Managing fibrinolysis without aprotinin

Intraoperative collection of autologous platelet-rich plasma from the cardiopulmonary bypass circuit upon initiation of extracorporeal circulation

Objectives

The aim of this study is to evaluate the possibility of the autologous platelet-rich plasma (PRP) collection from the cardiopulmonary bypass (CPB) circuit and to evaluate its effect on the aggregative function.

Methods

For seventy-two patients undergoing cardiac surgery with CPB, an autologous PRP was prepared using the Haemonetics Component Collection System® by drawing blood from the CPB circuit immediately after CPB was established. The blood samples were taken at three points for examination, A: beginning of surgery, B: immediately after heparin reversal with protamine following discontinuation of CPB, C: after the collected autologous PRP was returned to the patient. Platelet count and platelet aggregation ability were analyzed.

Results

The mean platelet count in autologous PRP was 5.5 (range: 3–14) units. Platelet count decreased by 115.0 (±27.3) × 1000/μl from A to B and increased by 27.3 ± 17.2 (× 1000/μl) from B to C.

When platelet aggregation was measured by Adenosine Diphosphate (ADP) 3.0 μM, it decreased by 42.6% ± 12.1% from A to B and increased by 8.7% ± 7.4% from B to C.

Conclusions

Autologous PRP can be safely collected by drawing blood from the CPB circuit, platelet count and aggregation ability significantly decreased after CPB including autologous PRP collection. Some improvement was detected in the number of the platelets count and platelet aggregation ability by administrating an autologous PRP even if autologous PRP is collected from CPB circuit.

Trial registration

UMI-CTR, UMIN000023776. Registered 1 October 2016.

Postoperative administration of tranexamic acid as approach to reduce blood loss after open-heart surgery

BACKGROUND: Tranexamic acid (TXA) reduces perioperative bleeding among patients undergoing heart surgery. It is uncertain whether its postoperative administration, after prior administration before cardiopulmonary bypass (CPB), has an additional benefit. OBJECTIVE: Our study aimed to evaluate whether the postoperative administration of TXA reduces the blood loss after heart surgery. METHODS: In a retrospective cohort study at the University Heart Center Dresden, patients who underwent on-pump open-heart surgery and received 1 g TXA before CPB were included. Patients with postoperative administration of 1 g TXA were compared to patients without. Primary endpoint was the postoperative blood loss within 24 hours. RESULTS: Among 2,179 patients undergoing heart surgery between 1 July 2013 and 31 October 2014, 92 (4.2%) received TXA postoperatively. After matching, 71 patients with postoperative administration of TXA were compared to 71 without (n = 142). Postoperative administration of TXA did not result in decreased blood loss (MD 146.7 mL; p = 0.064). There was no evidence of an increased risk for thromboembolic complications. CONCLUSIONS: The postoperative administration of TXA did not reduce blood loss. The use of TXA was shown to be safe in terms of thromboembolic events and hospital mortality. Unless there is no clear evidence, the postoperative administration of TXA should be restricted to patients with massive blood loss and signs of hyperfibrinolysis only.

The blood protective effect of autologous platelet separation in aortic dissection

OBJECTIVE

This study aimed to retrospectively analyze the blood protective effect of autologous platelet separation in operations for acute aortic dissection.

METHODS

A total of 130 patients with acute aortic dissection were enrolled into the present study. The average age of these patients was 52.962±10.5061 years old. These patients underwent the modified aortic arch replacement with the elephant trunk technique or endovascular aortic exclusion with covered stent. Among these patients, 68 patients who underwent autologous platelet separation were assigned to the platelet separation group, while the remaining patients were assigned to the control group. All operations were performed under deep hypothermic circulatory arrest. After anesthesia, 1-2 therapeutic doses of autologous platelets were isolated from patients in the platelet separation group, and these platelets were quickly infused back to these patients after heparin was neutralized by protamine at the end of the cardiopulmonary bypass. The preoperative and postoperative indexes in these two groups were compared.

RESULTS

There were no statistically significant differences in age, gender, smoking history, drinking history and hypertension history between these two groups. Compared with controls, the transfusion volume of allogeneic platelets in the perioperative period significantly decreased in the platelet separation group (1.919±1.6226 vs. 0.794±1.1789, P < #x003C;< #x200A;0.05), and the use rate of allogeneic platelets also significantly decreased (74.19% vs. 45.59%, P < #x003C;< #x200A;0.05).

CONCLUSION

The intraoperative auto transfusion of platelets significantly reduced the volume of allogeneic platelet transfusion after the operation for aortic dissection, which has a significant blood protective effect.

Effects of platelet-rich plasmapheresis during cardiovascular surgery: A meta-analysis of randomized controlled clinical trials

OBJECTIVE

This study aimed to explore the effects of platelet-rich plasmapheresis (PRP) on the amount of postoperative blood loss and the requirements for allogeneic fresh frozen plasma (FFP) and red blood cell (RBC) transfusions during cardiovascular surgery.

METHODS

A literature search of 7 online databases was conducted. Randomized control trials (RCT) comparing intraoperative PRP or appropriate control groups were considered suitable for this current study.

RESULTS

Fifteen RCTs enrolling a total of 1002 patients, including 501 patients who received PRP and 501 control patients. Meta-analysis of the data from these trials showed that PRP reduced the total volume of postoperative blood loss (standardized mean difference [SMD], -0.74; 95% confidence interval [CI], -1.18 to -0.31; P < 0.05), reduced postoperative fresh frozen plasma (FFP) transfusion (SMD, -0.38; 95%CI, -0.69 to -0.08; P < 0.05), reduced postoperative RBCs transfusion (SMD, -0.44; 95%CI, -0.77 to -0.10; P < 0.05), and reduced the proportion of patients receiving postoperative allogeneic RBC transfusions (relative risk [RR], 0.44; 95%CI, 0.21-0.91, P < 0.05) during cardiovascular surgery.

CONCLUSION

Conducting PRP before cardiopulmonary bypass (CPB) and transfusing autologous platelet-rich plasma (aPRP) after reversal of heparin could reduce postoperative blood loss, the requirements for blood products transfusion during cardiovascular surgery. A higher mean platelet count in aPRP may improve the final outcome. However, there was a high degree of undetermined heterogeneity among the analyzed trials, and larger and more precise RCTs are needed to confirm these conclusions.

Minimally invasive heart valve surgery: influence on coagulation and inflammatory response

OBJECTIVES

Minimally invasive valve surgery (MIVS) is associated with improved clinical outcome but longer cardiopulmonary bypass (CPB) time. The aim of the present study is to compare inflammatory and coagulation parameters in patients undergoing minimally invasive or standard valve surgery.

METHODS

A prospective non-randomized study was performed enrolling 79 patients undergoing mitral (20 right mini-thoracotomy and 18 standard sternotomy) and aortic valve (20 mini-sternotomy and 21 standard sternotomy) procedures. Blood samples were collected perioperatively to measure prothrombin fragment 1.2 (PF1.2, thrombin generation), plasmin antiplasmin complex (PAP, fibrinolysis), interleukin-6 (IL-6, inflammation). Plasma free haemoglobin (f-Hb) was assessed to evaluate haemolysis.

RESULTS

Patients in the minimally invasive group were younger and had less comorbidities CPB and cross-clamp times were comparable considering both aortic and mitral procedures, but longer in the mini-thoracotomy group. IL-6 and PAP were reduced in the minimally invasive group, particularly 2 h after CPB (respectively 102 ± 114 vs 34 ± 49 pg/ml, P < 0.001 and 2137 ± 1046 vs 1207 ± 675 ng/ml, P < 0.001), PF1.2 was also reduced during and after the operation (688 ± 514 vs 571 ± 470, P = 0.02; 1600 ± 1185 vs 1042 ± 548, P < 0.001; 1487 ± 676 vs 1042 ± 541). Despite the use of vacuum-assisted active venous drainage (VAVD) f-Hb was significantly reduced in the minimally invasive group. The other routine biomarkers such as C-reactive protein, fibrinogen and cTnI were also reduced in the minimally invasive group.

CONCLUSIONS

In a selected cohort of patients MIVS is associated to reduced inflammatory reaction and coagulopathy, supporting the clinical evidence of reduced postoperative bleeding and lower transfusion rate. Our data offer further suggestion supporting the adoption of minimally invasive approaches.

The hemostatic disturbance in patients with acute aortic dissection: A prospective observational study

Coagulopathy is still a frequent complication in the surgical treatment of acute aortic dissection. However, the physiopathology of surgically induced coagulopathy has never been systematically and comprehensively studied in patients with acute aortic dissection. The aim of the present study was to describe the perioperative hemostatic system in patients with acute aortic dissection.The 87 patients who underwent aortic arch surgery for acute Stanford type A aortic dissection from January 2013 to September 2015 were enrolled in this study. The perioperative biomarkers of hemostatic system were evaluated using standard laboratory tests and enzyme-linked immunosorbent assays (ELISAs) at 5 time points: anesthesia induction (T1), lowest nasopharyngeal temperature (T2), protamine reversal (T3), 4 hours after surgery (T4), and 24 hours after surgery (T5).The ELISAs biomarkers revealed activation of coagulation (thrombin-antithrombin III complex [TAT] and prothrombin fragment 1 + 2 [F1 + 2] were elevated), suppression of anticoagulation (antithrombin III [AT III] levels were depressed), and activation of fibrinolysis (plasminogen was decreased and plasmin-antiplasmin complex [PAP] was elevated). The standard laboratory tests also demonstrated that surgery resulted in a significant reduction in platelet counts and fibrinogen concentration.Systemic activation of coagulation and fibrinolysis, and inhibition of anticoagulation were observed during the perioperative period in patients with acute aortic dissection. Indeed, these patients exhibited consumption coagulopathy and procoagulant state perioperatively. Therefore, we believe that this remarkable disseminated intravascular coagulation (DIC)-like coagulopathy has a high risk of bleeding and may influence postoperative outcome of patients with acute aortic dissection.

Bleeding related to disturbed fibrinolysis

The components and reactions of the fibrinolysis system are well understood. The pathway has fewer reactants and interactions than coagulation, but the generation of a complete quantitative model is complicated by the need to work at the solid‐liquid interface of fibrin. Diagnostic tools to detect disease states due to malfunctions in the fibrinolysis pathway are also not so well developed as is the case with coagulation. However, there are clearly a number of inherited or acquired pathologies where hyperfibrinolysis is a serious, potentially life‐threatening problem and a number of antifibrinolytc drugs are available to treat hyperfibrinolysis. These topics will be covered in the following review.

Improving the Selectivity of Engineered Protease Inhibitors: Optimizing the P2 Prime Residue Using a Versatile Cyclic Peptide Library

Standard mechanism inhibitors are attractive design templates for engineering reversible serine protease inhibitors. When optimizing interactions between the inhibitor and target protease, many studies focus on the nonprimed segment of the inhibitor's binding loop (encompassing the contact β-strand). However, there are currently few methods for screening residues on the primed segment. Here, we designed a synthetic inhibitor library (based on sunflower trypsin inhibitor-1) for characterizing the P2' specificity of various serine proteases. Screening the library against 13 different proteases revealed unique P2' preferences for trypsin, chymotrypsin, matriptase, plasmin, thrombin, four kallikrein-related peptidases, and several clotting factors. Using this information to modify existing engineered inhibitors yielded new variants that showed considerably improved selectivity, reaching up to 7000-fold selectivity over certain off-target proteases. Our study demonstrates the importance of the P2' residue in standard mechanism inhibition and unveils a new approach for screening P2' substitutions that will benefit future inhibitor engineering studies.

Discovery and safety profiling of a potent preclinical candidate, (4-[4-[[(3R)-3-(hydroxycarbamoyl)-8-azaspiro[4.5]decan-3-yl]sulfonyl]phenoxy]-N-methylbenzamide) (CM-352), for the prevention and treatment of hemorrhage

Discovery of potent and safe therapeutics that improve upon currently available antifibrinolytics, e.g., tranexamic acid (TXA, 1) and aprotinin, has been challenging. Matrix metalloproteinases (MMPs) participate in thrombus dissolution. Then we designed a novel series of optimized MMP inhibitors that went through phenotypic screening consisting of thromboelastometry and mouse tail bleeding. Our optimized lead compound, CM-352 (2), inhibited fibrinolysis in human whole blood functional assays and was more effective than the current standard of care, 1, in the tail-bleeding model using a 30 000 times lower dose. Moreover, 2 reduced blood loss during liver hepatectomy, while 1 and aprotinin had no effect. Molecule 2 displayed optimal pharmacokinetic and safety profiles with no evidence of thrombosis or coagulation impairment. This novel mechanism of action, targeting MMP, defines a new class of antihemorrhagic agents without interfering with normal hemostatic function. Furthermore, 2 represents a preclinical candidate for the acute treatment of bleeding.

Fibrinolysis and the control of blood coagulation

Fibrin plays an essential role in hemostasis as both the primary product of the coagulation cascade and the ultimate substrate for fibrinolysis. Fibrinolysis efficiency is greatly influenced by clot structure, fibrinogen isoforms and polymorphisms, the rate of thrombin generation, the reactivity of thrombus-associated cells such as platelets, and the overall biochemical environment. Regulation of the fibrinolytic system, like that of the coagulation cascade, is accomplished by a wide array of cofactors, receptors, and inhibitors. Fibrinolytic activity can be generated either on the surface of a fibrin-containing thrombus, or on cells that express profibrinolytic receptors. In a widening spectrum of clinical disorders, acquired and congenital defects in fibrinolysis contribute to disease morbidity, and new assays of global fibrinolysis now have potential predictive value in multiple clinical settings. Here, we summarize the basic elements of the fibrinolytic system, points of interaction with the coagulation pathway, and some recent clinical advances.

A 2014 Update on Coagulation Management for Cardiopulmonary Bypass

Coagulopathy after cardiac surgery with cardiopulmonary bypass is a serious complication that may result in massive bleeding requiring transfusion of significant amounts of blood products, plasma, and platelets. In addition to increased patient morbidity and mortality it is associated with longer hospital stay and increased resource utilization. The current review discusses aspects in cardiopulmonary bypass–induced coagulopathy with emphasis on point-of-care testing and individualized “goal-directed” therapy in patients who develop excessive bleeding after cardiac surgery.

Major bleeding, transfusions, and anemia: the deadly triad of cardiac surgery

BACKGROUND

Postoperative bleeding is common after cardiac surgery. Major bleeding (MB) is a determinant of red blood cell (RBC) transfusion, especially in patients with preoperative anemia. Preoperative anemia and RBC transfusions are recognized risk factors for operative mortality. The present study investigates the role of MB as an independent determinant of operative mortality in cardiac surgery.

METHODS

A single-center retrospective study based on the institutional database of cardiac surgery in the period 2000-2012 was conducted. Sixteen thousand one hundred fifty-four (16,154) consecutive adult patients undergoing cardiac surgery were analyzed. The impact of postoperative bleeding and MB on operative (30 days) mortality was analyzed univariately and after correction for preoperative anemia, RBC transfusions, and other confounders.

RESULTS

Postoperative bleeding was significantly (p < 0.001) associated with operative mortality, both in univariate and multivariable models. The main complications associated with MB were thromboembolic complications, infections, and surgical reexploration. In a multivariable model, MB remained an independent predictor of operative mortality (odds ratio, 3.45; 95% confidence interval, 2.78 to 4.28). Preoperative anemia and RBC transfusions coexist in the model, acting with a multiplying effect when associated with MB.

CONCLUSIONS

Major bleeding is per se a risk factor for operative mortality. However, its deleterious effects are strongly enhanced by RBC transfusions and, to a lesser extent, preoperative anemia. Major bleeding is a partially modifiable risk factor, and adequate preemptive and treatment strategies should be applied to limit this event.

PAI-1 and t-PA/PAI-1 complex potential markers of fibrinolytic bleeding after cardiac surgery employing cardiopulmonary bypass

Background

Enhanced bleeding remains a serious problem after cardiac surgery, and fibrinolysis is often involved. We speculate that lower plasma concentrations of plasminogen activator inhibitor – 1 (PAI-1) preoperatively and tissue plasminogen activator/PAI-1 (t-PA/PAI-1) complex postoperatively might predispose for enhanced fibrinolysis and increased postoperative bleeding.

Methods

Totally 88 adult patients (mean age 66 ± 10 years) scheduled for cardiac surgery, were enrolled into a prospective study. Blood samples were collected pre-operatively, on admission to the recovery and at 6 and 24 hours postoperatively. Patients with a surgical bleeding that was diagnosed during reoperation were discarded from the study. The patients were allocated to two groups depending on the 24-hour postoperative chest tube drainage (CTD): Group I > 500ml, Group II ≤ 500ml. Associations between CTD, PAI-1, t-PA/PAI-1 complex and D-dimer were analyzed with SPSS.

Results

Nine patients were excluded because of surgical bleeding. Of the 79 remaining patients, 38 were allocated to Group I and 41 to Group II. The CTD volumes correlated with the preoperative plasma levels of PAI-1 (r = − 0.3, P = 0.009). Plasma concentrations of preoperative PAI-1 and postoperative t-PA/PAI-1 complex differed significantly between the groups (P < 0.001 and P = 0.012, respectively). Group I displayed significantly lower plasma concentrations of fibrinogen and higher levels of D-dimer from immediately after the operation and throughout the first 24 hours postoperatively.

Conclusions

Lower plasma concentrations of PAI-1 preoperatively and t-PA/PAI-1 complex postoperatively leads to higher plasma levels of D-dimer in association with more postoperative bleeding after cardiac surgery.

Early postoperative outcomes and blood product utilization in adult cardiac surgery: the post-aprotinin era

BACKGROUND

Aprotinin was a commonly used pharmacological agent for homeostasis in cardiac surgery but was discontinued, resulting in the extensive use of lysine analogues. This study tested the hypothesis that early postoperative adverse events and blood product utilization would affected in this post-aprotinin era.

METHODS AND RESULTS

Adult patients (n=781) undergoing coronary artery bypass, valve replacement, or both from November 1, 2005, to October 31, 2008, at a single institution were included. Multiple logistic regression modeling and propensity scoring were performed on 29 preoperative and intraoperative variables in patients receiving aprotinin (n=325) or lysine analogues (n=456). The propensity-adjusted relative risk (RR) for the intraoperative use of packed red blood cells (RR, 0.75; 95% confidence interval [CI], 0.57 to 0.99), fresh frozen plasma (RR, 0.37; 95% CI, 0.21 to 0.64), and cryoprecipitate (RR:0.06; 95% CI, 0.02 to 0.22) were lower in the aprotinin versus lysine analog group (all P<0.05). The risk for mortality (RR, 0.53; 95% CI, 0.16 to 1.79) and neurological events (RR, 0.87; 95% CI, 0.35 to 2.18) remained similar between groups, whereas a trend for reduced risk for renal dysfunction was observed in the aprotinin group.

CONCLUSIONS

In the post-aprotinin era, with the exclusive use of lysine analogues, the relative risk of early postoperative outcomes such as mortality and renal dysfunction have not improved, but the risk for the intraoperative use of blood products has increased. Thus, improvements in early postoperative outcomes have not been realized with the discontinued use of aprotinin, but rather increased blood product use has occurred with the attendant costs and risks inherent with this strategy.

The coagulopathy of cardiopulmonary bypass

There have been numerous publications on the coagulopathy of cardiopulmonary bypass (CPB). This review provides an introduction to the history and main components of current CPB circuits and summarizes the current knowledge of pathogenesis, prevention, and treatment of the CPB coagulopathy. It encompasses an overview of intra- and postoperative monitoring of coagulation with special emphasis on the near-patient testing, its main complications, and the transfusion support, while taking into account the major changes in the technology used and supportive care provided since its inception.

Continuous localized monitoring of plasmin activity identifies differential and regional effects of the serine protease inhibitor aprotinin: relevance to antifibrinolytic therapy

BACKGROUND

Antifibrinolytic therapy, such as the use of the serine protease inhibitor aprotinin, was a mainstay for hemostasis after cardiac surgery. However, aprotinin was empirically dosed, and although the pharmacological target was the inhibition of plasmin activity (PLact), this was never monitored, off-target effects occurred, and led to withdrawn from clinical use. The present study developed a validated fluorogenic microdialysis method to continuously measure PLact and tested the hypothesis that standardized clinical empirical aprotinin dosing would impart differential and regional effects on PLact.

METHODS/RESULTS

Pigs (30 kg) were instrumented with microdialysis probes to continuously measure PLact in myocardial, kidney, and skeletal muscle compartments (deltoid) and then randomized to high-dose aprotinin administration (2 mKIU load/0.5 mKIU/hr infusion; n = 7), low-dose aprotinin administration (1 mKIU load/0.250 mKIU/hr infusion; n = 6). PLact was compared with time-matched vehicle (n = 4), and PLact was also measured in plasma by an in vitro fluorogenic method. Aprotinin suppressed PLact in the myocardium and kidney at both high and low doses, indicative that both doses exceeded a minimal concentration necessary for PLact inhibition. However, differential effects of aprotinin on PLact were observed in the skeletal muscle, indicative of different compartmentalization of aprotinin.

CONCLUSIONS

Using a large animal model and a continuous method to monitor regional PLact, these unique results demonstrated that an empirical aprotinin dosing protocol causes maximal and rapid suppression in the myocardium and kidney and in turn would likely increase the probability of off-target effects and adverse events. Furthermore, this proof of principle study demonstrated that continuous monitoring of determinants of fibrinolysis might provide a novel approach for managing fibrinolytic therapy.

Interstitial plasmin activity with epsilon aminocaproic acid: temporal and regional heterogeneity

BACKGROUND

Epsilon aminocaproic acid (EACA) is used in cardiac surgery to modulate plasmin activity (PLact). The present study developed a fluorogenic-microdialysis system to measure in vivo region specific temporal changes in PLact after EACA administration.

METHODS

Pigs (25 to 35 kg) received EACA (75 mg/kg, n = 7) or saline in which microdialysis probes were placed in the liver, myocardium, kidney, and quadricep muscle. The microdialysate contained a plasmin-specific fluorogenic peptide and fluorescence emission, which directly reflected PLact, determined at baseline, 30, 60, 90, and 120 minutes after EACA/vehicle infusion.

RESULTS

Epsilon aminocaproic acid caused significant decreases in liver and quadricep PLact at 60, 90, 120 minutes, and at 30, 60, and 120 minutes, respectively (p < 0.05). In contrast, EACA induced significant biphasic changes in heart and kidney PLact profiles with initial increases followed by decreases at 90 and 120 minutes (p < 0.05). The peak EACA interstitial concentrations for all compartments occurred at 30 minutes after infusion, and were fivefold higher in the renal compartment and fourfold higher in the myocardium, when compared with the liver or muscle (p < 0.05).

CONCLUSIONS

Using a large animal model and in vivo microdialysis measurements of plasmin activity, the unique findings from this study were twofold. First, EACA induced temporally distinct plasmin activity profiles within the plasma and interstitial compartments. Second, EACA caused region-specific changes in plasmin activity profiles. These temporal and regional heterogeneic effects of EACA may have important therapeutic considerations when managing fibrinolysis in the perioperative period.