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

Comparing cost of F(.ab')2AV vs FabAV in the treatment of copperhead envenomation-One center's experience

The definitive treatment of North American crotalid snakebites is antivenin. In 2000, an FabAV antivenom (CroFab®) was introduced and in 2022, F(ab')2AV (Anavip®) was approved for treatment of copperhead bites. Our center that sees primarily copperhead snake bites added the recently approved treatment as a second option for the 2022 snake bite season. This brief report we describe our initial experience with the two antivenins via retrospective chart review: the cost, charge, laboratory differences, response to therapy, complications and duration of hospitalization of admitted patients with copperhead envenomation. Using three independent reviewers in this IRB exempt report we found 31 patients with copperhead bites (7 exclusions) leaving 19 adults and 7 children for analysis. We found there was no difference in age, sex, presence of lab abnormalities, total vials administered, or length of stay. There was significant differences in hospital costs and charges to the patient. Future research should include multi-center experiences comparing the two antivenins.

Delayed Recognition of Severe Systemic Envenomation after Copperhead Bite: A Case Report

Introduction

We report a case of severe systemic copperhead, Agkistrodon contortrix, envenomation that resulted in long-term sequelae.

Case Report

A 72-year-old man presented to the emergency department after suffering a copperhead snakebite. He developed severe systemic toxicity before local tissue injury developed. Clinicians did not initially recognize his envenomation syndrome and sought alternative explanations for his systemic symptoms before polyvalent immune fab (ovine) antivenom was administered. Although the patient improved, he was discharged with new stage three chronic kidney disease.

Conclusion

Although rare, copperhead envenomation can cause severe systemic toxicity. Envenomation should be promptly treated with antivenom.

Outcomes in intervention research on snakebite envenomation: a systematic review

INTRODUCTION

A core outcome set (COS) is a minimal list of consensus outcomes that should be used in all intervention research in a specific domain. COS enhance the ability to undertake meaningful comparisons and to understand the benefits or harms of different treatments. A first step in developing a COS is to identify outcomes that have been used previously. We did this global systematic review to provide the foundation for development of a region-specific COS for snakebite envenomation.  Methods: We searched 15 electronic databases, eight trial registries, and reference lists of included studies to identify reports of relevant trials, protocols, registry records and systematic reviews. We extracted verbatim data on outcomes, their definitions, measures, and time-points. Outcomes were classified as per an existing outcome taxonomy, and we identified unique outcomes based on similarities in the definition and measurement of the verbatim outcomes.

RESULTS

We included 107 records for 97 studies which met our inclusion criteria. These reported 538 outcomes, with a wide variety of outcome measures, definitions, and time points for measurement. We consolidated these into 88 unique outcomes, which we classified into core areas of mortality (1, 1.14 %), life impact (6, 6.82%), resource use (15, 17.05%), adverse events (7, 7.95%), physiological/clinical (51, 57.95%), and composite (8, 9.09%) outcomes. The types of outcomes varied by the type of intervention, and by geographic region. Only 15 of the 97 trials (17.04%) listed Patient Related Outcome Measures (PROMS).

CONCLUSION

Trials evaluating interventions for snakebite demonstrate heterogeneity on outcomes and often omit important information related to outcome measurement (definitions, instruments, and time points). Developing high quality, region-specific COS for snakebite could inform the design of future trials and improve outcome reporting. Measurement of PROMS, resource use and life impact outcomes in trials on snakebite remains a gap.

Control of venom-induced tissue injury in copperhead snakebite patients: a post hoc sub-group analysis of a clinical trial comparing F(ab')2 to Fab antivenom

INTRODUCTION

Fab antivenom (FabAV) halts progression of tissue injury and improves recovery in copperhead snakebite. It is unknown if F(ab')2AV does as well. The objective of this study was to compare control of tissue injury in copperhead snakebite patients treated with F(ab')2AV versus FabAV.

METHODS

We performed a post hoc analysis of copperhead envenomated patients in a clinical trial comparing F(ab')2AV to FabAV. The outcomes for this analysis are the number of repeat doses required to obtain initial control, the number of patients requiring unscheduled doses during maintenance, and the time from antivenom administration to initial control.

RESULTS

Twenty-one (13 F(ab')2AV, 8 FabAV) were copperhead patients. Median age was 46 years with a male predominance. Baseline severity was similar. One (8%) F(ab')2AV and 2(25%) FabAV patients required repeat initial dosing, difference = 17%, (95%CI -18, 57%). One (8%) F(ab')2AV and 1(13%) FabAV patients required additional doses after maintenance, difference = 5%, (95%CI -27, 45%). Median time to initial control was 2.7 range (2.0, 9.3) hours and 3.5 range (2.0, 7.4) for F(ab')2AV and FabAV respectively, difference -0.8 h (95% CI -2.6, 0.9).

CONCLUSIONS

This exploratory analysis suggests that the available measures of the control of venom-induced tissue injury are similar between antivenom subgroups.

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.

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.

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

Background

The immunologic pathways activated during snakebite envenoming (SBE) are poorly described, and their association with recovery is unclear. The immunologic response in SBE could inform a prognostic model to predict recovery. The purpose of this study was to develop pre- and post-antivenom prognostic models comprised of clinical features and immunologic cytokine data that are associated with recovery from SBE.

Materials and Methods

We performed a prospective cohort study in an academic medical center emergency department. We enrolled consecutive patients with Crotalinae SBE and obtained serum samples based on previously described criteria for the Surgical Critical Care Initiative (SC2i)(ClinicalTrials.gov Identifier: NCT02182180). We assessed a standard set of clinical variables and measured 35 unique cytokines using Luminex Cytokine 35-Plex Human Panel pre- and post-antivenom administration. The Patient-Specific Functional Scale (PSFS), a well-validated patient-reported outcome of functional recovery, was assessed at 0, 7, 14, 21 and 28 days and the area under the patient curve (PSFS AUPC) determined. We performed Bayesian Belief Network (BBN) modeling to represent relationships with a diagram composed of nodes and arcs. Each node represents a cytokine or clinical feature and each arc represents a joint-probability distribution (JPD).

Results

Twenty-eight SBE patients were enrolled. Preliminary results from 24 patients with clinical data, 9 patients with pre-antivenom and 11 patients with post-antivenom cytokine data are presented. The group was mostly female (82%) with a mean age of 38.1 (SD ± 9.8) years. In the pre-antivenom model, the variables most closely associated with the PSFS AUPC are predominantly clinical features. In the post-antivenom model, cytokines are more fully incorporated into the model. The variables most closely associated with the PSFS AUPC are age, antihistamines, white blood cell count (WBC), HGF, CCL5 and VEGF. The most influential variables are age, antihistamines and EGF. Both the pre- and post-antivenom models perform well with AUCs of 0.87 and 0.90 respectively.

Discussion

Pre- and post-antivenom networks of cytokines and clinical features were associated with functional recovery measured by the PSFS AUPC over 28 days. With additional data, we can identify prognostic models using immunologic and clinical variables to predict recovery from SBE.

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

INTRODUCTION

Anavip (F(ab')₂AV) is a lyophilized F(ab')₂ immunoglobulin fragment derived from horses immunized with venom from Bothrops asper and Crotalus durissus. It was approved by the FDA in 2015 for treatment of North American rattlesnake envenomation but not for Agkistrodon envenomation. Published data regarding the efficacy and safety of Anavip in treating Agkistrodon envenomations is limited. We present a case of a patient treated with Anavip after confirmed Agkistrodon laticinctus envenomation.

CASE DETAILS

A 77 year-old man was bitten on his fifth finger by a captive A. laticinctus. He was taken to a local emergency department where he received a 10 vial initial dose of F(ab')₂AV for pain and swelling and was transferred. At the receiving facility, his pain had improved and his swelling had not progressed. Over the next 30 h, his platelets declined to 132,000/mm³ and he received an additional 4 vials of F(ab')₂AV. The remainder of his course was unremarkable with complete recovery by 3 months.

DISCUSSION

This case provides an additional published datapoint on the use of this F(ab')₂AV in the treatment of envenomation by Agkistrodon.

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.

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.

Validity and reliability of telephone administration of the patient-specific functional scale for the assessment of recovery from snakebite envenomation

Objectives

Although more than 1.8 million people survive snakebite envenomation each year, their recovery is understudied. Obtaining long-term follow-up is challenging in both high- and low-resource settings. The Patient-Specific Functional Scale (PSFS) is an easily administered, well-accepted patient-reported outcome that is validated for assessing limb recovery from snakebite envenomation. We studied whether the PSFS is valid and reliable when administered by telephone.

Methods

This is a secondary analysis of data from a randomized clinical trial. We analyzed the results of PSFS collected in-person on days 3, 7, 14, 21, and 28 and by telephone on days 10, 17, and 24. We assessed the following scale psychometric properties: (a) content validity (ceiling and floor effects), (b) internal structure and consistency (Cronbach’s alpha), and (c) temporal and external validity using Intraclass Correlation Coefficient (ICC). Temporal stability was assessed using Spearman’s correlation coefficient and agreement between adjacent in-person and telephonic assessments with Cohen’s kappa. Bland Altman analysis was used to assess differential bias in low and high score results.

Results

Data from 74 patients were available for analysis. Floor effects were seen in the early post-injury time points (median: 3 (IQR: 0, 5) at 3 days post-enrollment) and ceiling effects in the late time points (median: 9 (IQR: 8, 10). Internal consistency was good to excellent with both in-person (Cronbach α: 0.91 (95%CI 0.88, 0.95)) and telephone administration (0.81 (0.73, 0.89). Temporal stability was also good (ICC: 0.83 (0.72, 0.89) in-person, 0.80 (0.68, 0.88) telephone). A strong linear correlation was found between in-person and telephone administration (Spearman’s ρ: 0.83 (CI: 0.78, 0.84), consistency was assessed as excellent (Cohen’s κ 0.81 (CI: 0.78, 0.84), and Bland Altman analysis showed no systematic bias.

Conclusions

Telephone administration of the PSFS provides valid, reliable, and consistent data for the assessment of recovery from snakebite envenomation.

Snakebite envenomation is an important but neglected tropical disease that impacts millions of people worldwide each year. These bites lead to both death and permanent disability. As they occur in tropical and subtropical regions, they primarily impact people from low-income areas of the world. As potential new treatments are being developed, we must understand their potential benefit in humans before they can be widely disseminated. Performing these human studies requires the ability to determine how patients recovered with these treatments. Having people return for evaluation during recovery is difficult in these low-income regions. We evaluated the ability to use a telephone version of an already accepted measurement of recovery in snakebite, the Patient-Specific Functional Scale. This study demonstrates that using this telephone-administered measure is feasible, valid, and reliable. With the results of this study, we now have an important tool to easily measure recovery in areas where snakebite predominates. This tool will help snakebite envenomation researchers evaluate the potential benefit of new treatments and accelerate the process of bringing new effective treatments to those snakebite patients in the most need.

Recovery from Copperhead Snake Envenomation: Role of Age, Sex, Bite Location, Severity, and Treatment

INTRODUCTION

Few data exist to understand the recovery phase of pit viper envenomation. A recently published placebo-controlled clinical trial affords this opportunity. The purpose of this study is to examine the time course of recovery from copperhead snake (Agkistrodon contortrix) envenomation patients managed with and without the use of antivenom, stratified by age, sex, anatomic site of envenomation, initial severity of envenomation, and geographic region.

METHODS

This is a post-hoc subgroup analysis of data from a multi-center double-blinded clinical trial of Fab antivenom (FabAV) vs. placebo. Outcomes were the Patient-Specific Functional Scale (PSFS) score at 3, 7, 10, and 14 days after envenomation. Least-squares mean PSFS score curves were calculated for each subgroup, and repeated measures ANOVA was used to estimate between-group comparisons.

RESULTS

Seventy-two subjects were included, of whom 44 received FabAV. Males demonstrated better overall recovery than females (model predicted PSFS score 6.18 vs 4.99; difference 1.19; 95% CI 0.12 to 2.25; p = 0.029). No sex difference was found in response to FabAV. Overall recovery and effect of FabAV were similar in adult vs adolescent patients, patients with upper vs lower extremity envenomation, and patients with initially mild vs moderate envenomation signs. Analysis by geographic location was not successful due to ANOVA mode instability.

CONCLUSIONS

Male victims of copperhead snake envenomation demonstrate slightly better recovery than females, but response to Fab antivenom overall is similar across all subgroups studied.

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.

Misidentification of copperhead and cottonmouth snakes following snakebites

INTRODUCTION

Copperhead (Agkistrodon contortrix) and cottonmouth or water moccasin (Agkistrodon piscivorus) snakes account for the majority of venomous snakebites in the southern United States. Cottonmouth snakes are generally considered to have more potent venom. Copperheads are considered less venomous and there is some controversy as to whether or not bites from copperhead snakes need to be treated with antivenom. Copperhead and juvenile cottonmouth snakes are both brown in color. The purpose of this study was to evaluate the accuracy of identification by the public and healthcare providers between these two species.

METHODS

Snakebite victims sometimes bring dead snakes to the hospital or have taken pictures of the snake. When this occurred, ED personnel were asked to take a picture of the snake, and forward the picture to the state poison control center. The identification of the snake by witnesses and/or hospital personnel was compared to the identification by the state herpetologist.

RESULTS

During the study period, there were 286 cases of snakebites reported to the state poison control center. Pictures were obtained on 49 of the responsible snakes. All copperhead snakes were identified correctly by callers. However, only 21% of cottonmouth snakes were identified correctly, with 74% of cottonmouth snakes being identified as copperheads. Both public and medical personnel performed poorly on identification of cottonmouth snakes.

CONCLUSIONS

Forty percent of the snakes identified as copperheads were actually cottonmouth snakes. Juvenile cottonmouth snakes were often identified as copperhead snakes.