Bedside Coagulation Tests in Diagnosing Venom-Induced Consumption Coagulopathy in Snakebite

Utility of Three Serum Biomarkers for Early Detection of Systemic Envenoming Following Viper Bites in Sri Lanka

STUDY OBJECTIVE

Early detection of systemic envenoming is critical for early antivenom therapy to minimize morbidity and mortality from snakebite. We assessed the diagnostic utility of 3 serum biomarkers in the early detection of systemic envenoming in viper bites in rural Sri Lanka.

METHODS

All confirmed snakebite patients admitted to Teaching Hospital Anuradhapura from July 2020 to June 2021 were included. On admission, blood was collected for venom concentrations, prothrombin time/international normalized ratio, fibrinogen concentration, serum creatinine concentration, and 3 serum biomarkers, namely secretory phospholipase A2 (sPLA2) activity, neutrophil gelatinase-associated lipocalin (sNGAL) concentration, and clusterin (sClu) concentration. Systemic envenoming was defined by the presence of venom-induced consumption coagulopathy, neurotoxicity, acute kidney injury, or the presence of nonspecific clinical effects.

RESULTS

A total of 237 confirmed snakebite patients (Russell's viper, 72; hump-nosed viper, 80; nonvenomous snakes, 31; and unidentified bites, 54) with sufficient preantivenom serum samples were recruited [median age: 42 years (interquartile range [IQR] 29 to 53 years); 173 men (73%)]. Systemic envenoming occurred in 68 (94%) Russell's viper bites, 48 (60%) hump-nosed viper bites, and 45 (83%) unidentified bites. The median sPLA2 activity was 72 nmol/mL/min (IQR 30 to 164) for Russell's viper envenoming, 12 nmol/mL/min (IQR 9 to 16) for hump-nosed viper envenoming, and 11 nmol/mL/min (IQR 9 to 14) for nonvenomous bites. There was no difference in sNGAL and sCLu concentrations among the 3 groups. The median sPLA2 activity of patients with systemic envenoming was 16 nmol/min/mL (IQR 11 to 59) compared to 11 nmol/min/mL (IQR 9 to 14) in patients without systemic envenoming; the difference between medians was 5 nmol/min/mL (95% confidence interval [CI] 4 to 12). The area under the receiver operator characteristic curve (AUC-ROC) of admission sPLA2 activity was the best predictor of systemic envenoming in all snakebites (AUC-ROC 0.72, 95% CI 0.66 to 0.79), whereas sNGAL and sClu concentrations were poor predictors. sPLA2 activity was a better predictor of systemic envenoming in Russell's viper bites (AUC-ROC 0.90, 95% CI 0.76 to 1.00) and in those presenting within 2 hours of a bite. A sPLA2 activity more than 23.5 nmol/min/mL had a sensitivity of 41% (95% CI 34% to 49%), and a specificity of 97% (95% CI 91% to 99.5%) in predicting systemic envenoming. A sPLA2 activity of more than 46 nmol/min/mL on admission had a sensitivity of 67% (95% CI 55% to 77%) and a specificity of 100% (95% CI 51% to 100%) in predicting systemic envenoming in Russell's viper bites.

CONCLUSIONS

sPLA2 activity is an early predictor of systemic envenoming following snakebite, particularly in Russell's viper bites and in those who present early.

Hemostasis Testing in the Emergency Department: A Narrative Review

Routine laboratory screening is typically performed at initial evaluation of the vast majority of presentations to the emergency department (ED). These laboratory results are crucial to the diagnostic process, as they may influence up to 70% of clinical decisions. However, despite the usefulness of biological assessments, many tests performed are inappropriate or of doubtful clinical relevance. This overutilization rate of laboratory testing in hospitals, which represents a significant medical-economic burden, ranges from 20 to 67%, with coagulation tests at the top of the list. While reviews frequently focus on nonintensive care units, there are few published assessments of emergency-specific interventions or guidelines/guidance to date. The aim of this review is to highlight current recommendations for hemostasis evaluation in the emergency setting with a specific analysis of common situations leading to ED admissions, such as suspected venous thrombosis or severe bleeding. We revisit the evidence related to the assessment of patient's hemostatic capacity based on comprehensive history taking and physical examination as well as best practice recommendations for blood sample collection to ensure the reliability of results. This review also includes an examination of various currently available point of care tests and a comprehensive discussion on indications, limitations, and interpretation of these tests.

Whole blood clotting time: Current practices among Thailand National External Quality Assessment Scheme for blood coagulation member laboratories

INTRODUCTION

The Thai National Guidelines for Hemostatic Laboratory Testing were established in 2018. The guidelines recommend that the 20-min whole blood clotting time (20WBCT) method be used to diagnose/monitor snake bites. The aim of this study was to survey members of the Thailand National External Quality Assessment Scheme (NEQAS) for Blood Coagulation to investigate the use of 20WBCT testing compared between the 2021 post-guideline and 2007 pre-guideline periods.

METHODS

In July 2021, questionnaires were sent from the Faculty of Medicine Siriraj Hospital, Mahidol University to 521 Thailand NEQAS for Blood Coagulation member laboratories to survey their WBCT practices. Current WBCT practices were compared with pre-guideline WBCT practices, and chi-square test (x2) was used to test for differences between groups.

RESULTS

Ninety-seven (18.6%) of 521 surveys were returned. Seventy-one laboratories (73.2%) reported knowing about 20WBCT from the Thai national guidelines. The reported average frequency of overall WBCT testing in 2021 was 12.4 times/month. The proportion of laboratories that reported using the 20WBCT test increased from 2.0% in 2007 to 46.4% in 2021 (p < 0.001), and the indications for performing WBCT were virtually unchanged from 2007 to 2021. The proportion of laboratories that reported having problems with WBCT testing decreased from 32.7% in 2007 to 16.5% in 2021.

CONCLUSION

Despite our findings that almost three-quarters of respondent laboratories reported knowing about 20WBCT testing from the WBCT guidelines, and that WBCT-specific problems decreased significantly from 2007 to 2021, more work and training is needed to improve WBCT guideline dissemination, understanding, and adherence in Thailand.

Acute splenic hematoma: A rare complication of snake bite

Splenic hematoma secondary to snake bite is a potential complication due to snake envenomation and poses a significant risk to the health of the patients. Although relatively rare, this complication once diagnosed, should be initiated with timely anti-venom administration and supportive care. Clinicians must be aware of any signs of hematological abnormalities in snakebite patients, as the development of splenic hematoma can have serious implications for patient outcomes. Awareness of this potential complication and multidisciplinary collaboration among medical teams are crucial to ensuring effective management and optimal patient care in these clinical scenarios. Understanding this concern can improve patient prognosis and advance the overall approach to snakebite management in healthcare settings.

Clinical Laboratory Investigations and Antivenom Administration after Malayan Pit Viper (Calloselasma rhodostoma) Envenoming: A Retrospective Study from Southernmost Thailand

The Malayan pit viper (MPV: Calloselasma rhodostoma) is a medically important venomous snake causing numerous envenomations in Thailand. Administration of specific snake antivenom is the only effective treatment for MPV-envenomed patients. However, inappropriate administration or misuse of snake antivenom is problematic in some remote areas of tropical countries where the snakebite envenoming rate is notable. Currently, the indications for administration of MPV antivenom are focused mainly on hematological factors. These include 1) venous clotting time > 20 min, 2) unclotted 20-minute whole-blood clotting time, 3) international normalized ratio > 1.2, 4) platelet count < 50 × 103/μL, 5) systemic bleeding, and 6) impending compartment syndrome. We aimed to determine the association between laboratory data and antivenom administration in MPV-envenomed patients. A retrospective study of data from 2016 to 2021 in Narathiwat Province, the southernmost province in Thailand, was conducted. A total of 838 MPV-bitten patients were included in this study. Local effects and systemic effects were observed in 58.8% and 27.7% of patients, respectively. Coagulopathies, which range from abnormal blood clotting to systemic bleeding, represented the majority of systemic effects. Acute kidney injury developed in 2.5% of patients. In this study, 57.3% of patients were considered appropriate antivenom recipients. Interestingly, the present study revealed that local bleeding and mild to moderate thrombocytopenia became the independent factors for inappropriate use of MPV antivenom. Reeducation and supervision regarding the rational use of snake antivenom are needed to minimize the misuse of antivenom.

Changes in attachment and metabolic activity of rat neonatal cardiomyocytes and nonmyocytes caused by Macrovipera lebetina obtusa venom

The Caucasian viper Macrovipera lebetina obtusa (MLO) is one of the most prevalent and venomous snakes in the Caucasus and the surrounding regions, yet the effects of MLO venom on cardiac function remain largely unknown. We examined the influence of MLO venom (crude and with inhibited metalloproteinases and phospholipase A2) on attachment and metabolic activity of rat neonatal cardiomyocytes (CM) and nonmyocytes (nCM), assessed at 1 and 24 h. After exposing both CM and nCM to varying concentrations of MLO venom, we observed immediate cytotoxic effects at a concentration of 100 μg/ml, causing detachment from the culture substrate. At lower MLO venom concentrations both cell types detached in a dose-dependent manner. Inhibition of MLO venom metalloproteinases significantly improved CM and nCM attachment after 1-hour exposure. At 24-hour exposure to metalloproteinases inhibited venom statistically significant enhancement was observed only in nCM attachment. However, metabolic activity of CM and nCM did not decrease upon exposure to the lower dose of the venom. Moreover, we demonstrated that metalloproteinases and phospholipases A2 are not the components of the MLO venom that change metabolic activity of both CM and nCM. These results provide a valuable platform to study the impact of MLO venom on prey cardiac function. They also call for further exploration of individual venom components for pharmaceutical purposes.

Current trends in digital camera-based bioassays for point-of-care tests

Point-of-care and bedside tests are analytical devices suitable for a growing role in the current healthcare system and provide the opportunity to achieve an exact diagnosis by an untrained person and in various conditions and sites where it is necessary. Using a digital camera integrated into a well-accessible device like a smartphone brings a new way in which a colorimetric point-of-care diagnostic test can provide unbiased data. This review summarizes basic facts about the colorimetric point-of-care tests, principles of how to use a portable device with a camera in the assay, applications of digital cameras for the current tests, and new devices described in the recent papers. An overview of the recent literature and a discussion of recent developments and future trends are provided.

Epidemiology, risk factors, and strategies to prevent and manage poisonings due to pharmaceuticals in children in low income and low-middle income countries: A systematic review

Background

There are significant disparities in the burden of disease due to poisoning between children in low- and high-income countries (HICs). However, there is limited data on the impact of increasing pharmaceutical access in low income countries (LICs) and low-middle income countries (LMICs) on the epidemiology of and risk factors associated with poisoning in children in these settings. Furthermore, while strategies in HICs have effectively reduced the burden of disease due to poisonings in children, there is limited information regarding the efficacy of these interventions in LICs/LMICs.

Methods

We conducted a systematic review in eight databases for literature published between January 2000 to April 2022 to evaluate the epidemiology and risk factors associated with poisonings due to pharmaceuticals and effective strategies to prevent and manage them in children in LICs/LMICs. From 16 061 retrieved articles, 41 were included in the final analysis.

Results

Pharmaceuticals were a common cause of poisoning in children in LICs/LMICs, occurring in between 12.4% and 72.36% of cases. Major risk factors were unsafe medication storage and inadequate caregiver knowledge. Delayed access to care and younger age were associated with increased mortality. Prevention strategies that included education demonstrated improvements in knowledge; however, their impact on incidence and mortality was unclear. Management strategies detailed individual patient care interventions, most commonly gastric lavage and activated charcoal. Meanwhile, delayed presentation, limited provider knowledge, and inadequate laboratory resources to support therapeutic monitoring hindered optimal management.

Conclusions

The combination of educational interventions for prevention, along with regulatory processes to maximise medication storage and formulation safety, could be effective in reducing the burden of poisoning in LICs/LMICs. The development of national or regional protocols for the management of common medication poisonings, augmented by the development of poison control centers and expansion of laboratory access in facilities may help reduce the morbidity and mortality associated with pharmaceutical poisonings in children in LICs/LMICs. Further evidence regarding contextual factors, risk and benefit profiles, the pattern of poisoning, and the impact of preventive and treatment interventions specific to LICs/LMICs is needed to better refine recommendations in these settings.

Registration

PROSPERO: CRD42022315686.

Clinical Risk Factors Associated with Poor Outcomes in Snake Envenoming: A Narrative Review

Snakebite-related fatalities disproportionately affect populations in impoverished socio-economic regions, marked by limited access to adequate healthcare and constrained antivenom availability. Early medical intervention is pivotal in mitigating mortality and morbidity associated with snakebite envenoming (SBE). While clinical assessment remains fundamental in treating SBE, this review aims to spotlight objective parameters that could also affect outcomes. Selected studies that identify factors associated with poor outcomes are predominantly region-specific, single-site, and observational, yet collectively reveal similar findings. They consistently report factors such as treatment delays, susceptibility in vulnerable groups such as children and pregnant women, as well as various biochemical and haematological abnormalities. Acute kidney injury (AKI), low platelets, leucocytosis, abnormal coagulation, and elevated creatine kinase (CK) all show an association with poor outcomes. Furthermore, recognising rare and unusual SBE presentations such as adrenal insufficiency, severe hypertension, intracranial haemorrhage, acute angle closure glaucoma, and bowel ischaemia also has a bearing on outcomes. Despite the integration of these parameters into clinical decision tools and guidelines, the validation of this evidence is limited. This review underscores the imperative for high-quality, multi-centre studies aligned with consensus-driven Core Outcome Sets (COS) and Patient-Reported Outcome Measures (PROMS) to validate and strengthen the current evidence.

Diagnostic characteristics of the 20-minute whole blood clotting test in detecting venom-induced consumptive coagulopathy following carpet viper envenoming

INTRODUCTION

Envenoming by Echis spp. (carpet or saw-scaled vipers) causes haemorrhage and coagulopathy and represents a significant proportion of snakebites in the savannah regions of West Africa. Early diagnosis of envenoming is crucial in the management of these patients and there is limited evidence on the utility of the 20-minute whole blood clotting test (20WBCT) in diagnosing venom-induced consumptive coagulopathy (VICC) following envenoming by Echis ocellatus.

METHODS

A prospective observational cohort study was conducted at the Kaltungo General Hospital in North-eastern Nigeria from September 2019 to September 2021. Standardised 20WBCTs were conducted by trained hospital staff and citrated plasma samples were collected at numerous timepoints. Prothrombin time (PT) and international normalised ratio (INR) were determined using a semi-automated analyser and INR values were calculated using international sensitivity indices (ISI). The sensitivity, specificity, positive predictive values (PPV), negative predictive values (NPV), and likelihood ratios of the 20WBCT compared to an INR ≥ 1.4 were calculated, alongside 95% confidence intervals.

RESULTS

We enrolled 121 patients into our study, with a median age of 26 (18.0-35.0) years and a male predominance (75.2%). The 20WBCT was positive (abnormal) in 101 out of 121 patients at timepoint 0h, of which 95 had an INR ≥ 1.4, giving a sensitivity of 87.2% (95%CI 79.4-92.8). Among patients with a negative 20WBCT (normal), six had an INR < 1.4 giving a specificity of 50% (95%CI 21.1-78.9%). The positive and negative likelihood ratios were 1.7 (95%CI 1.6-1.9) and 0.3 (95%CI 0.1-0.4) respectively.

CONCLUSION

The 20WBCT is a simple, cheap, and easily accessible bedside test with a high sensitivity for the detection of patients with venom induced consumptive coagulopathy (VICC) following envenoming by E. ocellatus, although false positives do occur. Repeated 20WBCTs can identify patients with new, persistent, and rebound coagulopathy.

Comparing modified Lee and White method against 20-minute whole blood clotting test as bedside coagulation screening test in snake envenomation victims

Background

Twenty-minute whole blood clotting test (20WBCT) and Modified Lee and White (MLW) method are the most routinely employed bedside tests for detecting coagulopathic snake envenomation. Our study compared the diagnostic utility of MLW and 20WBCT for snakebite victims at a tertiary care hospital in Central Kerala, South India.

Methods

This single-center study recruited 267 patients admitted with snake bites. 20WBCT and MLW were performed simultaneously at admission along with the measurement of Prothrombin Time (PT). The diagnostic utility of 20WBCT and MLW was determined by comparing the sensitivity (Sn), specificity (Sp), positive and negative predictive values, likelihood ratios, and accuracy at admission with an INR value > 1.4.

Results

Out of 267 patients, 20 (7.5%) patients had VICC. Amongst those who had venom-induced consumption coagulopathy (VICC), MLW was prolonged for 17 patients, (Sn 85% 95% confidence interval [CI]: 61.1-96.0) whereas 20WBCT was abnormal for 11 patients (Sn 55%, 95% CI: 32.04-76.17). MLW and 20WBCT were falsely positive for the same patient (Sp 99.6%, 95% CI: 97.4-99.9%).

Conclusion

MLW is more sensitive than 20WBCT to detect coagulopathy at the bedside amongst snakebite victims. However, further studies are necessary for standardizing bedside coagulation tests in snakebite cases.

Clinical aspects of snakebite envenoming and its treatment in low-resource settings

There is increasing recognition of the public health importance of snakebite envenoming. Worldwide annual incidence is likely to be 5 million bites, with mortality exceeding 150 000 deaths, and the resulting physical and psychological morbidity leads to substantial social and economic repercussions. Prevention through community education by trained health workers is the most effective and economically viable strategy for reducing risk of bites and envenoming. Clinical challenges to effective treatment are most substantial in rural areas of low-resource settings, where snakebites are most common. Classic skills of history taking, physical examination, and use of affordable point-of-care tests should be followed by monitoring of evolving local and systemic envenoming. Despite the profusion of new ideas for interventions, hyperimmune equine or ovine plasma-derived antivenoms remain the only specific treatment for snakebite envenoming. The enormous interspecies and intraspecies complexity and diversity of snake venoms, revealed by modern venomics, demands a radical redesign of many current antivenoms.

Comparison of bedside clotting tests for detecting venom-induced consumption coagulopathy following Sri Lankan viper envenoming

BACKGROUND

The whole blood clotting test (WBCT) is commonly used for diagnosing venom-induced consumption coagulopathy (VICC) in resource-poor settings. We aimed to investigate the diagnostic accuracy of the WBCT and capillary blood clotting test (CBCT) for detecting VICC in viper envenoming in Sri Lanka.

METHODS

All confirmed snakebites admitted to Teaching Hospital Anuradhapura from July 2020 to June 2021 were included. On admission, WBCTs after 15, 20 and 25 min observation times (WBCT-15, WBCT-20 and WBCT-25) and CBCT observed in 30 s intervals (CBCT-t), 5 and 10 min CBCT (CBCT-5 and CBCT-10) were done. Blood was collected simultaneously for prothrombin time (PT)/international normalized ratio (INR) and plasma fibrinogen. We defined VICC as an INR >1.5 (Incomplete VICC = INR>1.5 and complete VICC = ≥3.0).

RESULTS

A total of 272 confirmed snakebites (Russell's viper[76], hump-nosed viper[89], non-venomous snakes[51] and unidentified bites[56]) were recruited (median age: 42 y [interquartile range: 30- 53 y]; 189 males [69%]). On admission, 82 (30%) had incomplete VICC (INR >1.5 and <3) and 77 (28%) had complete VICC (INR ≥3). Sixteen (6%) developed clinically apparent bleeding. The WBCT-15 had the best sensitivity of 47% for detecting VICC and 68% for complete VICC. The sensitivities of the WBCT-20, WBCT-25, CBCT-5 and CBCT-10 was 30-35%. The sensitivities of all tests were better in detecting complete VICC, VICC in Russell's viper bites and more than 2 h post-bite. The WBCT-15 test had a sensitivity of 76% for VICC in confirmed Russell's viper bites. For detection of VICC, CBCT-t had an an excellent sensitivity of 97%, but a poor specificity of 35% for an optimal cut-off of >6.25 min.

CONCLUSION

WBCTs are poorly diagnostic for VICC in Russell's viper and hump-nosed viper envenoming, missing up to two-thirds of patients for some tests. The WBCT-15 was the best test, improving for more severe VICC and greater than 2 h post-bite.

Venom induced consumption coagulopathy and performance of 20-min whole blood clotting test for its detection in viperid envenomation

Background:

Venom induced consumption coagulopathy (VICC) and its underlying mechanisms have not been fully elucidated in viperid envenomation (VE), especially among Indian patients. We evaluated for VICC in VE, assessed the performance of 20-min whole blood clotting test (20WBCT) for VICC detection and also studied predictors of VICC.

Methods:

This hospital-based observational study enrolled 103 consecutive patients (age ⩾ 12 years) of snakebite admitted within 24 h of bite, with features of VE. They underwent 20WBCT, prothrombin time (PT)/international normalised ratio (INR), plasma fibrinogen and D-dimer testing during first 24 h after enrolment. Overt VICC (defined by overt bleeding), subclinical VICC (INR ⩾ 1.4 and/or fibrinogen < 2g/L, without overt bleeding), disseminated intravascular coagulation (DIC) (overt/non-overt, defined based on International Society on Thrombosis and Haemostasis (ISTH) DIC score) and primary defibrination (PDF) were evaluated among patients.

Results:

VICC overall was noted in 77 (≈75%) and overt VICC in 52 (≈50%). DIC (overt/non-overt) was noted in 59 (≈77%) and PDF in 2 (2.6%) patients with VICC. Sensitivity, specificity, positive predictive value and negative predictive value of 20WBCT for VICC detection were 98.7% (95%CI: 92.9–99.9%), 65.4% (95%CI: 44.3–82.8%), 89.4% (95%CI: 83.3–93.5%) and 94.4% (95%CI: 70.4–99.2%) respectively. Severe cellulitis in bitten limb predicted reduced VICC risk.

Conclusion:

Majority (75%) of patients with VE had VICC and 68% with VICC had overt bleeding. DIC (overt/non-overt) was the predominant contributor to VICC. Though 20WBCT is a good screening test for VICC, false positive results should be kept in mind before deciding on snake antivenom treatment.

Mild venom-induced consumption coagulopathy associated with thrombotic microangiopathy following a juvenile Russell's viper (Daboia russelii) envenoming: A case report

Russell's viper envenoming causes venom-induced consumption coagulopathy (VICC) within hours of a bite, which is associated with thrombotic microangiopathy (TMA) and acute kidney injury (AKI) in a proportion of cases. We report a juvenile Russell's viper bite in which a patient developed mild VICC after the usual 24-h observation period, which was subsequently associated with severe AKI due to TMA. This shows the clinical importance of detecting and treating mild VICC, which may be delayed or not detected with bedside clotting tests.

Hemostatic Analysis of Simulated Gloydius ussuriensis Envenomation Using Canine Blood: A Comparison of Thromboelastography and Classical Coagulation Tests

Snake envenomation may lead to venom-induced consumptive coagulopathy (VICC), usually diagnosed by classical coagulation tests (CCTs), such as prothrombin time (PT) and activated partial thromboplastin time (aPTT). However, the results of CCTs are frequently normal in the initial stages, which may delay anti-venom treatments. Thromboelastography (TEG) is a point-of-care and real-time diagnostic tool that enables a comprehensive assessment of the coagulation process. This in vitro study aimed to determine concentration-dependent changes in canine blood caused by Gloydius ussuriensis (G. ussuriensis) envenomation using TEG and CCTs. Lyophilized G. ussuriensis venom was reconstructed using mouse intravenous lethal dose 50 (LD50iv) and serially diluted to 25% LD50iv, 50% LD50iv, and 75% LD50iv to reproduce VICC at different concentrations. Normal saline was used for the control. We compared TEG values of the reaction time (R), kinetic time (K), rate of clot formation (α-angle), maximum amplitude (MA), fibrinolysis at 30 min (LY30), and global strength of the clot (G) with those of PT, aPTT, fibrinogen, and platelet counts (PLTs). Most TEG parameters, except R and LY30, demonstrated statistically significant changes compared with the control at all concentrations. CCTs, except PLTs, revealed significant changes at ≥50% LD50iv. Thus, TEG could be a useful diagnostic strategy for early VICC and preventing treatment delay.

Malayan Pit Viper Envenomation and Treatment in Thailand

Introduction

The Malayan pit viper (MPV; Calloselasma rhodostoma) is a hematotoxic snake found in all regions of Thailand and many countries in Southeast Asia. Treatment of MPV envenomation varies among facilities due to their capabilities.

Materials and Methods

This study was a retrospective review of patients with MPV envenomation who were reported to the Ramathibodi Poison Center from 1 July 2016 to 30 June 2018.

Results

Of the 167 patients (median age, 40.5 years; range, 1.3–87.0 years) bitten by an MPV, the most common bite site was the foot (29.3%). Most patients reached the hospital within 1 hour of being bitten. One-hundred fifty-six patients (93.4%) had local effects from envenomation; 17 patients (10.2%) had severe local complications including necrotizing fasciitis (3.0%) and compartment syndrome (7.2%). Systemic effects such as hemorrhage and abnormal hemostasis occurred in 147 patients (88.0%). Additional effects included abnormal venous clotting time in 123 patients (73.7%), unclotted 20-minute whole blood clotting time in 57 patients (34.1%), low platelet counts (<50,000/µL) in 29 patients (17.4%), prolonged international normalized ratio (>1.2) in 51 patients (30.5%), and systemic bleeding in 14 patients (8.4%). The median onset of bleeding disorder was 6 hours. Monitoring for 24, 48, and 49 hours after bite enabled detection of systemic effects in 94.2%, 99.3%, and 100.0%, respectively. Three hundred fifteen courses of antivenin were administered to 144 patients (86.2%). All the patients who received antivenin recovered from bleeding disorder. Only 7.0% of antivenin doses were administered without Thai Red Cross indications. Allergic reactions from antivenin occurred in 34.7% of the 144 patients. One hundred thirty patients (77.8%) received antibiotics, and 32 patients (19.2%) required surgical management, including debridement and fasciotomy.

Conclusion

MPV envenomation results in local and systemic effects. Most systemic effects were abnormal clotting test results. Most patients reported onset of bleeding disorder within 48 hours.

Splenic rupture and subsequent splenectomy in a young healthy victim following Russell's viper bite

Splenic rupture and/or splenectomy is/are not uncommon in clinical arena. Here we present this case of extensive haemorrhage-induced splenic rupture which resulted in splenectomy in a young healthy male (who did not have any previous medical conditions) following a Russell's viper bite. He developed upper abdominal and shoulder pain on his left side along with hypotension and reduced level of haemoglobin on the third day following bite despite antivenom treatment. Following confirmation of splenic rupture and haemoperitoneum by ultrasound and computed tomography scans, an emergency splenectomy was performed using laparotomy. Although Russell's viper bites are known to induce bleeding complications, splenic rupture due to haemorrhage in spleen has not been previously reported. Russell's viper venom toxins such as metalloproteases, serine proteases and phospholipase A2 might have affected the vascular permeability resulting in excessive bleeding and increased pressure in the spleen leading to rupture. Further investigations are required to underpin the impact of snake venom toxins on the architecture and functions of spleen. However, the clinicians who treat snakebites should be aware of this type of rare complications so as to provide appropriate management for such victims.

Viper venoms drive the macrophages and hepatocytes to sequester and clear platelets: novel mechanism and therapeutic strategy for venom-induced thrombocytopenia

Venomous snakebites cause clinical manifestations that range from local to systemic and are considered a significant global health challenge. Persistent or refractory thrombocytopenia has been frequently reported in snakebite patients, especially in cases caused by viperidae snakes. Viper envenomation-induced thrombocytopenia may persist in the absence of significant consumption coagulopathy even after the antivenom treatment, yet the mechanism remains largely unknown. Our study aims to investigate the mechanism and discover novel therapeutic targets for coagulopathy-independent thrombocytopenia caused by viper envenomation. Here we found that patients bitten by Protobothrops mucrosquamatus and Trimeresurus stejnegeri, rather than Naja. atra may develop antivenom-resistant and coagulopathy-independent thrombocytopenia. Crude venoms and the derived C-type lectin-like proteins from these vipers significantly increased platelet surface expression of neuraminidase and platelet desialylation, therefore led to platelet ingestion by both macrophages and hepatocytes in vitro, and drastically decreased peripheral platelet counts in vivo. Our study is the first to demonstrate that desialylation-mediated platelet clearance is a novel mechanism of viper envenomation-induced refractory thrombocytopenia and C-type lectin-like proteins derived from the viper venoms contribute to snake venom-induced thrombocytopenia. The results of this study suggest the inhibition of platelet desialylation as a novel therapeutic strategy against viper venom-induced refractory thrombocytopenia.

Differential Diagnosis Between Venomous (Bothrops jararaca, Serpentes, Viperidae) and "Nonvenomous" (Philodryas olfersii, Serpentes, Dipsadidae) Snakebites: Is It Always Possible?

Bites of "nonvenomous" snakes can sometimes be mistaken for the bites of venomous snakes. As an example of this confusion, this report describes confirmed bites by Philodryas olfersii and Bothrops jararaca. In the first case, a 55-y-old man with a history of controlled hypertension was bitten on his right forearm by P olfersii. Physical examination revealed extensive edema, erythema, and widespread ecchymoses throughout his right upper limb. Laboratory tests indicated leukocytosis and high D-dimer levels, but normal coagulation, suggestive of a resolved recent coagulopathy. He received only supportive treatment. In the second case, a healthy 35-y-old man was bitten by B jararaca. Although the anatomic region of the bite and the results of physical examination were similar to those in the first case, laboratory tests showed mild coagulopathy, leukocytosis, and high D-dimer levels. The patient was treated with antivenom. In both cases, the 20-min whole blood clotting test results were normal. Patients bitten by P olfersii may present with local symptoms resembling B jararaca envenomation. Without snake identification and the detection of venom-induced consumption coagulopathy, especially in places where the 20-min whole blood clotting test is the only clotting test available, it is almost impossible to establish an accurate and safe differential diagnosis. In this context, the best alternative is to take the risk of prescribing antivenom for a possible P olfersii bite rather than failing to do so for a real Bothrops bite. Late treatment for Bothrops bite can result in severe complications and sequelae.

Clinical management of snakebite envenoming: Future perspectives

Snakebite envenoming is a major cause of morbidity and mortality in rural communities throughout the tropics. Generally, the main clinical features of snakebites are local swelling, tissue necrosis, shock, spontaneous systemic hemorrhage, incoagulable blood, paralysis, rhabdomyolysis, and acute kidney injury. These clinical manifestations result from complex biochemical venom constituents comprising of cytotoxins, hemotoxins, neurotoxins, myotoxins, and other substances. Timely diagnosis of envenoming and identification of the responsible snake species is clinically challenging in many parts of the world and necessitates prompt and thorough clinical assessment, which could be supported by the development of reliable, affordable, widely-accessible, point-of-care tests. Conventional antivenoms based on polyclonal antibodies derived from animals remain the mainstay of therapy along with supportive medical and surgical care. However, while antivenoms save countless lives, they are associated with adverse reactions, limited potency, and are relatively inefficacious against presynaptic neurotoxicity and in preventing necrosis. Nevertheless, major scientific and technological advances are facilitating the development of new molecular and immunologic diagnostic tests, as well as a new generation of antivenoms comprising human monoclonal antibodies with broader and more potent neutralization capacity and less immunogenicity. Repurposed pharmaceuticals based on small molecule inhibitors (e.g., marimastat and varespladib) used alone and in combination against enzymatic toxins, such as metalloproteases and phospholipase A2s, have shown promise in animal studies. These orally bioavailable molecules could serve as early interventions in the out-of-hospital setting if confirmed to be safe and efficacious in clinical studies. Antivenom access can be improved by the usage of drones and ensuring constant antivenom supply in remote endemic rural areas. Overall, the improvement of clinical management of snakebite envenoming requires sustained, coordinated, and multifaceted efforts involving basic and applied sciences, new technology, product development, effective clinical training, implementation of existing guidelines and therapeutic approaches, supported by improved supply of existing antivenoms.

Snake Venoms in Diagnostic Hemostasis and Thrombosis

Snake venoms have evolved primarily to immobilize and kill prey, and consequently, they contain some of the most potent natural toxins. Part of that armory is a range of hemotoxic components that affect every area of hemostasis, which we have harnessed to great effect in the study and diagnosis of hemostatic disorders. The most widely used are those that affect coagulation, such as thrombin-like enzymes unaffected by heparin and direct thrombin inhibitors, which can help confirm or dispute their presence in plasma. The liquid gold of coagulation activators is Russell's viper venom, since it contains activators of factor X and factor V. It is used in a range of clotting-based assays, such as assessment of factor X and factor V deficiencies, protein C and protein S deficiencies, activated protein C resistance, and probably the most important test for lupus anticoagulants, the dilute Russell's viper venom time. Activators of prothrombin, such as oscutarin C from Coastal Taipan venom and ecarin from saw-scaled viper venom, are employed in prothrombin activity assays and lupus anticoagulant detection, and ecarin has a valuable role in quantitative assays of direct thrombin inhibitors. Snake venoms affecting primary hemostasis include botrocetin from the jararaca, which can be used to assay von Willebrand factor activity, and convulxin from the cascavel, which can be used to detect deficiency of the platelet collagen receptor, glycoprotein VI. This article takes the reader to every area of the diagnostic hemostasis laboratory to appreciate the myriad applications of snake venoms available in diagnostic practice.

Bites by Xenodon merremii (Wagler, 1824) and Xenodon neuwiedii (Günther, 1863) (Dipsadidae: Xenodontini) in São Paulo, Brazil: a retrospective observational study of 163 cases

Despite the biological relevance and abundance of non-front-fanged colubroid snakes, little is known about their medical significance. Here, we describe the clinical, epidemiological, and biological aspects of bites by two colubroid species. We retrospectively analyzed cases of Xenodon merremii and Xenodon neuwiedii bites in which the offending snake was clearly identified. Analyses included variables related to the snake and the patient, including demographic data, clinical findings, and treatments. Of the 163 cases, 123 were bites by X. merremii and 40 by X. neuwiedii. Most bites occurred in spring and summer, predominantly during the daytime. Most offending snakes were female. Bites by X. merremii juveniles were more frequent in autumn than in other seasons, whereas those by X. neuwiedii adults were in the summer. Hands and feet were the most frequently affected regions, with no significant difference between upper and lower limbs bitten by either X. merremii or X. neuwiedii. The main clinical findings were pain, transitory bleeding, erythema, and local edema. Local edema was proportionally more frequent with X. neuwiedii bites than with X. merremii bites. No patient had extensive edema or systemic envenomation. A significant association between the snout-vent-length and transitory bleeding in bites by X. merremii, but not in those by X. neuwiedii, was identified. Whole blood clotting tests were normal in all tested patients (62 cases). Sixteen patients were incorrectly treated with anti-Bothrops antivenom. In conclusion, most accidents caused by X. merremii and X. neuwiedii present mild local symptomatology. These snakes can be mistaken for lance-headed vipers, and some bites present symptoms that resemble mild bites by Bothrops sp. Physicians should be aware of X. merremii and X. neuwiedii bites to avoid unnecessary patient distress and overprescription of antivenom.

Attempt to Develop Rat Disseminated Intravascular Coagulation Model Using Yamakagashi (Rhabdophis tigrinus) Venom Injection

Disseminated intravascular coagulation, a severe clinical condition caused by an underlying disease, involves a markedly continuous and widespread activation of coagulation in the circulating blood and the formation of numerous microvascular thrombi. A snakebite, including that of the Yamakagashi (Rhabdophis tigrinus), demonstrates this clinical condition. Thus, an animal model using Yamakagashi venom was constructed. Yamakagashi venom was administered to rats, and its lethality and the changes in blood coagulation factors were detected after venom injection. When 300 μg venom was intramuscularly administered to 12-week-old rats, (1) they exhibited hematuria with plasma hemolysis and died within 48 h; (2) Thrombocytopenia in the blood was observed in the rats; (3) irreversible prolongation of prothrombin time in the plasma to the measurement limit occurred; (4) fibrinogen concentration in the plasma irreversibly decreased below the measurement limit; and (5) A transient increase in the plasma concentration of D-dimer was observed. In this model, a fixed amount of Rhabdophis tigrinus venom injection resulted in the clinical symptom similar to the human pathology with snakebite. The use of the rat model is very effective in validating the therapeutic effect of human disseminated intravascular coagulation condition due to snakebite.

The Treatment of Unidentified Hematotoxic Snake Envenomation and the Clinical Manifestations of a Protobothrops kelomohy Bite

Hematotoxic snake envenomation is clinically important and has serious complications. This case report describes the clinical manifestations of a bite from a newly described species of hematotoxic snake and the outcomes of treatment using locally available antivenom and supportive management. A 39-y-old male was bitten on his right ankle by an unidentified snake. The patient developed coagulopathy, rhabdomyolysis, and clinical signs of compartment syndrome of his right leg within the first day. Eight doses (30 mL, or 3 vials per dose), or a total of 240 mL, of hemato-polyvalent antivenin (Thai Red Cross, Thailand) were given. Aggressive intravenous hydration and alkalinization of urine were performed, and a fasciotomy was performed for the treatment of suspected compartment syndrome. The patient's clinical symptoms and laboratory results indicated progressive improvement during the 5 d of hospitalization. The snake was later identified as Protobothrops kelomohy, a novel snake species with no clinical data available regarding its envenomation of humans. This case shows that P kelomohy envenomation can produce severe effects that occur both locally and systemically. The benefits of the use of polyvalent antivenom in this situation were unclear. However, with supportive treatment in conjunction with serial clinical and laboratory monitoring, the patient recovered, albeit after 7 d of hospitalization.

Documentation of a proven Mountain Pitviper (Ovophis monticola) envenomation in Kathmandu, Nepal, with its distribution ranges: implications for prevention and control of pitviper bites in Asia

We document inadequately diagnosed coagulopathy (potential to be life threatening) due to Ovophis monticola bite. Although its bites are common in the hills of Nepal, associated envenomations have not been documented elaborately. Herein, we present the clinical and treatment details of a proven O. monticola bite and areas where it may pose the risk of envenomations (suggesting huge populations in Asia to be vulnerable to its bites). Its envenomation was managed symptomatically with several non-evidence-based interventions. Since no specific pitviper antivenom is available in Nepal yet, managing coagulopathy associated to O. monticola envenomation is still challenging. This case emphasizes the need of developing the standard protocol for the diagnosis and management of pitviper bites and study of effectiveness of the available pitviper antivenoms until specific pitviper antivenom is available. Further, the demonstrated distribution localities of this species may have implications for snakebite prevention and designing and distribution of the effective antivenoms.

Potential Role of Platelet-Activating C-Type Lectin-Like Proteins in Viper Envenomation Induced Thrombotic Microangiopathy Symptom

Envenomation by viperid snakes may lead to severe bleeding, consumption coagulopathy, and thrombotic microangiopathy symptoms. The exact etiology or toxins responsible for thrombotic microangiopathy symptoms after snake envenomation remain obscure. Snake C-type lectin-like proteins (snaclecs) are one of the main non-enzymatic protein constituents in viper venoms, of which a majority are considered as modulators of thrombosis and hemostasis. In this study, we demonstrated that two snaclecs (mucetin and stejnulxin), isolated and identified from Protobothrops mucrosquamatus and Trimeresurus stejnegeri venoms, directly induced platelet degranulation and clot-retraction in vitro, and microvascular thrombosis has been confirmed in various organs in vivo. These snaclecs reduced cerebral blood flow and impaired motor balance and spatial memories in mice, which partially represent the thrombotic microangiopathy symptoms in some snakebite patients. The functional blocking of these snaclecs with antibodies alleviated the viper venom induced platelet activation and thrombotic microangiopathy-like symptoms. Understanding the pathophysiology of thrombotic microangiopathy associated with snake envenoming may lead to emerging therapeutic strategies.