Aprotinin for primary coronary artery bypass grafting: a multicenter trial of three dose regimens

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.

The efficacy and safety of aprotinin use in cardiac surgery

BACKGROUND

The serine protease inhibitor aprotinin has received much attention in cardiac surgical practice as a pharmacologic intervention to improve the hemostatic derangement associated with cardiopulmonary bypass. This review highlights the major studies undertaken to investigate the efficacy and safety of aprotinin use in both primary and repeat coronary artery bypass graft surgical procedures.

METHODS

There have been at least 45 controlled studies in more than 7,000 patients in a variety of patient populations. These have ranged from primary coronary artery bypass graft and valve operations to complex reoperation procedures, including aortic arch reconstructions and thoracic organ transplantation. The recently completed International Multicenter Graft Patency Experience trial, the largest study to date, involved 870 patients at 13 international sites. The study examined the effects of aprotinin on graft patency, incidence of myocardial infarction, and blood loss in patients undergoing primary coronary artery bypass graft operations with cardiopulmonary bypass.

RESULTS

Twenty-one studies in approximately 5,000 patients undergoing primary coronary artery bypass graft or valve operations reported 33% to 66% reduction in blood loss with full-dose aprotinin therapy; 15 of the same studies reported significant reductions in transfusion requirements, ranging from 31% to 85%. The recently completed International Multicenter Graft Patency Experience study observed a significant reduction in thoracic-drainage volume of 43% (p < 0.0001) and a 49% (p < 0.001) reduction in the requirement for allogeneic blood transfusions. Aprotinin did not affect the occurrence of definite myocardial infarction (aprotinin, 2.9% versus placebo, 3.8%) or mortality (aprotinin, 1.4% versus placebo, 1.6%). There was no observed difference in the patency of internal mammary artery bypass grafts from all study sites in aprotinin- versus placebo-treated patients (aprotinin, 98.2% versus placebo, 98.0%).

CONCLUSIONS

Given the risks and costs associated with excessive bleeding and transfusions and the limited supply of banked blood, aprotinin represents an important and safe approach to blood conservation.

Analyses of coronary graft patency after aprotinin use: results from the International Multicenter Aprotinin Graft Patency Experience (IMAGE) trial

OBJECTIVE

We examined the effects of aprotinin on graft patency, prevalence of myocardial infarction, and blood loss in patients undergoing primary coronary surgery with cardiopulmonary bypass.

METHODS

Patients from 13 international sites were randomized to receive intraoperative aprotinin (n = 436) or placebo (n = 434). Graft angiography was obtained a mean of 10.8 days after the operation. Electrocardiograms, cardiac enzymes, and blood loss and replacement were evaluated.

RESULTS

In 796 assessable patients, aprotinin reduced thoracic drainage volume by 43% (P < .0001) and requirement for red blood cell administration by 49% (P < .0001). Among 703 patients with assessable saphenous vein grafts, occlusions occurred in 15.4% of aprotinin-treated patients and 10.9% of patients receiving placebo (P = .03). After we had adjusted for risk factors associated with vein graft occlusion, the aprotinin versus placebo risk ratio decreased from 1.7 to 1.05 (90% confidence interval, 0.6 to 1.8). These factors included female gender, lack of prior aspirin therapy, small and poor distal vessel quality, and possibly use of aprotinin-treated blood as excised vein perfusate. At United States sites, patients had characteristics more favorable for graft patency, and occlusions occurred in 9.4% of the aprotinin group and 9.5% of the placebo group (P = .72). At Danish and Israeli sites, where patients had more adverse characteristics, occlusions occurred in 23.0% of aprotinin- and 12.4% of placebo-treated patients (P = .01). Aprotinin did not affect the occurrence of myocardial infarction (aprotinin: 2.9%; placebo: 3.8%) or mortality (aprotinin: 1.4%; placebo: 1.6%).

CONCLUSIONS

In this study, the probability of early vein graft occlusion was increased by aprotinin, but this outcome was promoted by multiple risk factors for graft occlusion.

Fibrinolysis-adjusted perioperative low-dose aprotinin reduces blood loss in bypass operations

BACKGROUND

Postoperative bleeding still remains a serious problem in bypass surgery. This study evaluated fibrinolysis and perioperative low-dose antifibrinolytic regimens adjusted to the time course of fibrinolysis.

METHODS

In a prospective, randomized study of 42 patients undergoing bypass grafting, patients received low-dose aprotinin (group A; n = 14) or low-dose tranexamic acid (group TA; n = 14) intraoperatively and postoperatively, respectively, with no antifibrinolytics for comparison (group C; n = 14). Parameters of procoagulation, fibrinolysis, and activated factor VII were measured preoperatively, intraoperatively, and postoperatively. Blood loss was determined up to 24 hours.

RESULTS

The level of thrombin-antithrombin III complex was significantly decreased postoperatively in the treatment groups (group A and TA versus C: 25 +/- 14 and 19 +/- 10 microg/L, respectively, versus 40 +/- 21 microg/L; p < 0.05). Levels of plasmin-antiplasmin complexes were significantly decreased postoperatively in group A (607 +/- 231 microg/L) versus group C (825 +/- 225 microg/L) (p < 0.05) but were increased in group TA (1,145 +/- 394 microg/L) versus group C (p < 0.05). At all times intraoperatively and postoperatively, levels of D-dimers were significantly decreased in group A and group TA versus control (p < 0.001), indicating that fibrinolysis persists after the operation. Intraoperatively, the factor VIIa level decreased significantly in group A (20 +/- 8 mU/mL) versus group C (31 +/- 15 mU/mL) (p < 0.05), but not in group TA (32 +/- 15 mU/mL). Blood loss was significantly lower in group A (135 +/- 37 mL) and group TA (155 +/- 71 mL) versus group C (354 +/- 170 mL) (p < 0.001).

CONCLUSIONS

This low-dose aprotinin regimen adjusted to perioperative fibrinolysis reduces blood loss significantly in coronary bypass grafting. For further progress in this subject, clinical investigations of individual fibrinolysis-adjusted antifibrinolytic treatment seems warranted.

Tranexamic acid and aprotinin reduce postoperative bleeding and transfusions during primary coronary revascularization

We evaluated the blood conservation effects of tranexamic acid (TA) or aprotinin administered before and during cardiopulmonary bypass (CPB) in a prospective, randomized, double-blind study of 150 adult patients undergoing primary coronary artery bypass grafting surgery. Patients received either TA (2 g) or large-dose aprotinin (7 million KIU). Thirty additional untreated patients otherwise managed in a similar fashion were included from a recently completed study for comparison of outcomes. Demographic, medical, surgical, laboratory, mediastinal chest tube drainage (MCTD), transfusion, and outcome data were collected. Allogeneic blood product administration was tightly controlled. The demographic, medical, and surgical characteristics did not significantly differ between the two therapy groups. The median postoperative MCTD loss in the TA group did not significantly differ from that in the aprotinin-treated group (708 vs 600 mL). The percentage of patients that received no allogeneic blood products was 25% for the TA group and 27% for the aprotinin group (P = not significant). The median number of allogeneic blood products administered to the TA group (0 U) did not significantly differ from that administered to the aprotinin group (0 U). The percentage of patients with excessive MCTD (>1000 mL/24 h) did not significantly differ between groups (19% and 17%, respectively). In comparison, the control group had a significantly greater (P < 0.05) median MCTD (1020 mL), median allogeneic blood product exposure (4.5 U), and incidence of excessive MCTD (66%) and transfusion therapy (66%). These data help to support the use of pharmacologic methods to improve clinically relevant indicators of blood conservation for primary CPB procedures. Furthermore, the data show that TA is equivalent to aprotinin for blood conservation in patients at risk of excessive post-CPB bleeding and transfusion therapy.

IMPLICATIONS

In a randomized, blind trial, we evaluated the effects of tranexamic acid or aprotinin on blood conservation after primary cardiopulmonary bypass surgery. Both drugs were equally effective in reducing blood loss, the incidence of transfusion, and the amount of blood products transfused compared with placebon.

Activation of hemostasis during cardiopulmonary bypass and pediatric aprotinin dosage

BACKGROUND

Cardiopulmonary bypass results in inappropriate activation of the coagulation and fibrinolytic systems. Factors such as a greater degree of hemodilution, use of deep hypothermic circulatory arrest, the impact of cyanosis on coagulation, and the immature coagulation system of the newborn will increase the risk of problematic perioperative bleeding.

METHODS

This article describes the characteristics of the hemostatic system in children undergoing cardiac operations and addresses the effect of aprotinin on hemostasis. Hemostatic parameters were measured in 96 pediatric patients using three different doses of aprotinin. The high-dose group (group 1) received 30,000 KIU/kg (4.2 mg/kg) of aprotinin after induction of anesthesia and an additional bolus of 30,000 KIU/kg (4.2 mg/kg) into the pump prime. In the low-dose group (group 2), both the initial bolus and the pump-prime dose of aprotinin were halved to 15,000 KIU/kg (2.1 mg/kg). Group 3 received the high dose with an additional bolus of aprotinin to the pump prime.

RESULTS

Plasma levels of aprotinin in both groups 1 and 2 were lower than the 200 KIU/mL (0.03 mg/mL) value usually reached in adults with high-dose aprotinin treatment. Group 3 patients had levels greater than 200 KIU/mL (0.03 mg/mL) throughout the procedure. Biochemical indices of fibrinolysis (fibrin[ogen] degradation products, D-dimers) revealed significant and dose-dependent inhibition at all three aprotinin concentrations. In contrast, significant changes in coagulation activation markers (prothrombin fragments F1.2, thrombin-antithrombin III complex, and fibrin monomers) were found only in group 3.

CONCLUSIONS

The inverse relationship between a small patient's blood volume and the large pump-prime volume requires additional aprotinin to be added to the prime to achieve plasma levels sufficient to inhibit activation of the coagulation cascade.

Blood transfusion: influence of transfusion therapy on outcome

Few studies have addressed the influence of different transfusion therapies on outcome in a convincing way. Proven adverse impact of allogeneic blood on outcome is minimal. Acute mortality has declined to about 1 : 500,000 and the rate of transfusion-transmitted infections is decreasing, too. Data on postoperative infections and non-Hodgkin's lymphoma as possible adverse effects are controversial. Evidence for an increased risk of tumour recurrences is lacking. Alternatives to allogeneic blood may have appreciable risks: perioperative blood recovery had a fatality rate of more than 1 : 40,000. Reduction of allogeneic blood exposure may not be equated with improved outcome.

Influence of high- and low-dose aprotinin on activation of hemostasis in open heart operations

BACKGROUND

The protease inhibitor aprotinin reduces hemostatic activation and blood loss after cardiac operations. The aim of the present study was to investigate the influence of two different aprotinin doses on hemostatic activation and to identify the most effective dose to reduce the postoperative bleeding tendency.

METHODS

In a prospective, randomized, double-blind clinical trial, 230 patients scheduled for routine open heart operations received either high-dose (group H) or low-dose (group L) aprotinin. Primary outcome measures were the level of F(1+2) prothrombin fragments as a marker of thrombin generation, the level of D-dimers as an indicator of fibrinolysis, and the amount of postoperative blood loss. Allogeneic blood transfusion was recorded as a secondary outcome measure.

RESULTS

Aprotinin plasma concentrations 5 minutes after the onset of cardiopulmonary bypass were 166 +/- 45 kallikrein inactivator units per milliliter in group H and 118 +/- 30 kallikrein inactivator units per milliliter in group L (p < 0.05). Fibrinolytic activation was reduced significantly in group H compared with group L: the level of D-dimers at the end of CPB was 1,027 +/- 781 ng/mL and 1,977 +/- 1,001 ng/mL, respectively, in the two groups (p < 0.05). However, thrombin generation (F(1+2) fragments) did not differ between the two groups (7.4 +/- 3.5 nmol/L in group H and 8.6 +/- 4.3 nmol/L in group L). Twenty-four-hour postoperative blood loss was 663 +/- 461 mL in group H compared with 877 +/- 513 mL in group L (p < 0.05), and the corresponding allogeneic blood requirement was 1.3 +/- 1.9 U in group H and 1.9 +/- 2.3 U in group L (p < 0.05).

CONCLUSIONS

A high-dose aprotinin regimen was significantly more effective than a low-dose regimen in attenuating fibrinolysis and reducing the bleeding tendency and allogeneic blood requirements, but not in reducing F(1+2) prothrombin fragments. High-dose aprotinin therapy appears to be superior to low-dose therapy.

Drugs to minimize perioperative blood loss in cardiac surgery: meta-analyses using perioperative blood transfusion as the outcome. The International Study of Peri-operative Transfusion (ISPOT) Investigators

Concern about the side effects of allogeneic red blood cell transfusion has increased interest in methods of minimizing perioperative transfusion. We performed meta-analyses of randomized trials evaluating the efficacy and safety of aprotinin, desmopressin, tranexamic acid, and epsilon-aminocaproic acid in cardiac surgery. All identified randomized trials in cardiac surgery were included in the meta-analyses. The primary outcome was the proportion of patients who received at least one perioperative allogeneic red cell transfusion. Sixty studies were included in the meta-analyses. The largest number of patients (5808) was available for the meta-analysis of aprotinin, which significantly decreased exposure to allogeneic blood (odds ratio [OR] 0.31, 95% confidence interval [CI] 0.25-0.39; P < 0.0001). The efficacy of aprotinin was not significantly different regardless of the type of surgery (primary or reoperation), aspirin use, or reported transfusion threshold. The use of aprotinin was associated with a significant decrease in the need for reoperation because of bleeding (OR 0.44, 95% CI 0.27-0.73; P = 0.001). Desmopressin was not effective, with an OR of 0.98 (95% CI 0.64-1.50; P = 0.92). Tranexamic acid significantly decreased the proportion of patients transfused (OR 0.50, 95% CI 0.34-0.76; P = 0.0009). Epsilon-aminocaproic acid did not have a statistically significant effect on the proportion of patients transfused (OR 0.20, 95% CI 0.04-1.12; P = 0.07). There were not enough patients to exclude a small but clinically important increase in myocardial infarction or other side effects for any of the medications. We conclude that aprotinin and tranexamic acid, but not desmopressin, decrease the number of patients exposed to perioperative allogeneic transfusions in association with cardiac surgery.

IMPLICATIONS

Aprotinin, desmopressin, tranexamic acid, and epsilon-aminocaproic acid are used in cardiac surgery in an attempt to decrease the proportion of patients requiring blood transfusion. This meta-analysis of all published randomized trials provides a good estimate of the efficacy of these medications and is useful in guiding clinical practice. We conclude that aprotinin and tranexamic acid, but not desmopressin, decrease the exposure of patients to allogeneic blood transfusion perioperatively in relationship to cardiac surgery.

Hemostatic Drugs in Prothrombotic or Hypercoagulable States

Certain drug therapies, such as heparin, warfarin, and aspirin, are associated with prothrombotic or hypercoagulable states. If these agents that are administered to prevent thrombosis have been associated with its opposite effect, then agents that are specifically given to inhibit bleeding may produce a deleterious hypocoagulable effect. This article evaluates the risks presented by serine protease inhibitors (ie, aprotinin), lysine analog antifibrinolyics (ie, epsilon aminocaproic acid [Amicar, Wyeth-Ayerst, Philadelphia, PA] and tranexamic acid), and desmopressin acetate (DDAVP, Rhone-Poulenc Rorer, Collegeville, PA). It focuses on their mechanisms of action, particularly their effect on microvascular tone and endothelial function, coagulation factors, platelet function, and the fibrinolytic pathway. It discusses their use in the presence of known thrombin production or fibrinogen conversion and whether certain vascular beds are more prone to drug-related thrombosis.

Aprotinin Fifteen Years Later

Aprotinin, the broad-based bovine serine protease inhibitor, was first used as an antidote against the harmful proteases released through complement-induced neutrophil activation in the early 1980s. Since then, the safety and efficacy of aprotinin have been debated. Even now, fifteen years later, aprotinin's precise mechanism of action and clear indications for use have not been defined. This article discusses what aprotinin is, its role in the contact system of blood, how it improves hemostasis, the effect of temperature on it, its use in clinical practice, and which patients should receive it. The article concludes that aprotinin's hemostatic effects are useful in patients who are at increased risk from bleeding, but that it should not be considered a substitute for surgical skill. Early claims of absolute safety were premature. Risks between high- and low-dose regimens vary significantly, and more study is required. Alternatives to aprotinin such as the less expensive antifibrinolytic agent tranexamic acid are now available, but they also require additional study.