Diminished anticoagulant and fibrinolytic activity following liver transplantation

Antithrombin supplementation for prevention of vascular thrombosis after pediatric liver transplantation

AIMS

After liver transplantation (LT), synthesis of coagulation factors by the graft recovers faster for pro thrombotic than anti thrombotic factors, resulting in a potential pro thrombotic imbalance. We studied the thrombotic and hemorrhagic complications in our pediatric LT series, providing supplementation of fresh frozen plasma (FFP) and/or antithrombin (AT) in the prophylactic antithrombotic regimen.

METHODS

This was a retrospective observational single center study. All isolated pediatric LTs performed between 1/11/2009 and 31/12/2019 (n = 181) were included. Postoperatively, in addition to low molecular weight heparin, 22 patients (12%) received FFP (10 ml/kg twice daily for 10 days), 27 patients (15%) were given FFP (reduced duration) and AT (50-100 IU/kg/day if AT activity remained <70%), and 132 (73%) received AT only. Complications, outcome, and coagulation profiles in postoperative days 0-10 were analyzed.

RESULTS

In all three treatment groups, AT activity normalized by day 4 while prothrombin remained <70% of normal until day 9. Hepatic artery thrombosis (HAT), portal vein thrombosis (PVT), and hemorrhagic complications occurred in 2.8%, 3.3%, and 3.9% of LTs. One- and 5-year patient and graft survival were 88% (±2.4% Standard Error) and 84% (±2.5%), and 86% (±2.6%) and 84% (±2.7%), respectively, without difference between groups. HAT were associated with low AT on days 0 and 1, and PVT with low AT on day 0.

CONCLUSIONS

Low antithrombin activity after LT was associated with postoperative thromboses. FFP and/or AT supplementation allowed early normalization of AT activity, while thrombotic or hemorrhagic complications were rare, suggesting efficient and safe management of post-LT coagulopathy.

Coagulopathy and hemostasis management in patients undergoing liver transplantation: Defining a dynamic spectrum across phases of care

Patients with acute and chronic liver disease present with a wide range of disease states and severity that may require liver transplantation (LT). Physiologic alterations occur that are dynamic throughout all phases of perioperative care, creating complex management scenarios that necessitate multidisciplinary clinical care. Specifically, alterations in hemostasis in liver disease can be pronounced and evolve with disease progression over time. Recent studies and society guidance address this emerging paradigm and offer recommendations to assist with hemostatic management in patients with liver disease. However, patients undergoing LT are unique and diverse, often with unstable disease that requires specialized approaches. Our aim is to provide a focused review of hemostatic management of the LT patient, distinguish unique aspects of the three main phases of care (before LT, perioperative, and after LT), and identify knowledge gaps and critical areas of future research.

Late Bleeding Episodes Following Intestinal Transplantation: It Is Not Always Rejection or Infection

Ectopic varices have been reported in 5% of children presenting with variceal bleeding and are defined as portosystemic venous collaterals occurring anywhere in the abdomen except in the cardioesophageal region. The liver-intestinal transplant or isolated liver-intestinal transplant patient presenting several years post-transplant with ectopic variceal bleeding as a consequence of portal hypertension is a seldom reported complication. Etiologies such as rejection or infection are a more common source of bleeding, and only after excluding these can differentials such as portal hypertension secondary to a blocked portacaval shunt or native liver disease be considered.

Pharmacokinetics of human antithrombin III concentrate in the immediate postoperative period after liver transplantation

AIMS

Antithrombin III (AT-III) concentrates have been used to prevent critical thrombosis in the immediate post-liver transplantation period without clear evidence regarding the optimal dose or administration scheme. The relationship between the AT-III dosage and the plasma activity levels during the period was evaluated in this study.

METHODS

The plasma AT-III activity levels and clinical data obtained from patients who received liver transplantation from January 2017 to September 2018 were retrospectively analysed. A population pharmacokinetic (PK) model was developed using nonlinear mixed-effects method and externally validated thereafter. Several dosing scenarios were simulated to maintain the plasma AT-III activity level within the normal range using the developed PK model to search for an optimal AT-III dosing regimen.

RESULTS

The plasma AT-III activity levels were best described by a single compartment model with first order elimination kinetics. The recovery of endogenous AT-III level during the postoperative days was modelled using an E_max model. The typical values (95% confidence interval) of volume of distribution and clearance were 3.86 (3.40-4.32) L, and 0.129 (0.111-0.147) L h^-1 , respectively. Serum albumin and body weight had significant effect on clearance and were included in the model. External validation of the proposed model demonstrated adequate prediction performance. Furthermore, simulation of previously suggested or modified dosing scenarios showed successful maintenance of AT-III activity level within the normal range.

CONCLUSION

A population PK model of AT-III concentrate was developed using data from liver recipients. Dosing scenarios simulated in our study may help establish a practical guide for AT-III concentrate titration after liver transplantation.

Review: The Perioperative Use of Thromboelastography for Liver Transplant Patients

Thromboelastography (TEG) is a viscoelastic test that allows rapid evaluation of clot formation and fibrinolysis from a sample of whole blood. TEG is increasingly utilized to guide blood product resuscitation in surgical patients and transfusions for liver transplant patients. Patients with severe liver failure have significant derangement of their clotting function due to impaired production of procoagulant and anticoagulant factors. Traditional coagulation studies are limited by the short time needed for the result and provide little information about the dynamics and strength of clot formation. In addition, traditional coagulation studies do not correlate well with bleeding episodes and may lead to over-transfusion of various blood products. Evidence is less robust regarding the use of TEG for transfusion management decisions in severe liver failure patients awaiting, undergoing, or immediately after liver transplant surgery. However, the available evidence suggests that systematic implementation of TEG rather than traditional coagulation studies results in the administration of fewer blood products without increased mortality or complications. The purpose of this study is to review the literature regarding the use of TEG in liver failure patients prior to liver transplant, intraoperatively, and postoperatively. Additional high-quality randomized controlled studies should be performed to evaluate the use of TEG to guide transfusion decisions, particularly in the postoperative period following liver transplantation.

Effects of plasma transfusions on antithrombin levels after paediatric liver transplantation

BACKGROUND AND OBJECTIVES

Thrombotic complications affect 3-10% of patients after liver transplantation (LT), leading to potentially life-threatening complications. In the days following LT, antithrombin (AT) is decreased longer than pro-coagulant factors, thus favouring a pro-thrombotic profile. Plasma transfusions are given empirically in some centres to correct AT levels following LT. We assessed the effect of plasma transfusion on AT levels after paediatric LT.

MATERIALS AND METHODS

Prospective single-centre observational study in 20 consecutive paediatric LT recipients over a 24-month period. Plasma was administered twice daily (10 ml/kg/dose) according to an existing protocol. AT levels were measured once daily, immediately prior to and one hour after the morning plasma transfusion. Sample size was calculated based on a non-inferiority hypothesis.

RESULTS

The median age and weight were 11.6 years (IQR 2.8; 14.7) and 40 kg (IQR 12.75; 44.8), respectively. We collected 85-paired blood samples. The median AT level prior to plasma transfusion was 58%. The median difference in AT levels before and after plasma transfusion was 4.2% (P = 0.001). Changes in AT levels after plasma transfusion were not correlated with baseline AT levels (R = 0.19) or patient weight (R = 0.18).

CONCLUSION

Plasma transfusions only marginally increase AT levels in children after LT. Therefore, prophylactic plasma transfusions probably do not seem to confer an advantage in the routine management of paediatric LT patients. Randomized controlled trials are needed to identify the optimal anticoagulation strategy in this specific population.

Anesthesia for Liver Transplantation

Advances in surgical and anesthetic techniques have provided great success in liver transplantation, with more than 4,000 liver transplantations performed annu ally in the United States. Indications for transplanta tions include the various forms of cirrhosis, commonly resulting from hepatitis B or C, alcoholism, or acute hepatic failure from drug toxicity or poisoning. Cadav eric donor livers are resected and may be transplanted up to 24 hours later while the recipient is prepared for surgery. These operations may last 10 hours and require large amounts of blood products. Extrahepatic prob lems from their end-stage liver disease are common and affect nearly all organ systems. Intraoperative monitor ing of acid-base status, electrolytes, intravascular vol ume, and coagulation parameters is essential. Preexist ing coagulopathies from liver disease, complications of massive transfusions and fibrinolysis from the new liver create complex coagulation disturbances requiring prompt diagnosis and treatment. Metabolic (lactic) aci dosis is common and severe. Reperfusion of the donor liver can result in a dramatic and rapid fall in blood pressure as well as hyperkalemia.

Deep Vein Thrombosis and Pulmonary Embolism in Liver Transplant Patients: Risks and Prevention

Deep vein thrombosis (DVT) and pulmonary embolism (PE) are surgical complications estimated to occur in 5% to 10% of patients. There are limited data regarding DVT/PE in the early postoperative period in liver transplant patients. The aim of this study is to determine risk factors that influence the incidence of DVT/PE and the effectiveness of prophylaxis.

Do postliver transplant patients need thromboprophylactic anticoagulation?

Postoperative thromboprophylactic anticoagulation against Deep Vein Thrombosis (DVT) and Pulmonary Embolism (PE) is standard of care with current evidence-based guidelines. However, majority of liver transplant (LT) patients have thrombocytopenia and/or prolonged INR before surgery. Studies or guidelines regarding role of prophylactic anticoagulation after LT are lacking. There is a need to balance the risk of thrombosis with significant hemorrhage, implying those needing transfusion or return to OR due to bleeding. We conclude that after LT, anticoagulation is not required routinely for DVT/PE prophylaxis. Rather, it is indicated in specific circumstances, chiefly for prophylaxis of hepatic artery thrombosis or portal vein thrombosis in cases with use of grafts, pediatric cases, small size vessels, Budd Chiari syndrome, amongst others.

Low plasma levels of antithrombin III in the early post-operative period following pediatric liver transplantation: should they be replaced? A single-center pilot study

eHAT after LT remains a life-threatening complication. In the majority of anticoagulation protocols, heparin is used to prevent thromboses. Our study aimed to monitor AT-III levels in the early post-LT period to assess the need for the administration of AT-III concentrate to ensure the effectiveness of heparin. We monitored coagulation daily by measuring INR, APTT, fibrinogen, platelets, and AT-III. Anticoagulation therapy consisted of LMWH, AT-III, and dipyridamole. AT-III concentrate was administered when AT-III activity was ≤60%. DUS was performed daily for the first five post-operative days or whenever vascular thrombosis was suspected. Between October 2007 and October 2011, 39 LT were performed in our center. The median age was 26 months (6-196) with a median weight of 9 kg (5.5-49). AT-III activity was ≤60% in 27 patients. Lower levels were particularly observed in partial grafts and recipients weighing less than 10 kg. Patent arterial flow was present in all 39 LT during the first five post-operative days. AT-III levels were low in 70% of pediatric patients following LT, thereby risking heparin ineffectiveness. These results may implicate low AT-III levels in the etiology of eHAT post-LT. However, this is a small single-center pilot study and further larger prospective trials are required to confirm these results.

Hepatic artery reconstruction and successful management of its complications in living donor liver transplantation using a right lobe

BACKGROUND

The aim of the present study was to improve the techniques of hepatic artery (HA) reconstruction and to properly manage arterial complications after living donor liver transplantation (LDLT).

METHODS

Prospectively collected data collected from 371 patients who underwent adult LDLT using a right lobe from January 2000 to August 2009 were retrospectively reviewed.

RESULTS

Of 17 patients (4.6%, 17/371) with double HA stumps in the graft, 12 patients (70.6%) received dual HA reconstruction. HA complications were composed of thrombosis (n = 6), pseudoaneurysm (n = 2), and stenosis (n = 4), showing 3.2% (12/371) of incidence. In patients with HA thrombosis, whereas operative thrombectomies with re-anastomosis rescued all the grafts in early attack (n = 3, ≤1 wk), angiographic thrombolysis successfully reestablished the flow in patients with late attack (n = 3, >1 wk). In all patients with HA complications, except for one, all of our treatment modalities - operation and angiographic intervention - resulted in successful rescue of grafts and no patient received re-transplantation because of HA complications.

CONCLUSION

Prompt diagnosis of HA complications by serial post-operative Doppler ultrasound and corresponding treatment strategies, including operative and radiological intervention, can rescue both grafts and patients without necessitating re-transplantation.

Administration of dalteparin based on the activated clotting time for prophylaxis of hepatic vessel thrombosis in living donor liver transplantation

Beginning in 2004, dalteparin doses based on activated clotting time (ACT) were administered for hepatic vessel thrombosis prophylaxis in living donor liver transplantation (LDLT). We verified the feasibility of this new therapy by comparing it with the previous one. From 1993 through 2008, 42 metabolic liver patients who underwent LDLT were divided into two groups. Group A (1993-2003, n = 32) was administered a fixed dalteparin dose and a large amount of fresh frozen plasma (FFP); Group B (2004-2008, n = 10) was administered an appropriate dosage of dalteparin to maintain the ACT levels from 140 to 150 seconds and a small amount of FFP. Group B was administered a lesser amount of FFP and more dalteparin. This resulted in longer activated partial thromboplastin time, lower fibrinogen degradation products D-dimer, and lower aspartate aminotransferase levels compared to group A; all differences were significant. Group B showed neither thrombotic nor hemorrhagic complications. Anticoagulation therapy comprising adjustment of the dalteparin dose based on ACT reduces thrombotic complications without increasing hemorrhagic complications. ACT measurement is a simple, reliable method for bedside monitoring of dalteparin anticoagulant effects for LDLT.

Feasibility and effectiveness of a new algorithm in preventing hepatic artery thrombosis after liver transplantation

INTRODUCTION

The incidence of hepatic artery thrombosis (HAT) after liver transplantation (LTx) is up to 9% in adult recipients.

MATERIAL AND METHODS

To minimize HAT, we developed an algorithm that we have routinely applied since 2001. The algorithm is a cascade of potentially necessary procedures to improve hepatic artery blood flow before proceeding with LTx when arterial blood flow is impaired. Incidence, outcome, and possible therapeutic approaches of HAT were analyzed in prospectively non-controlled collected data during a 5-year period. There were 335 LTx in 299 adults (199 male, 100 female) with a median age of 49.7 years.

RESULTS

HAT was defined as early and late HAT (diagnosis within or after 30 days following LTx). After a mean follow-up of 17 months, nine HAT were documented (2.7%; five early and four late HAT). Treatment consisted of thrombolysis (n = 1), surgical thrombectomy (n = 4), and re-transplantation (n = 4). Five HAT patients died during follow-up.

DISCUSSION

Complex arterial reconstruction was associated with HAT compared to branch-patch anastomoses (P = 0.0193). Median arterial intraoperative blood flow was no risk factor for HAT. One-year patient survival after HAT was 31%. Once HAT occurs, complication rates are high and long-term results are devastating.

CONCLUSION

Therefore, we have implemented the presented algorithm, which showed an acceptable HAT rate.

Coagulation and fibrinolytic profiles and appropriate use of heparin after living-donor liver transplantation

Heparin is widely used to reduce the incidence of vascular thrombosis after liver transplantation. Appropriate use of heparin based on changes in coagulation and fibrinolytic profiles, however, has not yet been discussed in detail. We performed living-donor liver transplantation for 128 adult patients. In this series, dalteparin (25 IU/kg/d) was administered until post-operative day (POD) 2. On POD 3, the anticoagulant drug was changed to heparin (unfractionated heparin sodium, 5000 U/d), the dose of which was changed according to the level of activated clotting time (ACT) targeted between 130 and 160 s. The plasma level of plasmin-alpha2 plasmin inhibitor complex, thrombin-antithrombin III complex (TAT), and fibrin degradation product D-dimer (FDP-DD) were monitored in the 21 patients. Predictors for heparin doses were analyzed among clinical parameters (n = 128). Four patients (3%) were complicated with thrombosis despite the above-mentioned anticoagulation protocol. Transfusion and/or relaparotomy for hemostasis were necessary for bleeding in 19 patients (15%). The TAT level markedly elevated until POD 3 and FDP-DD peaked later. The required heparin dose to maintain adequate ACT levels increased linearly until POD 8, and kept constant thereafter, which correlated with the weight of the liver graft (p = 0.01). Thus, frequent monitoring of the heparin dosage is necessary to keep the ACT level in the target range in the first post-operative week. High hemorrhage complications in our series indicate that the lower target ACT range may be preferable in the second post-operative week.

Donor intracaval thrombus formation and pulmonary embolism after simultaneous piggyback liver transplantation and aortic valve replacement

Pulmonary embolism (PE) is a well known and serious complication that may develop after abdominal surgery. Liver transplant recipients are not immune to PE and tend to share many of the same risk factors with surgical patients who are stricken with this potential fatal complication. Liver transplantation using the piggyback (PB) technique is widely accepted, although there are reports of technique-specific-related vascular complications. We present a case of a 49-yr-old male liver transplant recipient who received his graft using the PB while simultaneously undergoing aortic valve replacement. His post-operative course was complicated by a PE 15 d after his surgery and was the result of an intracaval thrombus of the graft liver. The current case should alert clinicians to think of a donor intracaval thrombus as a complication of PB liver transplantation and a possible source of PE.

Repeated graft loss caused by recurrent hepatic artery thrombosis after liver transplantation

Hepatic artery thrombosis (HAT) is a main cause of graft loss and patient mortality after orthotopic liver transplantation (OLT). Several surgical and nonsurgical risk factors have been associated with HAT. Retransplantation often is the only possible treatment for this complication; however, the incidence of recurrence of HAT after retransplantation and the underlying conditions of this occurrence have never been investigated. Of 629 consecutive recipients transplanted at a single institution, 24 underwent retransplantion for HAT: in 4 of them (16%), HAT recurred in the second graft; 3 of these patients lost their first graft because of late HAT, whereas another one lost 4 consecutive grafts for early HAT. Antiphospholipid syndrome and paroxysmal nocturnal hemoglobinuria were diagnosed in three and one of these patients, respectively. Recurrent HAT is an uncommon occurrence that, in our experience, was linked to specific thrombophilic conditions; careful screening of these disorders should be included in the pretransplant workup, and adequate prophylaxis is advisable.

Heparin cofactor II deficiency

OBJECTIVES

To review of the state of the art relating to congenital heparin cofactor II deficiency as a potential risk factor for thrombosis, as reflected by the medical literature and the consensus opinion of recognized experts in the field, and to make recommendations for the use of laboratory assays for assessing this thrombotic risk in individual patients.

DATA SOURCES

Review of the medical literature, primarily from the last 10 years.

DATA EXTRACTION AND SYNTHESIS

After an initial assessment of the literature, including review of clinical study design and laboratory methods, a draft manuscript was prepared and circulated to participants in the College of American Pathologists Conference XXXVI: Diagnostic Issues in Thrombophilia. Recommendations were accepted if a consensus of experts attending the conference was reached. The results of the discussion were used to revise the manuscript into its final form.

CONCLUSIONS

Consensus was reached that there is insufficient evidence to recommend testing for heparin cofactor II deficiency in patients with thromboembolic disease.

Cigarette smoking is associated with an increased incidence of vascular complications after liver transplantation

Hepatic artery thrombosis (HAT) and other vascular complications are significant causes of morbidity after liver transplantation. Although cigarette smoking increases the risk of vascular complications after renal transplantation, its impact after liver transplantation remains unknown. Between May 1995 and April 2001, 288 liver transplantations were performed in 263 patients. Vascular complications developed in 39 patients (13.5%) (arterial complications, 28 patients [9.7%]; venous complications, 11 patients [3.8%]). Patient demographics, comorbid illnesses, and risk factors were analyzed using the Mann-Whitney U test, Chi-squared test, and Fisher's exact test. In patients with a history of cigarette smoking, incidence of vascular complications was higher than in those without history of cigarette smoking (17.8% v 8%, P =.02). Having quit cigarette smoking 2 years before liver transplantation reduced the incidence of vascular complications by 58.6% (24.4% v 11.8%, P =.04). The incidence of arterial complications was also higher in patients with a history of cigarette smoking compared with those without such history (13.5% v 4.8%, P =.015). Cigarette smoking cessation for 2 years also reduced the risk of arterial complications by 77.6% (21.8% v 5.9%, P =.005). However, the incidence of venous complications was not associated with cigarette smoking. Furthermore, there was no significant association between development of vascular complications and all other characteristics studied. Cigarette smoking is associated with a higher risk for developing vascular complications, especially arterial complications after liver transplantation. Cigarette smoking cessation at least 2 years before liver transplantation can significantly reduce the risk for vascular complications. Cigarette smoking cessation should be an essential requirement for liver transplantation candidates to decrease the morbidity arising from vascular complication after liver transplantation.

Adrenomedullin in liver transplantation and its relationship with vascular complications

Adrenomedullin (AM) is a potent vasodilating peptide that increases rat platelet cyclic adenosine monophosphate levels and acts on endothelial cells to stimulate nitric oxide release. Both mechanisms inhibit platelet function. Considering these effects, AM may have a role in cardiovascular regulation after orthotopic liver transplantation (OLT) and could have an antithrombotic effect. The aim of the present study is to investigate plasma AM levels in the early postoperative period after OLT and their relationship with vascular complications in OLT. We measured plasma AM levels in 35 patients with cirrhosis who underwent OLT at baseline and 1, 7, and 15 days postoperatively. We found that AM levels were significantly greater in patients with cirrhosis compared with healthy subjects. Of the 35 patients, 10 had vascular complications. In these 10 patients, AM concentrations were significantly greater than those observed in the nonthrombotic group in the early postoperative period. In addition, we also noticed in the nonthrombotic group a significant increase in AM levels from baseline to day 1, then a decrease to baseline levels in the early postoperative period. Our study shows that AM might act as a new humoral factor involved in the response to surgery in OLT and is significantly associated with vascular thrombosis in OLT.

Biphasic mechanism for hypothermic induced loss of protein synthesis in hepatocytes

BACKGROUND

A complication in liver transplantation is increased clotting times due to inhibition of protein synthesis resulting from prolonged hypothermic preservation. Protein synthesis is also blocked in cold preserved hepatocytes. In this study, the mechanism of inhibition of protein synthesis in cold preserved hepatocytes was investigated.

METHODS

Hepatocytes prepared from rat liver were cold preserved in University of Wisconsin solution for 4, 24, and 48 hr. Protein synthesis was measured as incorporation of radiolabeled leucine into acid precipitable proteins. Hepatocytes were treated with antioxidants (dithiothreitol, trolox or deferoxamine, nitric oxide synthase inhibitor (N(G)-monomethyl-L-arginine monoacetate), steroids (dexamethasone or methylprednisolone), methods to keep adenosine triphosphate high (aerobic storage), and cytoskeletal disrupting agents (cytochalasin D or colchicine).

RESULTS

There was a 26% decrease in protein synthesis after only 4 hr of cold storage and a further 25% decrease at 24 hr. Antioxidants, elevated adenosine triphosphate, and N(G)-monomethyl-L-arginine monoacetate did not affect the rate of loss of protein synthesis. Protein synthesis was not due to inhibition of amino acid transport or lack of amino acids in the storage medium. Steroid pretreatment of hepatocytes had no effect on the loss of protein synthesis occurring in the first 4 hr of storage but did suppress the loss occurring during the next 44 hr of storage. Cytoskeletal disrupting agents, added to freshly isolated cells, inhibited protein synthesis.

CONCLUSION

The mechanism of loss of protein synthesis in cold preserved liver cells is not mediated by: (1) oxygen free radical generation or improved by antioxidant therapy, (2) nitric oxide generation in hepatocytes, (3) an adenosine triphosphate-sensitive destruction of cell viability, and (4) decreased permeability of amino acids or loss of amino acids from the cells. Loss of protein synthesis due to hypothermic storage appears biphasic. The first phase, occurring within 4 hr of storage, may be the result of the effects of hypothermia on the cell cytoskeletal system and may be untreatable. The second phase, which occurs during the next 24 to 48 hr is sensitive to steroid pretreatment. This phase may be amenable to improved preservation methodology. Improved preservation of the liver may require the use of steroids to conserve protein synthetic capabilities.

Acquired protein S deficiency with multiple thrombotic complications after orthotopic liver transplant

BACKGROUND

Orthotopic liver transplantation (OLT) is frequently complicated by thrombotic events that may threaten the viability of the allograft and severely compromise the overall outcome in these patients. Although multiple prothrombotic pathogenic mechanisms may be involved, a role for inadequate natural anticoagulant levels in the early postoperative period has been postulated.

METHODS

We describe a case of a woman who suffered multiple thrombotic complications after a second OLT. Prospective assays of procoagulant and natural anticoagulant factor levels, in addition to screening tests for a variety of inherited and acquired hypercoagulable states, were carried out.

RESULTS

Serial studies confirmed an acquired, isolated deficiency of Protein S associated with the second transplanted liver. Protein S levels were normal after the patient's first and third OLTs. There was no laboratory evidence of other underlying prothrombotic conditions.

CONCLUSIONS

This unusual case of acquired Protein S deficiency demonstrates that the hypercoagulable phenotype may develop in the recipient of a liver from a heterozygous deficient donor. Furthermore, isolated low Protein S may be causally associated with hepatic artery thrombosis after OLT.

Anticardiolipin antibodies and hepatic artery thrombosis after liver transplantation

BACKGROUND

Hepatic artery thrombosis (HAT) remains a devastating complication after liver transplantation. Various factors have been implicated in the pathogenesis of HAT, such as clotting abnormalities, increased hematocrit, and technical complications, but the role of anticardiolipin antibodies has not been evaluated. We investigated the possible association between HAT and anticardiolipin antibodies in adult patients who underwent liver transplantation.

METHODS

Seven patients with HAT after orthotopic liver transplantation, 28 liver recipients without HAT, and 35 normal blood donors were evaluated. Determination of IgM and IgG anticardiolipin antibodies was performed by enzyme-linked immunosorbent assay using pretransplant serum from all allograft recipients. Clinical information was obtained from chart review. Fisher's exact test and Wilcoxon rank sum test were used for statistical analysis, and all P-values were two-tailed.

RESULTS

Overall, 22 of 35 (63%) liver recipients had a positive anticardiolipin antibody test (either IgG or IgM titer >4 SD from the normal controls). The test was positive in 7 liver recipients (100%) with HAT compared with 15 out of 28 patients (54%) without HAT (P=0.031). As compared with liver recipients without HAT, patients with HAT also tended to have a higher mean anticardiolipin titer of IgG and IgM and a lower pretransplant platelet count; however, these differences were not significant.

CONCLUSIONS

Our findings indicate that anticardiolipin antibodies are frequently elevated in patients with liver failure and may contribute to the pathogenesis of HAT after liver transplantation. Other potential consequences of anticardiolipin antibodies in end-stage liver disease remain to be determined.

The impact of microsurgical hepatic arterial reconstruction on the outcome of liver transplantation for congenital biliary atresia

BACKGROUND

Hepatic artery thrombosis (HAT) after liver transplantation for biliary atresia (BA) is a serious complication that most often leads to retransplantation (re-OLT). The purpose of the present study was: (1) to identify risk factors associated with HAT and (2) to analyze the impact of recently introduced microsurgical hepatic arterial reconstruction (MHR) on the incidence of HAT, subsequent need for re-OLT, and patient survival.

METHODS

A retrospective review of 194 patients transplanted for BA was performed. One hundred and sixty-six patients (group 1) underwent conventional arterial reconstruction and 28 (group 2) had MHR.

RESULTS

Actuarial survival for patients with HAT was significantly worse than for patients without HAT at 1, 2, and 5 years (71%, 61%, and 57% versus 85%, 85%, and 85%, P = 0.0007). Stepwise logistic regression analysis revealed that the risk of HAT correlated best with the type of arterial reconstruction (P = 0.007) followed by pretransplant bilirubin concentration (P = 0.04) and the number of acute rejection episodes (P = 0.03). In group 1, 32 patients developed HAT (19%), and of these, 18 underwent re-OLT for HAT. No patient in group 2 developed HAT (P = 0.006 versus group 1). One-year actuarial patient survival was 81% in group 1 and 100% in group 2 (P = 0.02).

CONCLUSIONS

In OLT for BA, (1) the predominant risk factor for HAT is the technique of arterial reconstruction, and (2) MHR markedly reduces the incidence of HAT and the need for re-OLT while improving patient survival.

Heterozygous protein C deficiency and dysfibrinogenemia acquired by liver transplantation

Orthotopic liver transplantation is now a successful treatment for end-stage liver diseases. Since most components of the coagulation system are synthesized by liver parenchymal cells, there is always a risk of genetic defects of hemostasis being transmitting by liver transplantation. Some coagulation factor defects, such as protein C deficiency, do not induce abnormalities in routine coagulation tests and, thus, go undetected before organ procurement. We report the first case, to our knowledge, of the transmission of heterozygous protein C deficiency, an autosomal recessive genetic defect, associated with dysfibrinogenemia, an autosomal dominant trait, by liver transplantation. Both the recipient and the donor presented with severe thrombotic complications. This case shows that potentially morbid genetic defects can be transmitted by organ transplantation, and it emphasizes the difficulty associated with organ procurement criteria, particularly for liver transplantation, in which routine blood tests appear insufficient for determining whether or not organs can or should be procured from a given donor.

Effect of platelet-activating factor on cold-preserved liver grafts

Platelet-activating factor (PAF) may play an important role in graft injury in liver transplantation. Livers excised from male Wistar rats were preserved in University of Wisconsin solution for 6 h and then perfused with Krebs-Henseleit solution containing vehicle (bovine serum albumin) or PAF. Impairment of parenchymal cells was assessed by reference to tissue adenosine triphosphate levels, oxygen consumption and alanine aminotransferase activity in the effluent. The effect on non-parenchymal cells was evaluated by measurement of purine nucleoside phosphorylase and alanine aminotransferase levels in the effluent. Administration of as little as 1.0 ng kg-1 PAF caused a significant decrease in adenosine 5'-triphosphate concentration and oxygen consumption (P < 0.05), although non-parenchymal cell injury was not affected. PAF can therefore cause liver graft dysfunction with hepatocytes as the main target, even in the absence of microcirculatory disturbance secondary to interaction between blood cells and endothelial cells.

Impairment of fibrinolysis during the growth of two murine mammary adenocarcinomas

The fibrinolytic activity present in the euglobulin (EU) fraction of BALB/c mice before and during the growth of M3 and MM3 murine mammary adenocarcinomas was characterized. The main plasminogen activator (PA) form contained in EUs from control mice was defined as murine urokinase-type PA (uPA). Overall fibrinolytic activity decreased significantly during tumor development. Zymographies showed that this fall was associated with a reduction in the free uPA band (47 kDa) and to the detection of a tissue-type PA (tPA) complexed band (117 kDa). Western blotting showed free tPA protein (68 kDa) in control mice, that disappeared in M3 tumor-bearing mice. In this model, high subcutaneous tumor burden induces a severe impairment in the circulating fibrinolytic system.