Ruthenium Antivenom Inhibits the Defibrinogenating Activity of Crotalus adamanteus Venom in Rabbits.

Eastern Diamondback Rattlesnake (Crotalus adamanteus) envenomation is a medical emergency encountered in the Southeastern United States. The venom contains a snake venom thrombin-like enzyme (SVTLE) that is defibrinogenating, causing coagulopathy without effects on platelets in humans. This investigation utilized thrombelastographic methods to document this coagulopathy kinetically on the molecular level in a rabbit model of envenomation via the analyses of whole blood samples without and with platelet inhibition. Subsequently, the administration of a novel ruthenium compound containing site-directed antivenom abrogated the coagulopathic effects of envenomation in whole blood without platelet inhibition and significantly diminished loss of coagulation in platelet-inhibited samples. This investigation provides coagulation kinetic insights into the molecular interactions and results of SVTLE on fibrinogen-dependent coagulation and confirmation of the efficacy of a ruthenium antivenom. These results serve as a rationale to investigate the coagulopathic effects of other venoms with this model and assess the efficacy of this site-directed antivenom.

Phosphate-Buffered Saline and Dimethyl Sulfoxide Enhance the Antivenom Action of Ruthenium Chloride against Crotalus atrox Venom in Human Plasma-A Preliminary Report.

Ruthenium chloride (RuCl3) is widely utilized for synthesis and catalysis of numerous compounds in academia and industry and is utilized as a key molecule in a variety of compounds with medical applications. Interestingly, RuCl3 has been demonstrated to modulate human plasmatic coagulation and serves as a constituent of a compounded inorganic antivenom that neutralizes the coagulopathic effects of snake venom in vitro and in vivo. Using thrombelastography, this investigation sought to determine if RuCl3 inhibition of the fibrinogenolytic effects of Crotalus atrox venom could be modulated by vehicle composition in human plasma. Venom was exposed to RuCl3 in 0.9% NaCl, phosphate-buffered saline (PBS), or 0.9% NaCl containing 1% dimethyl sulfoxide (DMSO). RuCl3 inhibited venom-mediated delay in the onset of thrombus formation, decreased clot growth velocity, and decreased clot strength. PBS and DMSO enhanced the effects of RuCl3. It is concluded that while a Ru-based cation is responsible for significant inhibition of venom activity, a combination of Ru-based ions containing phosphate and DMSO enhances RuCl3-mediated venom inhibition. Additional investigation is indicated to determine what specific Ru-containing molecules cause venom inhibition and what other combinations of inorganic/organic compounds may enhance the antivenom effects of RuCl3.

Evaluation of the Inhibitory Potential of Synthetic Peptides Homologous to CDR3 Regions of a Monoclonal Antibody against Bothropic Venom Serine Proteases.

Snakebite accidents, neglected tropical diseases per the WHO, pose a significant public health threat due to their severity and frequency. Envenomation by Bothrops genus snakes leads to severe manifestations due to proteolytic enzymes. While the antibothropic serum produced by the Butantan Institute saves lives, its efficacy is limited as it fails to neutralize certain serine proteases. Hence, developing new-generation antivenoms, like monoclonal antibodies, is crucial. This study aimed to explore the inhibitory potential of synthetic peptides homologous to the CDR3 regions of a monoclonal antibody targeting a snake venom thrombin-like enzyme (SVTLE) from B. atrox venom. Five synthetic peptides were studied, all stable against hydrolysis by venoms and serine proteases. Impressively, four peptides demonstrated uncompetitive SVTLE inhibition, with Ki values ranging from 10-6 to 10-7 M. These findings underscore the potential of short peptides homologous to CDR3 regions in blocking snake venom toxins, suggesting their promise as the basis for new-generation antivenoms. Thus, this study offers potential advancements in combatting snakebites, addressing a critical public health challenge in tropical and subtropical regions.

Fasciotomy following North American pit viper envenomation in Texas 2004-2021.

INTRODUCTION: North American pit viper envenomation occurs over 4,000 times annually in the United States, with polyvalent Fab antivenom being the primary treatment. Fasciotomy is occasionally performed due to concerns about compartment syndrome. We utilized our direct access to Texas Poison Center Network data to create a new snakebite abstraction form and database on relevant available information between 2004 and 2021 and to identify, describe, and estimate the incidence of fasciotomy following pit viper envenomation in Texas. METHODS: We searched the Texas Poison Center Network database for cases during 2004-2021 using keywords such as fasciotomy, surgery, compartment pressure, and compartment syndrome. Descriptive statistics summarized the data. RESULTS: Of 16,911 reported envenomations, 0.69 percent involved fasciotomies (n = 117). Most common bite sites were digits/hands and lower extremities. Patients who underwent fasciotomy were typically male, aged 20-59, and 10 years younger than the total snakebite population. Only 6 percent of reported compartment syndrome cases had a compartment pressure measurement. Antivenom was administered in 101 (86.3 percent) cases, 92 (91.1 percent) of which received only Fab antivenom product. Patients with bites from rattlesnakes (47.9 percent) were associated with most fasciotomies. DISCUSSION: Our findings suggest a potential increase in snakebite exposures, accompanied by a decrease in fasciotomies. Overall, copperheads constituted the majority of snakebites, but most fasciotomies were from rattlesnake envenomations (47.9 percent). In this cohort, compartment syndrome diagnosis and decisions regarding fasciotomy were primarily based on clinical evaluation/surgeon expertise without compartment pressure measurements. Despite the efficacy of antivenom, only 86.3 percent of patients in our study received antivenom. CONCLUSIONS: Fasciotomy after North American pit viper envenomation in Texas is uncommon (0.69 percent) and has decreased over time, possibly due to increased antivenom use or surgeon comfort with nonsurgical management.

The PLA2 inhibitor from Crotalus durissus terrificus blood plasma (CNF) inhibits group III-PLA2 from honeybee venom.

Crotalus neutralizing factor (CNF) is an endogenous glycoprotein from Crotalus durissus terrificus snake blood that inhibits secretory phospholipases A2 (sPLA2) from the Viperid but not from Elapid venoms (subgroups IA and IIA, respectively). In the present study, we demonstrated that CNF can inhibit group III-PLA2 from bee venom by forming a stable enzyme-inhibitor complex. This finding opens up new possibilities for the potential use of CNF and/or CNF-based derivatives in the therapeutics of bee stings.

Inhibition of enzymatic activities of Bothrops asper snake venom and docking analysis of compounds from plants used in Central America to treat snakebite envenoming.

ETHNOPHARMACOLOGICAL RELEVANCE: Snakebite envenoming is a public health problem of high impact in Central America. Bothrops asper, known as barba amarilla, terciopelo, and equis, is the snake species responsible for most snakebites in Central America. In this region, there is a long-standing tradition on the use of plants in the management of snakebites, especially in indigenous communities. Ethnomedical use of Eryngium foetidum L., Neurolaena lobata (L.) Cass. and Pimenta dioica (L.) Merr. to treat snakebite envenoming has been reported in Belice, Guatemala, Nicaragua, and Costa Rica. Extracts of the leaves of these plants have shown anti-venom activities in in vitro assays in previous studies. AIM OF THE STUDY: To assess the ability of organic fractions from these three plants to inhibit enzymatic activities associated with toxicity of the venom of B. asper, and to study, by docking analysis, the interaction of metalloproteinase and phospholipases A2 (PLA2) from B. asper venom with secondary metabolites previously described in these plants. MATERIALS AND METHODS: Organic fractions were obtained from these three plant species and their ability to neutralize proteolytic, PLA2 and in vitro coagulant activities of B. asper venom was assessed. A phytochemical analysis was carried out in these fractions. The interaction of secondary metabolites previously described in these plants with three toxins from B. asper venom (a metalloproteinase, a PLA2 and a PLA2 homologue) was investigated by docking analysis. RESULTS: The inhibitory activity of plants was mainly concentrated in their polar fractions. Acetonic fraction from P. dioica was the most active against PLA2 activity, while the acetonic fraction of E. foetidum completely inhibited the proteolytic activity of the venom. Coagulant activity was partially inhibited only by the acetone and ethyl acetate fractions of P. dioica. Phytochemical analysis of the most bioactive fractions identified flavonoids, saponins, essential oils, coumarins, alkaloids, tannins and sesquiterpene lactones. Docking analysis revealed high affinity interactions of several secondary metabolites of these plants with residues in the vicinity of the catalytic site of these enzymes and, in the case of PLA2 homologue myotoxin II, in the hydrophobic channel. CONCLUSIONS: Various fractions from these plants have inhibitory activity against enzymatic actions of B. asper venom which are directly associated with toxicological effects. Docking analysis showed structural evidence of the interaction of secondary metabolites with three toxins. These observations provide support to the potential of these plants to inhibit relevant toxic components of this snake venom.

Neutralization of toxic activities of Bothrops asper snake venom by ethnomedicinal plants used in Central America, with emphasis in Guatemala: a review / Neutralización de actividades tóxicas del veneno de la serpiente Bothrops asper por plantas etnomedicinales utilizadas en Centroamérica, con énfasis en Guatemala: Revisión

There are few scientific studies that explore the use of medicinal plants for snakebite envenoming in Central America, although plant-based therapies have been traditionally used in the region. This work reviews the studies conducted in Central America to assess the ability of extracts obtained from plants of local ethnomedical use to inhibit toxic activities of the venom of Bothrops asper, the snake responsible for approximately half of the snakebite envenomings in these countries. The search prioritized the description of the plants used in Guatemala, since most of the studies described in this work were conducted in that country, although references to other countries are included. Information concerning secondary metabolites and other pharmacological activities of these plant species, relevant to the treatment of snakebites, was also described. The literature search was conducted in the Google Scholar, PubMed and Scopus databases and completed with locally available literature. It was found that extracts of 12 plant species inhibited the hemorrhagic effect of the venom and three neutralized the edema-forming activity, while inhibition of proteolytic and phospholipase A2 (PLA2) activities was achieved by three and one plant species, respectively. Only Brownea rosa-de-monte was able to effectively counteract the in vitro coagulant effect of the venom. Some plant extracts screened in Guatemala demonstrated procoagulant or anti-thrombin intrinsic effects that might aggravate the coagulopathy induced by the venom. These findings underscore the need of carrying out scientific studies aimed to validate the inhibitory potential of Central American plant extracts and their metabolites against B. asper venom.

Pocos estudios científicos han explorado el uso de plantas medicinales para el tratamiento del envenenamiento ofídico en Centroamérica, a pesar de que las terapias basadas en plantas son de uso tradicional en la región. Este trabajo recopiló información sobre los estudios realizados en Centroamérica para evaluar la capacidad de extractos de plantas de uso etno-médico para inhibir las actividades tóxicas del veneno de Bothrops asper, la serpiente responsable de aproximadamente la mitad de los envenenamientos ofídicos en Centroamérica. La búsqueda priorizó la descripción de plantas utilizadas en Gua-temala, ya que la mayoría de los estudios aquí descritos fueron realizados en ese país. También se incluyó la descripción de los metabolitos secundarios y otras actividades farmacológicas de las especies evaluadas, que podrían explicar su uso como antiofídicos. La búsqueda de literatura se realizó en las bases de datos de Google Scholar, PubMed, Scopus, y se completó con literatura disponible localmente. Se determinó que 12 extractos de plantas inhibieron el efecto hemorrágico del veneno y tres el efecto edematígeno; la actividad proteolítica fue inhibida por extractos de tres especies y la fosfolipasa A2 (PLA2) por una especie. Solamente Brownea rosa-de-monte demostró inhibir efectivamente el efecto coagulante del veneno in vitro. Algunos extractos de las plantas tamizadas en Guatemala demostraron efectos procoagulantes o anti-trombina intrínsecos, que podrían agravar las alteraciones inducidas por el veneno en la coagulación. Estos hallazgos enfatizan la necesidad de validar el potencial de extractos de plantas centroamericanas y sus metabolitos secundarios para neutralizar el veneno de B. asper.

Observation of Bothrops atrox Snake Envenoming Blister Formation from Five Patients: Pathophysiological Insights.

In the Brazilian Amazon, Bothrops atrox snakebites are frequent, and patients develop tissue damage with blisters sometimes observed in the proximity of the wound. Antivenoms do not seem to impact blister formation, raising questions regarding the mechanisms underlying blister formation. Here, we launched a clinical and laboratory-based study including five patients who followed and were treated by the standard clinical protocols. Blister fluids were collected for proteomic analyses and molecular assessment of the presence of venom and antivenom. Although this was a small patient sample, there appeared to be a correlation between the time of blister appearance (shorter) and the amount of venom present in the serum (higher). Of particular interest was the biochemical identification of both venom and antivenom in all blister fluids. From the proteomic analysis of the blister fluids, all were observed to be a rich source of damage-associated molecular patterns (DAMPs), immunomodulators, and matrix metalloproteinase-9 (MMP-9), suggesting that the mechanisms by which blisters are formed includes the toxins very early in envenomation and continue even after antivenom treatment, due to the pro-inflammatory molecules generated by the toxins in the first moments after envenomings, indicating the need for local treatments with anti-inflammatory drugs plus toxin inhibitors to prevent the severity of the wounds.

Bleeding and Thrombosis: Insights into Pathophysiology of Bothrops Venom-Related Hemostasis Disorders.

Toxins from Bothrops venoms targeting hemostasis are responsible for a broad range of clinical and biological syndromes including local and systemic bleeding, incoagulability, thrombotic microangiopathy and macrothrombosis. Beyond hemostais disorders, toxins are also involved in the pathogenesis of edema and in most complications such as hypovolemia, cardiovascular collapse, acute kidney injury, myonecrosis, compartmental syndrome and superinfection. These toxins can be classified as enzymatic proteins (snake venom metalloproteinases, snake venom serine proteases, phospholipases A2 and L-amino acid oxidases) and non-enzymatic proteins (desintegrins and C-type lectin proteins). Bleeding is due to a multifocal toxicity targeting vessels, platelets and coagulation factors. Vessel damage due to the degradation of basement membrane and the subsequent disruption of endothelial cell integrity under hydrostatic pressure and tangential shear stress is primarily responsible for bleeding. Hemorrhage is promoted by thrombocytopenia, platelet hypoaggregation, consumption coagulopathy and fibrin(ogen)olysis. Onset of thrombotic microangiopathy is probably due to the switch of endothelium to a prothrombotic phenotype with overexpression of tissue factor and other pro-aggregating biomarkers in association with activation of platelets and coagulation. Thrombosis involving large-caliber vessels in B. lanceolatus envenomation remains a unique entity, which exact pathophysiology remains poorly understood.

Examination of the Efficacy and Cross-Reactivity of a Novel Polyclonal Antibody Targeting the Disintegrin Domain in SVMPs to Neutralize Snake Venom.

Snake envenomation can result in hemorrhage, local necrosis, swelling, and if not treated properly can lead to adverse systemic effects such as coagulopathy, nephrotoxicity, neurotoxicity, and cardiotoxicity, which can result in death. As such, snake venom metalloproteinases (SVMPs) and disintegrins are two toxic components that contribute to hemorrhage and interfere with the hemostatic system. Administration of a commercial antivenom is the common antidote to treat snake envenomation, but the high-cost, lack of efficacy, side effects, and limited availability, necessitates the development of new strategies and approaches for therapeutic treatments. Herein, we describe the neutralization ability of anti-disintegrin polyclonal antibody on the activities of isolated disintegrins, P-II/P-III SVMPs, and crude venoms. Our results show disintegrin activity on platelet aggregation in whole blood and the migration of the SK-Mel-28 cells that can be neutralized with anti-disintegrin polyclonal antibody. We characterized a SVMP and found that anti-disintegrin was also able to inhibit its activity in an in vitro proteolytic assay. Moreover, we found that anti-disintegrin could neutralize the proteolytic and hemorrhagic activities from crude Crotalus atrox venom. Our results suggest that anti-disintegrin polyclonal antibodies have the potential for a targeted approach to neutralize SVMPs in the treatment of snakebite envenomations.

Association of a Network of Immunologic Response and Clinical Features With the Functional Recovery From Crotalinae Snakebite Envenoming.

Background: The immunologic pathways activated during snakebite envenoming (SBE) are poorly described, and their association with recovery is unclear. The immunologic response in SBE could inform a prognostic model to predict recovery. The purpose of this study was to develop pre- and post-antivenom prognostic models comprised of clinical features and immunologic cytokine data that are associated with recovery from SBE. Materials and Methods: We performed a prospective cohort study in an academic medical center emergency department. We enrolled consecutive patients with Crotalinae SBE and obtained serum samples based on previously described criteria for the Surgical Critical Care Initiative (SC2i)(ClinicalTrials.gov Identifier: NCT02182180). We assessed a standard set of clinical variables and measured 35 unique cytokines using Luminex Cytokine 35-Plex Human Panel pre- and post-antivenom administration. The Patient-Specific Functional Scale (PSFS), a well-validated patient-reported outcome of functional recovery, was assessed at 0, 7, 14, 21 and 28 days and the area under the patient curve (PSFS AUPC) determined. We performed Bayesian Belief Network (BBN) modeling to represent relationships with a diagram composed of nodes and arcs. Each node represents a cytokine or clinical feature and each arc represents a joint-probability distribution (JPD). Results: Twenty-eight SBE patients were enrolled. Preliminary results from 24 patients with clinical data, 9 patients with pre-antivenom and 11 patients with post-antivenom cytokine data are presented. The group was mostly female (82%) with a mean age of 38.1 (SD ± 9.8) years. In the pre-antivenom model, the variables most closely associated with the PSFS AUPC are predominantly clinical features. In the post-antivenom model, cytokines are more fully incorporated into the model. The variables most closely associated with the PSFS AUPC are age, antihistamines, white blood cell count (WBC), HGF, CCL5 and VEGF. The most influential variables are age, antihistamines and EGF. Both the pre- and post-antivenom models perform well with AUCs of 0.87 and 0.90 respectively. Discussion: Pre- and post-antivenom networks of cytokines and clinical features were associated with functional recovery measured by the PSFS AUPC over 28 days. With additional data, we can identify prognostic models using immunologic and clinical variables to predict recovery from SBE.

Use of Crotalidae equine immune F(ab')2 antivenom for treatment of an Agkistrodon envenomation.

INTRODUCTION: Anavip (F(ab')2AV) is a lyophilized F(ab')2 immunoglobulin fragment derived from horses immunized with venom from Bothrops asper and Crotalus durissus. It was approved by the FDA in 2015 for treatment of North American rattlesnake envenomation but not for Agkistrodon envenomation. Published data regarding the efficacy and safety of Anavip in treating Agkistrodon envenomations is limited. We present a case of a patient treated with Anavip after confirmed Agkistrodon laticinctus envenomation. CASE DETAILS: A 77 year-old man was bitten on his fifth finger by a captive A. laticinctus. He was taken to a local emergency department where he received a 10 vial initial dose of F(ab')2AV for pain and swelling and was transferred. At the receiving facility, his pain had improved and his swelling had not progressed. Over the next 30 h, his platelets declined to 132,000/mm3 and he received an additional 4 vials of F(ab')2AV. The remainder of his course was unremarkable with complete recovery by 3 months. DISCUSSION: This case provides an additional published datapoint on the use of this F(ab')2AV in the treatment of envenomation by Agkistrodon.

Isohemigossypolone: Antiophidic properties of a naphthoquinone isolated from Pachira aquatica Aubl.

We investigated the antiophidic properties of isohemigossypolone (ISO), a naphthoquinone isolated from the outer bark of the Pachira aquatic Aubl. The inhibition of phospholipase A2, coagulant, fibrinogenolytic, hemorrhagic and myotoxic activities induced by Bothrops pauloensis venom (Pb) was investigated. For this, we use samples resulting from the incubation of Pb with ISO in different concentrations (1:1, 1:5 and 1:10 w/w), we also evaluated the condition of treatment using ISO after 15 min of venom inoculation. The activities of phospholipase A2, coagulant, fibrinogenolytic, hemorrhagic and myotoxic induced by the B. pauloensis venom were significantly inhibited when the ISO was pre-incubated with the crude venom. For in vivo neutralization tests, the results were observed even when the ISO was applied after 15 min of inoculation of the venom or metalloprotease (BthMP). Also, to identify the inhibition mechanism, we performed in silico assays, across simulations of molecular coupling and molecular dynamics, it was possible to identify the modes of interaction between ISO and bothropic toxins BmooMPα-I, Jararacussin-I and BNSP-7. The present study shows that naphthoquinone isohemigossypolone isolated from the P. aquatica plant inhibited part of the local and systemic damage caused by venom proteins, demonstrating the pharmacological potential of this compound in neutralizing the harmful effects caused by snakebites.

Pan-American Lancehead Pit-Vipers: Coagulotoxic Venom Effects and Antivenom Neutralisation of Bothrops asper and B. atrox Geographical Variants.

The toxin composition of snake venoms and, thus, their functional activity, can vary between and within species. Intraspecific venom variation across a species' geographic range is a major concern for antivenom treatment of envenomations, particularly for countries like French Guiana that lack a locally produced antivenom. Bothrops asper and Bothrops atrox are the most medically significant species of snakes in Latin America, both producing a variety of clinical manifestations, including systemic bleeding. These pathophysiological actions are due to the activation by the venom of the blood clotting factors Factor X and prothrombin, thereby causing severe consumptive coagulopathy. Both species are extremely wide-ranging, and previous studies have shown their venoms to exhibit regional venom variation. In this study, we investigate the differential coagulotoxic effects on human plasma of six venoms (four B. asper and two B. atrox samples) from different geographic locations, spanning from Mexico to Peru. We assessed how the venom variation of these venom samples affects neutralisation by five regionally available antivenoms: Antivipmyn, Antivipmyn-Tri, PoliVal-ICP, Bothrofav, and Soro Antibotrópico (SAB). The results revealed both inter- and intraspecific variations in the clotting activity of the venoms. These variations in turn resulted in significant variation in antivenom efficacy against the coagulotoxic effects of these venoms. Due to variations in the venoms used in the antivenom production process, antivenoms differed in their species-specific or geographical neutralisation capacity. Some antivenoms (PoliVal-ICP, Bothrofav, and SAB) showed species-specific patterns of neutralisation, while another antivenom (Antivipmyn) showed geographic-specific patterns of neutralisation. This study adds to current knowledge of Bothrops venoms and also illustrates the importance of considering evolutionary biology when developing antivenoms. Therefore, these results have tangible, real-world implications by aiding evidence-based design of antivenoms for treatment of the envenomed patient. We stress that these in vitro studies must be backed by future in vivo studies and clinical trials before therapeutic guidelines are issued regarding specific antivenom use in a clinical setting.

In-solution structural studies involving a phospholipase A2-like myotoxin and a natural inhibitor: Plasticity of oligomeric assembly affects mechanisms of inhibition.

Snakebite envenomation has been categorized by World Health Organization as a category A neglected tropical disease, since it causes chronic psychological disorders, physical disablement and death. Ophidian accidents may cause local myonecrosis that cause drastic sequelae, which are not efficiently neutralized via serum therapy. Phospholipase A2-like (PLA2-like) myotoxins have a major role in the local effects caused by several snake venoms. We previously demonstrated that chicoric acid (CA) is an efficient inhibitor of the BthTX-I myotoxin and solved the X-ray structure of complex. Herein, we assess the oligomeric behavior of the BthTX-I/CA complex in solution under different physical-chemical conditions and using toxin obtained by two different biochemical methodologies to fully elucidate structural bases of inhibition of myotoxins by CA. We demonstrated the ability of PLA2-like proteins to form different oligomeric assemblies in the presence of certain inhibitors, which can also be modulated by buffer polarity change. In the presence of ethanol, BthTX-I/CA remains predominantly in a monomeric conformation, which prevents it from being in its active form (dimeric conformation). In contrast, in the absence of ethanol, the tetramer assembly was observed, which hid key regions of the protein responsible for docking and disruption of the muscle membrane. Therefore, the "plasticity" of these proteins with regard to their abilities to form oligomeric assemblies is a key issue for the future development of therapeutic agents to complement of serum therapy.

Clinical manifestations and treatments of Protobothrops mucrosquamatus bite and associated factors for wound necrosis and subsequent debridement and finger or toe amputation surgery.

INTRODUCTION: Protobothrops mucrosquamatus bite induces wound necrosis, coagulopathy, thrombocytopenia, rhabdomyolysis, and acute renal failure. The severity of the hematological derangements and associated factors for wound necrosis and subsequent surgery and the appropriate management of these conditions have not been well characterized. Although severe renal failure requiring hemodialysis has been reported following P. mucrosquamatus bite, the culprit snake may be erroneously classified. MATERIALS AND METHODS: A total of 186 patients with P. mucrosquamatus bites were retrospectively evaluated. They were categorized into group 1 (patients receiving debridement or finger/toe amputation) and group 2 (all other patients) to identify the associated factors for surgery. Characteristic data were compared between groups 1 and 2 and between definite and suspected cases. RESULTS: No differences were observed between definite and suspected cases in terms of symptomatology and management. Of the 186 patients, 7 (3.8%) were asymptomatic, 179 (96.2%) experienced tissue swelling and pain, and 107 (57.5%) had local ecchymosis. Coagulopathy, thrombocytopenia, and renal impairment were found in 13 (7%), 19 (10.2%), and 7 (3.8%) patients, respectively. None of the patients required transfusion therapy or hemodialysis. Furthermore, no systemic bleeding or death occurred. Antivenom was administered to all 179 envenomed patients at a median of 1.5 h post-bite. The median total dose of the specific antivenom was 5.5 vials. In multivariate logistic regression analysis, finger as the bite site, bullae and blister formation, and wound infection were significantly associated with wound necrosis; whereas finger as the bite site and bullae and blister formation were related to debridement or finger/toe amputation. DISCUSSION AND CONCLUSIONS: Protobothrops mucrosquamatus envenomation mainly exerts effects on local tissue. Systemic effects are uncommon and generally nonsevere and transient after the treatment with the specific antivenom. We speculated that severe renal failure requiring hemodialysis is not a typical finding of P. mucrosquamatus envenomation. Patients with finger as the bite site and bullae or blister formation should be carefully examined for wound necrosis, secondary infection, and subsequent surgery. Further evaluations of the efficacy of antivenom against local tissue effects and the effect of selective antibiotics in the management of bite wound infection are urgently required. Although the antivenom manufacturer suggested a skin test prior to use, we believed that it could be omitted because it does not accurately predict the allergic responses.

Cardiac effect induced by Crotalus durissus cascavella venom: Morphofunctional evidence and mechanism of action.

Envenoming, resulting from snake bites, is a global public health problem. The present study was undertaken to investigate the influence of Crotalus durissus cascavella (Cdcas) venom on cardiac activity and the mechanisms of action underlying its effect. To investigate the inotropic and chronotropic effects induced by Cdcas, studies were performed on the left and right atria. A series of tests were conducted to investigate whether the negative inotropic effect, induced by Cdcas, was related to cardiac damage. Cdcas venom (0.1-30 µg/mL) elicited a significant negative inotropic effect. The addition of Cdcas crude venom (7.5, 15 and 30 µg/mL) did not induce significant alterations in cell proliferation, nor in the enzymatic activity of total-CK and CKMB. Ultrastructural evaluation demonstrated that cardiac cells from isoproterenol and Cdcas groups revealed discreet swelling and displaced intermyofibrillar mitochondria with disorganization of the cristae. No change was observed in cardiac electrical activity in perfused isolated rat hearts with Cdcas. In addition, Cdcas reduced contractility in isolated cardiomyocytes from the rat left ventricle. The negative inotropic effect of Cdcas was reduced by l-NAME (100 µM), PTIO (100 µM), ODQ (10 µM) and KT5823 (1 µM), suggesting the participation of NO/cGMP/PKG pathway due to Cdcas. In non-anesthetized rats, Cdcas induced hypotension followed by bradycardia, the latter was also observed by ECG (anesthetized animals). Our results suggest that the negative inotropic effect induced by Cdcas venom is unrelated to cardiac toxicity, at least, at the concentrations tested; and occurs through of NO/cGMP/PKG pathway, likely leading to hypotension and bradycardia when administered in vivo.

Use of both Fab and F(ab')2 fragment antivenom in a pediatric patient for treatment of a North American Crotalidae envenomation.

Crotalidae envenomation has been managed successfully in emergency departments across the world with antivenom. Over the years, antivenom has evolved and newer agents have been studied with the possibility of eliminating maintenance antivenom therapy. Here we report a patient who had worsening platelet and fibrinogen concentrations, as well as complaints of swelling and pain at the site of a rattlesnake envenomation following an initial dose of F(ab')2AV (Crotalidae immune F(ab')2 (equine) [ANAVIP®]) Crotalidae antivenom. The patient was subsequently transferred to a tertiary children's hospital for a higher level of care and received FabAV (Crotalidae polyvalent immune Fab (ovine) [CroFab®]) Crotalidae antivenom. The details of this patient's treatment course highlight the possibility that patients who receive F(ab')2AV, may require additional antivenom treatment. Furthermore, it appears that based on our single patient experience, giving FabAV after F(ab')2AV is safe and effective.

Failure of a Mexican antivenom on recovery from snakebite-related coagulopathy in French Guiana.

INTRODUCTION: In French Guiana, most snakebites are caused by crotalids, with the main signs being tissue damage and bleeding due to venom-induced coagulopathy. Since December 2014 the Western Guiana Hospital (WGH) has used Antivipmyn Tri TM, a Mexican polyvalent antivenom. The aim of the study was to assess its benefit on the correction of snakebite-related coagulopathy. METHODS: This retrospective study included patients hospitalized at the WGH with snakebite and a coagulopathy defined by: a prothrombin rate (PR) lower than 45%, an activated partial thromboplastin time ratio (aPTTr) greater than 2 or a fibrinogen lower than 100 mg.dL-1. The antivenom group included patients receiving Antivipmyn Tri TM from December 2014 to September 2017. The control group included patients admitted between January 2013 and November 2014 (when antivenom was unavailable) or admitted between December 2014 and September 2017 during times of antivenom shortage. We graphically compared the time courses of PR, aPTTr and fibrinogen between groups. Other endpoints were the length of hospital stay and the need for surgery or dialysis. RESULTS: 84 patients were included: 42 in the antivenom group, 42 in the control group. Both groups were similar for age, sex-ratio, proportion of bleedings, necrosis, and severity. Most patients in the antivenom group received 3 vials. There were no significant differences in recovery of PR, aPTTr and fibrinogen through the first 24 h. Fibrinogen declined again in the control group at 30 h and showed a slower rise to normal concentration. There were no significant differences in any secondary endpoint. CONCLUSION: Antivipmyn Tri TM as currently used did not show any benefit in recovery from coagulopathy.