Aprotinin therapy in cardiac operations: a report on use in 41 cardiac centers in the United Kingdom

Topical Use of Aprotinin in Coronary Artery Bypass Surgery

Objective: The internal mammary artery (IMA) ranks among excellent, widely used conduits for surgical coronary revascularization. Its harvesting and its using may cause other surgical and technical problems and complications and increase postoperative bleeding from wound surface after the IMA harvesting with significantly greater incidence of blood transfusion. The aim of this study was to get to know how much it increases postoperative bleeding losses and if the local application of aprotinin (to the wound surface after the IMA harvesting and into the pericardial cavity) can reduce them and thus decrease the number of blood transfusions. Methods: In this study there are compared groups of patients (n = 275) operated at the University Department of Cardiac Surgery in Hradec Králové on account of ischemic heart disease. In the first part of this study results of operations of 200 patients were comprised retrospectively. Group A1 comprised 50 patients where for revascularization of the myocardium venous grafts were used. Group B1 comprised 50 patients where also the internal mammary artery was used. Group C1 was formed by 50 patients where after preparation of the IMA aprotinin (100 000 KIU) was administered locally to the wound surface after the IMA harvesting. Group D1 was formed by 50 patients where aprotinin (500 000 KIU) was administered locally to the wound surface and poured into the pericardial cavity before closure of the median sternotomy. The postoperative blood losses and the number of the administered blood transfusions were compared between these groups. Results: The authors provided evidence that the using of the IMA increases significantly the postoperative blood losses (in group A1 675 ml ± 352.9, in group B1 1232 ml ± 336.5) and increases the number of required transfusions (in group A1 2.44 ± 1.7, in group B1 3.45 ± 1.0). By local aprotinin application to the wound surface after the IMA harvesting the blood losses and the number of administered transfusions were reduced in group C1 (896 ml (231.9, 2.74 ± 0.8). In group D1 (local aprotinin application to the wound surface and into the pericardial cavity) the blood losses and the number of transfusions were increasingly reduced than in group C1 (797 ml ± 280.5, 1.74 ± 1.3). In the second, prospective randomised part of this study 3 groups of patients were compared. Group A2 comprised 25 patients where venous grafts for revascularization of myocardium were used. Group B2 was formed by 25 patients where also the IMA was used. Group D2 comprised 25 patients where aprotinin (500 000 u.) was administered locally to the wound surface after the IMA harvesting and poured into the pericardial cavity before closure of sternotomy. The postoperative blood losses and the number of administered blood transfusions were again compared between these groups. The total postoperative blood losses were 778 ml ± 304.2 in group A2, 1072 ml ± 391.8 in group B2 and 754 ml ± 197.9 in group D2. There were compared blood losses after 6, 12 and 24 hours, too. There were the statistically significant differences among these groups during the whole postoperative period. The number of blood transfusions were 2.8 ± 2.3 in group A2 and 2.04 ± 1.1 in group B2. The use of aprotinin decreased this number in group D2, 1.44 ± 1.1. Conclusions: The authors provided evidence that the harvesting and the using of the internal mammary artery for myocardial revascularization increases significantly the postoperative bleeding and increases the number of required transfusions. By local application of aprotinin the author reduced the blood losses and need of transfusions.

Blood Conservation Strategies in Cardiac Surgery

Perioperative bleeding in cardiac surgery is related to both surgical trauma of blood vessels and defects in the hemostatic mechanism caused, in part, by cardiopulmonary bypass. Blood transfusion therefore remains a significant risk of cardiac surgery with important health and economic consequences. Blood conservation strategies for cardiac surgery have advanced over the years and the following discussion will focus on the current practices at Toronto General Hospital.

Aprotinin: No Justification for Current Use

Objective:

To review the pharmacology, pharmacokinetics, clinical efficacy, and safety of aprotinin.

Data Identification:

A literature search using Grateful Med from 1991 to 1994 and the search term “aprotinin” was performed.

Study Selection:

Open and controlled trials were reviewed.

Data Extraction:

Studies evaluating aprotinin for use in primary and repeat coronary artery bypass graft (CABG) surgery were evaluated and results of the effects of aprotinin on decreasing transfusion requirements as well as adverse effects were summarized.

Data Synthesis:

Many European studies have shown that aprotinin reduces blood loss and transfusion requirements during CABG. More recently, two studies in the US and one in Canada have been published that confirm the effects of aprotinin on blood loss, but raise questions concerning its safety. Combined data indicate that aprotinin is associated with an increased incidence of renal failure, and there are trends toward increases in myocardial infarction, graft occlusion, and mortality. There is no question that aprotinin reduces blood loss during CABG. How much it will save depends on surgical skill and the use of other blood conservation techniques. There are many theoretical benefits to patients from this reduction in blood loss. Whether the benefits of aprotinin administration exceed the risks associated with its use has not been adequately assessed, and further multicenter trials are currently in progress. Whether the cost of aprotinin is counterbalanced by a reduction in transfusion requirements will vary, depending on the cost and amount of blood products used at the specific institution, but this type of analysis does not account for the cost of adverse effects of aprotinin or transfusions, and no pharmacoeconomic evaluations have been published.

Conclusions:

Until studies can demonstrate a positive benefit/risk ratio in terms of patient outcome, aprotinin should not be added to the formulary or used in patients undergoing CABG.

The effect of sivelestat sodium hydrate on severe respiratory failure after thoracic aortic surgery with deep hypothermia

Patients who undergo thoracic aortic surgery with deep hypothermia frequently have postoperative respiratory failure as a complication. Severe lung injury in these patients results in a fatal outcome. A specific neutrophil elastase inhibitor, sivelestat sodium hydrate, is an innovative therapeutic drug for acute lung injury. We evaluated the protective effects of sivelestat sodium hydrate on severe lung injury after thoracic aortic surgery with deep hypothermia. From January 2002 to July 2007, 71 consecutive patients underwent thoracic aortic surgery with deep hypothermia. Of these patients, 22 had postoperative respiratory failure with PaO₂/FiO₂ ratios of less than 150. They were randomly assigned to one of two groups. The first group (Group S, n = 10) was administered sivelestat sodium hydrate continuously at 0.2 mg/kg/h until weaning from mechanical ventilation; the second group (Group C, n = 12) was not administered sivelestat sodium hydrate. The groups were comparable with respect to clinical data. There were no significant differences between the two groups in age, operation duration, total cardiopulmonary bypass time, circulatory ischemia time, cardiac arrest time, intraoperative blood loss, and total transfusion volume. The improvement of pulmonary function was observed in the both groups, but more marked in Group S by statistical analysis using analysis of variance for repeated measurements. Especially, in the early phase, pulmonary function improvement was more marked in Group S. The duration of mechanical ventilation, the length of stay in the intensive care unit, and the length of hospital stay were shorter in Group S, but not significantly. Sivelestat sodium hydrate is a specific neutrophil elastase inhibitor that improves pulmonary function in patients with severe postoperative respiratory failure following thoracic aortic surgery with deep hypothermia. The drug may shorten the duration of postoperative ventilation, intensive care unit stay, and hospital stay.

Impact of aprotinin and renal function on mortality: a retrospective single center analysis

BACKGROUND

An estimated up to 7% of high-risk cardiac surgery patients return to the operating room for bleeding. Aprotinin was used extensively as an antifibrinolytic agent in cardiac surgery patients for over 15 years and it showed efficacy in reducing bleeding. Aprotinin was removed from the market by the U.S. Food and Drug Administration after a large prospective, randomized clinical trial documented an increased mortality risk associated with the drug. Further debate arose when a meta-analysis of 211 randomized controlled trials showed no risk of renal failure or death associated with aprotinin. However, only patients with normal kidney function have been studied.

METHODS

In this study, we look at a single center clinical trial using patients with varying degrees of baseline kidney function to answer the question: Does aprotinin increase odds of death given varying levels of preoperative kidney dysfunction?

RESULTS

Based on our model, aprotinin use was associated with a 3.8-fold increase in odds of death one year later compared to no aprotinin use with p-value = 0.0018, regardless of level of preoperative kidney dysfunction after adjusting for other perioperative variables.

CONCLUSIONS

Lessons learned from our experience using aprotinin in the perioperative setting as an antifibrinolytic during open cardiac surgery should guide us in testing future antifibrinolytic drugs for not only efficacy of preventing bleeding, but for overall safety to the whole organism using long-term clinical outcome studies, including those with varying degree of baseline kidney function.

Aprotinin and renal dysfunction after pediatric cardiac surgery

BACKGROUND

Aprotinin is a potent antifibrinolytic drug, which reduces postoperative bleeding and transfusion requirements. Recently, two observational studies reported increased incidence of renal dysfunction after aprotinin use in adults. Therefore, the aim of the study was to investigate the safety of aprotinin use in pediatric cardiac surgery patients.

METHODS

Data were prospectively and consecutively collected from 657 pediatric patients undergoing cardiac surgery with cardiopulmonary bypass (CPB). The database was assessed with regard to a possible relationship between aprotinin administration and dialysis and between aprotinin and postoperative renal dysfunction [defined as 25% decrease in the creatinine clearance (Ccr) compared with the preoperative value] by propensity-score adjustment and multivariable methods.

RESULTS

The incidence of dialysis (9.6% vs 4.1%; P = 0.005) and renal dysfunction (26.3% vs 16.1%; P = 0.019) was higher in patients who received aprotinin; however, propensity adjusted risk ratios were not significant [odds ratio (OR) of dialysis: 1.22; 95% confidence interval (CI) 0.46-3.22; OR of renal dysfunction 1.26; 95% CI: 0.66-1.92]. Aprotinin significantly reduced blood loss in the first postoperative 24 h. The main contributors of renal dysfunction were CPB duration, cumulative inotropic support, age, preoperative Ccr, amount of transfusion and pulmonary hypertension.

CONCLUSIONS

Despite the higher incidences of renal dysfunction and failure in the aprotinin group, an independent role of the drug in the development of renal dysfunction or dialysis could not be demonstrated in pediatric cardiac patients undergoing CPB.

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.

Anaphylactic shock in a beta-blocked child: usefulness of isoproterenol

Like adults, children taking beta-blockers are at risk for serious hemodynamic instability in case of anaphylaxis. We report a case of severe bradycardia associated with anaphylactic shock after aprotinin in a beta-blocked child, which was resistant to intravenous epinephrine and vascular filling but was treated successfully with isoproterenol.

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.

Aprotinin; friend or foe? A review of recent medical literature

Recent articles published in peer review journals have questioned the safety of using aprotinin in patients having heart surgery. Also, evidence has been published to suggest an increase in renal events in patients given aprotinin when compared to those where tranexamic acid was used. The present review will focus principally on the first of these articles in relation to previously published data and experience.

Avoiding Transfusions in Children Undergoing Cardiac Surgery: A Meta-Analysis of Randomized Trials of Aprotinin

Aprotinin, a potent antifibrinolytic drug, reduces the proportion of adults who receive blood transfusions during cardiac surgery, although the effect in children remains unclear. We performed a systematic review of the literature to identify all English language, randomized controlled trials of aprotinin involving children undergoing corrective or palliative cardiac surgery with cardiopulmonary bypass. All studies were assessed for methodological quality, and sources of heterogeneity were examined. We measured the effect of aprotinin on the proportion of children transfused, the volume of blood transfused, and the volume of chest tube drainage. Twelve trials enrolling 626 eligible children met the inclusion criteria. Aprotinin reduced the proportion of children who received red blood cell or whole blood transfusions during cardiac surgery by 33% (relative risk = 0.67; 95% confidence interval, 0.51 to 0.89). Aprotinin did not have a significant effect on the volume of blood transfused or on the amount of postoperative chest tube drainage. Most of the studies were of poor methodological quality and predefined transfusion triggers were infrequently used. Overall, aprotinin reduced the proportion of children who received blood transfusion during cardiac surgery with cardiopulmonary bypass. Further high-quality trials with clinically important outcomes may be warranted before aprotinin can be routinely recommended in this population.

Kidney-specific proteins in patients receiving aprotinin at high- and low-dose regimens during coronary artery bypass graft with cardiopulmonary bypass

BACKGROUND AND OBJECTIVE

The aim was to determine whether the administration of aprotinin can cause deleterious effects on renal function in cardiac surgery with cardiopulmonary bypass (CPB).

METHODS

Sixty consecutive patients with normal preoperative renal function undergoing elective coronary artery bypass surgery with CPB using the same anaesthetic; CPB and surgical protocols were randomized into three groups. Patients received placebo (Group 1), low-dose aprotinin (Group 2) or high-dose aprotinin (Group 3). Renal parameters measured were plasma creatinine, alpha1-microglobulin and beta-glucosaminidase (beta-NAG) excretion. Measurements were performed before surgery, during CPB and 24 and 72 h, and 7 and 40 days postoperatively.

RESULTS

In the three groups, alpha1-microglobulin and beta-NAG excretions significantly increased during CPB, at 24 and 72 h, and 7 days postoperatively (P < 0.05) and had returned to preoperative levels at postoperative day 40. Plasma creatinine levels were within normal values at times recorded. In Groups 2 and 3, alpha1-microglobulin excretion during CPB was significantly higher than in Group 1 (P < 0.001), and 24h after surgery it still remained significantly higher in Group 3 compared to Groups 1 and 2 (P < 0.05).

CONCLUSIONS

Aprotinin caused a significant increase in alpha1-microglobulin excretion but not in beta-NAG excretion during CPB, which may be interpreted as a greater renal tubular overload without tubular damage. This effect persisted for 24 h after surgery when high-dose aprotinin doses had been administered. Creatinine plasma levels were not sensitive to detect these prolonged renal effects in our study.

Modulation of systemic inflammatory response after cardiac surgery

Cardiac surgery and cardiopulmonary bypass initiate a systemic inflammatory response largely determined by blood contact with foreign surfaces and the activation of complement. It is generally accepted that cardiopulmonary bypass initiates a whole-body inflammatory reaction. The magnitude of this inflammatory reaction varies, but the persistence of any degree of inflammation may be considered potentially harmful to the cardiac patient. The development of strategies to control the inflammatory response following cardiac surgery is currently the focus of considerable research efforts. Diverse techniques including maintenance of hemodynamic stability, minimization of exposure to cardiopulmonary bypass circuitry, and pharmacologic and immunomodulatory agents have been examined in clinical studies. This article briefly reviews the current concepts of the systemic inflammatory response following cardiac surgery, and the various therapeutic strategies being used to modulate this response.

Forty Years of Clinical Aprotinin Use: A Review of 124 Hypersensitivity Reactions

Since its clinical introduction, the anaphylactic potential of aprotinin has been a major concern. World wide, its use is expanding so there is an increased chance that patients have reexposure from various sources. The risk of anaphylaxis is approximately 2.8% in reexposed patients. From 1963 to 2003, 124 cases of aprotinin-induced anaphylaxis were reported in 61 publications. Eleven patients died. The reexposure interval was less than 3 months in 72% (38 of 53 patients). This review looks at the profile of patients at risk so preventive measures may be taken. Past and future exposures have to be taken into account before any aprotinin administration.

The systemic inflammatory response syndrome and cardiopulmonary bypass

Cardiac surgery using cardiopulmonary bypass (CPB) provokes a systemic inflammatory response. This is mainly triggered by contact activation of blood by artificial surfaces of the extracorporeal circuit. Although often remaining sub-clinical and resolving promptly at the end of CPB, in its most extreme form this inflammatory response may be associated with the development of the systemic inflammatory response syndrome (SIRS) that can often lead to major organ dysfunction (MODs) and death. Here, we review the pathophysiology behind the development of this "whole body" inflammatory response and some of the methods currently used to minimise it.

[Urgent or emergent coronary revascularization using bilateral internal thoracic artery after previous clopidogrel antiplatelet therapy]

BACKGROUND

Application of clopidogrel before diagnostic or therapeutical percutaneous coronary interventions has become standard for stent-thrombosis prevention. The irreversible platelet inhibition causes increasing bleeding complications if urgent coronary artery bypass grafting becomes necessary. This study evaluates the effect on bleeding complications of clopidogrel in urgent CABG using bilateral internal thoracic artery (ITA) and saphenous veins in all patients.

METHODS

We retrospectively analyzed 166 patients (operated between 1/00-12/02) with urgent or emergency CABG, using both ITAs and compared 83 patients with previous (within 5 days) clopidogrel and aspirin application to 83 patients without clopidogrel. We evaluated chest tube output, reexploration rate and necessity of blood products, ventilation time and ICU stay.

RESULTS

Both groups were comparable with age, gender, number of performed anastomoses (mean 4/ patient). Chest tube output (24 h) was higher in the clopidogrel group (935 +/- 599 ml vs 754 +/- 335 ml (p = 0.018)), as well as reexploration rate with 7.2% (6 of 83) vs 0% (0 of 83) (p < 0.001). Number of blood products in the clopidogrel group for red cells was 2.41 +/- 1.88 U vs 1.84 +/- 1.47 U p = 0.03, for plateletes 0.43 +/- 0.88 U vs 0.024 +/- 0.22 p = 0.0001, for fresh frozen plasma 0.41 +/- 1.14 U vs 0.096 +/- 0.59 U p = 0.029. Mechanical ventilation time was 11.35 +/- 8.77 h vs 10.57 +/- 9.12 h p = 0.51, ICU stay 32.1 +/- 21.8 h vs. 29.8 +/- 21.1 h (p = 0.48).

CONCLUSIONS

Previous application of clopidogrel in combination with aspirin before urgent CABG induces increased chest tube output, reexploration rate and necessity of blood products, especially of plateletes. Nevertheless, routine use of both ITAs in patients after clopidogrel exposure can be performed with acceptable bleeding complications.

Age and left ventricular impairment predict reopening for bleeding

Statistical analysis of data collected prospectively from all patients undergoing surgery under cardiopulmonary bypass from September 1994 to November 1998 (group 1) was performed to identify preoperative risk factors for reopening for bleeding. Multiple logistic regression analysis of 19 preoperative variables was carried out with reoperation for bleeding as the endpoint. The protocol for intraoperative use of aprotinin was then changed to include high-risk patients. Data collected from all subsequent patients from May 1999 to March 2002 (group 2) were analyzed. Subgroup analyses on primary isolated coronary artery surgery were also performed. Data were obtained from 1,946 patients aged 22 to 88 years (mean, 62.5 years). Older age, severe left ventricular impairment, redo surgery, and chronic renal failure were the independent predictors of reopening for bleeding in group 1. There were no independent predictors of reopening in group 2. Older age and chronic renal failure were the predictors of reexploration for bleeding in patients undergoing primary isolated coronary artery grafting. Prophylactic measures to prevent excessive bleeding should be used in elderly patients and those with severe left ventricular impairment, redo surgery, and chronic renal failure.

Pharmacotherapeutic considerations in anesthesia

This article focuses on new findings leading to improved understanding of the pathophysiology and mechanisms of potential drug interactions between anesthetic drugs or techniques and cardiovascular medications in patients scheduled for surgery. Only the most frequently used drugs are reviewed. Elective surgery provides the luxury to consider these risks and alter therapy accordingly. Under urgent circumstances, however, the increased risks associated with these agents should be anticipated with the goal to minimize adverse effects while maintaining optimal cardiovascular function in the perioperative period.

Soluble adhesion molecules in coronary surgery and cardiopulmonary bypass with pump prime aprotinin

OBJECTIVE

The purpose of the present study was to establish whether pump prime aprotinin could influence soluble adhesion molecules in patients undergoing elective coronary artery bypass surgery.

DESIGN

Thirty patients admitted for first-time elective coronary artery bypass surgery were randomized into control or aprotinin groups. Patients in the aprotinin group received 280 mg of aprotinin in the pump prime. Plasma levels of soluble adhesion molecules were analyzed perioperatively.

RESULTS

There were no significant changes in plasma sE-selectin after the operation in either group. Plasma sP-selectin increased significantly up to 20 h after reperfusion to the myocardium. Plasma sICAM-1 decreased in the early stage after cardiopulmonary bypass (CPB), then recovered at 4 h after reperfusion and a significant increase in sICAM-1 was observed 20 h later. There were no significant differences between the groups in postoperative changes in sP-selectin (p = 0.21) and sICAM-1 (p = 0.91).

CONCLUSION

Pump prime aprotinin did not influence plasma levels of E-selectin, P-selectin and ICAM-1 in the present patients. The present results do not support the concept of an anti-inflammatory effect of pump prime aprotinin.

Aprotinin: Antithrombotic and Vasoactive Mechanisms of Action

Aprotinin is a serine protease inhibitor that has been in clinical use since the late 1980s to reduce blood loss in patients undergoing cardiopulmonary bypass surgery. Its hemostatic mechanism of action is mediated predominantly through inhibition of plasmin, thus exerting a net antifibrinolytic effect. Compared to other antifibrinolytics, however, aprotinin provides an additional patient benefit at the level of improved platelet function and diminished inflammatory response to bypass. Recent work on platelets has identified a cell-associated target for aprotinin: the thrombin-receptor, protease-activated receptor 1. Selective blockade of the protease-activated receptor 1 limits thrombin-induced activation and consequent “exhaustion” of platelets in the bypass circuit, while maintaining the hemostatic activity of platelets in the pericardial cavity in response to nonproteolytic agonists, such as collagen, adenosine diphosphate and epinephrine. While no specific cellular receptors have as yet been identified to explain the antiinflammatory and vasoactive properties of aprotinin, awareness is growing that serine protease-sensitive receptors belonging to the protease-activated receptor family (1-4) may represent important aprotinin targets, since these receptors are expressed by all major cells of the vasculature and act as sensors of the coagulation, inflammatory and vasoactive pathways activated by major surgery or trauma. The possibility is discussed that endothelial protease-activated receptor 2, whose natural ligands are trypsin, tryptase and the ternary tissue factor-Vlla-Xa complex, may be targeted by aprotinin.

A model of the direct and indirect effects of aprotinin administration on the overall costs of coronary revascularization surgery in a university teaching hospital cardiothoracic unit

BACKGROUND

Cardiac patients sometimes bleed postoperatively and consequently require rethoracotomy, necessitating a longer stay in the intensive care unit (ICU) of the cardiothoracic unit (CTU). When ICU capacity is limited, rethoracotomy necessitates postponing treatment of the next patient. Aprotinin, a bovine lung-derived proteinase inhibitor, has been shown to reduce the frequency of rethoracotomies in cardiac patients.

OBJECTIVE

This study was undertaken to quantify the reduction of potentially avoidable cost to the CTU of postoperative bleeding, both directly and indirectly, by administering aprotinin before and during coronary artery bypass graft (CABG).

METHODS

A novel, validated operational research model was developed, featuring the principal CABG-related health care resource parameters believed to influence waiting lists and times. Factors and costs were derived from both local data from a CTU and relevant recent literature.

RESULTS

According to the model, aprotinin therapy reduced the waiting list by approximately 3% by reducing the number of rethoracotomies. Using data from the literature, for an annual throughput of 431 patients who would receive aprotinin costing 97,333 pounds per year, the annual net savings to the CTU would be 46,586 pounds, which comprised direct savings on blood products of 35,036 pounds and indirect marginal savings of 11,550 pounds derived from 3.2% fewer rethoracotomies (each at a marginal cost of 837 pounds). By reason, then, reinvesting savings in increasing CTU capacity would yield further waiting-list reductions and improve patient morbidity. These results had 2 major limitations. First, it was assumed that all operations would have the same duration and all surgeons would perform operations in the same manner. Second, nonurgent patients were assumed to have been treated in order of strict referral sequence, which may not be done in real-world practice.

CONCLUSIONS

Aprotinin reduced costs in CABG directly by reducing the use of blood products and indirectly by reducing waiting lists, as well as by reducing morbidity and mortality associated with waiting time.

Safety and efficacy of methods for reducing perioperative allogeneic transfusion: a critical review of the literature

A number of pharmacologic and nonpharmacologic technologies are in current use to minimize perioperative homologous blood use. Clinical trials, many of them randomized controlled trials, have been done evaluating these approaches and have demonstrated their efficacy. However, data on safety has relied mostly on case reports, uncontrolled studies, and, for the pharmacologic agents, extrapolation from the nonsurgical setting. In this review I analyze the data from the randomized trials and the lower-level evidence studies to provide the best estimates in safety with these alternatives. In general, these alternatives are safe with proper dosing and monitoring of effects. With aprotinin, the primary concern is anaphylaxis, and this predominantly with re-exposure. With aprotinin and with the anti-fibrinolytics, increased venous thromboembolic risk has not been a consistent finding. Tranexamic acid use intraoperatively is advantageous, but postoperative use appears to have no advantage and may be associated with renal dysfunction. DDAVP is low-risk, provided it is not overused, which can induce hyponatremia. Autologous predonation probably has similar risks as homologous blood with respect to transfusion errors and bacterial infection. As with most medical interventions, we must be vigilant to prevent human error.

The antithrombotic and antiinflammatory mechanisms of action of aprotinin

Aprotinin (Trasylol) is generally regarded to be an effective hemostatic agent that prevents blood loss and preserves platelet function during cardiac surgery procedures requiring cardiopulmonary bypass (CBP). However, its clinical use has been limited by the concern that such a potent hemostatic agent might be prothrombotic, particularly in relation to coronary vein graft occlusion. In this review we present a mechanism of action that challenges such a viewpoint and explains how aprotinin can be simultaneously hemostatic and antithrombotic. Aprotinin achieves these two apparently disparate properties by selectively blocking the proteolytically activated thrombin receptor on platelets, the protease-activated receptor 1 (PAR1), while leaving other mechanisms of platelet aggregation unaffected. We also review recent research leading to the discovery of novel antiinflammatory targets for aprotinin. A better understanding of its mechanisms of action has led to the conclusion that aprotinin is a remarkable drug with the capacity to correct many of the imbalances that develop in the coagulation system and the inflammatory system after CPB. Nonetheless, it has been clinically underused for fear of causing thrombotic complications, a fear that in light of recent evidence may be unfounded.

New antiinflammatory and platelet-preserving effects of aprotinin

The clinical benefit of aprotinin with respect to improved hemostasis, platelet function, and inflammatory response to cardiopulmonary bypass (CPB) surgery has been well documented, but these benefits have been overshadowed by the concern that such a potently hemostatic agent might also be prothrombotic. In this article, we discuss recent advances in the understanding of the basic mechanism of aprotinin that have led to the identification of new antiinflammatory targets and the discovery that aprotinin is, in fact, antithrombotic with respect to platelets. Its antithrombotic action is mediated by the selective blocking of the major thrombin receptor, the protease-activated receptor 1 (PAR1), but not other receptors of platelet activation (ie, collagen, adenosine diphosphate [ADP], or epinephrine receptors). The selective targeting of PAR1 enables aprotinin to protect platelets from unwanted activation by thrombin generated during CPB surgery (consistent with a role in platelet-preservation), while permitting the participation of platelets in the formation of hemostatic plugs at wound and suture sites, where collagen, ADP, and epinephrine are most likely to be expressed. Aprotinin therefore exerts a subtle hemostatic yet antithrombotic mechanism of action, which, when allied with its multitiered antiinflammatory effect, makes this drug a valuable companion to cardiac surgery.

Tranexamic acid in aortic valve replacement

OBJECTIVE

To assess the relative efficacy of tranexamic acid compared with a control group to decrease bleeding and transfusion requirements in a uniform population undergoing aortic valve replacement.

DESIGN

Prospective, randomized, double-blind study.

SETTINGS

University hospital.

PARTICIPANTS

Adult cardiac surgery patients (n = 300).

INTERVENTIONS

Patients were randomized into 2 groups to receive either a total of 5 g of tranexamic acid or a saline solution. Bleeding in the postoperative period, transfusions of bank blood products, coagulation profile, intensive care unit stay, and hospital length of stay were recorded.

MEASUREMENTS AND MAIN RESULTS

Postoperative bleeding in patients treated with tranexamic acid was significantly lower compared with the control group (p < 0.0001). Packed red blood cells and fresh frozen plasma usage were reduced in the tranexamic acid group compared with the control group (p = 0.0095 and p < 0.0001). Only 24.5% of tranexamic acid patients received blood products versus 45% of control patients (p < 0.01). There was no significant difference in hematologic and coagulation profiles after the operation between the groups.

CONCLUSIONS

Tranexamic acid reduces postoperative blood loss and transfusion requirements in elective aortic valve replacement.

Epsilon-aminocaproic acid promotes the release of alpha2-antiplasmin during and after cardiopulmonary bypass

This double-blind, randomized study compared the mechanisms by which low-dose aprotinin and epsilon-aminocaproic acid (EACA) inhibited fibrinolysis during cardiopulmonary bypass surgery. D-dimer levels during and after bypass were similar, indicating an equivalent inhibition of fibrinolysis. Effects on tissue plasminogen activator release were not associated with the inhibition of fibrinolysis by either drug. Treatment with EACA was associated with a substantial release of endogenous alpha2-antiplasmin, particularly 1 h after bypass. Compared with the aprotinin group, higher levels of the plasmin-alpha2-antiplasmin complex in the EACA group confirmed an increased inhibition of plasmin by alpha2-antiplasmin. In conclusion, it is hypothesized that EACA inhibited fibrinolysis by stimulating the release of the patients' own alpha2-antiplasmin.

Transfusion medicine : support of patients undergoing cardiac surgery

There is still no alternative that is as effective or as well tolerated as blood; nevertheless, the search for ways to conserve, and even eliminate blood transfusion, continues. Based on hemoglobin levels, practice guidelines for the use of perioperative transfusion of red blood cells in patients undergoing coronary artery bypass grafting have been formulated by the National Institutes of Health and the American Society of Anesthesiologists. However, it has been argued that more physiologic indicators of adequacy of oxygen delivery should be used to assess the need for blood transfusion. Methods used for conserving blood during surgery include autologous blood donation, acute normovolemic hemodilution and intra- and postoperative blood recovery and reinfusion. The guidelines for the use of autologous blood transfusion are controversial and it does not appear to be cost effective compared with allogeneic blood transfusion in patients undergoing cardiac surgery. Similarly, the cost effectiveness of intra- and postoperative blood recovery and reinfusion need further evaluation. Treatment with recombinant human erythropoietin (rhEPO) remains unapproved in the US for patients undergoing cardiac or vascular surgery, but it is a valuable adjunct in Jehovah's Witness patients, for whom blood is unacceptable. The characterization of darbepoetin alfa, a novel erythropoiesis stimulating protein with a 3-fold greater plasma elimination half-life compared with rhEPO, is an important advance in this field. Darbepoetin alfa appears to be effective in treating the anemia in patients with renal failure or cancer and trials in patients with surgical anemia are planned. Desmopressin has been used to effectively reduce intraoperative blood loss. Topical agents to prevent blood loss, such as fibrin glue and fibrin gel, and agents that alter platelet function, such as aspirin (acetylsalicylic acid) or dipyridamole, need further evaluation in patients undergoing cardiac surgery. Aprotinin has been shown to preserve hemostasis and reduce allogeneic blood exposure to a greater extent than the antifibrinolytic agents tranexamic acid and aminocaproic acid. Controlled clinical trials comparing the costs of these agents with clinical outcomes, along with tolerability profiles in patients at risk for substantial perioperative bleeding are needed.

Role of aprotinin in the management of patients during and after cardiac surgery

Management of patients undergoing cardiac surgery has evolved in recent years as more is understood about the physiological changes and responses that occur during and after cardiopulmonary bypass (CPB). In particular, our understanding of the mechanisms involved in haemostasis and in the inflammatory response to bypass surgery, has allowed significant refinements in patient management. Improvements in the pharmacological conservation of blood loss have been striking, particularly with the development of the serine protease inhibitor, aprotinin (Trasylol, Bayer). Aprotinin represents a significant improvement, especially for patients at high risk, since it reduces the need for allogeneic and (sometimes scarce) blood products. However, in view of its cost, making an appropriate selection of patients most at risk of serious blood loss is a major consideration in the use of aprotinin. While its mechanisms of action are not well understood, the use of aprotinin also appears to reduce inflammatory response to CPB.

SMA circuits reduce platelet consumption and platelet factor release during cardiac surgery

BACKGROUND

Platelet count and function are particularly damaged by cardiopulmonary bypass (CPB). This study evaluated the effects of a novel CPB circuit in terms of platelet count and activation, and postoperative need for blood products.

METHODS

One hundred patients undergoing coronary grafting were randomized in two groups: control group (n = 50) and test group (n = 50, surface modifying additives circuit, SMA group). Blood samples were taken before, during, and after CPB. Postoperative blood loss, number of transfused blood products, and postoperative variables were recorded.

RESULTS

The platelet count decreased less in the SMA group compared to the control group (end of CPB: respectively, 165 +/- 9 x 10(3)/mm3 vs 137 +/- 8 x 10(3)/mm3; p < 0.01). This was paralleled by a reduction in beta-thromboglobulin plasma levels in the SMA group. There was a trend to decreased blood loss in the SMA group, but the difference was significant only in patients taking aspirin preoperatively (p < 0.05). In the SMA group nearly 50% less fresh frozen plasma and platelet units were administered (p < 0.01). No operative deaths were observed.

CONCLUSIONS

The use of circuits with surface additives is clinically safe, preserves platelet levels, and attenuates platelet activation. This may lead to a reduced need for blood products.

Aprotinin and tranexamic acid for high transfusion risk cardiac surgery

BACKGROUND

Studies have shown that aprotinin and tranexamic acid can reduce postoperative blood loss after cardiac operation. However, which drug is more efficacious in a higher risk surgical group of patients, has yet to be defined in a randomized study.

METHODS

With informed consent, 80 patients undergoing elective high transfusion risk cardiac procedures (repeat sternotomy, multiple valve, combined procedures, or aortic arch operation) were randomized in a double-blind fashion, to receive either high dose aprotinin or tranexamic acid. Patient and operative characteristics, chest tube drainage and transfusion requirements were recorded.

RESULTS

There was no significant difference between the 2 treatment groups with respect to age, cardiopulmonary bypass time, complications (myocardial infarction, stroke, death), chest tube drainage (6, 12, or 24 hours), blood transfusions up to 24 hours postoperatively, total allogeneic blood transfusions for entire hospital stay, or induction/postoperative hemoglobin levels. However, multiple regression analysis revealed a positive relationship between cardiopulmonary bypass time and 24 hour blood loss in the tranexamic acid group (p = 0.001), unlike the aprotinin group where 24 hour blood loss is independent of cardiopulmonary bypass time (p = 0.423).

CONCLUSIONS

Overall, there was no significant difference in blood loss, or transfusion requirements, when patients received either aprotinin or tranexamic acid for high transfusion risk cardiac operation. Aprotinin, when given as an infusion in a high-dose regimen, was able to negate the usual positive effect of cardiopulmonary bypass time on chest tube blood loss.

[Allergic risk of aprotinin]

OBJECTIVE

To analyse the risk of anaphylactic reaction with the administration of aprotinin, either by i.v. route or as a biological sealant application and to propose updated guidelines in accordance with current data of the literature.

DATA SOURCES

Search in the Medline data base of articles in French, English and German, published since 1960, using following key words: aprotinin, allergy, anaphylaxis.

STUDY SELECTION

All categories of articles on this topic have been selected.

DATA EXTRACTION

Articles have been analysed for history, incidence and mechanisms of anaphylactic reactions, symptomatology, factors of risk, diagnosis and precautions of use.

DATA SYNTHESIS

Aprotinin is widely used for decreasing preoperative bleeding, especially in cardiac and orthopaedic surgery. This heterologue protein can cause anaphylactic reactions in 0.5 to 5.8% of patients, depending of the inclusion criteria. They are mediated by IgG and IgE antibodies. Aprotinin has also a direct, non specific, histaminoliberation effect. The clinical presentation includes various degrees of severity, up to cardiac arrest. Documented factors of risk are a previous parotinin administration, 15 days to 6 months before, and intolerance to beef meat, white of egg, cheese and milk. The immediate biological diagnosis is obtained on assessing the degranulation of basophiles (histamine) and mastocytes (tryptase), as well as the concentration of anti-aprotinin antibodies (RAST IgE), with a test of inhibition. The secondary assessment, six weeks later, includes prick-tests and intradermoreactions if the former are negative. The mean precaution consists to search factors of risk at preanaesthetic assessment. The predictive value of systematic prick-tests has not yet been validated. Anti H1 and anti H2 premedication is inefficient. A test dose can trigger a severe reaction.

CONCLUSION

Considering a significant anaphylactic risk, aprotinin administration becomes only licit after a careful evaluation of the benefit-risk ratio.

Maintenance of blood heparin concentration rather than activated clotting time better preserves the coagulation system in hypothermic cardiopulmonary bypass

In cardiopulmonary bypass (CPB), despite heparin regimens in which the activated clotting time (ACT) is kept at more than 400 s, there is biochemical evidence of thrombin generation indicating activation of the coagulation system and increased fibrinolytic activity. Therefore, to reduce the coagulant activation has been one of the main issues in the improvement of CPB. The purpose of this study was to compare the heparin concentration with the ACT and to evaluate the effect of keeping higher heparin concentration on the coagulation and fibrinolytic systems during hypothermic CPB, employing moderate hypothermia (MHT) or deep hypothermic circulatory arrest (DHT). Heparin was either administered to maintain an ACT >400 s (ACT group) or to maintain a whole blood heparin concentration of 3 mg/kg (heparin group). At the lowest core temperature during CPB, the ACT and the heparinase ACT (unrelated to heparin concentration) were increased the most whereas the whole blood heparin concentration was less than half the initial concentration in both ACT groups of MHT and DHT. The thrombin-antithrombin III (TAT) content just after CPB in both MHT and DHT was significantly lower in the heparin group than in the ACT group. In conclusion, ACT does not reflect the whole blood heparin concentration during hypothermic CPB. Furthermore, maintenance of the higher heparin concentration during hypothermic CPB may suppress the activation of the coagulation system via thrombin inhibition. That effect was more remarkable in deep hypothermic CPB. Therefore, we believe that anticoagulation management during hypothermic CPB should be based on the maintenance of the higher blood heparin concentration.

Economic evaluation of high-dose and low-dose aprotinin therapy during cardiopulmonary bypass

BACKGROUND

Aprotinin therapy is now widely used during cardiac surgery. This study examined the clinical and economic effectiveness of high-dose or low-dose aprotinin in comparison to placebo.

METHODS

In a double blind, randomized study, three groups of 50 patients received high-dose aprotinin costing AUS$614 per patient (AUS$ = Australian dollars), low-dose aprotinin costing AUS$220 per patient or placebo. Resource use influenced by aprotinin therapy was measured.

RESULTS

Both doses were effective in reducing chest drainage and postoperative transfusion requirements, high-dose being more effective than low-dose. Both doses reduced the rate of reoperations for hemostasis. A base case of statistically significant differences associated with the high-dose and low-dose aprotinin showed cost savings of AUS$77 and AUS$348 per patient, respectively. If the demonstrated less significant reductions in operating room and ward stay are included, these savings become AUS$463 and AUS$715, respectively. Alternately, if cross-matches are replaced by group-and-hold and cell savers are not used, the savings per patient would be AUS$196 and AUS$467, respectively.

CONCLUSIONS

While high-dose aprotinin is clinically more effective than low-dose aprotinin, low-dose therapy demonstrates greater cost savings.

Platelet function during cardiac surgery and cardiopulmonary bypass with low-dose aprotinin

OBJECTIVE

To determine whether two low-dose regimens of aprotinin influence platelet function.

DESIGN

Prospective, randomized, single-blinded trial.

SETTING

University teaching hospital performing 600 cardiac operations per year.

PARTICIPANTS

Fifty-nine patients scheduled for cardiac surgery undergoing cardiopulmonary bypass (CPB) of expected duration of 60 minutes or more.

INTERVENTIONS

Patients were randomized into three groups. Group C (control) included 21 patients who did not receive aprotinin. In group A2, 17 patients received 14,286 kallikrein inhibitor units (KIU)/kg (2 mg/kg) of aprotinin before surgery, followed by a continuous infusion of 7,143 KIU/kg/h (1 mg/kg/h) until the end of surgery. In group A4, 19 patients received 28,572 KIU/kg (4 mg/kg) of aprotinin before surgery, followed by the same infusion.

MEASUREMENTS AND MAIN RESULTS

Postoperative bleeding and transfusion requirements were significantly less in group A4. Changes in platelet number and function were similar in the three groups. Platelet aggregation was assessed in four periods: before CPB (T1), post-CPB (T2), and 2 hours (T3) and 4 hours (T4) after CPB. Platelet aggregation induced by adenosine diphosphate, 1 and 2 micromol/L; ristocetin, 1 mg/mL; and arachadonic acid (AA), 1.4 mmol/L, decreased at T2 (p < 0.001) in all groups, and for the ristocetin and AA groups, remained at less than baseline values at T3 and T4. In five patients from each group, platelet receptors for glycoprotein IIb-IIIa (GPIIb-IIIa) and expression of platelet activation markers, guanosine monophosphate 140 (GMP-140) and lysosomal protein, were measured by flow cytometry before and after CPB. Modifications in the expression of GPIIb-IIIa were always modest and without statistical significance. Platelet activation markers, GMP-140 or lysosomal protein, nearly doubled from baseline to post-CPB only in the A4 group, whereas they remained stable in both other groups (statistically not significant).

CONCLUSION

The two regimens of aprotinin, both considered low dosage, did not exert a protective effect on platelet function. Neither dose produced changes in platelet GPIIb-IIIa or platelet activation markers. However, bleeding and transfusion needs were decreased.

Platelet protection in coronary artery surgery: benefits of heparin-coated circuits and high-dose aprotinin therapy

OBJECTIVE

To examine the extent of platelet activation during extracorporeal circulation by using the combination of heparin-coated oxygenation systems and high-dose aprotinin therapy, and to examine the affinity and thereby the protective capacity of aprotinin to the glycoprotein (GP) receptors of the platelet membrane.

DESIGN

Experimental in vitro study.

SETTING

Research laboratory of a university hospital.

PARTICIPANTS

Thirty-two volunteers (blood donors).

MEASUREMENTS AND MAIN RESULTS

Thirty-two oxygenation circuits of the same construction series (16 heparin-coated and 16 noncoated) were investigated in a closed system of a heart-lung machine model with fresh human whole blood. In each of these two groups, eight circuits with and eight without a high-dose aprotinin application (250 kallikrein inhibitory units [KIU]/mL) were investigated. In all four groups, the number of platelets declined continuously during the 90-minute recirculation period. Group I (no heparin coating, no aprotinin) showed the greatest reduction; group IV (heparin coating, aprotinin) had a significantly smaller decrease in platelet number (p < 0.01). Platelet factor 4 (PF-4) levels, released from the alpha-granule, were in inverse proportion to the platelet loss. After 90 minutes of recirculation, the PF-4 values increased to 615.8% +/- 559.5% and 237.2% +/- 179.0% of the initial value for groups I and IV, respectively (p < 0.01). Affinity chromatography and immunoblotting techniques were used to evaluate the affinity of aprotinin for the GP receptors of the platelet membrane. The affinity appeared in the following order: GPIIb < GPIIIa < GPIb.

CONCLUSION

Heparin-coated oxygenation systems and additional aprotinin caused significantly less platelet damage in an in vitro cardiopulmonary bypass model. Chromatographic and immunologic methods could prove aprotinin's affinity for the platelet receptor proteins GPIb and GPIIb-IIIa and therefore its probable role in diminishing the triggering of the platelet activation cascade.

Is epsilon-aminocaproic acid as effective as aprotinin in reducing bleeding with cardiac surgery?: a meta-analysis

BACKGROUND

Although aprotinin is known to be effective in reducing postoperative hemorrhage after cardiac surgery, epsilon-aminocaproic acid, an alternative antifibrinolytic, is considerably less expensive. Because the results of 3 small randomized clinical trials comparing these 2 agents directly were inconclusive, we performed a meta-analysis to compare the relative effectiveness and adverse-effect profile of these 2 agents against placebo.

METHODS AND RESULTS

Data from 52 randomized clinical trials published between 1985 and 1998 involving the use of epsilon-aminocaproic acid (n=9) or aprotinin (n=46) in patients undergoing cardiac surgery were abstracted. Our primary outcomes were total blood loss, red blood cell transfusion rates and amounts, reexploration, stroke, myocardial infarction, and mortality. The meta-analysis revealed substantial reductions in total blood loss with epsilon-aminocaproic acid and low-dose aprotinin (each with a 35% reduction versus placebo, P<0.001) and high-dose aprotinin (53% reduction, P<0.001). There were identical reductions in total postoperative transfusions with epsilon-aminocaproic acid (61% reduction versus placebo, P<0. 010) and high-dose aprotinin (62% reduction, P<0.001). The proportion of patients transfused was similarly reduced with epsilon-aminocaproic acid (OR, 0.32; 95% CI, 0.15 to 0.69) and high-dose aprotinin (OR, 0.28; 0.22 to 0.37). Although both drugs reduced rates of reexploration to similar degrees, this effect was statistically significant only with high-dose aprotinin (OR, 0.39; 0. 24 to 0.61). epsilon-Aminocaproic acid and aprotinin had no effect on risks of postoperative myocardial infarction or overall mortality.

CONCLUSIONS

Because the 2 antifibrinolytic agents appear to have similar efficacies, the considerably less-expensive epsilon-aminocaproic acid may be preferred over aprotinin for reducing hemorrhage with cardiac surgery.