Perioperative Evaluation of Bleeding Diathesis

Substrate-Independent Robust and Heparin-Mimetic Hydrogel Thin Film Coating via Combined LbL Self-Assembly and Mussel-Inspired Post-Cross-linking

In this work, we designed a robust and heparin-mimetic hydrogel thin film coating via combined layer-by-layer (LbL) self-assembly and mussel-inspired post-cross-linking. Dopamine-grafted heparin-like/-mimetic polymers (DA-g-HepLP) with abundant carboxylic and sulfonic groups were synthesized by the conjugation of adhesive molecule, DA, which exhibited substrate-independent adhesive affinity to various solid surfaces because of the formation of irreversible covalent bonds. The hydrogel thin film coated substrates were prepared by a three-step reaction: First, the substrates were coated with DA-g-HepLP to generate negatively charged surfaces. Then, multilayers were obtained via LbL coating of chitosan and the DA-g-HepLP. Finally, the noncovalent multilayers were oxidatively cross-linked by NaIO4. Surface ATR-FTIR and XPS spectra confirmed the successful fabrication of the hydrogel thin film coatings onto membrane substrates; SEM images revealed that the substrate-independent coatings owned 3D porous morphology. The soaking tests in highly alkaline, acid, and concentrated salt solutions indicated that the cross-linked hydrogel thin film coatings owned high chemical resistance. In comparison, the soaking tests in physiological solution indicated that the cross-linked hydrogel coatings owned excellent long-term stability. The live/dead cell staining and morphology observations of the adhered cells revealed that the heparin-mimetic hydrogel thin film coated substrates had low cell toxicity and high promotion ability for cell proliferation. Furthermore, systematic in vitro investigations of protein adsorption, platelet adhesion, blood clotting, and blood-related complement activation confirmed that the hydrogel film coated substrates showed excellent hemocompatibility. Both the results of inhibition zone and bactericidal activity indicated that the gentamycin sulfate loaded hydrogel thin films had significant inhibition capability toward both Escherichia coli and Staphylococcus aureus bacteria. Combined the above advantages, it is believed that the designed heparin-mimetic hydrogel thin films may show high potential for applications in various biological and clinical fields, such as long-term hemocompatible and drug-loading materials for implants.

Unclassified bleeding disorders: outcome of haemostatic challenges following tranexamic acid and/or desmopressin

INTRODUCTION

In a minority of patients with a significant bleeding history no cause is found despite extensive testing and we diagnose such cases as unclassified bleeding disorders (UBD). UBDs may have diverse underlying causes and currently no standard management strategy exists in the event of a haemorrhage or to cover surgery.

AIM

To document the clinical characteristics and response to treatment of UBDs.

METHODS

We performed a retrospective chart review of all patients with UBDs who had an invasive procedure at our centre between 1998 and 2014.

RESULTS

The commonest symptoms were menorrhagia (89%) and bleeding at the time of surgery (88%) or dental extraction (85%). A total of 33 patients underwent 78 minor and major haemostatic challenges. Haemostatic cover was provided in 28 procedures with tranexamic acid alone, two with desmopressin and 45 with both agents in combination. A successful haemostatic outcome was observed in 70/78 (90%) cases. No patient required additional surgical intervention to achieve haemostasis, but one patient required a platelet transfusion to control postoperative bleeding.

CONCLUSIONS

This is the first study to report on the investigation and treatment of UBD. Future studies are needed to further our understanding of the bleeding phenotype and identify any underlying causes.

Versatile and Rapid Postfunctionalization from Cyclodextrin Modified Host Polymeric Membrane Substrate

Surface modification has long been of great interest to impart desired functionalities to the bioimplants. However, due to the limitations of recent technologies in surface modification, it is highly desirable to explore novel protocols, which can advantageously and efficiently endow the inert material surfaces with versatile biofunctionalities. Herein, to achieve versatile and rapid postfunctionalization of polymeric membrane, we demonstrate a new strategy for the fabrication of β-cyclodextrin (β-CD) modified host membrane substrate that can recognize a series of well-designed guest macromolecules. The surface assembly procedure was driven by the host-guest interaction between adamantane (Ad) and β-CD. β-CD immobilized host membrane was fabricated via two steps: (1) epoxy groups enriched poly(ether sulfone) (PES) membrane was first prepared via in situ cross-linking polymerization and subsequently phase separation; (2) mono-6-deoxy-6-ethylenediamine-β-CD (EDA-β-CD) was then anchored onto the surface of the epoxy functionalized PES membrane to obtain PES-CD. Subsequently, three types of Ad-terminated polymers, including Ad-poly(styrenesulfonate-co-sodium acrylate) (Ad-PSA), Ad-methoxypoly(ethylene glycol) (Ad-PEG), and Ad-poly(methyl chloride-quaternized 2-(dimethylamino)ethyl methacrylate (Ad-PMT), were separately assembled onto the β-CD immobilized surfaces to endow the membranes with anticoagulant, antifouling, and antibacterial capability, respectively. Activated partial thromboplastin time (APTT), thrombin time (TT), and prothrombin time (PT) measurements were carried out to explore the anticoagulant activity. The antifouling capability was evaluated via protein adsorption and platelet adhesion measurements. Moreover, Staphyllococcous aureus (S. aureus) was selected as model bacteria to evaluate the antibacterial ability of the functionalized membranes. The results indicated that well-regulated blood compatibility, antifouling capability, and bactericidal activity could be achieved by the proposed rapid postfunctionalization on polymeric membranes. This approach of versatile and rapid postfunctionalization is promising for the preparation of multifunctional polymeric membrane materials to meet with various demands for the further applications.

In situ cross-linking of stimuli-responsive hemicellulose microgels during spray drying

Chemical cross-linking during spray drying offers the potential for green fabrication of microgels with a rapid stimuli response and good blood compatibility and provides a platform for stimuli-responsive hemicellulose microgels (SRHMGs). The cross-linking reaction occurs rapidly in situ at elevated temperature during spray drying, enabling the production of microgels in a large scale within a few minutes. The SRHMGs with an average size range of ∼ 1-4 μm contain O-acetyl-galactoglucomannan as a matrix and poly(acrylic acid), aniline pentamer (AP), and iron as functional additives, which are responsive to external changes in pH, electrochemical stimuli, magnetic field, or dual-stimuli. The surface morphologies, chemical compositions, charge, pH, and mechanical properties of these smart microgels were evaluated using scanning electron microscopy, IR, zeta potential measurements, pH evaluation, and quantitative nanomechanical mapping, respectively. Different oxidation states were observed when AP was introduced, as confirmed by UV spectroscopy and cyclic voltammetry. Systematic blood compatibility evaluations revealed that the SRHMGs have good blood compatibility. This bottom-up strategy to synthesize SRHMGs enables a new route to the production of smart microgels for biomedical applications.

Successful management of severe refractory acquired immune bleeding disorder: Prior to insisting surgery

INTRODUCTION

Acquired bleeding disorders are rare and may be missed before surgery. Additionally, they may be refractory to conventional treatments.

PRESENTATION OF CASE

A 50-year-old patient experienced prolonged post-operative bleeding when his bleeding disorder was missed prior to his undergoing inguinal herniorrhaphy. Post-operative investigations revealed severe acquired von Willebrand syndrome associated with a monoclonal gammopathy of undetermined significance. A few months later, he required umbilical herniorrhaphy, but he did not respond to attempts to raise his von Willebrand factor antigen and activity levels using conventional therapies, including desmopressin, cryoprecipitate, intravenous immunoglobulin, and Von Willebrand factor concentrate. A triple therapy combination of dexamethasone, intravenous immunoglobulin, and mycophenolate mofetil was administered, with a successful and sustained response, lasting about 2 months. The surgery was performed safely, without any complications.

DISCUSSION

Conventional acquired von Willebrand syndrome treatment is usually aimed at replacing von Willebrand factor or stimulating its secretion from storage in endothelial cells. In the present case, the alternative treatment was directed against both the humoral and cell-mediated immune mechanisms.

CONCLUSION

This case of acquired bleeding disorder showed that more attention must be given to a patient's coagulation profile, even if only very minor laboratory coagulation derangements are detected prior to surgery, to avoid missing such rare disorders. The described triple therapy demonstrated good effects and may be considered for inclusion in a controlled randomized study to determine its usefulness for other surgeries delayed due to severe acquired bleeding disorders. To the best of our knowledge, this triple combination treatment has not been previously used for the treatment of severe acquired bleeding disorders that are refractory to conventional therapies.

Surface modification of poly(ether sulfone) membrane with a synthesized negatively charged copolymer

In this study, we provide a new method to modify poly(ether sulfone) (PES) membrane with good biocompatibility, for which diazotized PES (PES-N2(+)) membrane is covalently coated by a negatively charged copolymer of sodium sulfonated poly(styrene-alt-maleic anhydride) (NaSPS-MA). First, aminated PES (PES-NH2) is synthesized by nitro reduction reaction of nitro-PES (PES-NO2), and then blends with pristine PES to prepare PES/PES-NH2 membrane; then the membrane is treated with NaNO2 aqueous solution at acid condition; after surface diazo reaction, surface positively charged PES/PES-N2(+) membrane is prepared. Second, poly(styrene-alt-maleic anhydride) (PS-alt-MA) is synthesized, then sulfonated and treated by sodium hydroxide solution to obtain sodium sulfonated (PS-alt-MA) (NaSPS-MA). Finally, the negatively charged NaSPS-MA copolymer is coated onto the surface positively charged PES/PES-N2(+) membrane via electrostatic interaction; after UV-cross-linking, the linkage between the PES-N2(+) and NaSPS-MA changes to a covalent bond. The surface-modified PES membrane is characterized by FT-IR spectroscopy, X-ray photoelectron spectroscopy (XPS) analyses, and surface zeta potential analyses. The modified membrane exhibits good hemocompatibility and cytocompatibility, and the improved biocompatibility might have resulted from the existence of the hydrophilic groups (sodium carboxylate (-COONa) and sodium sulfonate (-SO3Na)). Moreover, the stability of the modified membrane is also investigated. The results indicated that the modified PES membrane using negatively charged copolymers had a lot of potential in blood purification fields and bioartificial liver supports for a long time.

Synthesis and anticoagulant activity of polyureas containing sulfated carbohydrates

Polyurea-based synthetic glycopolymers containing sulfated glucose, mannose, glucosamine, or lactose as pendant groups have been synthesized by step-growth polymerization of hexamethylene diisocyanate and corresponding secondary diamines. The obtained polymers were characterized by gel permeation chromatography, nuclear magnetic resonance spectroscopy, and Fourier transform infrared spectroscopy. The nonsulfated polymers showed similar results to the commercially available biomaterial polyurethane TECOFLEX in a platelet adhesion assay. The average degree of sulfation after reaction with SO₃ was calculated from elemental analysis and found to be between three and four −OSO₃ groups per saccharide. The blood-compatibility of the synthetic polymers was measured using activated partial thromboplastin time, prothrombin time, thrombin time, anti-IIa, and anti-Xa assays. Activated partial thromboplastin time, prothrombin time, and thrombin time results indicated that the mannose and lactose based polymers had the highest anticoagulant activities among all the sulfated polymers. The mechanism of action of the polymers appears to be mediated via an anti-IIa pathway rather than an anti-Xa pathway.

The Role of Bleeding History and Clinical Markers for the Correct Diagnosis of VWD

Quantification of the bleeding severity by use of bleeding assessment tools (BAT) and bleeding score (BS) has been consistently shown to improve the clinical diagnosis of von Willebrand disease (VWD) while helping researchers establish phenotype/genotype correlations. Subjects with a BS equal or higher than 3 may be consider having a bleeding tendency, and should be referred for a laboratory investigation, particularly for VWD. In the diagnosis of type 1 VWD, the use of the BS has been shown to be highly specific (>95%) with reported sensitivities ranging from 40 to 100%. The BS is related to all available measurements of von Willebrand factor activity, including the PFA-100 closure time. Therefore, in clinical practice the use of BAT should always be the first step to standardize the assessment of patients with suspected VWD. The use of the recent ISTH consensus BAT is suggested to harmonize the collection of bleeding symptoms in patients with a suspected or confirmed hemostatic disorder, particularly VWD. The ISTH BAT is also coupled with a Web-based repository of bleeding symptoms, therefore providing an integrated framework for collaboration in the field of clinical evaluation of VWD and mild bleeding disorders.

Further removal of factor v related antigen from bovine thrombin by utilizing a membrane-filtration step

Topical bovine thrombin is commonly used during surgery to maintain hemostasis and is rarely associated with abnormalities in hemostasis, including coagulopathies and bleeding. Coagulopathies may be related to the formation of cross-reactive antibodies to bovine factor V. Effectiveness of a new filtration step to remove factor V/Va from bovine thrombin was evaluated. A highly sensitive and specific Western blot capable of detecting minute amounts of factor V/Va and/or its fragments was developed. Samples were evaluated for bovine factor V related antigens using the Western blot method and a competitive enzyme-linked immunosorbent assay. Factor Va light chain fragment levels were detectable in crude thrombin and chromatographically purified thrombin but not in chromatographically purified and virally filtered preparations. Therefore, inclusion of the viral-filtration step during purification of thrombin is effective in reducing factor V or its fragments to undetectable levels, thus enhancing product purity.

How to estimate bleeding risk in mild bleeding disorders

The concept of mild bleeding disorders (MBD) has evolved in contrast to severe hemophilia A and B to indicate less severe disorders, characterized by the presence of more frequent and/or more prominent bleeding symptoms than in the normal population. These symptoms occur mostly after a recognizable challenge and do not lead to major discomfort or organ damage, even in the absence of specific medical intervention. However, it has become clear that, from the most severe to the mildest hemostatic disorders, there is a continuous spectrum of bleeding manifestations, which overlap with the occasional bleeding occurring in people without any identifiable hemostatic abnormality. By reviewing the principal hemorrhagic disorders we have tried to identify those entities that could fit a diagnosis of MBD and result, at the same time, in a net benefit for treatment or prophylaxis of patients rather than being simply accurate. This goal can usually be achieved by comparing the patient's phenotype with known nosological entities. However, limitations of this approach are evident, considering the paucity of clinical data and the biases of most published reports on the different disorders. In addition, in a partial deficiency of a clotting factor, a reliable relationship between the residual activity and bleeding severity is not invariably found. Molecular characterization of the defects is also generally useless. Accordingly, an accurate bleeding history in the propositus and his/her family remains of major importance. For this purpose, new standardized and possibly quantitative tools are being developed in several institutions. Innovative approaches, combining into a single probability phenotypic and genetic data, could possibly estimate better the bleeding risk in specific disorders.