Wilderness Medical Society Practice Guidelines for the Treatment of Pitviper Envenomations in the United States and Canada

Impact of tourniquet use on severity of snakebite envenoming in Chongqing, China: a single-center retrospective study

OBJECTIVE

To identify risk factors associated with snakebite severity and determine whether tourniquet use can affect the severity and outcome of snakebites.

METHODS

The clinical data of patients who sustained limb snakebites from 1 March 2021 to 31 October 2022 were reviewed. The patients were divided into three groups according to snakebite severity: mild (517 cases), moderate (112 cases), and severe (8 cases). We compared the clinical data of mild versus moderate to severe snakebites. Multivariate logistic regression was used to determine the independent risk factors for moderate to severe snakebites.

RESULTS

The study involved 637 patients. There were statistically significant differences in age, tourniquet use, onset time, white blood cell increase, platelet decrease, creatine kinase (CK) increase, activated partial thromboplastin time shortening, and length of stay between patients with mild snakebites and those with moderate to severe snakebites. Multivariate logistic regression analysis showed that age, tourniquet use, and CK increase were independent risk factors for moderate to severe snakebites.

CONCLUSION

The overall severity of snakebites in Chongqing is mild, and the prognosis is good. Age, tourniquet use, and CK increase are independent risk factors for the severity of snakebites. We do not recommend tourniquet use after snakebites in Chongqing.

Original algorithms for the detection of cardiovascular involvement of neglected tropical diseases

INTRODUCTION

Neglected tropical diseases (NTDs) introduce considerable morbidity and mortality on a global scale, directly impacting over 1 billion individuals as well as their families and communities. Afflicted individuals may have limited access to resources and care in these regions, contributing to a high proportion of chronic, progressive, and systemic disease. The cardiovascular system is at particular risk of demise for several NTDs, yet remains largely unstudied due in part to the lack of robust data collection mechanisms in the most impacted regions.

AREAS COVERED

The present review is a part of the Neglected Tropical Diseases and other Infectious Diseases affecting the Heart (NET-Heart) Project, aiming at summarizing the current knowledge on cardiovascular implications of NTDs and providing diagnostic as well as management recommendations which can be tailored to low-resource settings. The diagnostic and management algorithms of 13 unique NTDs are presented and summarized.

EXPERT OPINION

Recognizing cardiac manifestations of NTDs can significantly alter disease trajectory and all physicians benefit from improved knowledge about NTDs. Great potential exists to advance patient care by improving data collection, communication, and international collaboration.

Case fatality rate and burden of snakebite envenoming in children - A systematic review and meta-analysis

Snakebite is a major public health problem with an estimated global burden of 5 million people per annum. Data on snakebite envenoming in children are very limited and is unclear whether there is a significant difference in severity between adults and children. We therefore conducted a meta-analysis of observational studies on snakebite in children to obtain a more precise estimate of case fatality rate (CFR) as well as to explore the differences in outcome between children and adults. Studies from all over the world reported until the end of February 2023 were included. Analysis was conducted consistent with the Meta-analysis of Observational Studies in Epidemiology (MOOSE) criteria. Estimates were obtained from Random Effects Model (REM). Sub-analysis was conducted for studies from sub-Saharan Africa (SSA) to provide estimates for the continent. Adverse outcomes comprising composite endpoints (CE), defined as fatality and or complications, were compared between children and adults in sub-analysis of studies reporting on both groups. The annual burden and fatality of snakebite envenoming were derived based on lifetime prevalence of bite, meta-analysis estimates, and other data inputs. The pooled estimate of the CFR from 35 studies included worldwide was 1.98% [95%CI:1.38-2.58%] while the estimates from 6 studies within SSA was 2.43% (95%CI:0.67-4.20%). The odds of adverse outcomes were 2.52 times higher in children compared to adults. The estimated annual burden was 178,491 cases with 4346 deaths among children in SSA. These estimates compare favorably to those reported in the literature.

Neurotoxic respiratory failure absent following Arizona rattlesnake bites

Warnings of neurotoxic respiratory paralysis following envenomation by rattlesnakes (Crotalus sp.) have been included in numerous scholarly publications over the past 60 years, resulting in fear and anxiety in the public and among clinicians. We examine the validity of the widespread belief that rattlesnakes in the arid southwestern United States, and particularly the Mohave Rattlesnake (Crotalus scutulatus), pose a significant risk of medically relevant respiratory weakness and paralysis in humans. A retrospective review of 3440 suspected rattlesnake bites reported to the Arizona Poison and Drug Information Center between 1999 and 2020 produced no evidence of respiratory weakness in a region with three species known to express significant amounts of neurotoxin in their venoms: Crotalus concolor, C. tigris, and the more widely distributed C. scutulatus. A literature review produced numerous warnings regarding respiratory paralysis following envenomation by rattlesnakes in our region that either lacked references or cited sources that did not contain strong supportive data. We found no case reports of neurotoxic respiratory weakness following Arizona rattlesnake bites in the literature and such reports in surrounding states were scant. We conclude that neurotoxic respiratory failure in this region following rattlesnake envenomation is extraordinarily rare. All rattlesnake bites should receive the same consideration and critical care, and warnings about significant risk of respiratory failure are unwarranted, regardless of species involved.

BITES study: A qualitative analysis among emergency medicine physicians on snake envenomation management practices

INTRODUCTION

Antivenom is currently considered standard treatment across the full spectrum of severity for snake envenomation in the United States. Although safe and effective antivenoms exist, their use in clinical practice is not universal.

OBJECTIVE

This study explored physicians' perceptions of antivenom use and experience with snake envenomation treatment in order to identify factors that influence treatment decisions and willingness to administer.

METHODS

We conducted a qualitative study including in-depth interviews via online video conferencing with physicians practicing in emergency departments across the United States. Participants were selected based on purposive sampling methods. Data analysis followed inductive strategies, conducted by two researchers. The codebook and findings were discussed within the research team.

FINDINGS

Sixteen in-depth interviews with physicians from nine states across the US were conducted. The participants' specialties include emergency medicine (EM), pediatric EM, and toxicology. The experience of treating snakebites ranged from only didactic education to having treated over 100 cases. Emergent themes for this manuscript from the interview data included perceptions of antivenom, willingness to administer antivenom and influencing factors to antivenom usage. Overall, cost-related concerns were a major barrier to antivenom administration, especially in cases where the indications and effectiveness did not clearly outweigh the potential financial burden on the patient in non-life- or limb-threatening cases. The potential to decrease recovery time and long-term functional impairments was not commonly reported by participants as an indication for antivenom. In addition, level of exposure and perceived competence, based on prior education and clinical experience, further impacted the decision to treat. Resources such as Poison Center Call lines were well received and commonly used to guide the treatment plan. The need for better clinical guidelines and updated treatment algorithms with clinical and measurable indicators was stated to help the decision-making process, especially among those with low exposure to snake envenomation patients.

CONCLUSIONS

A major barrier to physician use of antivenom is a concern about cost, cost transparency and cost-benefit for the patients. Those concerns, in addition to the varying degrees of awareness of potential long-term benefits, further influence inconsistent clinical treatment practices.

Predictors of FabAV use in copperhead envenomation

CONTEXT

Crotaline snake envenomation is a serious medical condition affecting thousands of Americans each year. Variation in the treatment of Crotaline snakebites exists among physicians in the United States. Management of copperhead snakebites is controversial with some experts advocating minimal intervention, rarely necessitating antivenom use and, even more rarely, surgical intervention. This study assessed the use of Crotaline Polyvalent Immune Fab antivenom (Ovine) (FabAV) and explored factors influencing the decision to prescribe antivenom for copperhead envenomation in patients in Northeastern Oklahoma.

METHODS

A retrospective cohort study examining electronic medical records of patients with copperhead snakebites from July 1, 2014 to August 31, 2019. Data collected included: patient demographics, transfer information, snake species, bite site, progression of local tissue effects, additional clinical and lab results, patient comorbidities, and treatment strategy. Associations between patient variables and treatment were evaluated using the chi-square test of independence, median test, and logistic regression analysis. Associations were statistically significant if p < 0.05.

DISCUSSION

Of the 130 patients bitten by a copperhead, a majority (75%) received FabAV. Symptoms of copperhead envenomation were mostly limited to the progression of tissue damage. Predictors of treatment with FabAV included progression of venom effects across major joints, younger age, comorbidities, and upper extremity bites.

CONCLUSIONS

Patients who have multiple comorbidities, upper extremity bites and progression of venom effects across major joints are more likely to be treated with FabAV. The high usage of FabAV at the study site underscores the need for continued work to optimize the use of antivenom for copperhead envenomations.

Rattlesnake envenomation in 2 Visayan warty pigs

Rattlesnake envenomation is an important cause of morbidity and mortality in humans and animals in the southwestern United States and elsewhere. Two Visayan warty pigs (Sus cebifrons) from a regional zoo were submitted for autopsy after being found dead close to a southern Pacific rattlesnake (Crotalus helleri) in their enclosure. Both pigs had severe regionally extensive cutaneous, subcutaneous, and muscle hemorrhage and edema with myonecrosis. Additionally, both pigs had lesions consistent with puncture wounds within the oral cavity, and one pig had a similar wound on a forelimb. The history, and gross and histologic findings, were consistent with envenomation by rattlesnake bite. There are few documented cases of snakebite envenomation in pigs, and it had been suggested that pigs may have some degree of resistance to envenomation. Our results indicate that warty pigs are susceptible to the action of rattlesnake venom.

No Change in the Use of Antivenom in Copperhead Snakebites in Ohio

INTRODUCTION

Historically, copperhead snake (Agkistrodon contortrix) envenomations were not treated with antivenom owing to related adverse events and little benefit. However, recent studies have shown improved outcomes with antivenom use. We hypothesized that the frequency of antivenom use for copperhead envenomation in Ohio has increased as benefits of administration became more widely known.

METHODS

All copperhead snakebites reported to the Ohio poison control centers from 2006 through 2016 were compiled. Antivenom use, bite severity, and disposition were abstracted. A nonparametric test for trend was used to evaluate changes over time for the number of patients treated with antivenom and patient disposition. Logistic regression was used to assess the odds of admission vs discharge with antivenom administration, bite severity, age, and sex as independent variables.

RESULTS

Ninety-eight patients reported copperhead snakebites to the poison control centers. The test of trend showed no change in the proportion of patients treated with antivenom by year (P=0.42). There was no difference in the proportion of patients discharged home (P=0.38) per year. Logistic regression showed antivenom use was associated with an odds ratio for admission of 46.7 (95% CI: 7.3-296.4).

CONCLUSIONS

The frequency of antivenom use for copperhead bites did not significantly increase between 2006 and 2016. Administration of antivenom was associated with a large increase in the odds of admission to the hospital, even when controlling for bite severity. Further education regarding the benefits and safety of antivenom may increase its use for copperhead snakebites, but may lead to an increase in hospital admissions.

Wilderness Medicine

With more families spending time outdoors or embarking on wilderness adventures, pediatricians may be tasked with providing appropriate counseling to parents and children. Although the breadth of wilderness medicine can be extensive, this article will focus on preventive measures, common injuries, and injury treatment options in an outdoor environment. [Pediatr Ann. 2021;50(6):e234-e239.].

Snakebites Reported to the Kentucky Regional Poison Control Centers for the Years 2012-2016

INTRODUCTION

Snake envenomations cause significant morbidity and mortality. The goals of this study were to assess the epidemiology of snakebites in Kentucky and treatment strategies used by physicians reporting to the Kentucky Regional Poison Control Centers.

METHODS

This was a descriptive epidemiologic study compiling clinical data on snakebites reported to the Kentucky Regional Poison Control Centers from 2012 to 2016. We built a database of the patient demographics, treatment, and clinical course of each snakebite reported in the study period. Attention was paid to all antivenom interventions and use of contraindicated therapies.

RESULTS

We compiled 674 total records. Patient age was 34±18 y (mean±SD), with males (71%) predominating. Most (97%) bites were to a distal upper or lower extremity. The majority (78%) occurred at a private residence. Most reports came between May and September (88%). Of the 674 patients, 24% (n=159) were classified as moderate or severe. Two hundred thirty (34%) patients were admitted to the hospital. Forty-six patients (7%) received surgical consultation, and 12 (2%) underwent surgical intervention. One hundred fifty-three patients received antivenom, with 6±3 vials used per patient. Length of stay was 3±2 d when antivenom was administered and 2±2 d when not administered. Six cases of coagulopathy were noted. Multiple contraindicated therapies were noted.

CONCLUSIONS

Snake envenomations are a prevalent public health concern for residents of Kentucky, chiefly during summer months. Significant medical intervention is being performed for many patients, with a high prevalence of contraindicated therapies. More data are needed to fully characterize the epidemiologic impact and appropriateness of the interventions being applied.

Snakebite Envenomation and Heart: Systematic Review

Snakebite envenomation is a neglected tropical disease which can result in morbidity and mortality. Cardiac implications are poorly understood due to the low frequency of cardiotoxicity combined with a lack of robust information, as snakebites commonly occur in remote and rural areas. This review aims to assess cardiovascular implications of snakebite envenoming and proposes an algorithm for screening of cardiovascular manifestations. A systematic review was performed and 29 articles relating to cardiovascular involvement in snakebite envenomation were selected. Cardiovascular involvement seems to be rare and includes a wide spectrum of outcomes, such as myocardial infarction, ventricular dysfunction, hypotension, cardiac arrest, and myocarditis. In a significant proportion of the cases analyzed (24.39%), the cardiovascular manifestations had major consequences (cardiac arrest, myocardial infarction, malignant ventricular arrhythmias, or death). Clinical monitoring, physical examination, and early electrocardiogram should be considered as key measures to detect cardiovascular involvement in patients with evidence of systemic illness.

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.

How Should Native Crotalid Envenomation Be Managed in the Emergency Department?

BACKGROUND

Pit vipers, also known as crotalids, are a group of snakes including rattlesnakes, copperheads, and cottonmouths (water moccasins). Crotalids have a broad geographic distribution across the United States, and bites from these snakes can carry significant morbidity. Their envenomations are characterized by local tissue effects, hematologic effects, and systemic effects. Envenomations are generally treated with 1 of 2 antivenoms available in the United States.

OBJECTIVE

We developed a series of clinical questions to assist and guide the emergency physician in the acute management of a patient envenomated by a crotalid.

METHODS

We conducted a PubMed literature review from January 1970 to May 2020 in English for articles with the keywords "bite" and "crotalidae."

RESULTS

Our literature search resulted in 177 articles. A total of 33 articles met criteria for rigorous review and citation in the development of these consensus guidelines.

CONCLUSIONS

Patients should be initially evaluated, stabilized, and assessed for local effects, hematologic effects, and systemic toxicity suggestive of envenomation. Antivenom should be given if toxic effects are present. Surgical intervention including debridement and fasciotomy should be avoided. Prophylactic antibiotics are not necessary.

Wilderness Cardiology: A Case of Envenomation-Associated Cardiotoxicity Following a Rattlesnake Bite

Cardiac injury is infrequently described as a complication of snake bite envenomation. We present the case of a 62-year-old male with shortness of breath, right lower extremity edema, and elevated cardiac troponin 6 days after a Northern Pacific rattlesnake bite.

The role of a point-of-care ultrasound protocol in facilitating clinical decisions for snakebite envenomation in Taiwan: a pilot study

BACKGROUND

The incidence of acute compartment syndrome (ACS) following snakebite envenomation may be seriously overestimated in Taiwan. Snakebite-induced ACS is difficult to determine solely by clinical examination. Snakebite patients previously underwent surgical intervention based on speculation and general clinical examinations suggesting ACS presentations instead of direct intracompartmental pressure (IP) measurement prior to fasciotomy. Point-of-care ultrasound (POCUS) is a relatively widely available noninvasive tool. This study aimed to evaluate snakebite-envenomated patients for the presence of subcutaneous edema and diastolic retrograde arterial flow (DRAF).

MATERIALS AND METHODS

Snakebite patients were prospectively recruited between 2017 and 2019. All patients were examined with POCUS to locate edema and directly visualize and measure the arterial flow in the compressed artery. The presence of DRAF in the compressed artery is suggestive of ACS development because when compartment space restriction occurs, increased retrograde arterial flow is observed in the artery.

RESULTS

Twenty-seven snakebite patients were analyzed. Seventeen patients (63%) were bitten by Crotalinae snakes, seven (26%) by Colubridae, one (4%) by Elapidae, and two (7%) had unidentified snakebites. All Crotalinae bit patients received antivenom, had subcutaneous edema and lacked DRAF in a POCUS examination series.

DISCUSSION

POCUS facilitates clinical decisions for snakebite envenomation. We also highlighted that the anatomic site of the snakebite is an important factor affecting the prognosis of the wounds. There were limitations of this study, including a small number of patients and no comparison with the generally accepted invasive evaluation for ACS.

CONCLUSIONS

We are unable to state that POCUS is a valid surrogate measurement of ACS from this study but see this as a starting point to develop further research in this area. Further study will be needed to better define the utility of POCUS in patients envenomated by snakes throughout the world.

Review of North American pit viper antivenoms

PURPOSE

For the first time in nearly 20 years, 2 antigen-binding fragment (Fab) antivenoms are available to treat patients who incur North American pit viper snakebites: Crotalidae polyvalent immune Fab (ovine), or simply FabAV; and Crotalidae immune F(ab')2 (equine), or simply F(ab')2. Pharmacists are in a key position for the selection, dosing, reconstitution, administration, and monitoring of antivenom therapy; however, they encounter inconsistent exposure and experience with these drugs. Thus, an updated review of the literature is necessary.

METHODS

The search strategy and selection incorporated both controlled vocabulary terms and keywords to describe concepts relevant to the search. Retrieval was limited to literature published from 1997 to the present in English, Portuguese, or Spanish.

RESULTS

Given the paucity of available prospective literature, the authors elected to include all prospective evidence to best describe the role of antivenom. For the primary literature review, manuscripts were excluded if they were observational studies, conference abstracts, narrative or opinion articles, letters to the editor, or in-progress studies.

CONCLUSION

While there is limited evidence-based guidance on the superiority of F(ab')2 to FabAV, or vice versa, individual and regional considerations should contribute to formulary decisions. Pharmacists must play a role in the development of clinical pathways to ensure appropriate evaluation, supportive care, and antivenom procurement, administration, and monitoring.

When It Comes to Snakebites, Kids Are Little Adults: a Comparison of Adults and Children with Rattlesnake Bites

BACKGROUND

Rattlesnake envenomations are a significant cause of morbidity in the USA. While pediatric rattlesnake envenomations are relatively common, data comparing adult and pediatric patients with rattlesnake envenomations remain limited.

METHODS

This multi-center retrospective study used the North American Snakebite Registry (NASBR), a sub-registry of the Toxicology Investigator's Consortium (ToxIC). All cases of rattlesnake envenomations between January 1, 2013, and December 31, 2017, which were entered into the NASBR, were reviewed. Clinical and laboratory parameters, as well as treatment and outcome measurements, were compared between adult and pediatric patients.

RESULTS

A total of 420 unique cases were identified, including 94 pediatric patients. Adult patients were more likely to be male (76% vs. 62%; OR 1.98) and sustain upper extremity envenomations (57% vs. 25%; OR 4.4). After adjusting for bite location, adults were more likely to exhibit edema compared with pediatric patients. After controlling for envenomation location, there was no difference in rates of necrosis between adult and pediatric patients. Adults exhibited early hematologic toxicity less frequently than pediatric patients, but there was no difference in the rates of late hematologic toxicity. There were no differences in the rates of hypotension or intubation.

CONCLUSION

While adult and pediatric patients have some differences in envenomation characteristics and laboratory parameters, adults and pediatric patients had similar rates of systemic toxicity, severity, length of stay, and late hematologic toxicity.

Envenomations during pregnancy reported to the national poison data system, 2009-2018

Envenomations during pregnancy have consequences affecting both maternal and fetal outcomes. U.S. poison center data on envenomations offers a comparative view of envenomations in pregnant and non-pregnant women. The National Poison Data System of the American Association of Poison Control Centers was searched for cases of envenomation during pregnancy between January 1, 2009 and December 31, 2018 and compared with exposures to non-pregnant females of childbearing age. Odds ratios and descriptive statistics were used where appropriate. There were a total of 3,555 venomous animal exposures in pregnant women during this 10-year period, most commonly with scorpion stings. These were compared with 87,553 envenomations in non-pregnant women of childbearing age during that time period. Overall, drug treatment was administered in 350 (9.9%) cases of envenomation in pregnant women compared with 21,381 (24.4%) of non-pregnant patients. Antihistamines were less likely to be used in pregnant patients with scorpion (1.8% v. 9.2%), hymenoptera (bee, wasp, or hornet) (12.4% v. 37.1%), black widow spider (2.8% v. 8.1%), and caterpillar (10.4% v. 37.7%) exposures. There was an increased likelihood of antivenom use during pregnancy with rattlesnake envenomations (85.0% v. 58.9%) and black widow spider bites (4.8% v. 2.2%). There were no maternal deaths, and most maternal outcomes were coded as having no (1.0%) or minor (87.6%) effects. Three fetal deaths occurred, all following snakebites and all before 20 weeks gestation. Two were attributed as related, and one as of uncertain relationship to the exposure, by the managing poison centers. Most envenomations caused no or minor effects to pregnant women.

Does This Patient Have a Severe Snake Envenomation?: The Rational Clinical Examination Systematic Review

Importance

Venomous snakebite severity ranges from an asymptomatic dry bite to severe envenomation and death. The clinical evaluation aids in prognosis and is essential to determine the risks and potential benefits of antivenom treatment.

Objectives

To identify historical features, clinical examination findings, basic laboratory testing, and clinical grading scales that will risk-stratify patients with pit viper snake envenomation for severe systemic envenomation, severe tissue injury, and/or severe hematologic venom effects.

Data Sources

We conducted a structured search of PubMed (1966-October 3, 2017) and Embase database (1980-October 3, 2017) to identify English-language studies that evaluated clinical features predictive of severe envenomation.

Study Selection

We included studies that evaluated the test performance of at least 1 clinical finding with an acceptable reference standard of severe envenomation for venomous snakes of the Western Hemisphere. Only studies involving the most common subfamily, Crotalinae (pit vipers), were evaluated. Seventeen studies with data were available for abstraction.

Data Extraction and Synthesis

The clinical features assessed and severity outcome measures were extracted from each original study. We assessed severity in 3 categories: systemic toxicity, tissue injury, and hematologic effects. Differences were resolved by author consensus.

Results

The pooled prevalence of severe systemic envenomation was 14% (95% CI, 9%-21%). The pooled prevalence of severe tissue injury and severe hematologic venom effects were 14% (95% CI, 12%-16%) and 18% (95% CI, 8%-27%), respectively. Factors increasing the likelihood of severe systemic envenomation included the time from bite to care of 6 or more hours (likelihood ratio [LR], 3.4 [95% CI, 1.1-6.4]), a patient younger than 12 years (LRs, 3.2 [95% CI, 1.5-7.1] and 2.9 [95% CI, 1.3-6.2]), large snake size (LR, 3.1 [95% CI, 1.5-5.7]), and ptosis (LRs, 1.4 [95% CI, 1.0-2.1] and 3.8 [95% CI, 1.8-8.3]). Envenomation by the genus Agkistrodon (copperhead and cottonmouth), as opposed to rattlesnakes, decreased the likelihood of severe systemic envenomation (LR, 0.28 [95% CI, 0.10-0.78]). Initial hypofibrinogenemia (LR, 5.1 [95% CI, 1.7-15.0]) and thrombocytopenia (LR, 3.7 [95% CI, 1.9-7.3]) increased the likelihood of severe hematologic venom effects. Other clinical features from history, physical examination, or normal laboratory values were not discriminative.

Conclusions

Clinical features can identify patients at increased risk of severe systemic envenomation and severe hematologic venom effects, but there are few features that are associated with severe tissue injury or can confidently exclude severe envenomation. Physicians should monitor patients closely and be wary of progression from nonsevere to a severe envenomation and have a low threshold to escalate therapy as needed.

Caring for patients with venomous Crotalinae snakebites

Venomous snakebites are surprisingly common in the US. This article provides an overview of what to do when a patient has been bitten by a North American pit viper, a venomous subset of indigenous snakes.

Obstetric Management of Copperhead Snake Envenomation in Pregnancy: A Case Report

Snakebites in pregnancy can result in significant maternal and fetal harm; however, the literature to guide management of this rare obstetric complication remains limited. We describe our approach to envenomation in pregnancy based on the currently available evidence. A 27-year-old G2P1 female presented at 27 weeks’ gestation after suffering a copperhead snakebite. She received antivenom and antenatal steroids without adverse maternal or fetal event. Antenatal testing was reassuring throughout admission, and she was discharged home with plans for close outpatient surveillance. She later developed preterm premature rupture of membranes and preterm labor, with delivery of a live infant at 33 weeks’ gestation. The risk of adverse maternal and fetal outcomes following snake envenomation in pregnancy may warrant closer antenatal surveillance than has been previously described.

Envenomation by a western green mamba (Dendroaspis viridis) - A report of three episodes in Switzerland

The African elapid snake genus Dendroaspis comprises four species, with D. polylepsis the most dangerous of them. D. viridis is believed to cause stronger neurotoxic symptoms than the potentially least toxic of the genus, D. angusticeps, but seems less toxic compared to either of the D. jamesoni species (D. j. jamesoni(TRAILL 1843) and D. j. kaimosae (Loveridge 1936)). We present three episodes of bites byD. viridis in the same patient, sustained on three different occasions, caused by three different and unrelated snakes. While the first bite remained oligosymptomatic with a slight tightness of the throat and speedy resolution of symptoms without specific therapy, episodes two and three resulted in the patient developing massive local swelling. However, the patient showed only minimal neurologic and systemic symptoms such as tightness of the throat and a tingling sensation of the body. Episode two resolved with fasciotomy after compartment syndrome was diagnosed with a measured intracompartmental pressure of 52 mmHg. In episode three, antivenom was administered with good resolution of symptoms. The clinical courses in this patient were remarkable as he displayed mainly local symptoms after three individual bites by a supposedly neurotoxic snake.

Cottonmouth snake bites reported to the ToxIC North American snakebite registry 2013-2017

Introduction: The majority of venomous snake exposures in the United States are due to snakes from the subfamily Crotalinae (pit vipers). There are three types of US pit vipers: rattlesnakes (Crotalus and Sisturus spp.) copperheads (Agkistrodon contortrix), and cottonmouths (Agkistrodon piscivorus) also known as water moccasins. Cottonmouth bites are reported less frequently than other pit viper envenomations, and data on cottonmouth envenomation are limited. Our objective was to describe the epidemiology, clinical manifestations, and management of cottonmouth envenomations using prospective data reported to the Toxicology Investigators Consortium's (ToxIC) North American Snakebite Registry (NASBR)Methods: Cottonmouth envenomation cases reported to NASBR for the period from January 1, 2013, through December 31, 2017 were reviewed. Variables collected included patient demographics, bite location, clinical manifestations, and management.Results: Thirty-one cottonmouth envenomations were reported. Most bites occurred in children aged 7-12 (39%). Most bites involved the lower extremity (72%). Intentional interaction with the snake occurred in three cases (10%). Swelling was the most reported clinical effect and occurred in all patients. Gastrointestinal symptoms were reported in 19% of patients, and 19% developed coagulopathy. Antivenom treatment was used in 84% of patients. Nineteen patients (61%) required hospital stays of >24 hours.Discussion: Our study represents the first systematic prospective data collection on cottonmouth bites. Our data demonstrate that cottonmouth envenomations cause primarily local effects and, occasionally, systemic toxicity. Our study also demonstrates that antivenom is often indicated for these envenomations per published guidelines and recommendations.Conclusions: Cottonmouth envenomations are relatively infrequent. However, they can cause significant local and systemic toxicity. Most cottonmouth envenomations in this series were treated with antivenom and were hospitalized beyond 24 hours.

Current Management of Copperhead Snakebites in Missouri

The past two decades have seen changes to the management of copperhead snakebites. We review the current use of antivenom, analgesics, and laboratory testing as well as the declining role of surgical management.

Antivenom Treatment Is Associated with Fewer Patients using Opioids after Copperhead Envenomation

Introduction

Copperhead envenomation causes local tissue destruction, leading people to seek treatment for the pain and swelling. First-line treatment for the pain is opioid medications. There is rising concern that an initial opioid prescription from the emergency department (ED) can lead to long-term addiction. This analysis sought to determine whether use of Fab antivenom (FabAV) for copperhead envenomation affected opioid use.

Methods

We performed a secondary analysis using data from a randomized clinical trial designed to determine the effect of FabAV on limb injury recovery following mild to moderate copperhead envenomation. Opioid use was a defined secondary outcome in the parent trial. Patients were contacted after discharge, and data were obtained regarding medications used for pain and the patients’ functional status. This analysis describes the proportion of patients in each treatment group reporting opioid use at each time point. It also assesses the interaction between functional status and use of opioids.

Results

We enrolled 74 patients in the parent trial (45 received FabAV, 29 placebo), of whom 72 were included in this secondary analysis. Thirty-five reported use of any opioids after hospital discharge. A smaller proportion of patients treated with FabAV reported opioid use: 40.9% vs 60.7% of those in the placebo group. The proportion of patients using opioids remained smaller in the FabAV group at each follow-up time point. Controlling for confounders and interactions between variables, the model estimated that the odds ratio of using opioids after hospital discharge among those who received placebo was 5.67 times that of those who received FabAV. Patients who reported higher baseline pain, those with moderate as opposed to mild envenomation, and females were more likely to report opioid use at follow-up. Patients with ongoing limitations to functional status had an increased probability of opioid use, with a stronger association over time. Opioid use corresponded with the trial’s predefined criteria for full recovery, with only two patients reporting opioid use in the 24 hours prior to achieving full limb recovery and no patients in either group reporting opioid use after full limb recovery.

Conclusion

In this study population, the proportion of patients using opioids for pain related to envenomation was smaller in the FabAV treatment group at all follow-up time points.

Venomous Snakebites in Canada: A National Review of Patient Epidemiology and Antivenom Usage

INTRODUCTION

There are 3 pit viper species in Canada. Limited Canadian literature exists on the epidemiology of venomous snakebites and the treatment patterns with antivenom. This study described the epidemiology, the utilization of antivenom, and estimated expenditures due to forfeited antivenom for pit viper envenomations in Canada.

METHODS

A retrospective review of the Health Canada Special Access Program records to generate descriptive statistics. Data are presented as mean±SD (range), as appropriate.

RESULTS

The geographic distribution of Canadian pit viper species is presented. There were 99 envenomations reported in Canada from January 2009 to December 2015. The number of envenomations per year was 14±6 (6-21). CroFab and Antivipmyn are used in Canada to treat envenomations. The number of vials for patient treatment was 17±12 (3-66) and 16±9 (6-42) for CroFab and Antivipmyn, respectively. Antivenom stock usage for patient treatment varied across the country with provincial means reported for British Columbia (33%), Alberta (37%), Saskatchewan (27%), and Ontario (71%). The costs incurred secondary to forfeited stock where estimated as: $1,280,000 USD in British Columbia, $255,000 in Alberta, $60,000 in Saskatchewan, and $0 in Ontario.

CONCLUSIONS

The absolute number of annual envenomations is small and the 3 Crotalinae species are limited to relatively narrow geographic areas in British Columbia, Alberta, Saskatchewan, and Ontario. The utilization of antivenom in the treatment of patients revealed that regions where the western and prairie rattlesnake reside forfeited a substantial amount of antivenom from 2009 to 2015. Organizations responsible for maintaining antivenom supplies on a provincial or regional level could use these data to guide antidote stocking and reduce costs.

Early administration of Fab antivenom resulted in faster limb recovery in copperhead snake envenomation patients

BACKGROUND

No previous research has studied whether early snake antivenom administration leads to better clinical outcomes than late antivenom administration in North American pit viper envenomation.

METHODS

A secondary analysis of data from a clinical trial of Fab antivenom (FabAV) versus placebo for copperhead snake envenomation was conducted. Patients treated before the median time to FabAV administration were classified as receiving early treatment and those treated after the median time were defined as the late treatment group. A Cox proportional hazards model was used to compare time to full recovery on the Patient-Specific Functional Scale (PSFS) instrument between groups. Secondary analyses compared estimated mean PSFS scores using a generalized linear model and the estimated proportion of patients with full recovery at each time point using logistic regression. To evaluate for confounding, the main analysis was repeated using data from placebo-treated subjects.

RESULTS

Forty-five subjects were treated with FabAV at a median of 5.47 h after envenomation. Patients in the early treatment group had a significantly shorter time to full recovery than those treated late (median time: 17 versus 28 days, p = .025). Model-estimated PSFS scores were numerically higher at each time point in the early group. No difference was found between patients treated early versus late with placebo.

CONCLUSIONS

In this secondary analysis of trial data, recovery of limb function was faster when Fab antivenom was administered soon after envenomation, as opposed to late administration.

Research Gaps in Wilderness Medicine

INTRODUCTION

Wilderness medicine involves the treatment of individuals in remote, austere environments. Given the high potential for injuries as well as the unique treatment modalities required in wilderness medicine, evidence-based clinical practice guidelines are necessary to provide optimal care. In this study, we identify evidence gaps from low-quality recommendations in wilderness medicine clinical practice guidelines and identify new/ongoing research addressing them.

METHODS

We included relevant clinical practice guidelines from the Wilderness Medical Society and obtained all 1C or 2C level recommendations. Patient/Problem/Population, intervention, comparison, outcome (PICO) questions were created to address each recommendation. Using 24 search strings, we extracted titles, clinical trial registry number, and recruitment status for 8899 articles. We categorized the articles by trial design to infer the effect they may have on future recommendations.

RESULTS

Twelve clinical practice guidelines met inclusion criteria. From these we located 275 low-quality recommendations and used them to create 275 PICO questions. Thirty-three articles were relevant to the PICO questions. Heat-related illness had the highest number of relevant articles (n=9), but acute pain and altitude sickness had the most randomized clinical trials (n=6).

CONCLUSION

Overall, few studies were being conducted to address research gaps in wilderness medicine. Heat-related illness had the most new or ongoing research, whereas no studies were being conducted to address gaps in eye injuries, basic wound management, or spine immobilization. Animals, cadavers, and mannequin research are useful in cases in which human evidence is difficult to obtain. Establishing research priorities is recommended for addressing research gaps identified by guideline panels.

Safety of nonsteroidal anti-inflammatory drugs in copperhead snakebite patients

Introduction: Current management guidelines for pit viper envenomations recommend against the use of nonsteroidal anti-inflammatory drugs (NSAIDs) for pain control due to concern for platelet dysfunction and resulting coagulopathy. However, prior research suggests that copperhead snakes generally do not cause coagulopathy and they are responsible for most of the venomous snakebites in the USA. Thus, we compared the occurrences of clinically apparent bleeding and most abnormal laboratory values of coagulation between copperhead envenomation patients who received NSAIDs and those who did not. Methods: We conducted a retrospective chart review of patients who presented to our adult and pediatrics emergency department with copperhead snakebites. We recorded patient demographics, snake type, any NSAIDs given, any opioid analgesics given, any documented bleeding, and most abnormal laboratory values of coagulation. Results: There was no significant difference in most abnormal PTT, fibrinogen, platelet count, and serum creatinine values between copperhead snakebite patients who received NSAIDs and those who did not. Mean INR was lower (p = .011) and hematocrit was higher (p = .018) for NSAID-treated patients than for patients treated without NSAIDs. Three patients demonstrated clinically apparent bleeding; two had epistaxis reported at an outside hospital but received NSAIDs without further bleeding at our hospital. The third had 3 + blood on a urinalysis that was attributed to a urinary tract infection and also received NSAIDs without any other bleeding. Conclusions: There were no bleeding outcomes attributable to NSAID usage among copperhead snakebite patients. The use of NSAIDs in managing pain and inflammation in identified copperhead snakebite patients appears safe.

First Aid and Pre-Hospital Management of Venomous Snakebites

BACKGROUND

Antivenom is the definitive treatment for venomous snakebites, but is expensive and not available in many rural and poorly developed regions. Timely transportation to facilities that stock and administer antivenom may not be available in rural areas with poorly developed emergency medical services. These factors have led to consideration of measures to delay onset of toxicity or alternatives to antivenom therapy.

METHODS

PubMed searches were conducted for articles on snakebite treatment, or that contained first aid, emergency medical services, tourniquets, pressure immobilization bandages, suction devices, and lymphatic flow inhibitors.

RESULTS

The reviewed articles describe how venoms spread after a venomous snakebite on an extremity, list the proposed first aid measures for delaying the spread of venoms, and evaluate the scientific studies that support or refute methods of snakebite first aid. The recommendations for field treatment of venomous snakebites will be discussed.

CONCLUSIONS

The evidence suggests that pressure immobilization bandages and related strategies are the best interventions to delay onset of systemic toxicity from venomous snakebites but may increase local toxicity for venoms that destroy tissue at the site of the bite, so their use should be individualized to the circumstances and nature of the venom.

Animal, Microbial, and Fungal Borne Skin Pathology in the Mountain Wilderness: A Review

Mountains are home to numerous organisms known to cause skin disease. Bites, stings, poisons, chemicals, toxins, trauma, and infections all contribute to this end. Numerous plants, animals, fungi, bacteria, viruses, and protozoa are responsible. This paper aims to review skin illness and injury sustained from organisms in the mountains of North America. Other factors such as increased ultraviolet radiation, temperature extremes, and decreasing atmospheric pressure along with human physiologic parameters, which contribute to disease severity, will also be discussed. After reading this review, one should feel more comfortable identifying potentially harmful organisms, as well as diagnosing, treating, and preventing organism-inflicted skin pathology sustained in the high country.

A Survey of Snakebite Knowledge among Field Forces in China

Background: A snakebite is a neglected extrinsic injury associated with high morbidity and global mortality. Members of Chinese field forces are at high risk of snakebites, and their perception and knowledge of snakebites are unknown. The aim of this study is to assess perception and knowledge of snakebites in field forces in southeast China; Methods: A cross-sectional questionnaire-based survey was conducted in July 2016. A total of 216 field force members participated in this study; Results: A total of 10.3% had experienced snakebites and 86.4% rated their demands for knowledge about snakebite as “high”. No significant correlation between the actual and perceived snakebite knowledge status was detected (κ = 0.0237, p = 0.3852). Ineffective and harmful traditional first-aid methods, such as the application of tourniquets, sucking the venom out of the wound, and making local incisions, were used by more than three quarters of the respondents. However, pressure immobilization bandages were applied by only 17.3% of members. The proportion of responses for each question was not significantly different among the respondents when considering separate demographic groups; Conclusions: Snakebite knowledge among Chinese field force members is inadequate and in some cases misleading, when focusing on manifestation, prevention, and first-aid. A pragmatic, intensive educational scheme should be undertaken in at-risk populations.

Coagulation parameters in copperhead compared to other Crotalinae envenomation: secondary analysis of the F(ab')2 versus Fab antivenom trial

CONTEXT

Coagulation derangements in copperhead envenomation are considered less severe than other crotaline envenomations, resulting in recommendations to limit both coagulation testing and antivenom treatment. A prospective, blinded, multicenter, randomized clinical trial comparing the effectiveness of F(ab')₂ versus Fab antivenom in crotaline envenomation patients was completed in 2011. We determined the difference between coagulation parameters in copperhead compared to other crotaline envenomations.

METHODS

We performed a post hoc analysis comparing the coagulation parameters (platelets and fibrinogen) prospectively obtained in the aforementioned trial. All the patients received antivenom in one of three treatment arms [F(ab')₂ with maintenance, F(ab')₂ with placebo maintenance, or Fab with maintenance]. Coagulation parameters were measured at pretreatment baseline, during acute hospitalization, day 5, day 8, and day 15 post-envenomation. Mean platelet count and fibrinogen levels for the copperhead and other crotaline groups were compared. The platelet and fibrinogen point estimates with distribution are presented graphically over time.

RESULTS

122 patients were enrolled in the study. There were 22 patients with copperhead envenomation, 93 with other crotaline envenomations, and 7 that could not be definitively determined. The mean age was 42 (SD 20) years. There was a minor pretreatment difference in mean baseline platelet count between the copperhead group (246 × 109/L 95% CI 215, 277) compared to other crotaline envenomation patients (184 × 109/L 95% CI 167, 202). There was a modest pretreatment difference in mean fibrinogen level between copperhead patients (345 mg/dL 95% CI 277, 415) and other crotaline patients (261mg/dL 95% CI 241, 281). Pretreatment coagulation parameter means were normal and converged post treatment.

CONCLUSION

On average, copperhead envenomations have less severe initial coagulation derangements. However, in mild envenomations, differences in laboratory values are minimal and there is substantial variation in individual patients regardless of species. Species alone should not be used to determine the need for laboratory testing or treatment in crotaline snakebite.