A multicenter, double-blind, placebo-controlled trial of aprotinin for reducing blood loss and the requirement for donor-blood transfusion in patients undergoing repeat coronary artery bypass grafting

Pharmacological strategies to decrease excessive blood loss in cardiac surgery: a meta-analysis of clinically relevant endpoints

BACKGROUND

Excessive bleeding may complicate cardiac surgery, and is associated with increased morbidity and mortality. Pharmacological strategies to decrease perioperative bleeding have been investigated in a large number of controlled trials, most of which have shown a decrease in blood loss. However, most studies lacked sufficient power to detect a beneficial effect on clinically more relevant outcomes. We did a meta-analysis of all randomised, controlled trials of the three most frequently used pharmacological strategies to decrease perioperative blood loss (aprotinin, lysine analogues [aminocaproic acid and tranexamic acid], and desmopressin).

METHODS

Studies were included if they reported at least one clinically relevant outcome (mortality, rethoracotomy, proportion of patients receiving a transfusion, or perioperative myocardial infarction) in addition to perioperative blood loss. In addition, a separate meta-analysis was done for studies concerning complicated cardiac surgery.

FINDINGS

We identified 72 trials (8409 patients) that met the inclusion criteria. Treatment with aprotinin decreased mortality almost two-fold (odds ratio 0.55 [95% CI 0.34-0.90]) compared with placebo. Treatment with aprotinin and with lysine analogues decreased the frequency of surgical re-exploration (0.37 [0.25-0.55], and 0.44 [0.22-0.90], respectively). These two treatments also significantly decreased the proportion of patients receiving any allogeneic blood transfusion. By contrast, the use of desmopressin resulted in a small decrease in perioperative blood loss, but was not associated with a beneficial effect on other clinical outcomes. Aprotinin and lysine analogues did not increase the risk of perioperative myocardial infarction; however, desmopressin was associated with a 2.4-fold increase in the risk of this complication. Studies in patients undergoing complicated cardiac surgery showed similar results.

INTERPRETATION

Pharmacological strategies that decrease perioperative blood loss in cardiac surgery, in particular aprotinin and lysine analogues, also decrease mortality, the need for rethoracotomy, and the proportion of patients receiving a blood transfusion.

Impact of innovations on transfusion medicine

The final decade of the last century of the second millennium ad has seen dramatic changes in all aspects of science and health care. In transfusion medicine, the blood supply is the safest it has ever been. Newer refinements and innovations are continuously being researched and implemented to achieve and further enhance safety. Advances in blood conservation, pharmacologic manipulation, engineered blood derivatives, and recombinant growth factors can now provide safer and more effective alternatives to blood transfusions for many patients. This overview highlights selective innovations in transfusion medicine and emphasizes some significant advances that have occurred in blood donor screening, blood component collections and therapy, and laboratory testing. Newer technologies are anticipated that will further enhance the safety of blood and transfusions and potentially augment annually the blood supply on a worldwide basis.

Aprotinin inhibits thrombin formation and monocyte tissue factor in simulated cardiopulmonary bypass

BACKGROUND

Aprotinin reduces perioperative bleeding after open heart surgery, primarily by inhibiting fibrinolysis. In addition, the drug has both procoagulant and anticoagulant effects that involve complex reactions of coagulation proteins and cells that are incompletely understood. This study tests the hypothesis that aprotinin has an anticoagulant effect on the extrinsic coagulation pathway.

METHODS

Human heparinized blood was recirculated through a membrane oxygenator with and without high concentrations of aprotinin (18.4 microM). Serial plasma samples were obtained at intervals up to 240 minutes.

RESULTS

Aprotinin significantly reduced the progressive increase in prothrombin fragments (F1.2) and thrombin-antithrombin complex beginning immediately. Aprotinin also significantly reduced monocyte expression of tissue factor and Mac-1. Aprotinin did not significantly reduce factor VII or factor VIIa.

CONCLUSIONS

During simulated cardiopulmonary bypass, aprotinin immediately inhibits kallikrein and thrombin formation via the intrinsic coagulation pathway. Later, aprotinin inhibits monocyte expression of tissue factor and the extrinsic coagulation pathway. The ability of aprotinin to inhibit monocyte tissue factor provides a means to reduce thrombin formation in blood aspirated from the wound during open heart surgery.

Thromboelastography-guided transfusion algorithm reduces transfusions in complex cardiac surgery

Transfusion therapy after cardiac surgery is empirically guided, partly due to a lack of specific point-of-care hemostasis monitors. In a randomized, blinded, prospective trial, we studied cardiac surgical patients at moderate to high risk of transfusion. Patients were randomly assigned to either a thromboelastography (TEG)-guided transfusion algorithm (n = 53) or routine transfusion therapy (n = 52) for intervention after cardiopulmonary bypass. Coagulation tests, TEG variables, mediastinal tube drainage, and transfusions were compared at multiple time points. There were no demographic or hemostatic test result differences between groups, and all patients were given prophylactic antifibrinolytic therapy. Intraoperative transfusion rates did not differ, but there were significantly fewer postoperative and total transfusions in the TEG group. The proportion of patients receiving fresh-frozen plasma (FFP) was 4 of 53 in the TEG group compared with 16 of 52 in the control group (P < 0.002). Patients receiving platelets were 7 of 53 in the TEG group compared with 15 of 52 in the control group (P < 0.05). Patients in the TEG group also received less volume of FFP (36 +/- 142 vs 217 +/- 463 mL; P < 0.04). Mediastinal tube drainage was not statistically different 6, 12, or 24 h postoperatively. Point-of-care coagulation monitoring using TEG resulted in fewer transfusions in the postoperative period. We conclude that the reduction in transfusions may have been due to improved hemostasis in these patients who had earlier and specific identification of the hemostasis abnormality and thus received more appropriate intraoperative transfusion therapy. These data support the use of TEG in an algorithm to guide transfusion therapy in complex cardiac surgery.

IMPLICATIONS

Transfusion of allogeneic blood products is common during complex cardiac surgical procedures. In a prospective, randomized trial, we compared a transfusion algorithm using point-of-care coagulation testing with routine laboratory testing, and found the algorithm to be effective in reducing transfusion requirements.

Pump prime only aprotinin inhibits cardiopulmonary bypass-induced neutrophil CD11b up-regulation

BACKGROUND

The expression of neutrophil integrin CD11b is up-regulated after cardiopulmonary bypass (CPB) and is the neutrophil adhesive molecule of most importance in neutrophil- endothelial adherence. This neutrophil-endothelial adherence is responsible for post-CPB neutrophil-induced reperfusion injury. Low-dose aprotinin protocols inhibit the CPB-induced neutrophil CD11b up-regulation. This investigation was undertaken to evaluate the effects of pump prime only aprotinin (280 mg) on the CPB-induced up-regulation of this neutrophil integrin.

METHODS

Twenty-two patients scheduled for elective myocardial revascularization were randomized into two groups: (1) control (n = 12), or (2) pump prime only aprotinin (280 mg) (n = 10). Neutrophils were isolated at baseline, 50 minutes of CPB, and 30 minutes after CPB and neutrophil CD11b expression was measured.

RESULTS

The control group demonstrated a significant (p < 0.05) increase in neutrophil CD11b immunofluorescent staining at 50 minutes of CPB and at 30 minutes after CPB when compared to same group baseline and to the pump prime only aprotinin group at similar time intervals.

CONCLUSIONS

These results indicate that pump prime only aprotinin modulates the CPB-induced up-regulation of neutrophil CD11b integrin, an important indicator of the systemic inflammatory response to CPB. In addition to blunting of the CPB-induced up-regulation of this neutrophil integrin expression, this pump prime only dose of aprotinin is also reported to be effective at reducing post-CPB bleeding and transfusion requirements. This salutary effect of pump prime only aprotinin suggests that such low-dose regimens can be both therapeutically effective and cost effective.

Thromboelastography-guided transfusion algorithm reduces transfusions in complex cardiac surgery

Transfusion therapy after cardiac surgery is empirically guided, partly due to a lack of specific point-of-care hemostasis monitors. In a randomized, blinded, prospective trial, we studied cardiac surgical patients at moderate to high risk of transfusion. Patients were randomly assigned to either a thromboelastography (TEG)-guided transfusion algorithm (n = 53) or routine transfusion therapy (n = 52) for intervention after cardiopulmonary bypass. Coagulation tests, TEG variables, mediastinal tube drainage, and transfusions were compared at multiple time points. There were no demographic or hemostatic test result differences between groups, and all patients were given prophylactic antifibrinolytic therapy. Intraoperative transfusion rates did not differ, but there were significantly fewer postoperative and total transfusions in the TEG group. The proportion of patients receiving fresh-frozen plasma (FFP) was 4 of 53 in the TEG group compared with 16 of 52 in the control group (P < 0.002). Patients receiving platelets were 7 of 53 in the TEG group compared with 15 of 52 in the control group (P < 0.05). Patients in the TEG group also received less volume of FFP (36 +/- 142 vs 217 +/- 463 mL; P < 0.04). Mediastinal tube drainage was not statistically different 6, 12, or 24 h postoperatively. Point-of-care coagulation monitoring using TEG resulted in fewer transfusions in the postoperative period. We conclude that the reduction in transfusions may have been due to improved hemostasis in these patients who had earlier and specific identification of the hemostasis abnormality and thus received more appropriate intraoperative transfusion therapy. These data support the use of TEG in an algorithm to guide transfusion therapy in complex cardiac surgery.

IMPLICATIONS

Transfusion of allogeneic blood products is common during complex cardiac surgical procedures. In a prospective, randomized trial, we compared a transfusion algorithm using point-of-care coagulation testing with routine laboratory testing, and found the algorithm to be effective in reducing transfusion requirements.

The effects of aprotinin on outcome from cerebral ischemia in the rat

The administration of aprotinin has been associated with a reduction in cardiac surgery-related stroke. Intrinsic neuroprotective properties of this drug have not been evaluated in laboratory outcome models of cerebral ischemia. The purpose of this study was to determine whether aprotinin exhibits neuroprotective effects against either global or focal cerebral ischemia in the rat. Fasted rats were administered aprotinin (30,000 or 60,000 KIU/kg) or vehicle (0.9% NaCl) IV before global ischemia (10 min bilateral carotid occlusion with mean arterial pressure 30 mm Hg) or focal ischemia (75 min of transient middle cerebral artery occlusion [MCAO]). Five days after global ischemia, the percentage of dead hippocampal CA1 neurons (mean +/- SD) was similar among the groups (small-dose aprotinin: 49+/-31, n = 15; large-dose aprotinin: 55+/-31, n = 13; vehicle: 47+/-31, n = 16; P = 0.74). After 7 days' recovery from MCAO, no difference among the groups was observed for either neurologic score (P = 0.99) or cerebral infarct volume (small-dose aprotinin: 136+/-80 mm3, n = 23; large-dose aprotinin: 132+/-101 mm3, n = 11; vehicle: 121+/-81 mm3, n = 21; P = 0.87).

IMPLICATIONS

Aprotinin offers no neuroprotection against either global or focal cerebral ischemia in the rat when administered as a single preischemic bolus.

A retrospective study of the effects of small-dose aprotinin on blood loss and transfusion needs during total hip arthroplasty

Aprotinin is a proteinase inhibitor that reduces blood loss in total hip arthroplasty when administered in large doses. Little is known about the capability of smaller doses of aprotinin in reducing blood loss and transfusion needs in this surgical setting. We reviewed the medical records of 372 patients who had undergone unilateral primary total hip arthroplasty under general anaesthesia during a 6-year period (1989 to 1994) at our institution. Successively, 193 patients had and 179 patients had not received aprotinin in a dose of 20,000 kallikrein inhibitor units per kilogram body weight intravenously before surgery. Neither the volume of red blood cells lost nor that of red blood cells transfused during hospitalization differed significantly between the patients who had and those who had not received aprotinin (520 +/- 406 vs. 549 +/- 394 mL and 463 +/- 379 vs. 475 +/- 367 mL; P = 0.49 and P = 0.76 respectively). These results suggest that small-dose aprotinin was not effective in reducing blood loss and transfusion needs in patients undergoing unilateral primary total hip replacement.

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.

Aprotinin versus epsilon-aminocaproic acid for aortic surgery using deep hypothermic circulatory arrest

OBJECTIVE

To compare the relative efficacy of aprotinin and epsilon-aminocaproic acid (EACA) in decreasing blood loss and transfusion requirements after aortic surgery involving deep hypothermic circulatory arrest (DHCA).

DESIGN

A retrospective chart review.

SETTING

A university medical center.

PARTICIPANTS

Forty-nine patients who had undergone thoracic aortic surgery with the use of circulatory arrest.

INTERVENTIONS

Charts were examined for variables believed to influence postoperative blood loss, including the use of medications, and for the amount of postoperative chest tube drainage and perioperative transfusion.

MEASUREMENTS AND MAIN RESULTS

Median chest tube output (CTO) at 6 and 12 hours postoperatively was nearly identical in patients treated with aprotinin or EACA (660 and 1,015 v 700 and 950 mL for aprotinin and EACA at 6 and 12 hours, respectively), as were total perioperative blood transfusions. Complications were not significantly different between groups with the exception of a trend toward increased incidence of renal failure in the group receiving EACA.

CONCLUSION

Aprotinin and EACA appear to be equally efficacious in reducing perioperative blood loss and transfusion requirements in patients undergoing aortic surgery involving DHCA. Questions of safety remain about the use of EACA in this setting that could not be addressed by this small retrospective study. A prospective, placebo-controlled study is warranted to confirm the absolute efficacy of these agents and to better define safety issues.

Modifying risk for extracorporeal circulation: trial of four antiinflammatory strategies

BACKGROUND

Despite recent rediscovery of beating heart cardiac surgical techniques, extracorporeal circulation remains appropriate for most heart operations. To minimize deleterious effects of cardiopulmonary bypass, antiinflammatory strategies have evolved.

METHODS

Four state-of-the-art strategies were studied in a prospective, randomized, preoperatively risk stratified, 400-patient study comprising primary (n = 358), reoperative (n = 42), coronary (n = 307), valve (n = 27), ascending aortic (n = 9), and combined operations (n = 23). Groups were as follows: standard, roller pump, membrane oxygenator, methylprednisolone (n = 112); aprotinin, standard plus aprotinin (n = 109); leukocyte depletion, standard plus a leukocyte filtration strategy (n = 112); and heparin-bonded circuitry, centrifugal pumping with surface modification (n = 67).

RESULTS

Analysis of variance, linear and logistic regression, and Pearson correlation were applied. Actual mortality (2.3%) was less than half the risk stratification predicted mortality (5.7%). The treatment strategies effectively attenuated markers of the inflammatory response to extracorporeal circulation. Compared with the other groups the heparin-bonded circuit had highly significantly decreased complement activation (p = 0.00001), leukocyte filtration blunted postpump leukocytosis (p = 0.043), and the aprotinin group had less fibrinolysis (p = 0.011). Primary end points, length of stay, and hospital charges, were positively correlated with operation type, age, pump time, body surface area, stroke, pulmonary sequelae, predicted risk for stroke, predicted risk for mortality, and risk strata/treatment group interaction (p = 0.0001). In low-risk patients, leukocyte filtration reduced length of stay by 1 day (p = 0.02) and mean charges by $2,000 to $6,000 (p = 0.05). For high-risk patients, aprotinin reduced mean length of stay up to 10 fewer days (p = 0.02) and mean charges by $6,000 to $48,000 (p = 0.0007).

CONCLUSIONS

These pharmacologic and mechanical strategies significantly attenuated the inflammatory response to extracorporeal circulation. This translated variably into improved patient outcomes. The increased cost of treatment was offset for selected strategies through the added value of significantly reduced risk.

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.

Hematologic and economic impact of aprotinin in reoperative pediatric cardiac operations

BACKGROUND

Aprotinin consistently reduces blood loss and transfusion requirements in adults during and after cardiac surgical procedures, but its effectiveness in children is debated. We evaluated the hemostatic and economic effects of aprotinin in children undergoing reoperative cardiac procedures with cardiopulmonary bypass.

METHODS

Control, low-dose aprotinin, and high-dose aprotinin groups were established with 15 children per group. Platelet counts, fibrinogen levels, and thromboelastographic values at baseline and after protamine sulfate administration, number of blood product transfusions, and 6-hour and 24-hour chest tube drainage were used to evaluate the effects of aprotinin on postbypass coagulopathies. Time needed for skin closure after protamine administration and lengths of stay in the intensive care unit and the hospital were recorded prospectively to determine the economic impact of aprotinin.

RESULTS

Coagulation tests performed after protamine administration rarely demonstrated fibrinolysis but did show significant decreases in platelet and fibrinogen levels and function. The thromboelastographic variables indicated a preservation of platelet function by aprotinin. Decreased blood product transfusions, shortened skin closure times, and shortened durations of intensive care unit and hospital stays were found in the aprotinin groups, most significantly in the high-dose group with a subsequent average reduction of nearly $3,000 in patient charges.

CONCLUSIONS

In children undergoing reoperative cardiac surgical procedures, aprotinin is effective in attenuating postbypass coagulopathies, decreasing blood product exposure, improving clinical outcome, and reducing patient charges.

Anesthesia for deep hypothermic circulatory arrest in adults: experience with the first 50 patients

OBJECTIVE

To evaluate the efficacy of a simple method of central nervous system (CNS) protection in patients undergoing deep hypothermic circulatory arrest (DHCA) lasting less than 30 minutes, for a variety of complex cardiovascular procedures.

DESIGN

A retrospective case review.

SETTING

A university teaching hospital.

PARTICIPANTS

Fifty consecutive patients (25 women, 25 men) undergoing elective or emergency cardiovascular operations requiring DHCA between August 1991 and December 1996.

INTERVENTIONS

Patients underwent DHCA for a variety of surgical procedures. Neurologic protection was with thiopental, ice packs to the head, and systemic core hypothermia to a nasopharyngeal temperature (NPT) of 18 degrees to 20 degrees C.

MEASUREMENTS AND MAIN RESULTS

The mean duration of circulatory arrest was 18 +/- 10 minutes (range, 5 to 42 minutes). The mean NPT at time of arrest was 18.7 degrees +/- 1.7 degrees C. Three patients (6%) had gross CNS morbidity, one of whom died. The circulatory arrest times for these three patients were 8, 39, and 40 minutes. Perioperative mortality was 8% (n = 4). The circulatory arrest times for the patients who died were 12, 13, 23, and 39 minutes.

CONCLUSION

The anesthetic management of DHCA described is simple, effective, and safe, and can be performed in any institution that performs cardiac surgery.

Incidence of hypersensitivity reactions

BACKGROUND

Aprotinin is a naturally occurring serine protease inhibitor derived from bovine lung. In common with all foreign proteins, it possesses antigenic properties and has the possibility of allergic reactions on reexposure.

METHODS

Data are presented on the incidence of adverse reactions to aprotinin and the time course of antibody development after initial exposure. Recommendations for reducing the risk and sequelae of these adverse reactions are emphasized and case reports are reviewed.

RESULTS

The incidence rates of aprotinin-related reactions to date (May 1997) at the German Heart Center are 2.7% in the adult population in reexposures (5/183) and 1.2% in the pediatric population (3/254), with an overall incidence of 1.8% (8/437).

CONCLUSIONS

With the recommended precautions, reexposure to aprotinin in patients with a high risk of bleeding is justified, and the benefits of aprotinin treatment outweigh the relative risk of a serious allergic reaction.

Management of bleeding complications in redo cardiac operations

Bleeding remains a complication of certain complex surgical procedures, particularly those cardiac operations associated with long bypass times and profound hypothermia. Clinical and novel experimental strategies to reduce bleeding and the need for blood and blood-product transfusions are the focus of this review. Preoperative assessment of the patient will identify drug-induced, acquired, or inherited coagulation defects that may contribute to this problem. The main attention is directed to the perioperative period, and broad areas discussed include the preoperative use of erythropoietin to increase red blood cell mass, autologous donation either preoperatively or before bypass, autotransfusion/hemofiltration, and acceptance of relative anemia both during the operation and into the postoperative period. A further, often overlooked, management strategy in treating major coagulopathies is the consideration of the cost and half-lives of the coagulation factors in individual blood components. Prevention of bleeding has become possible both by manipulation of the control of coagulation and inflammatory processes and by the introduction of pharmacologic agents such as aprotinin. Aprotinin is widely used and has proven efficacy in the management of excess bleeding. It is a serine protease inhibitor and has several possible mechanisms of action, including inhibition of the plasma enzyme systems activated by contact with the foreign surface of the bypass circuit and preservation of platelet function. Safety issues include the possibility of hypersensitivity and anaphylactic reaction on a second exposure. Concerns that aprotinin may induce a prothrombotic or coagulant state have no basis in theory or any good evidence in the current literature. A recent study specifically sought to identify the presence of disseminated microvascular platelet-fibrin thrombi present at autopsy in patients who had received aprotinin therapy. The study concluded that diffuse platelet-fibrin thrombi were not a direct complication of aprotinin therapy. Finally, modern molecular biology has led to the recent development of an inhibitor for factor IXa that competitively replaced IXa in the intrinsic complex and blocked the conversion of factor X to factor Xa. This compound is under investigation in animal studies. These have so far shown efficacy in reducing blood loss after bypass in comparison with standard heparin anticoagulation.

Negative reexploration for cardiac postoperative bleeding: can it be therapeutic?

BACKGROUND

Reexploration of the mediastinum for bleeding is required in 3% to 7% of patients after cardiac operation, with many proving to have no surgically correctable cause. In spite of a "negative exploration," the bleeding often ceases. We propose the hypothesis that such a negative exploration can be therapeutic by reducing marked fibrinolytic activity in the mediastinal cavity.

METHODS

Fibrinolytic activity in shed mediastinal blood was compared with that in the system blood in 5 patients after cardiac operation by measuring fibrinogen, fibrin degradation product, plasminogen activator inhibitor-1, and alpha2-antiplasmin levels.

RESULTS

Fibrinolytic activity in mediastinal blood was markedly increased when compared with paired systemic venous blood. This was indicated by the mediastinal blood's lower fibrinogen levels (0.47 versus 1.91 U/mL; p < 0.001), very high levels of fibrin degradation products (1,350 versus 200 ng/mL; p < 0.05), and higher levels of plasminogen activator inhibitor-1 (55.5 versus 28.1 ng/mL; p < 0.005). Decreased levels of alpha2-antiplasmin were also observed in the mediastinum (0.50 versus 0.61 U/mL; p < 0.05).

CONCLUSIONS

Our data confirm that fibrinolytic activity can be extremely high in the mediastinum in response to clot formation. This may explain the hemostatic effects of a negative reexploration, where irrigation and the removal of clots may reduce the fibrinolytic process; this may allow the bleeding ends of capillaries and small vessels to thrombose. Decreased levels of alpha2-antiplasmin observed suggest that lysine analogs, such as epsilon-aminocaproic acid, may have a beneficial role when locally delivered into the mediastinum.

Aprotinin versus lysine analogues: the debate continues

The decision to use any pharmacologic intervention inevitably rests on balancing the efficacy and safety of the intervention. The advent of the acquired immunodeficiency syndrome epidemic greatly increased awareness of transfusion-related illnesses and focused attention on methods to prevent the need for blood and blood products. This has led, especially in the last decade, to increased use of drugs to help reduce perioperative bleeding. This chapter focuses on the lysine analogues and aprotinin as the serine protease inhibitor currently available in clinical practice. Both groups of compounds have recently shown promise in reducing surgical bleeding. However, the reader will notice that none of these agents are new; they have all been available for more than 30 years. What is new is their use in preventing bleeding. We therefore have considerable knowledge regarding the safety of these compounds. The first part of this review will compare the actions of these two types of agents on the processes related to thrombosis, hemostasis, and fibrinolysis. This is followed by a comparison of the efficacy of each intervention and any dose-response relationship. This section highlights the reported reduction in postoperative bleeding with both classes of agent. There is, however, no obvious or consistent reduction in the transfusion of blood and blood products in patients given lysine analogues. In contrast, there is a consistent reduction in the need for blood transfusions in patients given aprotinin therapy. The next major section will discuss the evidence to suggest that these drugs may, because of their known effects on the processes related to inflammation, hemostasis, and cellular repair, contribute to an improvement or worsening of outcome after cardiac operations. In particular, this section focuses on the antiinflammatory actions and modifications in vascular tone associated with aprotinin therapy. These effects may be related to improved outcome in patients by reducing the incidence of permanent neurologic deficit or stroke after heart operations, as well as inhibiting pulmonary vascular hyperreactivity and hypertension in susceptible individuals. Finally, this brief review discusses the safety issues that have been raised in regard to each of these classes of agents, specifically problems associated with abnormal renal function, hypersensitivity reactions, and thrombotic complications.

Comprehensive multimodality blood conservation: 100 consecutive CABG operations without transfusion

BACKGROUND

Despite the recent introduction of a number of technical and pharmacologic blood conservation measures, bleeding and allogeneic transfusion remain persistent problems in open heart surgical procedures. We hypothesized that a comprehensive multimodality blood conservation program applied algorithmically on the basis of bleeding and transfusion risk would provide a maximum, cost-effective, and safe reduction in postoperative bleeding and allogeneic blood transfusion.

METHODS

One hundred consecutive patients undergoing coronary artery bypass grafting were prospectively enrolled in a risk factor-based multimodality blood conservation program (MMD group). To evaluate the relative efficacy and safety of this comprehensive approach, comparison was made with a similar group of 90 patients undergoing coronary artery bypass grafting to whom the multimodality blood conservation program was not applied but in whom an identical set of transfusion guidelines was enforced (control group). To evaluate the cost effectiveness of the multimodality program, comparison was also made between patients in the MMD group and a consecutive series of contemporaneous, diagnostic-related group-matched patients.

RESULTS

One hundred consecutive patients in the MMD group underwent coronary artery bypass grafting without allogeneic transfusion. This compared favorably with the control population in whom a mean of 2.2 +/- 6.7 units of allogeneic blood was transfused per patient (34 patients [38%] received transfusion). In addition, the volume of postoperative blood loss at 12 hours in the control group was almost double that of the MMD group (660 +/- 270 mL versus 370 +/- 180 mL [p < 0.001]). Total costs for the MMD group in each of the three major diagnostic-related groups were equivalent to or significantly less than those in the consecutive series of diagnostic-related group-matched patients.

CONCLUSIONS

Comprehensive risk factor-based application of multiple blood conservation measures in an optimized, integrated, and algorithmic manner can significantly decrease bleeding and need of allogeneic transfusion in coronary artery bypass grafting in a safe and cost-effective manner.

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.

Cost-effective management of high-risk patients: a case-map approach

BACKGROUND

The case-management approach to patient care used by most cardiac surgical practices frequently highlights patients designated as high-risk. Increased risk might be because of advanced age, the need for complex reoperations, high risk of bleeding, and renal failure, all of which may be superimposed on poor ventricular performance.

METHODS

A small consensus panel of cardiac surgeons, anesthesiologists, perfusionists, cardiac-care nurse managers, and coagulation experts met to assess the potential for development of case-management pathways targeted towards high-risk coronary artery bypass graft patients. The process comprised review of the literature to identify risk factors and strategies most cost-effective in reducing risk.

RESULTS

A series of management strategies driven by data from the literature--or by consensus when such information was not available--were developed to cost-effectively manage the high-risk patient. The process was then converted to a multidimensional computer program. This personal computer-driven program served as a framework upon which any institution could impose its own practice style and modify recommendations. The program was designed to be interactive and to allow easy transition from patient-management strategies to support data. A facilitator generally coordinates the interaction between the local patient-care group and the computer information base to evolve a case-management map.

CONCLUSIONS

By using stored information based on current literature and easily updated, the system is both educational and product oriented, and provides a case-map approach to the cost-effective management of patients during the preoperative, intraoperative, and postoperative phases of hospital care.

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.

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.

A comparison of transvenous atrial defibrillation of acute and chronic atrial fibrillation and the effect of intravenous sotalol on human atrial defibrillation threshold

The comparative efficacy and safety of transvenous defibrillation for acute and chronic AF and the effect of antiarrhythmic agents on this therapy have not been evaluated. Transvenous atrial defibrillation was performed in 25 patients with chronic AF and 13 patients with acute AF by delivering R wave synchronized, biphasic shocks between the right atrium and coronary sinus. The lowest energy and voltage resulting in successful defibrillation were considered to be atrial defibrillation threshold (ADFT). Intravenous sotalol (1.5 mg/kg) was then given over 15 minutes and ADFT was determined again. The mean ADFT was 1.5 J and 3.6 J for acute and chronic AF, respectively, and the threshold was highly reproducible. Sotalol reduced ADFT in patients with acute AF while the reduction in chronic AF group was not significant. There was no significant increase in creatinine kinase nor reduction in blood pressure, but prolonged pause after successful defibrillation required ventricular supporting pacing. We conclude that transvenous atrial defibrillation is a safe and effective means for defibrillating both acute and chronic AF. ADFT was lower in acute AF than in chronic AF. ADFT was highly reproducible during repeated defibrillation. Sotalol reduced ADFT in acute AF and to a lesser extent in chronic AF, and increased the defibrillation success rate. Ventricular pacing will often be required because of prolonged pause after successful defibrillation.

Effects of minimal-dose aprotinin on coronary artery bypass grafting

OBJECTIVE

To evaluate the effects of minimal-dose aprotinin in patients undergoing coronary artery bypass grafting, we conducted a prospective randomized study.

METHODS

A total of 167 patients were randomized to receive no aprotinin treatment (control, n = 57), minimal-dose aprotinin (1.0 x 10(6) KIU; n = 55), or low-dose aprotinin (2.7 +/- 0.5 x 10(6) KIU; n = 55). Blood loss and transfusion requirements, parameters of clotting and fibrinolysis, renal function, and early graft patency rates were assessed.

RESULTS

Postoperative blood loss and transfusion requirements were significantly (p = 0.01) lower in both the minimal-dose and low-dose groups than in the control group. The increase in D-dimer level after cardiopulmonary bypass was significantly (p < 0.05) less marked in the low-dose group than in the control group. The alpha 2-plasmin inhibitor and plasminogen activator inhibitor-1 levels were significantly (p < 0.05) greater in the minimal-dose and low-dose groups than in the control group after bypass, suggesting the prevention of fibrinolysis by both aprotinin doses. No statistically significant differences in postoperative renal function and early vein graft patency rates were noted (control group, 93.8%; minimal-dose group, 95.5%; low-dose group, 92.3%; p = 0.25).

CONCLUSIONS

Aprotinin was not associated with a significant increase in the prevalence of renal dysfunction or early vein graft occlusion. Minimal-dose aprotinin inhibited enhanced fibrinolytic activity and reduced blood loss and transfusion requirements after bypass equivalently to low-dose aprotinin. The dose of 1 x 10(6) KIU added to the pump prime may be acceptably effective in reducing blood loss in patients undergoing primary coronary operations.

Low-energy transvenous cardioversion of atrial fibrillation using a single atrial lead system

INTRODUCTION

Clinical studies have shown that electrical conversion of atrial fibrillation (AF) is feasible with transvenous catheter electrodes at low energies. We developed a single atrial lead system that allows atrial pacing, sensing, and defibrillation to improve and facilitate this new therapeutic option.

METHODS AND RESULTS

The lead consists of a tripolar sensing, pacing, and defibrillation system. Two defibrillation coil electrodes are positioned on a stylet-guided lead. A ring electrode located between the two coils serves as the cathode for atrial sensing and pacing. We used this lead to cardiovert patients with acute or chronic AF. The distal coil was positioned in the coronary sinus, and the proximal coil and the ring electrode in the right atrium. R wave synchronized biphasic shocks were delivered between the two coils. Atrial signal detection and pacing were performed using the proximal coil and the ring electrode. Eight patients with acute AF (38 +/- 9 min) and eight patients with chronic AF (6.6 +/- 5 months) were included. The fluoroscopy time for lead placement was 3.5 +/- 4.3 minutes. The atrial defibrillation threshold was 2.0 +/- 1.4 J for patients with acute AF and 9.2 +/- 5.9 J for patients with chronic AF (P < 0.01). The signal amplitude detected was 1.7 +/- 1.1 mV during AF and 4.0 +/- 2.9 mV after restoration of sinus rhythm (P < 0.001). Atrial pacing was feasible at a threshold of 4.4 +/- 3.3 V (0.5-msec pulse width).

CONCLUSIONS

Atrial signal detection, atrial pacing, and low-energy atrial defibrillation using this single atrial lead system is feasible in various clinical settings. This system might lead to a simpler, less invasive approach for internal atrial cardioversion.