Comparison of streptokinase, urokinase, and recombinant tissue plasminogen activator in an in vitro model of venous thrombolysis

Urokinase versus Alteplase in Patients with Intermediate-High-Risk Pulmonary Embolism Treated with Ultrasound-Accelerated Endovascular Thrombolysis

BACKGROUND

Ultrasound-accelerated thrombolysis (USAT) is a safe and effective treatment for patients with intermediate-high-risk pulmonary embolism (PE). In all studies investigating USAT in the setting of PE, the recombinant tissue-plasminogen activator (rt-PA) alteplase or actilyse was used. Currently, there is a shortage of alteplase (Alteplase, Boehringer Ingelheim) in Europe. It is unknown whether the efficacy of urokinase (UK) is comparable with alteplase for USAT in patients with PE.

METHODS

Patients with intermediate-high-risk PE undergoing USAT with urokinase and alteplase were included in this study. One-to-one nearest neighbour matching was performed to account for baseline differences. We identified one patient treated with USAT and UK (n = 9) for each patient treated with USAT and alteplase (n = 9).

RESULTS

A total of 56 patients underwent USAT. The treatment was successful in all patients. The propensity score matched the identified nine pairs of patients. There were no statistically significant differences in the change in right ventricle-to-left ventricle (RV/LV) ratio (0.4 ± 0.3 versus 0.5 ± 0.4, p = 0.54), systolic pulmonary artery pressure (17.3 ± 8.0 versus 18.1 ± 8.1, p = 0.17), or improvement of RV function (5.8 ± 3.8 versus 5.1 ± 2.6, p = 1.0). The complication rates were comparable (11% in both groups, p = 0.55). There were no deaths in hospital or during 90 days in either group.

CONCLUSIONS

In this case-matched comparison, the short-term clinical and echocardiographic outcomes showed comparable results between USAT-UK and USAT-rt-PA.

How do i salvage that flap?; An evidence-based primer on salvage techniques for head & neck microvascular free flaps

Interventional strategies for dealing with microvascular free flap failure are varied among institutions and even individual surgeons. This systematic review aims to identify the published methods for salvaging a failing free flap and provide surgeons with a comprehensive toolset for successful intervention. A title and abstract search of the PubMed, Embase, and Web of Science databases was performed. 1694 abstracts were screened by three reviewers according to Prisma guidelines. 62 full text articles meeting inclusion criteria detailed techniques which were separated into the categories of thrombectomy, thrombolysis, leech therapy, vascular fistula, and an "other" category outlining techniques which did not fit into the prior framework. Assessment of the efficacy of individual salvage techniques is limited due to limited empirical data, however, the approach to successful salvage should be based on timely identification of flap compromise, followed by the implementation of one or several of the aforementioned techniques.

Current Perspectives on the Physiological Activities of Fermented Soybean-Derived Cheonggukjang

Cheonggukjang (CGJ, fermented soybean paste), a traditional Korean fermented dish, has recently emerged as a functional food that improves blood circulation and intestinal regulation. Considering that excessive consumption of refined salt is associated with increased incidence of gastric cancer, high blood pressure, and stroke in Koreans, consuming CGJ may be desirable, as it can be made without salt, unlike other pastes. Soybeans in CGJ are fermented by Bacillus strains (B. subtilis or B. licheniformis), Lactobacillus spp., Leuconostoc spp., and Enterococcus faecium, which weaken the activity of putrefactive bacteria in the intestines, act as antibacterial agents against pathogens, and facilitate the excretion of harmful substances. Studies on CGJ have either focused on improving product quality or evaluating the bioactive substances contained in CGJ. The fermentation process of CGJ results in the production of enzymes and various physiologically active substances that are not found in raw soybeans, including dietary fiber, phospholipids, isoflavones (e.g., genistein and daidzein), phenolic acids, saponins, trypsin inhibitors, and phytic acids. These components prevent atherosclerosis, oxidative stress-mediated heart disease and inflammation, obesity, diabetes, senile dementia, cancer (e.g., breast and lung), and osteoporosis. They have also been shown to have thrombolytic, blood pressure-lowering, lipid-lowering, antimutagenic, immunostimulatory, anti-allergic, antibacterial, anti-atopic dermatitis, anti-androgenetic alopecia, and anti-asthmatic activities, as well as skin improvement properties. In this review, we examined the physiological activities of CGJ and confirmed its potential as a functional food.

Noninvasive thrombectomy of graft by nano-magnetic ablating particles

Artificial vascular treatment is an emerging interdisciplinary subject of medicine. Although the use of artificial vessels has led to many successful advancements, blood clotting remains a major challenge, especially in terms of mural clots created along the vessel wall that do not completely block the vessel. The main objective of this study is to present a method for declotting artificial vessels. This research introduces a novel thrombectomy technique in artificial vessels by employing nano-magnetic particles under a rotating magnetic field to remove mural clots in artificial vessels. A mathematical model describes the relationship between process parameters. In vitro tests confirm the feasibility of nano-magnetic thrombectomy in cleaning and declotting artificial vessels. The results show that the clot fragments are nano-sized, which eliminates the risk of distal emboli as a concern of using current atherectomy techniques. Meanwhile, no damage to the artificial vessels is observed. The results show that the frequency of rotating the magnetic field has the greatest effect on clot removal. The conceptual principles stated in this study also have the potential to be used in other vascular depositions, such as the accumulation of lipids, and calcification atherosclerosis.

Fibrinolytic-Facilitated Chronic Subdural Hematoma Drainage-A Systematic Review

BACKGROUND

The current treatment options for chronic subdural hematoma (CSDH) include burr hole drainage, twist drill drainage, and craniotomy with or without postoperative catheter drainage. Although generally effective, these treatments have continued to be complicated by recurrence, especially in partially hemolyzed or septated hematomas. Recently, interest in the use of fibrinolytic agents as an adjunct to surgical treatment to address this limitation has been increasing. We conducted a systematic review, focusing on the efficacy and safety profile of fibrinolytic agents and compared the different fibrinolytic agents.

METHODS

The PubMed, EMBASE, CINAHL Plus, and Cochrane Library databases were searched for trials relevant to fibrinolytic administration in the treatment of CSDH. The findings are reported in accordance with the PRISMA (preferred reporting items for systematic reviews and meta-analyses) guidelines. The data from 1702 subjects from 6 retrospective observational studies were qualitatively analyzed. In addition, we included 11 case series and reports for discussion.

RESULTS

For 1449 patients, the use of urokinase or tissue plasminogen activator improved hematoma drainage and shortened the hospital stay (7.04 days), with an overall hematoma recurrence rate of 1.59%. The incidence of infection, seizure, and intracranial bleeding was 3.18%, 0.80%, and 0.41%, respectively, which compared favorably with previously reported findings for surgical drainage without the use of fibrinolytic agents.

CONCLUSIONS

The routine use of intrathecal urokinase and tissue plasminogen activator could be a new direction in the management of CSDH. Conclusive clinical evidence is lacking, however, and further prospective controlled studies are warranted to confirm the benefit and safety of this treatment strategy and to identify the optimal agent and dosing regimen.

Thrombus Imaging Using 3D Printed Middle Cerebral Artery Model and Preclinical Imaging Techniques: Application to Thrombus Targeting and Thrombolytic Studies

Diseases with the highest burden for society such as stroke, myocardial infarction, pulmonary embolism, and others are due to blood clots. Preclinical and clinical techniques to study blood clots are important tools for translational research of new diagnostic and therapeutic modalities that target blood clots. In this study, we employed a three-dimensional (3D) printed middle cerebral artery model to image clots under flow conditions using preclinical imaging techniques including fluorescent whole-body imaging, magnetic resonance imaging (MRI), and computed X-ray microtomography (microCT). Both liposome-based, fibrin-targeted, and non-targeted contrast agents were proven to provide a sufficient signal for clot imaging within the model under flow conditions. The application of the model for clot targeting studies and thrombolytic studies using preclinical imaging techniques is shown here. For the first time, a novel method of thrombus labeling utilizing barium sulphate (Micropaque^®) is presented here as an example of successfully employed contrast agents for in vitro experiments evaluating the time-course of thrombolysis and thus the efficacy of a thrombolytic drug, recombinant tissue plasminogen activator (rtPA). Finally, the proof-of-concept of in vivo clot imaging in a middle cerebral artery occlusion (MCAO) rat model using barium sulphate-labelled clots is presented, confirming the great potential of such an approach to make experiments comparable between in vitro and in vivo models, finally leading to a reduction in animals needed.

Prospective Audit to Study urokinaSe use to restore Patency in Occluded centRal venous caTheters in haematology and oncology patients (PASSPORT 2)

BACKGROUND

Central venous catheter dysfunction may be associated with intraluminal clots, drug precipitates and lipid residues or extra luminal causes such as fibroblastic sleeve, tip malposition, pinch-off syndrome and venous thrombosis at the tip of central venous catheter. Failure to restore patency after addressing these causes, empirical treatment with thrombolytic agents should be considered. Urokinase is used widely as a thrombolytic agent but very few outcome studies have been published.

METHODS

A multicentre group conducted a prospective audit of management of central venous catheter dysfunction after exclusion of common causes using in centre standardised doses of urokinase from September 2017 to February 2018 in haematology and oncology units. Data of catheter blood flow were collected anonymously following administration of 5000- to 25,000-IU urokinase in dysfunctional central venous catheter.

RESULTS

A total of 117 patients were recruited from eight centres, 54 females and 63 males, median age was 60 (46-68). In total, 53% presented as partial withdrawal occlusion and 47% total occlusion. In partial withdrawal occlusion, patency was restored in 80% of interventions, in 82% of interventions using push lock and in 76% using dwell lock. In total occlusion, patency was restored in 88% of the interventions. The central venous catheter clearance rate was dose dependent; patency was restored in 83% of central venous catheter with 5000 IU, 89% with 10,000 IU and 92% with high dose of 25,000 IU. No adverse events were recorded.

CONCLUSION

In this study, treatment of dysfunctional central venous catheter using standardised urokinase doses was safe and effective in restoring patency when no other mechanical causes could account for central venous catheter dysfunction.

Breaking the vicious loop between inflammation, oxidative stress and coagulation, a novel anti-thrombus insight of nattokinase by inhibiting LPS-induced inflammation and oxidative stress

Thrombosis is a principle cause of cardiovascular disease, the leading cause of morbidity and mortality worldwide; however, the conventional anti-thrombotic approach often leads to bleeding complications despite extensive clinical management and monitoring. In view of the intense crosstalk between inflammation and coagulation, plus the contributing role of ROS to both inflammation and coagulation, it is highly desirable to develop safer anti-thrombotic agent with preserved anti-inflammatory and anti-oxidative stress activities. Nattokinase (NK) possesses many beneficial effects on cardiovascular system due to its strong thrombolytic and anticoagulant activities. Herein, we demonstrated that NK not only effectively prevented xylene-induced ear oedema in mice, but also remarkably protected against LPS-induced acute kidney injury in mice through restraining inflammation and oxidative stress, a central player in the initiation and progression of inflammation. Fascinatingly, in line with our in vivo data, NK elicited prominent anti-inflammatory activity in RAW264.7 macrophages via suppressing the LPS-induced TLR4 and NOX2 activation, thereby repressing the corresponding ROS production, MAPKs activation, and NF-κB translocation from the cytoplasm to the nucleus, where it mediates the expression of pro-inflammatory mediators, such as TNF-α, IL-6, NO, and PAI-1 in activated macrophage cells. In particular, consistent with the macrophage studies, NK markedly inhibited serum PAI-1 levels induced by LPS, thereby blocking the deposition of fibrin in the glomeruli of endotoxin-treated animals. In summary, we extended the anti-thrombus mechanism of NK by demonstrating the anti-inflammatory and anti-oxidative stress effects of NK in ameliorating LPS-activated macrophage signaling and protecting against LPS-stimulated AKI as well as glomeruler thrombus in mice, opening a comprehensive anti-thrombus strategy by breaking the vicious cycle between inflammation, oxidative stress and thrombosis.

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NK protects against LPS-induced AKI via inhibiting inflammation and oxidative stress.

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NK inhibits LPS-induced TRL4 and NOX2 activation in macrophages.

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NK inhibits inflammation and oxidative stress both in vitro and in vivo.

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NK inhibits LPS-induced PAI-I levels, thereby blocking glomerular thrombus in mice.

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NK may break the vicious loop between inflammation, oxidative stress and coagulation.

In-Vitro Study of Urokinase Thrombolysis Following Stereotactic Aspiration of Intracerebral Hematoma

Objective

A consensus regarding the ideal regimen for urokinase (UK) thrombolysis subsequent to stereotactic spontaneous intracerebral hemorrhage aspiration has yet to be established. The purpose of this study is to evaluate the efficacy of UK thrombolysis relative to when the regimen is changed.

Methods

Venous blood from 30 heathy volunteers was obtained for this in-vitro study. Various concentrations of UK solution were added to microcentrifuge tubes containing the clotted blood. The efficacy of UK thrombolysis was identified by checking the weight of lysed hematoma following various time intervals with different concentrations of UK solution. Group one, the “3×4” group involved four administrations every 3 hours over 12 hours, and group two, the “6×2” group involved two administrations every 6 hours over 12 hours.

Results

More hematoma was lysed in the 3×4 group than the 6×2 group across all concentration levels (however, the differences were only significant between groups at the 500 and 1000 IU concentration levels, p<0.05). There were no significant differences of lysed hematoma among the various UK solution concentrations within groups.

Conclusion

This study suggests that frequent administrations of UK thrombolysis may result in a greater degree of lysed hematoma in comparison to a higher concentration of UK.

A bioinspired hyperthermic macrophage-based polypyrrole-polyethylenimine (Ppy-PEI) nanocomplex carrier to prevent and disrupt thrombotic fibrin clots

Fibrinolytic treatments for venous or arterial thrombotic syndromes using systemic administration of thrombolytics, such as streptokinase, can induce life-threatening bleeding complications. In this study, we offer the first proof of concept for a targeted photothermal fibrin clot prevention and reduction technology using macrophages loaded with polypyrrole-polyethylenimine nanocomplexes (Ppy-PEI NCs) and subjected to near-infrared radiation (NIR). We first show that the developed Ppy-PEI NCs could be taken up by defensive macrophages in vitro through endocytosis. The Ppy-PEI NCs generated local hyperthermia upon NIR treatment, which appeared to produce reactive oxygen species in Ppy-PEI NC-loaded macrophages. Preliminary evidence of efficacy as an antithrombotic tool is provided, in vitro, using fibrinogen-converted fibrin clots, and in vivo, in a rat femoral vascular thrombosis model generated by exposure to ferric chloride substance. The in vivo biocompatibility, photothermal behavior, biodistribution, and histological observation of cellular interactions with the Ppy-PEI NCs in the rat model provide rationale in support of further preclinical studies. This Ppy-PEI NC/NIR-based method, which uses a unique macrophage-guided targeting approach to prevent and lyse fibrin clots, may potentially overcome some of the disadvantages of current thrombolytic treatments. STATEMENT OF SIGNIFICANCE: Fibrinolytic treatments for venous or arterial thrombotic syndromes using systemic administration of thrombolytics, such as streptokinase, can induce life-threatening bleeding complications. In this study, we offer the first proof of concept for a targeted photothermal fibrin clot reduction technology using macrophages loaded with polypyrrole-polyethylenimine nanocomplexes (Ppy-PEI NCs) and subjected to near-infrared radiation (NIR). We first show that the developed Ppy-PEI NCs can be taken up by defensive macrophages in vitro through endocytosis. The Ppy-PEI NCs generated local hyperthermia upon NIR treatment, which appeared to produce reactive oxygen species in Ppy-PEI NC-loaded macrophages. Preliminary evidence of efficacy as an antithrombotic tool is provided, in vitro, using fibrinogen-converted fibrin clots, and in vivo, in a rat femoral vascular thrombosis model generated by exposure to ferric chloride substance. The in vivo biocompatibility, photothermal behavior, biodistribution, and histological observation of cellular interactions with the Ppy-PEI NCs in the rat model provide rationale in support of further preclinical studies. This Ppy-PEI NC/NIR-based method, which uses a unique macrophage-guided targeting approach to disintegrate fibrin clots, may potentially overcome some of the disadvantages of current thrombolytic treatments.

Prospective Audit to Study urokinaSe use to restore Patency in Occluded centRal venous caTheters (PASSPORT 1)

OBJECTIVES

Tunnelled central venous catheters dysfunction can be defined as failure to provide blood flow above 200 mL/min during dialysis often caused by thrombosis. Although urokinase is used routinely for thrombolysis, there is wide variation in dose regimens. A multidisciplinary group was formed to address this issue and offer guidance.

METHODS

Dialysis centres that used urokinase in the United Kingdom took part in a prospective study to determine the safety and outcomes of thrombolysis using agreed protocols. Data were collected anonymously from September 2017 until February 2018. Catheter blood flow was measured before and after the following interventions: catheter dwell or push locks with 12,500-50,000 IU or catheter infusion with 100,000-250,000 IU of urokinase. Interventions were repeated if the blood flow remained below 200 mL/min.

RESULTS

10 centres took part and recruited 200 patients; 45.5% were female and 54.5% were male with mean age of 63.6 (±15.2) years. The cumulative success rate for thrombolysis was 90.5% after first intervention, 97% after second intervention, and 99% after more than 2 interventions. Although there was trend towards benefit with dose increments, the success rate between push/dwell locks and high-dose infusion of urokinase was not significantly different (p = 0.069). Seventeen (8.5%) tunnelled central venous catheters were removed due to failure of treatment. No urokinase-related adverse events were reported.

CONCLUSION

In this study, urokinase was safe and efficacious; there was no difference between dwell and push locks. There was some benefit with high-dose infusion of urokinase compared to the dwell and push lock.

Pulmonary embolism management in the critical care setting

The American Heart Association (AHA) categorizes pulmonary embolism (PE) into three main categories based on the presence or absence of hemodynamic changes and evidence of right ventricular dysfunction. The AHA characterizes massive PE as occurring in the setting of persistent hypotension, profound bradycardia, or pulselessness; submassive PE as occurring with evidence of right ventricular dysfunction or myocardial necrosis in the absence of hemodynamic changes; and low-risk PE as occurring in the absence of markers of massive and submassive PE. This chapter provides an overview of how to identify and manage patients with submassive and massive pulmonary embolism. Delivery planning considerations are discussed. We also address the management of critically ill obstetric patients with respect to VTE risk. The American Heart Association (AHA) categorizes pulmonary embolism (PE) into three main categories based on the presence or absence of hemodynamic changes and evidence of right ventricular dysfunction. The AHA characterizes massive PE as occurring in the setting of persistent hypotension, profound bradycardia, or pulselessness; submassive PE as occurring with evidence of right ventricular dysfunction or myocardial necrosis in the absence of hemodynamic changes; and low-risk PE as occurring in the absence of markers of massive and submassive PE.¹ This chapter provides an overview of how to identify and manage patients with submassive and massive pulmonary embolism. Delivery planning considerations are discussed. We also address the management of critically ill obstetric patients with respect to VTE risk.

Small Molecule Catalysts with Therapeutic Potential

Catalysts are employed in many areas of research and development where they combine high efficiency with often astonishing selectivity for their respective substrates. In biology, biocatalysts are omnipresent. Enzymes facilitate highly controlled, sophisticated cellular processes, such as metabolic conversions, sensing and signalling, and are prominent targets in drug development. In contrast, the therapeutic use of catalysts per se is still rather limited. Recent research has shown that small molecule catalytic agents able to modulate the redox state of the target cell bear considerable promise, particularly in the context of inflammatory and infectious diseases, stroke, ageing and even cancer. Rather than being "active" on their own in a more traditional sense, such agents develop their activity by initiating, promoting, enhancing or redirecting reactions between biomolecules already present in the cell, and their activity therefore depends critically on the predisposition of the target cell itself. Redox catalysts, for instance, preferably target cells with a distinct sensitivity towards changes in an already disturbed redox balance and/or increased levels of reactive oxygen species. Indeed, certain transition metal, chalcogen and quinone agents may activate an antioxidant response in normal cells whilst at the same time triggering apoptosis in cancer cells with a different pre-existing "biochemical redox signature" and closer to the internal redox threshold. In pharmacy, catalysts therefore stand out as promising lead structures, as sensor/effector agents which are highly effective, fairly selective, active in catalytic, i.e., often nanomolar concentrations and also very flexible in their structural design.

Pediatric Thrombolysis: A Practical Approach

The incidence of pediatric venous thromboembolic disease is increasing in hospitalized children. While the mainstay of treatment of pediatric thrombosis is anticoagulation, reports on the use of systemic thrombolysis, endovascular thrombolysis, and mechanical thrombectomy have steadily been increasing in this population. Thrombolysis is indicated in the setting of life- or limb-threatening thrombosis. Thrombolysis can rapidly improve venous patency thereby quickly ameliorating acute signs and symptoms of thrombosis and may improve long-term outcomes such as postthrombotic syndrome. Systemic and endovascular thrombolysis can result in an increase in minor bleeding in pediatric patients, compared with anticoagulation alone, and major bleeding events are a continued concern. Also, endovascular treatment is invasive and requires technical expertise by interventional radiology or vascular surgery, and such expertise may be lacking at many pediatric centers. The goal of this mini-review is to summarize the current state of knowledge of thrombolysis/thrombectomy techniques, benefits, and challenges in pediatric thrombosis.

Comparative study on the inhibition of plasmin and delta-plasmin via benzamidine derivatives

The potent fibrinolytic enzyme, plasmin has numerous clinical applications for recannulizing vessels obstructed by thrombus. Despite its diminutive size, 91 kDa, success in the recombinant expression of this serine protease has been limited. For this reason, a truncated non-glycosylated plasmin variant was developed capable of being expressed and purified from E. coli. This mutated plasmin, known as δ-plasmin, eliminates four of the five kringle domains present on native plasmin, retaining only kringle 1 fused directly to the unmodified catalytic domain of plasmin. This study demonstrates that δ-plasmin exhibits similar kinetic characteristics to full length plasmin despite its heavily mutated form; KM = 268.78 ± 19.12, 324.90 ± 8.43 μM and Kcat = 770.48 ± 41.73, 778.21 ± 1.51 1/min for plasmin and δ-plasmin, respectively. A comparative analysis was also carried out to investigate the inhibitory effects of a range of benzamidine based small molecule inhibitors: benzamidine, p-aminobenzamidine, 4-carboxybenzamidine, 4-aminomethyl benzamidine, and pentamidine. All of the small molecule inhibitors, with the exception of unmodified benzamidine, demonstrated comparable competitive inhibition constants (Ki) for both plasmin and δ-plasmin ranging from Ki < 4 μM for pentamidine to Ki > 1000 μM in the case of aminomethyl benzamidine. This result further supports that δ-plasmin retains much of the same functionality as native plasmin despite its greatly reduced size and complexity. This study serves the purpose of demonstrating the tunable inhibition of plasmin and δ-plasmin with potential applications for the improved clinical delivery of δ-plasmin to treat various thrombi.

Support vector machine (SVM) based multiclass prediction with basic statistical analysis of plasminogen activators

Background

Plasminogen (Pg), the precursor of the proteolytic and fibrinolytic enzyme of blood, is converted to the active enzyme plasmin (Pm) by different plasminogen activators (tissue plasminogen activators and urokinase), including the bacterial activators streptokinase and staphylokinase, which activate Pg to Pm and thus are used clinically for thrombolysis. The identification of Pg-activators is therefore an important step in understanding their functional mechanism and derives new therapies.

Methods

In this study, different computational methods for predicting plasminogen activator peptide sequences with high accuracy were investigated, including support vector machines (SVM) based on amino acid (AC), dipeptide composition (DC), PSSM profile and Hybrid methods used to predict different Pg-activators from both prokaryotic and eukaryotic origins.

Results

Overall maximum accuracy, evaluated using the five-fold cross validation technique, was 88.37%, 84.32%, 87.61%, 85.63% in 0.87, 0.83,0.86 and 0.85 MCC with amino (AC) or dipeptide composition (DC), PSSM profile and Hybrid methods respectively. Through this study, we have found that the different subfamilies of Pg-activators are quite closely correlated in terms of amino, dipeptide, PSSM and Hybrid compositions. Therefore, our prediction results show that plasminogen activators are predictable with a high accuracy from their primary sequence. Prediction performance was also cross-checked by confusion matrix and ROC (Receiver operating characteristics) analysis. A web server to facilitate the prediction of Pg-activators from primary sequence data was implemented.

Conclusion

The results show that dipeptide, PSSM profile, and Hybrid based methods perform better than single amino acid composition (AC). Furthermore, we also have developed a web server, which predicts the Pg-activators and their classification (available online at http://mamsap.it.deakin.edu.au/plas_pred/home.html). Our experimental results show that our approaches are faster and achieve generally a good prediction performance.

Medical therapy for ischemic stroke: review of intravenous and intra-arterial treatment options

BACKGROUND

Thrombolytic therapy is of proven and substantial benefit for select patients with acute cerebral ischemia. Diagnostic options and medical treatment options for acute stroke ischemia have undergone enormous changes in the past decades. Whereas initially stroke treatment was reduced to prevention, management of symptoms, and rehabilitation, nowadays a multitude of different fibrinolytic drugs are available. The wide availability of computed tomography in the late 1980s made thrombolysis a real therapeutic option because it allowed a fast and accurate differentiation between ischemic and hemorrhagic stroke.

METHODS

This study reviews these developments and how they have shaped our current use and understanding of thrombolytics in the treatment of acute ischemic stroke.

RESULTS

Patient selection remains a central aspect of thrombolytic treatment, and to date, the use of different fibrinolytics has been studied in over 20 large randomized trials for different clinical settings, time windows, and routes of administration. These studies included over 7000 patients, and led to our current understanding of the use of thrombolysis in acute stroke.

CONCLUSIONS

Intravenous fibrinolytic therapy within the first 3 hours of ischemic stroke onset offers substantial benefits for virtually all patients with potentially disabling deficits. In the 3- to 4.5-hour treatment window, intravenous fibrinolytic therapy has been shown to offer moderate net benefits when applied to all patients with potentially disabling deficits. Intra-arterial fibrinolytic therapy in the 3- to 6-hour window offers moderate net benefits when applied to all patients with potentially disabling deficits and large-artery cerebral thrombotic occlusions.

Whole blood clot dissolution: in vitro study on the effects of permeation pressure

Dissolution of a blood clot in thrombolytic procedure is affected by permeation of a thrombolytic agent into a clot, and permeation of plasminogen activator into a clot is dependent on the permeation pressure. A controlled experimental study on the effects of permeation pressure on clot lysis was carried out. The effects of intra-thrombus perfusion on thrombolyis were also explored. In vitro clot lysis tests were performed for perfusion pressures of 0, 1, and 10 kPa. Two perfusion media were used: buffer and urokinase solution. Clot lysis by diffusion was enhanced in urokinase solution compared with buffer solution, but the effects of perfusion medium were not significant in pressurized perfusion. Clot lysis was accelerated with the perfusion pressure in the early stage of perfusion, but the pressure effect on thrombolysis was not significant in the later stage (after 2 h). Intra-thrombus perfusion was more efficient in clot lysis than surface perfusion was. It is suggested that fluid flow inside the thrombus should be the most important factor in thrombolytic therapy.

Numerical analysis of forced injection of enzyme during thrombolysis

Numerical analysis was performed on the enzyme transport and the flow fields in order to predict the effectiveness of forced injection in thrombolytic therapy. The species and momentum transport equations were numerically solved for the case of uniform perfusion of enzyme into the fibrin clot, and the validity of our methods were verified. In order to predict the lysis efficiency of continuous and forced intermittent injections, enzyme perfusion and clot lysis were simulated for the different injection velocities and frequencies. Intermittent injection showed faster clot lysis compared to continuous perfusion, and lysis efficiency was increased as the injection velocity and period increased.

Peripheral Arteries: Treatment with Antibodies of Platelet Receptors and Reteplase for Thrombolysis—APART Trial

PURPOSE

To prospectively compare the safety and efficacy of combination therapy with the glycoprotein IIb/IIIa antagonist abciximab plus the third-generation thrombolytic agent reteplase versus those of therapy with the standard thrombolytic agent urokinase plus abciximab.

MATERIALS AND METHODS

The study was approved by the local ethics committee, and patient informed consent was obtained. Patients with peripheral arterial occlusions less than 60 days old (n=120) were enrolled in the study: 50 patients (32 men, 18 women; mean age, 67 years; range, 23-88 years) received reteplase plus abciximab and 70 patients (36 men, 34 women; mean age, 68 years; range, 28-88 years) received urokinase plus abciximab. Study end points were the rate of major complications at 30 days, therapeutic success, and survival without open surgery or major amputation at follow-up. Fisher exact test was used to compare treatment groups with respect to dichotomous variables, and the event-free-survival probabilities were calculated with the Kaplan-Meier method. For the comparison of the lengths of occlusions among the groups, a two-sample t test was used.

RESULTS

Therapeutic success (P=.7) did not differ between the groups, whereas the time required for thrombolysis was lower in the urokinase-plus-abciximab group (P=.001). Patients who received reteplase plus abciximab tended to develop more minor complications (mainly bleeding events) (P<.001). During long-term follow-up (2-4 years), no group differences were observed. The reocclusion rate was 48% (22 of 46) in the reteplase-plus-abciximab group and 45% (29 of 64) in the urokinase-plus-abciximab group. Only two of 120 major amputations were counted in the follow-up period.

CONCLUSION

The proposed regimen resulted in only a limited number of major complications, and the low amputation rate in both groups may be attributed to abciximab.

Plasminogen activators: A comparison

Thrombolytic drugs play a crucial role in the management of patients with acute myocardial infarction, pulmonary embolism, deep vein thrombosis, arterial thrombosis, acute thrombosis of retinal vessel, extensive coronary emboli, and peripheral vascular thromboembolism. Recognition of the importance of fibrinolytic system in thrombus resolution has resulted in the development of different fibrinolytic agents. Now a days several newer plasminogen activators with different pharmacokinetic and pharmacodynamic properties have been developed to treat thrombotic disease, which are fibrin specific with prolonged half-life and can be administered as a single bolus.

Comparative Safety and Efficacy of Urokinase and Recombinant Tissue Plasminogen Activator for Peripheral Arterial Occlusion: A Meta-Analysis

STUDY OBJECTIVE

To evaluate differences in the efficacy and safety of recombinant tissue plasminogen activator (rt-PA) and urokinase in the treatment of peripheral arterial occlusion.

DESIGN

Systematic review and meta-analysis of prospective comparative trials.

DATA SOURCE

PubMed/MEDLINE database from 1966-October 2004.

MEASUREMENTS AND MAIN RESULTS

The literature was systematically searched to identify prospective comparative trials of urokinase and rt-PA for the treatment of peripheral arterial occlusion. The primary outcome measure was successful complete lysis of the occlusion. Other outcome measures were hemorrhage (major, minor, or combined), intracranial hemorrhage, limb loss, and mortality. Six trials were identified, five of which were randomized. On meta-analysis, the rate of clot lysis was higher with rt-PA than with urokinase (odds ratio [OR] 1.54, 95% confidence interval [CI] 1.12-2.10, p=0.007). However, urokinase was associated with lower rates of minor (OR 0.52, 95% CI 0.28-0.97, p=0.04) and total (OR 0.51, 95% CI 0.29-0.91, p=0.02) bleeding. Rates of major hemorrhage, intracranial hemorrhage, limb loss, and mortality were similar between agents.

CONCLUSION

Urokinase was less effective than rt-PA in successfully lysing acute peripheral arterial occlusion, but it was associated with lower rates of total and minor bleeding. Overall, rt-PA was a reasonable substitute for urokinase, now that urokinase has been removed from the market in the United States. However, judicious monitoring for minor bleeding is necessary.

Intraarterial catheter-directed thrombolysis: urokinase versus tissue plasminogen activator

The purpose of this study was to evaluate the differences between tissue plasminogen activator (TPA) and urokinase (UK) in the management of ischemic limbs. A total of 58 limbs (24 in the TPA group and 34 in the UK group) in 53 patients were studied prospectively. The two groups were based on the surgeon's preference for lytic agent. The dose regimen for UK was 150,000 IU/hr over 1/2 to 2 hr followed by a continuous infusion of 50,000 IU/hr. TPA was given as a 5-mg bolus followed by 1 mg/hr. Both groups received heparin at a rate of 400 IU/hr through the side arm of the arterial sheath. There was no significant difference in efficacy between UK and TPA, but TPA acted faster and had a higher incidence of bleeding complications.

Intrapulmonary artery infusion of urokinase for treatment of massive pulmonary embolism: a review of 26 patients with and without contraindications to systemic thrombolytic therapy

BACKGROUND

Pulmonary emboli (PE) are a common event seen in over 600,000 patients a year. Occurring suddenly, PE often result in a high rate of mortality. To combat the high rate of mortality, more aggressive therapies including the use of thrombolytics are often indicated. The use of intrapulmonary artery infusion of urokinase has been shown to promote rapid resolution of emboli and restoration of normal pulmonary hemodynamics.

HYPOTHESIS

The study was undertaken to review the effectiveness and safety of pulmonary artery infusion of urokinase in 26 patients with and without contraindications to the use of systemic thrombolytic therapy.

METHODS

We reviewed the outcomes of 26 patients who received infusion of urokinase, using a usual loading dose of 4,000 U/kg body weight given as a bolus, followed by 4,000 U/kg/h for 12 to 24 h, using either/or unilateral or bilateral infusions. Pulmonary angiograms were obtained prior to and following the urokinase infusions.

RESULTS

Intrapulmonary artery infusion of urokinase was given to 26 patients, 9 of whom had contraindications to the use of systemic thrombolytic therapy. Six patients were recent post operative, one was receiving oral anticoagulants, one was receiving chemotherapy with bleeding complications, and one had received cardiopulmonary resuscitation. Twenty of the patients returned to their baseline state (normal heart rate, blood pressure, and p02), one was minimally improved, and five deaths occurred. Of the five deaths, three occurred within 1 h of starting urokinase infusion, the remaining two died more than 36 h after treatment with urokinase as a result of their basic underlying disease. Minor bleeding occurred from puncture sites, two hematomas occurred at the puncture site, and there were two gastrointestinal bleeds, one of which occurred a week post urokinase therapy while the patient was receiving heparin and coumadin. No central nervous system bleeds occurred and no transfusions were required as a result of urokinase intrapulmonary artery infusions. The overall mortality rate in this series was 11.5%.

CONCLUSIONS

Intrapulmonary artery infusion of urokinase in extensive pulmonary embolism is a safe and efficient treatment in patients with and without contraindication to the use of systemic thrombolytic therapy. With a usual loading dose of 4,000 U/kg body weight, followed by an infusion of 4,000 U/kg/h for 12 to 24 h, it produces significant and rapid resolution of pulmonary emboli with a low morbidity and mortality rate. In our series, the mortality rate was 11.5%, and none of the deaths was the direct result of urokinase therapy.

Quantitative evaluation of selective thrombolysis techniques: influence of catheter characteristics and delivery parameters

Here, we evaluate in vitro the site-specific delivery ability of thrombolysis catheters and compare continuous infusion (CI) and periodic injection (PI) protocols with reference to this parameter. Thrombotic occlusion was simulated by placing a porcine blood clot proximal to an eccentric stenosis in a flow phantom. Iodinated contrast agent was used as the marker. Part I-Evaluation of thrombolysis catheters: four CI and three PI catheters were tested. The marker was delivered as an infusion at 1 ml/min for 1 min (CI), or as two 0.25 ml boluses 30 sec apart (PI). Iodine content of the clot was then estimated with x-ray fluorescence spectrometry. This value as a ratio of the delivered dose was defined as the targeting efficiency. Part II-Evaluation of thrombolysis protocols: CI and PI were compared. The marker was delivered for 3 or 5 min using one of seven protocols. The iodine content of both clot and effluent were estimated. Among PI catheters, the Jet-Lysis catheter proved to be the best (P = 0.02). The EDM catheter had the lowest targeting efficiency in the CI group (P = 0.01). With CI, median iodine recovery dropped from 0.21 (95% confidence interval: 0.08, 0.25) for 1 min to 0.13 (0.05, 0.16) for 3 min and 0.07 (0.03, 0.10) for 5 min; for PI the values remained unchanged. The fraction lost in the effluent increased with the duration of regimen with both CI (P = 0.014) and PI (P = 0.004). Reducing the rate of infusion or the bolus frequency resulted in major improvements with respect to this parameter (P = 0.005). For CI, the targeting efficiency increased as well (P = 0.03). We conclude that currently used thrombolysis protocols do not fully exploit the delivery advantage offered by CI or PI. Fortunately, simple modifications offer the possibility of overcoming these drawbacks.