Aprotinin Reduces Bleeding and Blood Product Use in Patients Treated With Clopidogrel Before Coronary Artery Bypass Grafting

Strategies for blood conservation in pediatric cardiac surgery

Cardiac surgery accounts for the majority of blood transfusions in a hospital. Blood transfusion has been associated with complications and major adverse events after cardiac surgery. Compared to adults it is more difficult to avoid blood transfusion in children after cardiac surgery. This article takes into account the challenges and emphasizes on the various strategies that could be implemented, to conserve blood during pediatric cardiac surgery.

The current place of aprotinin in the management of bleeding

There is a considerable difference between the mechanism of action of the lysine analogues, tranexamic acid and epsilon-aminocaproic acid, and the serine protease inhibitor aprotinin. Aprotinin acts to inactivate free plasmin, but with little effect on bound plasmin, whereas the lysine analogues are designed to prevent excessive plasmin formation by fitting into plasminogen's lysine-binding site to prevent the binding of plasminogen to fibrin. Aprotinin is associated with a reduction in bleeding and transfusion requirements following major surgery, and has a dose-response profile, compared with no dose-response effect in the one study investigating tranexamic acid in cardiac surgical patients. Following its withdrawal in 2007, which is explained in detail in this review, the regulators have now licensed aprotinin for myocardial revascularisation only, which is relatively low-risk for bleeding.

Clinical evaluation of leukocyte filtration as an alternative anti-inflammatory strategy to aprotinin in high-risk patients undergoing coronary revascularization

PURPOSE

The use of aprotinin in cardiac surgery is associated with overriding safety concerns. Therefore, there is increased research on alternatives. This study investigated the relative benefits of strategic leukofiltration on polymer-coated extracorporeal circuits (ECC), aprotinin, and combined therapy in high-risk patients.

METHODS

Eight hundred and seventy-five patients (EuroSCORE 6+) undergoing coronary revascularization over a 4-year period were prospectively randomized to one of four perfusion protocols: Group 1: polymethoxyethylacrylate (PMEA)-coated circuits + leukocyte filters (n = 214); Group 2: uncoated ECC + full Hammersmith aprotinin (n = 212); Group 3: PMEA-coated ECC + leukofilters + full Hammersmith aprotinin (n = 199); and Group 4: control-no treatment (n = 250). Blood samples were collected at times T1: following the induction of anesthesia; T2: following heparin administration; T3: 15 min after cardiopulmonary bypass (CPB); T4: before cessation of CPB; T5: 15 min after protamine reversal; and T6: in the intensive care unit.

RESULTS

The serum interleukin-2 levels were significantly lower at T3, T4, and T5 in all study groups. C3a levels were significantly lower at T3. Creatine kinase MB and lactate levels demonstrated well-preserved myocardia in both leukofiltration groups (P < 0.05). Neutrophil CD11b/CD18 levels were significantly lower for all study groups. Postoperative bleeding and respiratory support time were lower in all study groups.

CONCLUSION

Leukofiltration on coated circuits significantly reduced bleeding and inflammatory response related to CPB with no adverse effects, and may be a possible alternative to pharmacological intervention.

Dual antiplatelet therapy in patients requiring urgent coronary artery bypass grafting surgery: a position statement of the Canadian Cardiovascular Society

Acute coronary syndrome (ACS) guidelines recommend that most patients receive dual antiplatelet therapy with clopidogrel and acetylsalicylic acid (ASA) at the time of presentation to prevent recurrent ischemic events. Approximately 10% of ACS patients require coronary artery bypass grafting surgery (CABG) during the index admission. Most studies show that patients who receive ASA and clopidogrel within five days of CABG have an increase in operative bleeding. Current consensus guidelines recommend discontinuation of clopidogrel therapy at least five days before planned CABG to reduce bleeding-related events. However, high-risk individuals may require urgent surgery without delay, to reduce the risk of potentially fatal ischemic events. The present multidisciplinary position statement provides evidence- based recommendations for the optimal use of dual antiplatelet therapy to balance ischemic and bleeding risks in patients with recent ACS who may require urgent CABG.

RECOMMENDATIONS

1. All ACS patients should be considered for dual antiplatelet therapy with ASA and clopidogrel at the earliest opportunity, despite the possibility of a need for urgent CABG. 2. For patients who have received clopidogrel and ASA, and require CABG: * Those at high risk of an early fatal event (eg, with refractory ischemia despite optimal medical treatment, and with high-risk coronary anatomy (eg, severe left main stenosis with severe right coronary artery disease), should be considered for early surgery without discontinuation of clopidogrel. * In patients with a high bleeding risk (eg, previous surgery, complex surgery) who are also at high risk for an ischemic event, consideration should be given to discontinuing clopidogrel for three to five days before surgery. * Patients at a lower risk for ischemic events (most patients) should have clopidogrel discontinued five days before surgery. 3. For patients who have CABG within five days of receiving clopidogrel and ASA, the risk of major bleeding and transfusion can be minimized by applying multiple strategies before and during surgery. 4. Patients who receive clopidogrel pre-CABG for a recent ACS indication should have clopidogrel restarted after surgery to decrease the risk of recurrent ACS. 5. For patients with a recent coronary stent, the decision to continue clopidogrel until the time of surgery or to discontinue will depend on the risk and potential impact of stent thrombosis. Restarting clopidogrel after CABG will depend on whether the stented vessel was revascularized, the type of stent and the time from stent implantation. Clopidogrel should be restarted when hemostasis is assured to prevent recurrent acute ischemic events.

Aprotinin for patients exposed to clopidogrel before off-pump coronary bypass

To verify whether low-dose aprotinin reduces blood loss and blood product usage in patients with clopidogrel exposure within 5 days before off-pump coronary artery bypass, 51 patients with clopidogrel exposure were randomized in a double-blind fashion to receive low-dose aprotinin (25 patients), or placebo (26 patients). The baseline characteristics and number of distal anastomoses in the patients in each group were comparable. Time between the last dose of clopidogrel and start of the operation was similar in both groups, as was mean left ventricular ejection fraction. Chest tube drainage, blood product usage, and reoperation rate were significantly higher in the placebo group. In patients with unstable angina and recent clopidogrel exposure who are undergoing off-pump coronary artery bypass, intraoperative administration of low-dose aprotinin is recommended to reduce blood loss and transfusion requirements.

Novel antithrombotic agents and the risk of bleeding

Many coronary patients on antiplatelet (PLT) drugs require coronary artery bypass grafting surgery under conditions that may not allow sufficient time for or warrant discontinuation of anti-PLT treatment. Recent clinical data show that intraoperative aprotinin significantly reduces postoperative bleeding and transfusion requirements in this patient population. If surgical bleeding persists, the administration of Factor VIIa should be considered.

Coronary artery bypass grafting following in-stent restenosis of drug-eluting stents deployed in the left main coronary artery

Two cases of drug-eluting stent restenosis after percutaneous coronary intervention in the left main coronary artery and its bifurcation are presented. An off-pump coronary artery bypass grafting following in-stent restenosis was performed. Drug-eluting stents have shown a reduced frequency of in-stent restenosis and a good safety profile compared with bare metal stents. However, intervention with drug-eluting stents for left main coronary artery disease should be undertaken with care. It is also important to note that preoperative anti-platelet drug administration can increase the risk of major bleeding during and after emergent surgery.

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.

Protease activated receptors: clinical relevance to hemostasis and inflammation

The protease-activated receptors (PARs) are a unique family of vascular receptors that confer on cells an ability to sense, and respond to, local changes in the proteolytic environment. They are activated by serine proteases of the blood coagulation cascade, notably thrombin, and are linked to thrombotic and inflammatory effector pathways. In surgery with cardiopulmonary bypass (CPB), thrombin is generated in large quantities in the extracorporeal circuit and can exert systemic effects by way of platelet and endothelial PAR1. Aprotinin (Trasylol), a serine protease inhibitor used in cardiac surgery, preserves platelet function, and attenuates the inflammatory response by protecting the PAR 1 receptor on platelets and endothelium.

The effect of preoperative clopidogrel on bleeding after coronary artery bypass surgery

INTRODUCTION

Clopidogrel treatment is associated with a reduction in thrombotic complications in coronary stent placement, improved outcome after acute coronary syndromes, and decreased mortality in patients with coronary artery disease. The purpose of this study was to analyze the effect of preoperative clopidogrel exposure on bleeding complications, blood transfusions requirements, and reoperations in patients undergoing coronary artery bypass grafting (CABG).

PATIENTS AND METHODS

This study included 320 patients from a single institution that underwent an isolated CABG who were discharged between July 2003 and June 2004. The cohort of 320 patients was classified into 3 groups. The control group consisted of 255 patients that did not receive clopidogrel or stopped clopidogrel 7 days before surgery but were treated with aspirin instead. Clopidogrel I consisted of 25 patients that were taking clopidogrel within 3 days of surgery, and Clopidogrel II consisted of 40 patients that were taking clopidogrel 4 to 7 days before surgery. Patients were compared based on preoperative data (age, gender, use of clopidogrel, preoperative hemoglobin, and ejection fraction), intraoperative data (cross-clamp time), postoperative data (chest tube output, rate of reoperation, units of transfused blood, length of stay in the intensive care unit, and length of intubation).

RESULT

There were no significant differences among the 3 groups concerning age, sex, ejection fraction, or preoperative hemoglobin. There were no differences in length of intensive care unit stay and length of intubation among the 3 groups of patients. Patients in the clopidogrel I group had more units of blood transfused than either the control or the Clopidogrel II group (p=0.027). There is also a trend toward more chest tube output in clopidogrel I group compared with the control group. Fifteen patients (4.6%) of the total group required reoperation secondary to bleeding: 2 (8.0%) in the Clopidogrel I group, 2 (5%) in the clopidogrel II group, and 11 (4.3%) in the control group (p=0.41).

CONCLUSION

This study demonstrated that clopidogrel within 3 days preoperatively increases the requirement for blood transfusion in patients undergoing CABG. Waiting more than 3 days after the last dose of clopidogrel decreases blood transfusion requirements. There is also a trend toward more postoperative bleeding for those patients that took clopidogrel within 3 days before their CABG. The reoperation rate of patients that took clopidogrel within 3 days of their procedure required almost twice as many reoperations as the patients that did not take clopidogrel.

Management of antiplatelet therapy for minimization of bleeding risk before cardiac surgery

Antiplatelet therapy is commonly administered for primary and secondary prevention of stroke, recurrent angina, myocardial infarction, and death in patients with cardiovascular disorders. It also is associated with an increased risk of bleeding. We describe the management of antiplatelet therapy in patients undergoing coronary artery bypass graft surgery. In addition, we provide basic information about the mechanisms of action by which the most common antiplatelet agents inhibit platelet function. This information is integrated with results from pharmacologic studies and clinical trials. Determining the net effect in patients undergoing coronary artery bypass graft surgery requires knowledge about the pharmacokinetics, pharmacodynamics, and clinical efficacy of each drug, and an estimation of the absolute thrombotic versus hemorrhagic risk for each patient.

Is There Still a Role for Aprotinin in Cardiac Surgery?

Cardiac surgery is associated with a systemic inflammatory response and systemic coagulopathy, which can result in significant organ dysfunction and bleeding. Aprotinin, a serine protease inhibitor, can limit systemic inflammation, and has been associated with myocardial, pulmonary and cerebral protection in addition to its proven haemostatic efficacy. Data are currently conflicting regarding the haemostatic efficacy of aprotinin relative to alternative agents including tranexamic acid. Recent studies have demonstrated aprotinin usage is associated with increased rates of thrombotic and renal complications, but these findings are at odds with the majority of studies relating to aprotinin safety to date. The lack of adequately powered, randomised studies evaluating aprotinin and alternative agents limits drawing conclusions about the complete use or disuse of aprotinin presently and requires individualised patient selection based on bleeding risk and co-morbidities for its usage.

Non ST segment elevation acute coronary syndromes: A simplified risk-orientated algorithm

Non-ST segment elevation acute coronary syndromes (NSTE ACS) include a clinical spectrum that ranges from unstable angina to NSTE myocardial infarction. Management goals aim to prevent recurrent ACS and improve long-term outcomes by choosing a treatment strategy according to an estimate of the risk of an adverse outcome. Recent registry data suggest that patients with NSTE ACS frequently do not receive recommended treatment, and that risk stratification is not used to determine either the choice of treatment or the speed of access to coronary angiography. The present article evaluates the evidence for recommended treatment using information from recent trials and guidelines published by the major cardiac organizations in Europe and North America. Using this information, a multidisciplinary group developed a simplified algorithm that uses risk stratification to select an optimal early management strategy. Long-term outcomes are improved by a multi-faceted vascular protection strategy that is initiated at the time of hospitalization for NSTE ACS.

Antiplatelet agents and perioperative bleeding

PURPOSE

To briefly review the risks, in patients presenting for surgery, associated with the available antiplatelet agents, and to present the principles that should guide the evaluation of these risks and how to manage them.

METHODS

A narrative review of the current medical literature in English and French.

MAIN FINDINGS

Antiplatelet agents [mainly acetylsalicylic acid, clopidogrel and glycoprotein (GP) IIb/IIIa inhibitors] are used increasingly to prevent arterial thrombosis. Clinicians are confronted with the hemorrhagic risk associated with the continuation of antiplatelet agents throughout surgery or, conversely, with the thrombotic risk associated with their discontinuation. Most experts recommend surgery while maintaining acetylsalicylic acid for most vascular procedures and in several additional settings where the bleeding risk has been shown (or is likely) to be low. It is commonly recommended that clopidogrel be stopped five days before surgery to allow replacement of half the platelet pool. This approach has been associated with thrombotic events in patients waiting for urgent myocardial revascularization. In this context, aprotinin may reduce blood losses and transfusion requirements. Withdrawal of the competitive GPIIb/IIIa inhibitors at the beginning of surgery will decrease the risk of bleeding, less so for abciximab owing to its avid binding to platelet receptors. Platelets should not be transfused prophylactically, but only to those few patients with abnormal bleeding thought to be related to the persisting effect of antiplatelet therapy.

CONCLUSIONS

Unfortunately, data regarding the management of antiplatelet agent-treated patients undergoing surgery, especially non-cardiovascular, are scarce. Further clinical trials must be conducted to guide the clinical management of these patients.

Correlation of perioperative platelet function and coagulation tests with bleeding after cardiopulmonary bypass surgery

The authors evaluated the correlation of post-cardiopulmonary bypass surgery bleeding, measured as 24-hour chest tube output/kilogram body weight, with platelet function tests using glass bead adhesion and Thrombelastograph Platelet Mapping (Haemoscope Corporation, Niles, Ill); coagulation tests; patient characteristics; surgery parameters; and visual assessment of surgical field bleeding before closure as not bleeding (code 1), oozing (code 2), and excessive bleeding (code 3). All platelet function and coagulation tests indicated significant dysfunction 15 minutes after protamine neutralization of heparin. With the exception of glass bead adherence, these assays indicated poor recovery of function 1 hour postoperatively. By multiple regression, the most significant predictors of postoperative bleeding were a low body mass index (BMI) (P < 0.0001), lowest core body temperature (P = 0.0006), and cross clamp time (P < 0.0001). Low core temperature was significantly (P < 0.0001) correlated with cross clamp time, which the authors believe is the most likely cause of coagulation and platelet dysfunction. None of the platelet function tests significantly correlated with bleeding. Looking at the highest quartile of chest tube output patients (n = 19) versus the upper and lower 50th percentile of coagulation and platelet function, bleeding could be explained for 11 patients by BMI plus surgery parameters along with coagulation and/or platelet dysfunction. In three cases without negative surgery parameters, coagulation dysfunction was observed. The remaining five cases did not give a clear indication of which parameters were primarily responsible for the bleeding.