Aprotinin in orthotopic liver transplantation: evidence for a prohemostatic, but not a prothrombotic, effect

No increase in blood transfusions during liver transplantation since the withdrawal of aprotinin

The aims of this study were to determine whether the withdrawal of aprotinin (APRO) led to an increased bleeding risk in patients undergoing orthotopic liver transplantation (OLT). A retrospective analysis compared consecutive patients undergoing OLT and treated with aprotinin (APRO group; n = 100) with a group in which aprotinin was not used (no-APRO group; n = 100). Propensity score matching was then performed for each group to identify 2 matched cohorts. Patients were matched by their primary diagnoses and Model for End-Stage Liver Disease scores. This resulted in 2 matched cohorts with 55 patients in each group. None of the patients in the APRO group had significant fibrinolysis. In the no-APRO group, 23.6% of the patients developed fibrinolysis (P < 0.003). Tranexamic acid was used in 61.5% of the patients (n = 8) in the no-APRO group in whom lysis was present, and this resolved the fibrinolysis in all but 1 of these patients. There were no differences in red blood cell, fresh frozen plasma, platelet concentrate, or cryoprecipitate transfusions between the 2 groups. In conclusion, we have shown a significant increase in the prevalence of fibrinolysis during OLT since the withdrawal of APRO. However, there has been no increase in transfusion requirements.

Methods to decrease blood loss and transfusion requirements for liver transplantation

BACKGROUND

Excessive blood loss and increased blood transfusion requirements may have significant impact on the short-term and long-term outcomes after liver transplantation.

OBJECTIVES

To compare the potential benefits and harms of different methods of decreasing blood loss and blood transfusion requirements during liver transplantation.

SEARCH METHODS

We searched The Cochrane Central Register of Controlled Trials in The Cochrane Library, MEDLINE, EMBASE, Science Citation Index Expanded, and metaRegister of Controlled Trials until September 2011.

SELECTION CRITERIA

We included all randomised clinical trials that were performed to compare various methods of decreasing blood loss and blood transfusion requirements during liver transplantation.

DATA COLLECTION AND ANALYSIS

Two authors independently identified the trials and extracted the data. We analysed the data with both the fixed-effect and the random-effects model using RevMan Analysis. For each outcome we calculated the risk ratio (RR), mean difference (MD), or standardised mean difference (SMD) with 95% confidence intervals (CI) based on available data analysis. We also conducted network meta-analysis.

MAIN RESULTS

We included 33 trials involving 1913 patients. The sample size in the trials varied from 8 to 209 participants. The interventions included pharmacological interventions (aprotinin, tranexamic acid, epsilon amino caproic acid, antithrombin 3, recombinant factor (rFvIIa), oestrogen, prostaglandin, epinephrine), blood substitutes (blood components rather than whole blood, hydroxy-ethyl starch, thromboelastography), and cardiovascular interventions (low central venous pressure). All the trials were of high risk of bias. Primary outcomes were reported in at least two trials for the following comparisons: aprotinin versus control, tranexamic acid versus control, recombinant factor VIIa (rFVIIa) versus control, and tranexamic acid versus aprotinin. There were no significant differences in the 60-day mortality (3 trials; 6/161 (3.7%) in the aprotinin group versus 8/119 (6.7%) in the control group; RR 0.52; 95% CI 0.18 to 1.45), primary graft non-function (2 trials; 0/128 (0.0%) in the aprotinin group versus 4/89 (4.5%) in the control group; RR 0.15; 95% CI 0.02 to 1.25), retransplantation (3 trials; 2/256 (0.8%) in the aprotinin group versus 12/178 (6.7%) in the control group; RR 0.21; 95% CI 0.02 to 1.79), or thromboembolic episodes (3 trials; 4/161 (2.5%) in the aprotinin group versus 5/119 (4.2%) in the control group; RR 0.59; 95% CI 0.19 to 1.84) between the aprotinin and control groups. There were no significant differences in the 60-day mortality (3 trials; 4/83 (4.8%) in the tranexamic acid group versus 5/56 (8.9%) in the control group; RR 0.55; 95% CI 0.17 to 1.76), retransplantation (2 trials; 3/41 (7.3%) in the tranexamic acid group versus 3/36 (8.3%) in the control group; RR 0.79; 95% CI 0.18 to 3.48), or thromboembolic episodes (5 trials; 5/103 (4.9%) in the tranexamic acid group versus 1/76 (1.3%) in the control group; RR 2.20; 95% CI 0.38 to 12.64) between the tranexamic acid and control groups. There were no significant differences in the 60-day mortality (3 trials; 8/195 (4.1%) in the recombinant factor VIIa (rFVIIa) group versus 2/91 (2.2%) in the control group; RR 1.51; 95% CI 0.33 to 6.95), thromboembolic episodes (2 trials; 24/185 (13.0%) in the rFVIIa group versus 8/81 (9.9%) in the control group; RR 1.38; 95% CI 0.65 to 2.91), or serious adverse events (2 trials; 90/185 (48.6%) in the rFVIIa group versus 30/81 (37.0%) in the control group; RR 1.30; 95% CI 0.94 to 1.78) between the rFVIIa and control groups. There were no significant differences in the 60-day mortality (2 trials; 6/91 (6.6%) in the tranexamic acid group versus 1/87 (1.1%) in the aprotinin group; RR 4.12; 95% CI 0.71 to 23.76) or thromboembolic episodes (2 trials; 4/91 (4.4%) in the tranexamic acid group versus 2/87 (2.3%) in the aprotinin group; RR 1.97; 95% CI 0.37 to 10.37) between the tranexamic acid and aprotinin groups. The remaining outcomes in the above comparisons and the remaining comparisons included only only trial under the primary outcome or the outcome was not reported at all in the trials. There were no significant differences in the mortality, primary graft non-function, graft failure, retransplantation, thromboembolic episodes, or serious adverse events in any of these comparisons. However, the confidence intervals were wide, and it is not possible to reach any conclusion on the safety of the interventions. None of the trials reported the quality of life in patients.Secondary outcomes were reported in at least two trials for the following comparisons - aprotinin versus control, tranexamic acid versus control, rFVIIa versus control, thromboelastography versus control, and tranexamic acid versus aprotinin. There was significantly lower allogeneic blood transfusion requirements in the aprotinin group than the control group (8 trials; 185 patients in aprotinin group and 190 patients in control group; SMD -0.61; 95% CI -0.82 to -0.40). There were no significant differences in the allogeneic blood transfusion requirements between the tranexamic acid and control groups (4 trials; 93 patients in tranexamic acid group and 66 patients in control group; SMD -0.27; 95% CI -0.59 to 0.06); rFVIIa and control groups (2 trials; 141 patients in rFVIIa group and 80 patients in control group; SMD -0.05; 95% CI -0.32 to 0.23); thromboelastography and control groups (2 trials; 31 patients in thromboelastography group and 31 patients in control group; SMD -0.73; 95% CI -1.69 to 0.24); or between the tranexamic acid and aprotinin groups (3 trials; 101 patients in tranexamic acid group and 97 patients in aprotinin group; SMD -0.09; 95% CI -0.36 to 0.19). The remaining outcomes in the above comparisons and the remaining comparisons included only only trial under the primary outcome or the outcome was not reported at all in the trials. There were no significant differences in the blood loss, transfusion requirements, hospital stay, or intensive care unit stay in most of the comparisons.

AUTHORS' CONCLUSIONS

Aprotinin, recombinant factor VIIa, and thromboelastography groups may potentially reduce blood loss and transfusion requirements. However, risks of systematic errors (bias) and risks of random errors (play of chance) hamper the confidence in this conclusion. We need further well-designed randomised trials with low risk of systematic error and low risk of random errors before these interventions can be supported or refuted.

Aprotinin and the risk of thrombotic complications after liver transplantation: a retrospective analysis of 1492 patients

Aprotinin is an antifibrinolytic drug that reduces blood loss during orthotopic liver transplantation (OLT). Case reports have suggested that aprotinin may be associated with an increased risk of thromboembolic complications. Recent studies in cardiac surgery also have suggested a higher risk of renal failure and postoperative mortality. Despite these concerns, no large-scale safety assessment has been performed in OLT. In a retrospective observational study involving 1492 liver transplants, we studied the occurrence of postoperative thromboembolic or thrombotic events and mortality in patients who received aprotinin (n = 907) and patients who did not (n = 585). The overall incidence of hepatic artery thrombosis and central venous complications (pulmonary embolism or inferior vena cava thrombosis) was 3.2% and 0.9%, respectively. In propensity score-adjusted analyses (C-index = 0.79), aprotinin was not associated with an increased risk of hepatic artery thrombosis [odds ratio (OR) = 1.00, 95% confidence interval (CI) = 0.50-2.01, P = 0.86]. Although central venous complications were found more frequently in patients receiving aprotinin, the difference was not statistically significant (OR = 2.95, 95% CI = 0.54-16.23, P = 0.32). In addition, no significant differences were found in 1-year mortality (OR = 1.21, 95% CI = 0.86-1.71, P = 0.32). In conclusion, this study did not demonstrate an increased risk of thrombotic complications or mortality when aprotinin is used during OLT.

Requirements for transfusion and postoperative outcomes in orthotopic liver transplantation: A meta-analysis on aprotinin

AIM: To study the effect of aprotinin used in orthotopic liver transplantation (OLT) on the intraoperative requirement for blood products and on the incidence of laparotomy for bleeding, thrombotic events and mortality.

METHODS: A systematic review of the literature in the electronic database Medline and the Clinic Trials Registry Database was performed. Literature that did not fit our study were excluded. Patients in the reviewed studies were divided into two groups; one group used aprotinin (aprotinin group) while the other did not (control group). The data in the literature that fit our requirements were recorded. Weighted mean differences (WMD) in the requirements for blood products between the aprotinin group and the control group were tested using a fixed effect model. A Z test was performed to examine their reliability; the Fleiss method of fixed effect model was used to analyze data on postoperative events, and odds ratios (ORs) were tested and merged.

RESULTS: Seven citations were examined in our study. Among them, a requirement for blood products was reported in 4 studies including 321 patients, while postoperative events were reported in 5 studies including 477 patients. The requirement for red blood cells and fresh frozen plasma in the aprotinin group was statistically lower than that in the control group (WMD = -1.80 units, 95% CI, -3.38 to -0.22; WMD = -3.99 units, 95% CI, -6.47 to -1.50, respectively). However, no significant difference was indicated in the incidence of laparotomy for bleeding, thrombotic events and mortality between the two groups. Analysis on blood loss, anaphylactic reactions and renal function was not performed in this study due to a lack of sufficient information.

CONCLUSION: Aprotinin can reduce the intraoperative requirement for blood products in OLT, and has no significant effect on the incidence of laparotomy for bleeding, thrombotic events and mortality.

Safety aspects of aprotinin therapy in cardiac surgery patients

Aprotinin is the only agent with Class A Level 1 evidence for reduction in rates of transfusion and return to operating theatre to control bleeding after heart surgery. Principal on the list of safety issues raised over the years are increased risk for: a) thrombosis; and b) renal dysfunction. With multiple administrations, hypersensitivity reactions have emerged as a further safety concern. This review discusses these issues, based on the examination of > 500 published articles. The article also specifically places in context the data presented recently from the observational McSPI database analysis. This report suggested that aprotinin should be withdrawn from human use as serious safety issues have been ignored or missed, an inference not in agreement with the majority of the human safety literature.

Four cases of cardiopulmonary thromboembolism during liver transplantation without the use of antifibrinolytic drugs

Orthotopic liver transplantation (OLT) is one of the most demanding surgical procedures performed. Intraoperative bleeding can be substantial and related to both surgical and nonsurgical causes. A less common but previously reported phenomenon is intraoperative cardiopulmonary thromboembolism precipitating major patient morbidity and mortality. In this paper, we present four cases of intraoperative thromboembolism during OLT. These cases were performed without the concomitant use of antifibrinolytic drugs. We performed a review and analysis of previously reported cases of intraoperative thromboembolism during OLT. Possible causes of thromboembolism, clinical management, use of thromboelastography, and the role of antifibrinolytic drugs are discussed.

The effect of aprotinin in a model of uncontrolled hemorrhagic shock

BACKGROUND

Aprotinin has been shown to promote clot formation through its antifibrinolytic activity, by inhibiting the plasmin-induced complement activation and by protecting the platelets adhesive surface receptors. It has been successfully used in cardiac and liver transplantation surgery.

OBJECTIVE

To evaluate the effect of aprotinin in a model of uncontrolled intra-abdominal bleeding as a basis for its potential use in trauma patients.

METHODS

Twenty rats were randomly divided into 2 groups. All animals were operated on and bleeding was induced by transecting 1 lobe of the liver. In the treatment group a single dose of 30,000 U/kg of aprotinin was administered 5 minutes after the injury. The animals were monitored for hemodynamic parameters, blood loss volume, and mortality rates.

RESULTS

At 120 minutes from trauma induction a significant difference in mean blood pressure was observed: 67+/-22 mm Hg in the treatment group versus 53+/-28 mm Hg in the control group (P=.04). This difference remained consistent until the end of the experiment. Treatment with aprotinin also resulted in a tendency to an increased survival rate (P=.05) and increased mean survival time: 175+/-46 minutes as compared to 123+/-48 minutes in the controls (P=.027).

CONCLUSIONS

Early administration of aprotinin resulted in temporary hemodynamic stabilization and prolonged survival in a model of uncontrolled bleeding. Further studies are needed to establish the possible use of aprotinin in the treatment of trauma patients.

Safety and efficacy of a single bolus administration of recombinant factor VIIa in liver transplantation due to chronic liver disease

Orthotopic liver transplantation (OLT) can be associated with excessive blood loss. As a result, there may be increased risk of adverse outcomes. Activated recombinant factor VII (rFVIIa) has demonstrated the ability to improve hemostasis in a variety of disorders; however, there has been a limited amount of research into its use in OLT. The purpose of this dose-finding study was to examine the efficacy and safety of rFVIIa in the reduction of bleeding in patients undergoing OLT. In this double-blind trial, patients with end-stage liver disease scheduled for OLT were randomized to 1 of 4 parallel study groups. They received a single intravenous bolus of rFVIIa (20, 40, or 80 microg/kg) or placebo prior to surgery. The primary assessment endpoint was the total number of red blood cell (RBC) units transfused perioperatively. Safety was evaluated by adverse events reported. Eighty-three comparable patients were randomized to receive study product, with 82 ultimately undergoing OLT. There were no significant differences in required RBC units between the placebo and rFVIIa study groups. The number of adverse events was comparable between study groups. In conclusion, rFVIIa has a good safety profile in patients undergoing OLT. However, the doses studied did not have any effect on the number of RBC transfusions required.

Medical haemostasis in acute hepatocyte injury and experimental liver trauma

BACKGROUND

The aim of the present study was to test the effectiveness of aprotinin to reduce bleeding in liver resection of guinea pigs with acutely injured hepatocyte using intraperitoneal d(+)Galactosamine.

METHODS

Thirty-two guinea pigs were divided equally into four groups. Group 1 was the control group. Group 2 received intraperitoneal D(+)galactosamine. Group 3 received intraperitoneal d(+)galactosamine prior to a standard liver resection. Group 4 received 10.000 KIU/kg aprotinin infusion via jugular catheter in 10 min prior to standard liver resection in pretreated animals with d(+)galactosamine. All of the measurements and surgical interventions were made 24 h after the administration of d(+)galactosamine. Bleeding amounts were recorded in groups 3 and 4 for 1 h by weighing the sponges placed into the abdomen. Liver function tests, histologic, haematologic and fibrinolytic parameters were measured.

RESULTS

Hepatocyte injury and hyperfibrinolysis were seen at the end of 24 h after application of d(+)galactosamine in groups 2, 3, and 4. Statistically significant amounts of bleeding from the resected livers were observed in group 3 and 4. In group 4, the bleeding was reduced (P < 0.05) and fibrinolytic parameters were normalized (P < 0.05) with aprotinin infusion.

CONCLUSIONS

Significant bleeding diathesis and hyperfibrinolysis occurred in groups 2, 3, and 4, which had hepatocyte injury proved with histopathologic and haematologic tests. Prothrombin time (PT) and partial thromboplastin time (aPTT) in groups 3 and 4 were fivefold higher than that in the control group (P = 0.0001). The bleeding tendency according to high PT and aPTT levels were continued with application of aprotinin while reduction of bleeding was seen. Parenchymatous organ haemorrhage in acute liver failure or hyperfibrinolytic conditions could be reduced significantly with aprotinin without procoagulant effect.

Antifibrinolytics in orthotopic liver transplantation: current status and controversies

This article reviews the current status and controversies of the 3 commonly used antifibrinolytics-epsilon-aminocaproic acid, tranexamic acid and aprotinin-during liver transplantation. There is no general consensus on how, when or which antifibrinolytics should be used in liver transplantation. Although these drugs appear to reduce blood loss and decrease transfusion requirements during liver transplantation, their use is not supported uniformly in clinical trials. Aprotinin has been studied more extensively in clinical trials and appear to offer more advantages compared to two other antifibrinolytics. Because of the diverse population of liver transplant recipients and the potential adverse effects of antifibrinolytics, especially life-threatening thromboembolism, careful patient selection and close monitoring is prudent. Further studies addressing the risks and benefits of antifibrinolytics in the setting of liver transplantation are warranted.

Aprotinin inhibits local platelet trapping and improves tissue destruction in hepatic cryosurgery

BACKGROUND

During the last decade, cryosurgery became an interesting alternative in the treatment of nonresectable liver neoplasms. The freeze-thaw procedure, however, may be associated with life-threatening thrombocytopenia due to local platelet trapping, and success of neoplasm ablation may be compromised by inadequate parenchymal cell destruction.

METHODS

Because aprotinin is capable of inhibiting the initiation of both coagulation and fibrinolysis, we studied-by whole body scintigraphy of Indium-111-labeled platelets and histomorphology in a porcine model of hepatic cryosurgery-whether this serine protease inhibitor is effective in attenuating platelet trapping and in improving tissue destruction.

RESULTS

Fifteen minutes of cryotherapy (-168 degrees C at the tip of the cryoprobe) induced a 30 +/- 4 cm(3) cryolesion, which presented with massive platelet trapping (14.0 +/- 1.7% cryolesion activity/whole body activity) and incomplete parenchymal cell destruction (0.9 +/- 0.3; score of hepatocyte nuclear destruction within the margin of the cryolesion). Aprotinin treatment with 500,000 IU initial bolus injection and additional 500,000 IU infusion over 3 hours did not affect the size of the cryolesion (29 +/- 3 cm(3)) but reduced local platelet activity (1.9 +/- 1.9%; P<.001) and induced hepatocyte nuclear destruction (3.0 +/- 0.0; P<.001).

CONCLUSIONS

Thus, our study indicates that aprotinin inhibits cryoablation-associated platelet trapping and improves tissue destruction. The serine protease inhibitor may represent a valuable adjunct in cryosurgery of hepatic neoplasms.

The management of coagulopathy and blood loss in liver surgery

Liver surgery has long been associated with massive perioperative blood loss and high rates of postsurgery morbidity and mortality. Recent advances in our knowledge of hepatic segmental anatomy have led to the evolution of liver resection, and a growing awareness of the coagulopathy present in cirrhotic patients has produced a greater understanding of the factors influencing surgical hemostasis. This review will examine the risk factors for perioperative hemorrhage in liver disease patients, and will describe current pharmacological, surgical, and radiological methods available for controlling bleeding and achieving effective hemostasis during liver resection and orthotopic liver transplantation (OLT). The potential role of recombinant factor VIIa (rFVIIa) in providing safe hemostasis during such procedures will also be explored. Today, due to careful monitoring and correction of coagulopathy, improved surgical techniques, and judicious patient selection, liver surgery is no longer a high-risk specialty with an unfavorable risk profile, but a safe and widely practiced procedure.

The prophylactic use of tranexamic acid and aprotinin in orthotopic liver transplantation: a comparative study

The efficacy of tranexamic acid (TA) and aprotinin (AP) in reducing blood product requirements in orthotopic liver transplantation (OLT) was compared in a prospective, randomized and double-blind study. One hundred and twenty seven consecutive patients undergoing OLT were enrolled; TA was administered to 64 OLT patients at a dose of 10mg /kg/h and aprotinin was administered to 63 OLT patients at a loading dose of 2 x 10(6) KIU followed by an infusion of 500,000 KIU/h. The portocaval shunt could not be performed in 14 OLT patients in the TA group and in 13 OLT patients in the AP group. However, all OLT patients that received either drug were included in the analysis. Perioperative management was standardized. Hemogram, coagulation tests, and blood product requirements were recorded during OLT and during the first 24 hours. No differences in diagnosis, Child score, preoperative coagulation tests, and intraoperative data were found between groups. No significant differences were observed in hemogram and intraoperative coagulation tests with the exception of activated partial thromboplastin time (aPTT). Similarly, there were no intergroup differences in transfusion requirements. Thromboembolic events, reoperations and mortality were similar in both groups. In conclusion, administration of regular doses of TA and AP during OLT did not result in large differences between the two groups.

Intravascular thrombosis and thromboembolism during liver transplantation: antifibrinolytic therapy implicated?

This case report describes a patient who underwent orthotopic liver transplantation and developed extensive hyperacute venous and arterial intravascular thromboses and thromboemboli intraoperatively. The patient was receiving antifibrinolytic therapy with aprotinin. The safety of routine aprotinin therapy in liver transplantation is examined. The value of the thrombelastograph (TEG) as a qualitative assessment of the coagulation system is emphasized.

Pharmacological strategies to decrease transfusion requirements in patients undergoing surgery

Surgical procedures are inevitably associated with bleeding. The amount of blood loss may vary widely between different surgical procedures and depends on surgical as well as non-surgical factors. Whereas adequate surgical haemostasis may suffice in most patients, pro-haemostatic pharmacological agents may be of additional benefit in patients with (diffuse) surgical bleeding or in patients with a specific underlying haemostatic defect. In general, surgical haemostasis and pharmacological therapies can be complementary in controlling blood loss. The use of pharmacological therapies to reduce blood loss and blood transfusions in surgery has historically been restricted to a few drugs. Antifibrinolytic agents (aprotinin, tranexamic acid and aminocaproic acid) have the best evidence supporting their use, especially in cardiac surgery, liver transplantation and some orthopaedic surgical procedures. Meta-analyses of randomised, controlled trials in cardiac patients have suggested a slight benefit of aprotinin, compared with the other antifibrinolytics. Desmopressin is the treatment of choice in patients with mild haemophilia A and von Willebrand disease. It has also been shown to be effective in patients undergoing cardiac surgery who received aspirin up to the time of operation. However, overall evidence does not support a beneficial effect of desmopressin in patients without pre-existing coagulopathy undergoing elective surgical procedures. Topical agents, such as fibrin sealants have been successfully used in a variety of surgical procedures. However, only very few controlled clinical trials have been performed and scientific evidence supporting their use is still limited. Novel drugs, like recombinant factor VIIa (eptacog alfa), are currently under clinical investigation. Recombinant factor VIIa has been introduced for the treatment of haemophilia patients with inhibitors, either in surgical or non-surgical situations. Preliminary data indicate that it may also be effective in surgical patients without pre-existing coagulation abnormalities. More clinical trials are warranted before definitive conclusions can be drawn about the safety and the exact role of this new drug in surgical patients. Only adequately powered and properly designed randomised, clinical trials will allow us to define the most effective and the safest pharmacological therapies for reducing blood loss and transfusion requirements in surgical patients. Future trials should also consider cost-effectiveness because of considerable differences in the costs of the available pro-haemostatic pharmacological agents.

A Model Incorporating Some of the Mechanical and Biochemical Factors Underlying Clot Formation and Dissolution in Flowing Blood

Multiple interacting mechanisms control the formation and dissolution of clots to maintain blood in a state of delicate balance. In addition to a myriad of biochemical reactions, rheological factors also play a crucial role in modulating the response of blood to external stimuli. To date, a comprehensive model for clot formation and dissolution, that takes into account the biochemical, medical and rheological factors, has not been put into place, the existing models emphasizing either one or the other of the factors. In this paper, after discussing the various biochemical, physiologic and rheological factors at some length, we develop a model for clot formation and dissolution that incorporates many of the relevant crucial factors that have a bearing on the problem. The model, though just a first step towards understanding a complex phenomenon, goes further than previous models in integrating the biochemical, physiologic and rheological factors that come into play.