Aprotinin and preservation of myocardial function after ischemia-reperfusion injury

Leukocyte filtration and aprotinin: synergistic anti-inflammatory protection

Cardiopulmonary bypass activates an array of cellular and humoral inflammatory mechanisms that culminate in diverse or organ-specific injury. A manifestation of inflammatory injury to the heart, atrial fibrillation ranks among the most frequent and potentially life-threatening postsurgical complications. Pulmonary manifestations of the inflammatory response are also of major concern. Neutrophils activated by passage through the extracorporeal circuit inflict local injury and provoke the inflammatory cascade by producing oxyradicals and proinflammatory factors. This study tested if a combination of leukocyte depletion and aprotinin suppression of neutrophils could minimize postbypass atrial fibrillation and pulmonary dysfunction. In part one, two randomized groups of 90 patients undergoing primary coronary artery bypass grafting received full Hammersmith aprotinin alone (control group) or combined with leukofiltration (study group) and were prospectively examined. The dual treatment decreased the incidence of postoperative atrial fibrillation (7 of 90, 7.8%) by 67% versus aprotinin alone (21 of 90, 23.3%). Respiratory gas exchange in these patients was assessed from pulmonary shunt fraction. In the first two hours postbypass, pulmonary shunt fraction in the dual treatment group increased 40% less than in the group receiving aprotinin alone (p = 0.002), and subsided more quickly and completely over the next six hours. In part two, the cardiopulmonary bypass group receiving aprotinin+leukofiltration was retrospectively compared with 45 patients undergoing off-pump coronary revascularization. A strong, albeit not statistically significant trend (p= 0.08) toward a lower incidence of atrial fibrillation was found in the dual treatment group versus the off-pump group (8 of 45, 17.8%). These findings suggest that combining mechanical and pharmacologic suppression of the systemic inflammatory response could mitigate its deleterious arrhythmic and pulmonary complications.

Role of proteases in the pathophysiology of cardiac disease

Cardiovascular disease is a major cause of death and thus a great deal of effort has been made in salvaging the diseased myocardium. Although various factors have been identified as possible causes of different cardiac diseases such as heart failure and ischemic heart disease, there is a real need to elucidate their role for the better understanding of the cardiac disease pathology and formulation of strategies for developing newer therapeutic interventions. In view of the intimate involvement of different types of proteases in maintaining cellular structure, the role of proteases in various cardiac diseases has become the focus of recent research. Proteases are present in the cytosol as well as are localized in a number of subcellular organelles in the cell. These are known to use extracellular matrix, cytoskeletal, sarcolemmal, sarcoplasmic reticular, mitochondrial and myofibrillar proteins as substrates. Work from different laboratories using a wide variety of techniques has shown that the activation of proteases causes alterations of a number of specific proteins leading to subcellular remodeling and cardiac dysfunction. Inhibition of protease action by different drugs and agents, therefore, has a clinical relevance and is expected to form a part of new treatment paradigm for improving heart function. This review examines the biochemistry and localization of some of the proteases in the cardiac tissue in addition to identification of the sites of action of some protease inhibitors. (Mol Cell Biochem 263: 241-256, 2004).

Aprotinin in cardiac surgery

Aprotinin is a naturally occurring serine protease inhibitor that is being used with increasing frequency in cardiac surgery and beyond to reduce blood loss and the need for perioperative blood transfusion. Through inhibition of serine proteases such as plasmin, aprotinin significantly reduces fibrinolysis, thereby aiding hemostasis during surgical procedures. In addition, aprotinin interacts with other factors in the coagulation and fibrinolytic cascade, creating a hemostatic balance, without increasing the risk of thrombosis. These proven benefits are supplemented by the anti-inflammatory properties of aprotinin, which may help curb some of the deleterious effects of cardiopulmonary bypass. This article will review the discovery of aprotinin, its mechanism of action, dosing and adverse effects, and highlight the major recent trials demonstrating its efficacy.

Proangiogenic microtemplated fibrin scaffolds containing aprotinin promote improved wound healing responses

Survival of tissue engineered constructs after implantation depends heavily on induction of a vascular response in host tissue, promoting a quick anastomosis of the cellular graft. Additionally, implanted constructs typically induce fibrous capsule formation, effectively preventing graft integration with host tissue. Previously we described the development of a high density microtemplated fibrin scaffold for cardiac tissue engineering applications with tunable degradation and mechanical properties which promoted seeded cell survival and organization in vitro (Thomson et al., Tissue Eng Part A, 2013). Scaffold degradation in vitro was controllable by addition of the serine protease inhibitor aprotinin and/or the fibrin cross-linker Factor XIII (FXIII). The goal of this study was to assess host tissue responses to these fibrin scaffold formulations by determining effects on scaffold degradation, angiogenic responses, and fibrous capsule formation in a subcutaneous implant model. Aprotinin significantly decreased scaffold degradation over 2 weeks of implantation. A significant increase in capillary infiltration of aprotinin implants was found after 1 and 2 weeks, with a significantly greater amount of capillaries reaching the interior of aprotinin scaffolds. Interestingly, after 2 weeks the aprotinin scaffolds had a significantly thinner, yet apparently more cellular fibrous capsule than unmodified scaffolds. These results indicate aprotinin not only inhibits fibrin scaffold degradation, but also induces significant responses in the host tissue. These included an angiogenic response resulting in increased vascularization of the scaffold material over a relatively short period of time. In addition, aprotinin release from scaffolds may reduce fibrous capsule formation, which could help promote improved integration of cell-seeded scaffolds with host tissue.

Prevascularized microtemplated fibrin scaffolds for cardiac tissue engineering applications

Myocardial infarction (MI) causes significant cell loss and damage to myocardium. Cell-based therapies for treatment of MI aim to remuscularize the resultant scar tissue, but the majority of transplanted cells do not survive or integrate with the host tissue. Scaffolds can improve cell retention following construct implantation, but often do little to enhance host-graft integration and/or show limited biodegradation. Fibrin is an ideal biomaterial for cardiac tissue engineering as it is a natural, biodegradable polymer that can induce neovascularization, promote cell attachment, and has tunable mechanical properties. Here we describe a novel, high-density microtemplated fibrin scaffold seeded with a tri-cell mixture of cardiomyocytes, endothelial cells (ECs), and fibroblasts to mimic native cardiac tissue in structure and cellular composition to improve cell retention and promote integration with the host tissue. Scaffolds were designed with uniform architecture of parallel 60 μm microchannels surrounded by an interconnected microporous network of 27-μm-diameter pores and mechanical stiffness comparable to native cardiac tissues (70-90kPa). Scaffold degradation was controlled with the addition of Factor XIII (FXIII) and/or protease inhibitor (aprotinin). Unmodified scaffolds had a fast degradation profile both in vitro (19.9%±3.9% stiffness retention after 10 days) and in vivo. Scaffolds treated with FXIII showed an intermediate degradation profile in vitro (45.8%±5.9%), while scaffolds treated with aprotinin or both FXIII and aprotinin showed significantly slowed degradation in vitro (60.9%±5.2% and 76.4%±7.6%, respectively, p<0.05). Acellular aprotinin scaffold myocardial implants showed decreased collagen deposition after 7 days. Unmodified and aprotinin implants could not be located by 14 days, while 2 of 8 FXIII implants were found, but were significantly degraded. Constructs supported seeded cell survival and organization in vitro, promoting EC-lined lumen structure formation in construct channels and colocalization of viable ECs and cardiomyocytes. In addition, constructs promoted extracellular matrix deposition by seeded cells, as shown by collagen staining within construct channels and by significant increases in construct stiffness over 10 days in vitro (209%±32%, p<0.05). The data suggest our fibrin scaffolds are ideally designed to promote graft cell survival and organization, thus improving chances of promoting construct integration with the host tissue upon implantation.

A comparative study of the immune modulating properties of antifibrinolytics in cardiac surgery

PURPOSE

Antifibrinolytics, used in cardiac surgery to abate postoperative blood loss, share anti-inflammatory properties by suppression of pro-inflammatory D-dimer and plasmin levels. Additional drug specific immune modulating qualities are often mentioned in the discussion on which antifibrinolytic can best be used. To determine the extent and relevance of these effects, we investigated cytokine and growth factor plasma levels in cardiac surgery patients randomized to receive either tranexamic acid, aprotinin, or placebo. Corticosteroid-treated patients served to put the effects in perspective.

METHODS

Using a biochip immunoassay, plasma of 36 cardiac surgery patients was quantified for 12 cytokines and growth factors, assessed preoperatively and 6, 12, 24, and 48 h after the start of cardiopulmonary bypass. Eight patients were treated with tranexamic acid, nine with aprotinin, and nine received placebo. Ten placebo-treated patients received corticosteroids.

RESULTS

IL-1ß, IL-6, IL-8, IL-10, IFN-γ, TNF-α, VEGF, MCP-1, and EGF plasma concentrations significantly changed over time across all patients. Aprotinin-treated patients showed decreased pro-inflammatory TNF-α and peak MCP-1 plasma levels when compared with placebo. However, corticosteroids attenuated the inflammatory response to a much larger extent, lowering postoperative IL-6, IL-10, IFN-γ, and VEGF concentrations also.

CONCLUSIONS

Aprotinin attenuates postoperative pro-inflammatory levels TNF-α and MCP-1 whereas tranexamic acid does not. The majority of plasma proteins studied, however, were not affected by the use of antifibrinolytics when compared with placebo. A clinically relevant common anti-inflammatory effect through inhibition of fibrinolysis seems therefore unlikely.

Plasmin inhibitors prevent leukocyte accumulation and remodeling events in the postischemic microvasculature

Clinical trials revealed beneficial effects of the broad-spectrum serine protease inhibitor aprotinin on the prevention of ischemia-reperfusion (I/R) injury. The underlying mechanisms remained largely unclear. Using in vivo microscopy on the cremaster muscle of male C57BL/6 mice, aprotinin as well as inhibitors of the serine protease plasmin including tranexamic acid and ε-aminocaproic acid were found to significantly diminish I/R-elicited intravascular firm adherence and (subsequent) transmigration of neutrophils. Remodeling of collagen IV within the postischemic perivenular basement membrane was almost completely abrogated in animals treated with plasmin inhibitors or aprotinin. In separate experiments, incubation with plasmin did not directly activate neutrophils. Extravascular, but not intravascular administration of plasmin caused a dose-dependent increase in numbers of firmly adherent and transmigrated neutrophils. Blockade of mast cell activation as well as inhibition of leukotriene synthesis or antagonism of the platelet-activating-factor receptor significantly reduced plasmin-dependent neutrophil responses. In conclusion, our data suggest that extravasated plasmin(ogen) mediates neutrophil recruitment in vivo via activation of perivascular mast cells and secondary generation of lipid mediators. Aprotinin as well as the plasmin inhibitors tranexamic acid and ε-aminocaproic acid interfere with this inflammatory cascade and effectively prevent postischemic neutrophil responses as well as remodeling events within the vessel wall.

Drugs mediating myocardial protection

The occurrence of myocardial ischaemia will result in either reversible or irreversible myocardial dysfunction. Even when revascularization is successful, some reperfusion injury may occur that transiently impairs myocardial function. Therefore, treatment should not only be directed towards prompt restoration of myocardial blood flow but measures should also be taken to prevent or alleviate the consequences of myocardial reperfusion injury. Over the years, various strategies have been developed. The present contribution reviews a number of these strategies focusing on pharmacological treatments that have been developed to address myocardial reperfusion injury.

Aprotinin modifies left ventricular contractility and cytokine release after ischemia-reperfusion in a dose-dependent manner in a murine model

BACKGROUND

Periods of ischemia-reperfusion (I/R) during cardiac surgery are associated with transient left ventricular (LV) dysfunction and an inflammatory response. In this study, we examined the potential dose-dependent effects of aprotinin (APRO) on LV contractility and cytokine release in the setting of I/R.

METHODS

An index of LV contractility, LV maximal elastance (E(max)), was measured at baseline, 30 min of ischemia, and 60 min of reperfusion by microtransducer volumetry. Mice were randomized as follows: (a) APRO 20,000 kallikrein-inhibiting units (KIU)/kg (n = 11); (b) APRO 4 x 10(4) KIU/kg (n = 10); (c) APRO 8 x 10(4) KIU/kg (n = 10); and (d) vehicle (saline; n = 10). APRO doses were calculated to reflect half, full, and twice the clinical Hammersmith dosing schedule. After I/R, plasma was collected for cytokine measurements.

RESULTS

After I/R, E(max) decreased from the baseline value by more than 40% in the vehicle group as well as in the APRO 4 x 10(4) KIU/kg and APRO 8 x 10(4) KIU/kg groups (P < 0.05). However, E(max) returned to near baseline values in the APRO 2 x 10(4) KIU/kg group. Tumor necrosis factor (TNF) increased 10-fold after I/R, but it was reduced with higher APRO doses.

CONCLUSIONS

This study demonstrated that a low dose of APRO provided protective effects on LV contractility, whereas higher doses suppressed TNF release. These unique findings suggest that there are distinct and independent mechanisms of action of APRO in the context of I/R.

Aprotinin exacerbates left ventricular dysfunction after ischemia/reperfusion in mice lacking tumor necrosis factor receptor I

Aprotinin is a serine protease inhibitor with diverse biological effects; until recently, it was utilized in the context of ischemia/reperfusion (I/R). It has been hypothesized that a signaling pathway modulated by aprotinin in the context of I/R is the tumor necrosis factor-alpha receptor (TNFR) pathway. An intact mouse model of I/R (30 min ischemia and 60 min reperfusion) was used and left ventricular (LV) peak + maximal rate of left ventricular (LV) peak pressure (dP/dt) was measured in wild-type mice (WT, C57BL/6; n = 10), WT mice with aprotinin (4 mL/kg; n = 10), transgenic mice devoid of the TNFRI (TNFRI-null; n = 10), and TNFRI-null with aprotinin (n=10). Following I/R, LV peak + dP/dt decreased in both WT groups, but remained similar to baseline values in the TNFRI-null group. In contrast, aprotinin caused a marked reduction in LV peak + dP/dt in the TNFRI-null group following I/R. Soluble plasma TNF levels increased in the WT and TNFRI-null mice with I/R and was reduced with aprotinin. Soluble TNFRI and TNFRII levels, indicative of TNF activation, increased in the WT mice following I/R and remained elevated with aprotinin. Soluble TNFRII levels were increased in the TNFRI-null mice following I/R and remained elevated with aprotinin. The new and unique findings of this study were twofold. First, aprotinin failed to improve LV function after I/R despite a reduction in circulating TNF levels. Second, genetic ablation of TNFRI uncovered a negative inotropic effect of aprotinin. These findings demonstrate that complex biological pathways and interactions are affected with broad spectrum serine protease inhibition, which are relevant to myocardial function in the context of I/R.

Aprotinin exerts differential and dose-dependent effects on myocardial contractility, oxidative stress, and cytokine release after ischemia-reperfusion

BACKGROUND

Cardiac surgery can result in left ventricular ischemia and reperfusion (I/R), the release of cytokines such as tumor necrosis factor, and oxidative stress with release of myeloperoxidase. Although aprotinin has been used in cardiac surgery, the likely multiple effects of this serine protease inhibitor limit clinical utility. This study tested the hypothesis that different aprotinin doses cause divergent effects on left ventricular contractility, cytokine release, and oxidative stress in the context of I/R.

METHODS

Left ventricular I/R (30 minutes I, 60 minutes R) was induced in mice, and left ventricular contractility (maximal end-systolic elastance) determined. Mice were randomly allocated to 2 x 10(4) kallikrein inhibitory units (KIU)/kg aprotinin (n = 11), 4 x 10(4) KIU/kg aprotinin (n = 10), and vehicle (saline, n = 10). Based upon a fluorogenic assay, aprotinin doses of 2 and 4 x 10(4) KIU/kg resulted in plasma concentrations similar to those of the half and full Hammersmith doses, respectively.

RESULTS

After I/R, maximal end-systolic elastance fell by more than 40% from baseline (p < 0.05), and this effect was attenuated by 2 x 10(4) KIU/kg but not 4 x 10(4) KIU/kg aprotinin. Tumor necrosis factor increased by more than 60% from control (p < 0.05) with I/R, but was reduced with 4 x 10(4) KIU/kg aprotinin. Myeloperoxidase increased with I/R, and was reduced to the greatest degree by 2 x 10(4) KIU/kg aprotinin.

CONCLUSIONS

Aprotinin influences left ventricular contractility, cytokine release, and oxidative stress, which are dose dependent. These results provide mechanistic evidence that multiple pathways are differentially affected by aprotinin in a context relevant to cardiac surgery.

Anti-inflammatory actions of aprotinin provide dose-dependent cardioprotection from reperfusion injury

BACKGROUND AND PURPOSE

Myocardial injury following ischaemia and reperfusion has been attributed to activation and transmigration of polymorphonuclear leukocytes (PMNs) with release of mediators including oxygen-derived radicals and proteases causing damage.

EXPERIMENTAL APPROACH

We studied the serine protease inhibitor aprotinin in an in vivo rabbit model of 1 h of myocardial ischaemia followed by 3 h of reperfusion (MI+R). Aprotinin (10,000 Ukg(-1)) or its vehicle were injected 5 min prior to the start of reperfusion.

KEY RESULTS

Myocardial injury was significantly reduced with aprotinin treatment as indicated by a reduced necrotic area (11+/-2.7% necrosis as percentage of area at risk after aprotinin; 24+/-3.1% after vehicle; P<0.05) and plasma creatine kinase activity (12.2+/-1.5 and 17.3+/-2.3 IU g(-1) protein in aprotinin and vehicle groups, respectively, P<0.05). PMN infiltration (assessed by myeloperoxidase activity) was significantly decreased in aprotinin-treated animals compared to vehicle (P<0.01). Histological analysis also revealed a substantial increase in PMN infiltration following MI+R and this was significantly reduced by aprotinin therapy (44+/-15 vs 102+/-2 PMN mm2 in aprotinin vs vehicle-treated animals, P<0.05). In parallel in vitro experiments, aprotinin inhibited neutrophil-endothelium interaction by reducing PMN adhesion on isolated, activated aortic endothelium. Finally, immunohistochemical analysis illustrated aprotinin significantly reduced myocardial apoptosis following MI+R.

CONCLUSIONS AND IMPLICATIONS

Inhibition of serine proteases by aprotinin inhibits an inflammatory cascade initiated by MI+R. The cardioprotective effect appears to be at least partly due to reduced PMN adhesion and infiltration with subsequently reduced myocardial necrosis and apoptosis.

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.

Aprotinin in Cardiac Surgery: A Review of Conventional and Novel Mechanisms of Action

Induction of the coagulation and inflammatory cascades can cause multiorgan dysfunction after cardiopulmonary bypass (CPB). In light of these observations, strategies that can stabilize the coagulation process as well as attenuate the inflammatory response during and after cardiac surgery are important. Aprotinin has effects on hemostasis. In addition, aprotinin may exert multiple biologically relevant effects in the context of cardiac surgery and CPB. For example, it decreases neutrophil and macrophage activation and chemotaxis, attenuates release and activation of proinflammatory cytokines, and reduces oxidative stress. Despite these perceived benefits, the routine use of aprotinin in cardiac surgery with CPB has been called into question. In this review, we examined this controversial drug by discussing the classical and novel pathways in which aprotinin may be operative in the context of cardiac surgery.

Effects of Aprotinin on Gene Expression and Protein Synthesis After Ischemia and Reperfusion in Rats

Background— Reperfusion injury of ischemic myocardium has been attributed to neutrophil infiltration, inflammatory activation and cardiac necrosis/apoptosis. Serine protease inhibition with aprotinin is cardioprotective, but the mechanism is unknown.

Methods and Results— We studied aprotinin in a rat model of myocardial ischemia for 20 minutes and reperfusion for 20 minutes, 8 hours or 24 hours. Aprotinin (20 000 IU/kg) given 5 minutes before reperfusion significantly reduced leukocyte accumulation ( P <0.01), myocardial injury (determined by CK depletion, P <0.01) and myocyte apoptosis ( P <0.05) compared with vehicle treated rats. Differential gene expression analysis showed myocardial ischemia plus reperfusion increased expression of proinflammatory genes like P-selectin, E-selectin, intercellular adhesion molecule, tumor necrosis factor-α, tumor necrosis factor-α receptor, interleukin-6, monocyte chemoattractant protein-1, p53, and Fas (CD59). Aprotinin before reperfusion suppressed expression of these inflammatory genes. Finally, differential protein expression analysis demonstrated increased intercellular adhesion molecule-1, tumor necrosis factor-α, and p53 after myocardial ischemia plus reperfusion, and this effect was diminished by aprotinin.

Conclusions— We demonstrated myocardial ischemia plus reperfusion induced leukocyte accumulation, inflammation, gene expression, protein expression and finally tissue injury and showed aprotinin limiting reperfusion injury through each of these stages, even after 24 hours of reperfusion. This effect seems partly attributable to suppression of proinflammatory genes and leukocyte accumulation. This work casts further light on the complex signaling of ischemia and reperfusion.

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.

Effects of half-dose aprotinin in off-pump coronary artery bypass grafting

OBJECTIVE

The effects of half-dose aprotinin in off-pump coronary artery bypass (OPCAB) surgery have not yet been described. The present prospective study was designed to investigate its effects in OPCAB.

METHODS

Seventy-six patients were randomized into two groups, receiving aprotinin (1 x 10(6) Kallikrein-inactivating units [KIU] loading dose before surgery and 5 x 10(5) KIU/h during surgery, gross dose: 2.5 x 10(6) KIU, n=36) and saline solution (control, n=40) respectively. Perioperative blood samples were collected. Hematologic and hemostatic parameters including platelet adhesion rate, D-dimer, and fibrinopeptide-A (FPA) were analyzed. Perioperative CKMB release was measured. Volume of blood loss, blood transfusion, and other clinical data were recorded throughout the perioperative period.

RESULTS

Postoperative blood loss was significantly reduced in patients treated with aprotinin (2 hours; median [25th-75th]: aprotinin: 90.0 [70.0-125.0] ml, control: 145.0 [70.0-180.0] ml, P<0.05; 6 hours: aprotinin: 150.0 [100.0-220.0] ml, control: 225.0 [200.0-347.5.0] ml, P<0.01; 24 hours: aprotinin: 370.0 [220.0-510.0] ml, control: 655.0 [500.0-920.0] ml, P<0.01). The number of patients receiving blood transfusion in each group was similar. Levels of D-dimer rose significantly after surgery, and were significantly lower in the aprotinin group than in the controls (end of surgery, aprotinin, 0.4 [0.2-0.5] mg/l versus controls, 1.4 [0.8-2.3] mg/l; 2 hours, aprotinin, 0.3 [0.2-0.4] mg/l versus controls, 0.9 [0.5-1.4] mg/l; 6 hours, aprotinin, 0.3 [0.2-0.5] mg/l versus controls, 0.6 [0.4-0.9] mg/l; 24 hours, aprotinin, 0.3 [0.2-0.4] mg/l versus controls, 0.5 [0.4-0.9] mg/l; ANOVA for repeated measures, P<0.01). Platelet adhesion rate and FPA levels remained at baseline levels after the operation in the two groups. Early clinical outcomes were similar in the groups. Levels of CKMB were significantly lower in the aprotinin group than in the controls (6 hours after surgery, aprotinin, 10.0 [8.0-16.0] U/l versus controls, 15.5 [11.0-20.3] U/l; 12 hours, aprotinin, 13.5 [10.0-20.0] U/l versus controls, 19.0 [12.8-24.3] U/l; 24 hours, aprotinin, 19.0 [13.5-33.8] U/l versus controls, 25.0 [15.0-43.3] U/l; 72 hours, aprotinin, 13.0 [8.0-18.0] U/l versus controls, 16.0 [10.0-29.0] U/l; ANOVA for repeated measures, P=0.018).

CONCLUSION

The results indicated that half-dose aprotinin limits fibrinolysis and myocardial injury, and reduces blood loss after OPCAB surgery.

Full-dose aprotinin use in coronary artery bypass graft surgery: an analysis of perioperative pharmacotherapy and patient outcomes

BACKGROUND

Inappropriate activation of hemostasis and inflammation may contribute to postoperative morbidity and mortality. The serine protease inhibitor, aprotinin, has been shown to prevent tissue and organ injury in laboratory and animal studies. In this retrospective analysis, we evaluated the relationship of aprotinin therapy with organ dysfunction in humans undergoing coronary artery bypass graft surgery (CABG).

METHODS

Data from prospective randomized, double-blind, placebo-controlled studies evaluating the safety and efficacy of full-dose aprotinin (2 million KIU load, 2 million KIU pump prime, and 0.5 million KIU/h continuous infusion) to reduce blood loss and transfusion requirements in patients undergoing CABG (placebo, n = 861; aprotinin, n = 862) were examined retrospectively. Primary end-points were death, adverse cerebrovascular outcome, myocardial infarction (MI), and pharmacological interventions (inotropic drugs, vasopressors, and antiarrhythmics).

RESULTS

Univariate analysis showed that relative to placebo, full-dose aprotinin therapy was associated with significant effects on the incidence of adverse cerebrovascular outcome (odds ratio [OR] 0.42, 95% confidence interval [CI] 0.19-0.93; P = 0.03) and use of inotropic drugs (OR 0.79, 95% CI 0.65-0.97; P = 0.02), vasopressors (OR 0.74, 95% CI 0.61-0.90; P < 0.01), and antiarrhythmics (OR 0.79, 95% CI 0.65-0.96; P = 0.02), but not death (OR = 1.00, 95% CI 0.54-1.85; P = 1.0) or MI (OR 0.92, 95% CI 0.64-1.31; P = 0.6). Multivariate analysis confirmed results of univariate analysis.

CONCLUSIONS

This retrospective analysis of data collected from prospective, randomized, placebo-controlled studies in CABG shows that full-dose aprotinin use was associated with a lower risk of adverse cerebrovascular outcomes and a reduced need for use of vasoactive drugs; the risk of death and perioperative MI was not affected by aprotinin therapy.

Chemically Modified Tetracycline Improves Contractility in Porcine Coronary Ischemia/Reperfusion Injury

BACKGROUND

Reperfusion of ischemic myocardium has been implicated in extension of infarct size and deleterious clinical outcomes. Anti-inflammatory agents reduce this reperfusion injury. Chemically modified tetracycline-3 (CMT-3) (Collagenex Pharmaceuticals, Newtown, PA, USA) lacks antimicrobial properties yet retains anti-inflammatory activity. We examined infarct size and myocardial function in a porcine coronary artery occlusion/reperfusion model in CMT-3-treated and control animals.

METHODS

Yorkshire pigs (n = 8) underwent median sternotomy, pretreatment with heparin (300 U/kg and 67 U/kg/hr IV) and lidocaine (1 mg/kg IV) and were divided into two groups. Group one (n = 4) had the left anterior descending artery (LAD) occluded for 1 hour, after which it was reperfused for 2 hours. Group two (n = 4) had an identical protocol to group one except CMT-3 (2 mg/kg IV) was administered prior to occlusion of the LAD.

RESULTS

Animals receiving CMT-3 had significantly decreased infarct size in relation to the ventricular area-at-risk (AAR) (28 +/- 9% vs. 64 +/- 8%; p < 0.05). Myocardial contractile function was superior in the CMT-3 treatment, indicated by a higher cardiac index (2.9 +/- 0.3 vs. 2.0 +/- 0.3 L/min/m(2); p < 0.05) and stroke volume index (22 +/- 2 vs. 17 +/- 1 L/m(2)/beat; p < 0.05).

CONCLUSIONS

CMT-3 decreased infarct size in relation to the AAR resulting in relative preservation of contractility, suggesting CMT-3 may improve outcomes during myocardial ischemia reperfusion.

Preoperative White Blood Cell Count is Independently Associated With Higher Perioperative Cardiac Enzyme Release and Increased 1-Year Mortality After Coronary Artery Bypass Grafting

BACKGROUND

Elevated preprocedural systemic markers of inflammation, including white blood cell count, have been associated with adverse clinical outcomes after percutaneous coronary intervention. The relationship between preoperative white blood cell count and clinical outcomes after coronary artery bypass grafting is less clear despite increasing evidence that neutrophils participate in reperfusion injury. We sought to determine the relationship between preoperative white blood cell count and in hospital major morbidity and 1-year survival after coronary artery bypass grafting.

METHODS

We prospectively studied 3,024 consecutive isolated coronary artery bypass graft procedures. Preoperative white blood cell count was determined by automated counter, perioperative cardiac enzyme release by the creatine kinase-myocardial band isoenzyme, and all-cause mortality over the first postoperative year taken from a national death registry. Multivariate logistic regression and Cox proportional hazards analyses were performed.

RESULTS

Preoperative white blood cell count offered as a continuous variable and as five predetermined groups was independently associated with cardiac enzyme release three or more times the upper limit of the reference range (adjusted odds ratio = 1.5 per 10 x 10(9)/L increase, 95% confidence interval: 1.2 to 2.0, p = 0.002) and higher 1-year mortality (adjusted hazard ratio = 1.6 per 10 x 10(9)/L increase, 95% confidence interval: 1.2 to 2.1, p < 0.001).

CONCLUSIONS

Higher preoperative white blood cell count is independently associated with higher perioperative myonecrosis and 1-year mortality after coronary artery bypass grafting.

Aortic Valve Repair in a Patient with Congenital Afibrinogenemia

We describe the management of cardiopulmonary bypass (CPB) in a patient with congenital afibrinogenemia (AF). Although this state is akin to the state after hirudin administration, where CPB has been successfully performed, heparinization is still essential to preserve other clotting factors and prevent excessive bleeding. Aprotinin further helps in preservation of clotting factors. There are case reports of thrombosis associated with AF, but aprotinin can be safely used because it is, by definition, an anticoagulant. Cryoprecipitate effectively restores the fibrinogen and produces normal clotting.

The effect of aprotinin in a model of uncontrolled hemorrhagic shock

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Reduction of myocardial reperfusion injury by aprotinin after regional ischemia and cardioplegic arrest

BACKGROUND

Surgical coronary revascularization with cardiopulmonary bypass and cardioplegia has been associated with reperfusion injury. The serine protease inhibitor aprotinin has been suggested to reduce reperfusion injury, yet a clinically relevant study examining regional ischemia under conditions of cardiopulmonary bypass and cardioplegia has not been performed.

METHODS

Pigs were subjected to 30 minutes of regional myocardial ischemia by distal left anterior descending coronary artery occlusion, followed by 60 minutes of cardiopulmonary bypass with 45 minutes of cardioplegic arrest and 90 minutes of post-cardiopulmonary bypass reperfusion. The treatment group (n = 6) was administered aprotinin systemically (40,000 kallikrein-inhibiting units [KIU]/kg intravenous loading dose, 40,000 KIU/kg pump prime, and 10,000 KIU x kg(-1) x h(-1) intravenous continuous infusion). Control animals (n = 6) received crystalloid solution. Global and regional myocardial functions were analyzed by the left ventricular+dP/dt and the percentage segment shortening, respectively. Left ventricular infarct size was measured by tetrazolium staining. Tissue myeloperoxidase activity was measured. Myocardial sections were immunohistochemically stained for nitrotyrosine. Coronary microvessel function was studied by videomicroscopy.

RESULTS

Myocardial infarct size was decreased with aprotinin treatment (27.0% +/- 3.5% vs 45.3% +/- 3.0%, aprotinin vs control; P <.05). Myocardium from the ischemic territory showed diminished nitrotyrosine staining in aprotinin-treated animals versus controls, and this was significant by grade (1.3 +/- 0.2 vs 3.2 +/- 0.2, aprotinin vs control; P <.01). In the aprotinin group, coronary microvessel relaxation improved most in response to the endothelium-dependent agonist adenosine diphosphate (44.7% +/- 3.2% vs 19.7% +/- 1.7%, aprotinin vs control; P <.01). No significant improvements in myocardial function were observed with aprotinin treatment.

CONCLUSIONS

Aprotinin reduces reperfusion injury after regional ischemia and cardioplegic arrest. Protease inhibition may represent a molecular strategy to prevent postoperative myocardial injury after surgical revascularization with cardiopulmonary bypass.

Neutrophils both reduce and increase permeability in a cell culture model of the blood-brain barrier

This study was carried out to determine the effects that human neutrophils have on permeability across a model of the blood-brain barrier (BBB) formed by primary cultures of bovine brain microvessel endothelial cells (BBMEC). Transendothelial electrical resistance (TEER) was used to measure changes in permeability across BBMEC monolayers in a dual compartment system, during neutrophil interactions. When neutrophils (5 x 10(6)/ml) were applied to monolayers, TEER increased (permeability decreased). Adenosine was implicated, since the TEER increase was blocked by adenosine deaminase (1 U/ml) and the adenosine A2 receptor antagonist ZM 241385 (at 10(-6) M but not 10(-8) M, implicating A2B receptors). Oxygen free radicals were implicated as the TEER increase was blocked by combined catalase (100 U/ml) and superoxide dismutase (60 U/ml). When a gradient of the bacterial chemoattractant peptide formyl methionyl leucine phenylalanine (fMLP, 10(-7) M) was applied to neutrophils, the TEER decreased (permeability increased), concurrent with migration. When fMLP (10(-7) M) was added to the neutrophils, without migration, no change occurred. The TEER decrease was blocked by loading endothelium with the calcium buffer BAPTA (10 microM) and partially blocked by the serine protease inhibitor aprotinin (20 microg/ml). Measures to block the potential extracellular triggers heparin binding protein, glutamate, oxygen free radicals and binding to intercellular cell adhesion molecule-1 (ICAM-1) were ineffective. These data indicate that neutrophils both reduce and increase permeability in a cell culture model of the BBB, correlated to their proximity and migration through the endothelium. They explore the role of neutrophils in BBB breakdown, and the formation or amelioration of vasogenic cerebral edema.