77-5.20]; P = .004), major hepatectomy (OR = 2.96 [2.07-4.23]; P < .001), and estimated intraoperative blood loss ≥1000 mL (OR = 1.85 [1.08-3.18]; P = .025) were associated with postoperative coagulopathy.

CONCLUSIONS

Coagulopathy is frequent (53.5% [95% confidence interval, 50.0-57.1]) after liver resection. Epidural analgesia seems safe in patients undergoing minor hepatic resection without preexisting hepatic cirrhosis, showing a normal preoperative INR and platelet count.

Coagulation failure is associated with bleeding events and clinical outcome during systemic inflammatory response and sepsis in acute-on-chronic liver failure: An observational cohort study

BACKGROUND

Patients with acute-on-chronic liver failure (ACLF) have coagulation failure in the setting of systemic inflammatory syndrome (SIRS), sepsis and extra-hepatic organ failures.

METHODS

Consecutive ACLF patients without sepsis at baseline were assessed at days 0, 3 and 7 with thromboelastography (TEG) and specific assays (Factor VIII, von Willebrand factor [vWF], protein C and antithrombin III [ATIII]) and followed for development of sepsis, bleeding and outcome.

RESULTS

Of 243 patients, 114 (63% ethanol related; mean age 44.3 ± 11.7 years; 90% male) were recruited. SIRS was noted in 39 (34.2%), 45 (39.5%) and 46 (40%) patients at days 0, 3 and 7 and sepsis in 28 (24%) and 52 (56.1%) patients at days 3 and 7 respectively. The 28- and 90-day survivals were 62% and 51% respectively. A hypocoagulable TEG at baseline was a predictor of bleeding (hazard ratio [HR] 2.1; CI 1.6-4.9; P = 0.050) and mortality (HR 1.9; CI 1.3-7.9; P = 0.043). ACLF patients had increased Factor VIII, vWF, tissue factor levels and tissue plasminogen activator (tPA) activity with reduced protein C and ATIII. Coagulation parameters like Coagulation Index (HR 2.1; CI 1.1-4.5; P = 0.044),clot lysis (HR 3.2; CI 1.9-3.4; P = 0.033), low protein C < 30% (HR 2.1; CI 1.5-2.8; P = 0.017), ATIII (HR 1.4; CI 1.7-3.1; P = 0.052) and tPA (HR 1.5; CI 1.1-2.4; P = 0.052) were predictors of mortality at day 28. Protein C activity <30% (HR 1.3; CI 1.0-2.9; P = 0.042) and tPA >20 ng/mL (HR 1.2; CI 1.1-2.1; P = 0.040) predicted mortality when adjusted for age, gender and baseline MELD.

CONCLUSIONS

Dynamic coagulation derangements, measured by TEG, determine the likelihood of bleeding and mortality in ACLF.

Perioperative thromboprophylaxis in liver transplant patients

Improvements in surgical and anesthetic procedures have increased patient survival after liver transplantation (LT). However, the perioperative period of LT can still be affected by several complications. Among these, thromboembolic complications (intracardiac thrombosis, pulmonary embolism, hepatic artery and portal vein thrombosis) are relatively common causes of increased morbidity and mortality. The benefit of thromboprophylaxis in general surgical patients has already been established, but it is not the standard of care in LT recipients. LT is associated with a high bleeding risk, as it is performed in a setting of already unstable hemostasis. For this reason, the role of routine perioperative prophylactic anticoagulation is usually restricted. However, recent data have shown that the bleeding tendency of cirrhotic patients is not an expression of an acquired bleeding disorder but rather of coexisting factors (portal hypertension, hypervolemia and infections). Furthermore, in cirrhotic patients, the new paradigm of ‘‘rebalanced hemostasis’’ can easily tip towards hypercoagulability because of the recently described enhanced thrombin generation, procoagulant changes in fibrin structure and platelet hyperreactivity. This new coagulation balance, along with improvements in surgical techniques and critical support, has led to a dramatic reduction in transfusion requirements, and the intraoperative thromboembolic-favoring factors (venous stasis, vessels clamping, surgical injury) have increased the awareness of thrombotic complications and led clinicians to reconsider the limited use of anticoagulants or antiplatelets in the postoperative period of LT.

Donor Selection and Prophylactic Strategy for Venous Thromboembolic Events in Living Donors of Liver Transplantation Based on Results of Thrombophilia Screening Tests

Background

We reported a strategy of thrombophilia testing-guided venous thromboembolic events (VTE) prophylaxis for living donors of liver transplantation in 2011. The aim of the present study was to evaluate the safety and efficacy of this protocol for VTE prophylaxis.

Material/Methods

Thrombophilia testing, including protein S (PS), protein C (PC), antithrombin (AT) III, and anti-phospholipid antibody (APLA), was performed in 306 living donor candidates between July 2005 and June 2016. Donors who met any of the criteria of PS <60%, PC <64%, AT-III <70%, and positive APLA were classified into the borderline group and received continuous venous infusion of heparin immediately after surgery, in addition to use of elastic stockings and intermittent pneumatic compression (IPC) until patients were ambulatory. Other donors who were classified into the normal group used elastic stockings and IPC with no anticoagulants. The efficacy and safety endpoints were VTE occurrence and bleeding events, respectively.

Results

PS was considerably decreased in 3 candidates and PC was considerably reduced in 1 candidate, and they were excluded for high risk of VTE. Seventeen candidates in the borderline group and 137 in the normal group underwent donor surgery. One donor in the borderline group developed a wound hematoma. Postoperative complications were similar between the 2 groups. None of the donors in either group developed VTE.

Conclusions

Thrombophilia testing-guided VTE prophylaxis is safe and may contribute to reduced VTE risk in donors, although further investigations are warranted to assess the necessity of thrombophilia testing prior to surgery among living donors.

Real-time kinetic binding studies at attomolar concentrations in solution phase using a single-stage opto-biosensing platform based upon infrared surface plasmons

Here we present a new generic opto-bio-sensing platform combining immobilised aptamers on an infrared plasmonic sensing device generated by nano-structured thin film that demonstrates amongst the highest index spectral sensitivities of any optical fibre sensor yielding on average 3.4 × 10⁴ nm/RIU in the aqueous index regime (with a figure of merit of 330) This offers a single stage, solution phase, atto-molar detection capability, whilst delivering real-time data for kinetic studies in water-based chemistry. The sensing platform is based upon optical fibre and has the potential to be multiplexed and used in remote sensing applications. As an example of the highly versatile capabilities of aptamer based detection using our platform, purified thrombin is detected down to 50 attomolar concentration using a volume of 1mm³ of solution without the use of any form of enhancement technique. Moreover, the device can detect nanomolar levels of thrombin in a flow cell, in the presence of 4.5% w/v albumin solution. These results are important, covering all concentrations in the human thrombin generation curve, including the problematic initial phase. Finally, selectivity is confirmed using complementary and non-complementary DNA sequences that yield performances similar to those obtained with thrombin.

Role of Fibrin(ogen) in Progression of Liver Disease: Guilt by Association?

Strong experimental evidence indicates that components of the hemostatic system, including thrombin, exacerbate diverse features of experimental liver disease. Clinical studies have also begun to address this connection and some studies have suggested that anticoagulants can improve outcome in patients with liver disease. Among the evidence of coagulation cascade activation in models of liver injury and disease is the frequent observation of thrombin-driven hepatic fibrin(ogen) deposition. Indeed, hepatic fibrin(ogen) deposition has long been recognized as a consequence of hepatic injury. Although commonly inferred as pathologic due to protective effects of anticoagulants in mouse models, the role of fibrin(ogen) in acute liver injury and chronic liver disease may not be universally detrimental. The localization of hepatic fibrin(ogen) deposits within the liver is connected to the disease stimulus and in animal models of liver toxicity and chronic disease, fibrin(ogen) deposition may not always be synonymous with large vessel thrombosis. Here, we provide a balanced review of the experimental evidence supporting a direct connection between fibrin(ogen) and liver injury/disease pathogenesis, and suggest a path forward bridging experimental and clinical research to improve our knowledge on the nature and function of fibrin(ogen) in liver disease.

Alterations in coagulation following major liver resection

The international normalised ratio is frequently raised in patients who have undergone major liver resection, and is assumed to represent a potential bleeding risk. However, these patients have an increased risk of venous thromboembolic events, despite conventional coagulation tests indicating hypocoagulability. This prospective, observational study of patients undergoing major hepatic resection analysed the serial changes in coagulation in the early postoperative period. Thrombin generation parameters and viscoelastic tests of coagulation (thromboelastometry) remained within normal ranges throughout the study period. Levels of the procoagulant factors II, V, VII and X initially fell, but V and X returned to or exceeded normal range by postoperative day five. Levels of factor VIII and Von Willebrand factor were significantly elevated from postoperative day one (p < 0.01). Levels of the anticoagulants, protein C and antithrombin remained significantly depressed on postoperative day five (p = 0.01). Overall, the imbalance between pro- and anticoagulant factors suggested a prothrombotic environment in the early postoperative period.

Balance between von Willebrand factor and ADAMTS13 following major partial hepatectomy

BACKGROUND

Conventional coagulation tests are frequently prolonged after liver surgery, suggesting a postoperative bleeding tendency. At the same time, thrombotic complications following partial hepatectomy (PH) are not uncommon. Little is known about changes in the platelet adhesive protein von Willebrand factor (VWF) and its cleaving protease a disintegrin and metalloprotease with a thrombospondin type 1 motif, member 13 (ADAMTS13) following a PH.

METHODS

Plasma samples were collected before and after PH and pylorus-preserving pancreaticoduodenectomy (PPPD), and from 24 healthy individuals. Plasma levels of VWF and ADAMTS13, VWF activity and VWF-dependent platelet adhesion were measured, and compared between the groups.

RESULTS

Median (i.q.r.) VWF levels increased more after PH (17 patients) than following PPPD (10), reaching the highest level on postoperative day (POD) 3 (570 (473-656) versus 354 (305-476) per cent respectively; P = 0·009). VWF levels remained raised on POD 30. A decrease in median (i.q.r.) ADAMTS13 activity was observed for both patient groups, reaching the lowest level on POD 7 (24 (16-32) versus 38 (23-66) per cent for PH and PPPD respectively; P = 0·049), and levels remained significantly reduced at POD 30. VWF activity was significantly higher on day 7 following PH compared with PPPD (median (i.q.r.) 517 (440-742) versus 385 (322-484) per cent respectively; P = 0·009), and remained increased at POD 30. VWF-dependent platelet adhesion under conditions of flow was increased until POD 30 in patients after PH and PPPD, but was more pronounced in the PH group.

CONCLUSION

There are changes in the balance between VWF and ADAMTS13 levels and activity in patients after both PH and PPPD. Changes in the VWF-ADAMTS13 axis were more pronounced and of longer duration after PH than following PPPD.

Venous Thromboembolism Prophylaxis in Liver Surgery

BACKGROUND

At a recently concluded Americas Hepato-Pancreato-Biliary Association Annual Meeting, a Clinical Practice Guidelines Conference Series was convened with the topic focusing on Venous Thromboembolism (VTE) Prophylaxis in Liver Surgery. The symposium brought together hepatobiliary surgeons from three continents as well as medical experts in hematology and coagulation.

METHODS

The content of the discussion included literature reviews, evaluation of multi-institutional VTE outcome data, and examination of practice patterns at multiple high-volume centers.

RESULTS

Literature review demonstrated that, within gastrointestinal surgery, liver resection patients are at particularly high-risk for VTE. Recent evidence clearly indicates a direct relationship between the magnitude of hepatectomy and postoperative VTE rates, however, the PT/INR does not accurately reflect the coagulation status of the post-hepatectomy patient. Evaluation of available data and practice patterns regarding the utilization and timing of anticoagulant VTE prophylaxis led to recommendations regarding preoperative and postoperative thromboprophylaxis for liver surgery patients.

CONCLUSIONS

This conference was effective in consolidating our knowledge of coagulation abnormalities after liver resection. Based on the expert review of the available data and practice patterns, a number of recommendations were developed.

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.