Crotalidae polyvalent immune Fab antivenom limits the decrease in perfusion pressure of the anterior leg compartment in a porcine crotaline envenomation model

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

INTRODUCTION

North American pit viper envenomation occurs over 4,000 times annually in the United States, with polyvalent Fab antivenom being the primary treatment. Fasciotomy is occasionally performed due to concerns about compartment syndrome. We utilized our direct access to Texas Poison Center Network data to create a new snakebite abstraction form and database on relevant available information between 2004 and 2021 and to identify, describe, and estimate the incidence of fasciotomy following pit viper envenomation in Texas.

METHODS

We searched the Texas Poison Center Network database for cases during 2004-2021 using keywords such as fasciotomy, surgery, compartment pressure, and compartment syndrome. Descriptive statistics summarized the data.

RESULTS

Of 16,911 reported envenomations, 0.69 percent involved fasciotomies (n = 117). Most common bite sites were digits/hands and lower extremities. Patients who underwent fasciotomy were typically male, aged 20-59, and 10 years younger than the total snakebite population. Only 6 percent of reported compartment syndrome cases had a compartment pressure measurement. Antivenom was administered in 101 (86.3 percent) cases, 92 (91.1 percent) of which received only Fab antivenom product. Patients with bites from rattlesnakes (47.9 percent) were associated with most fasciotomies.

DISCUSSION

Our findings suggest a potential increase in snakebite exposures, accompanied by a decrease in fasciotomies. Overall, copperheads constituted the majority of snakebites, but most fasciotomies were from rattlesnake envenomations (47.9 percent). In this cohort, compartment syndrome diagnosis and decisions regarding fasciotomy were primarily based on clinical evaluation/surgeon expertise without compartment pressure measurements. Despite the efficacy of antivenom, only 86.3 percent of patients in our study received antivenom.

CONCLUSIONS

Fasciotomy after North American pit viper envenomation in Texas is uncommon (0.69 percent) and has decreased over time, possibly due to increased antivenom use or surgeon comfort with nonsurgical management.

Compartment Syndrome after Crotalid Envenomation in the United States: A Review of the North American Snakebite Registry from 2013 to 2021 on Behalf of the ToxIC Snakebite Study Group

INTRODUCTION

Compartment syndrome (CS) is a rare but serious complication after crotalid envenomation in the United States. Few data are available regarding the epidemiology and management of these cases. Significant controversy and misunderstanding over best practices, including measurement of compartment pressures and use of fasciotomy, exist for this syndrome. This study aims to describe presentation and management of suspected CS cases after native snakebite reported to the North American Snakebite Registry (NASBR).

METHODS

This is an analysis of snakebite cases reported to the Toxicology Investigators Consortium NASBR between January 1, 2013 and December 31, 2021. Cases of native snakebite with documented concern for CS were included.

RESULTS

Over an 8-y period, 22 cases of suspected CS were identified, representing 1% of all cases reported to the NASBR. Fasciotomies were performed in 41% (n=9) of these cases, most commonly to the upper extremity (67%, n=6). In cases of suspected CS, intracompartmental pressures (ICPs) were rarely measured (23%, n=5) and fasciotomies were performed without measurement of ICPs frequently (56%, n=5). In 1 case, ICPs were measured and found to be low (8 mm Hg) and fasciotomy was avoided.

CONCLUSIONS

Measurement of compartment pressures in cases of suspected CS was uncommon in cases reported to the NASBR. Fasciotomy was commonly performed without measurement of compartment pressures.

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.

Prospective review of cytotoxic snakebite envenomation in a paediatric population

Cytotoxic snakebite envenomation is prevalent in Kwazulu-Natal and may be associated with significant physical disability. The aim of this study was to provide an overview of the effects of cytotoxic envenomation in children. The patient population were all patients attending the Emergency Department at Ngwelezana Tertiary Hospital with snakebite from December 2014 to March 2015. All children 13 years or younger presenting with painful progressive swelling (PPS) following snakebite were included in this study. They were further classified according to severity: mild, moderate and severe. Patient demographic and clinical data was collected prospectively. Fifty-one children were included in this study. Nine were classified as mild, 24 as moderate and 18 as severe. The median time of presentation after bite was 6 h in the mild group, 7 h in the moderate group and 12 h in the severe group. There was a positive correlation between increasing severity and INR (p=< .00001) and no correlation between WCC (p = .175) or renal function and severity (p = .963). A total of 11 children (22%) developed an acute kidney injury (AKI). A total of 23/51 patients received antivenom; 25% of patients with moderate cytotoxicity and 94% of patients with severe cytotoxicity. Thirteen percent developed allergic reactions (3/23) and 57% (13/23) anaphylaxis. A total of 15 patients underwent one or more procedures on their affected limbs. There was one recorded mortality during this period, related to severe anaphylaxis following antivenom administration. Access to healthcare for antivenom administration is often delayed and ongoing education within affected areas is advised. Whilst majority of snakebite victims can be adequately managed with basic supportive measures, early identification of severe envenomation is crucial to enable timeous antivenom administration and prevention of further complications such as compartment syndrome and loss of limb. Hypersensitivity reactions are alarmingly common following antivenom administration in children and strict protocols should be followed when administering antivenom.

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.

Is there a role for fasciotomy in Crotalinae envenomations in North America?

CONTEXT

The local effects of Crotalinae envenomation can cause significant tissue destruction, pain, paresthesias, and deformity of the limb, which mimic findings of compartment syndrome, despite rare subfascial penetration of the fangs. Complicating this are the various techniques and ideas about what determines compartment syndrome combined with the fact that elevated intracompartmental pressures have been documented after Crotalinae envenomation, without clear evidence of compartment syndrome or tissue hypoperfusion.

OBJECTIVE

The purpose of this review is to evaluate the North American literature to provide an evidenced-based conclusion about the indications for fasciotomy in Crotalinae envenomations.

METHODS

The search was conducted with studies published only in the English language. The search included all human and animal publications, regardless of the format of study. The Cochrane Central Register, MEDLINE/ Pub Med, Scopus, and Biological Science databases were searched. Citations from all the articles were also cross-referenced if they were pertinent to the review. Major toxicology and emergency medicine and surgical textbooks were also referenced. Abstracts from the North American Congress of Clinical Toxicology, Poisonidex®, and personal articles were also scanned to complete the process, resulting in a total of 640 sources. Papers were excluded if they were duplicates, non-North American, involved excisional therapy, or did not discuss fasciotomy. This left 99 publications applicable to our study.

FINDINGS

No randomized controlled trials, 8 animal experiments, 1 human prospective observational study, 24 retrospective reviews, 32 review articles, 10 case reports, 15 textbooks references, 2 abstracts, and 7 editorials were included in the analysis. Controlled animal experiments show that crotaline Fab antivenin reduces intracompartmental pressure and increases tissue perfusion, while fasciotomy either has no beneficial effect or worsens myonecrosis. The case reports and opinions supporting fasciotomy come from the surgical literature and precede the modern crotaline Fab antivenin.

CONCLUSION

The current evidence does not support the use of fasciotomy or dermotomy following Crotalinae envenomation with elevated intracompartmental pressures. At present, early and adequate administration of crotaline Fab antivenin is the treatment of choice. Fasciotomy cannot be recommended until further well-designed investigations are completed.

A localizing circumferential compression device increases survival after coral snake envenomation to the torso of an animal model

BACKGROUND

Pressure immobilization bandages have been shown to delay onset of systemic toxicity after Eastern coral snake (Micrurus fulvius) envenomation to the distal extremity.

OBJECTIVES

To assess the efficacy of a novel compression device in delaying onset of systemic toxicity after truncal envenomations with Eastern coral snake (Micrurus fulvius) venom in a porcine model.

METHODS

With University approval, nine juvenile pigs (11 kg to 22 kg) were sedated, anesthetized, and intubated but not paralyzed to ensure continuous spontaneous respirations in a university animal laboratory. Each animal was injected subcutaneously with 10 mg of M. fulvius venom in a pre-selected area of the trunk. After 1 min, six animals had the application of a novel, localizing circumferential compression (LoCC) device applied to the bite site (treatment group) and three animals had no treatment (control group). The device was composed of a rigid polymer clay form molded into a hollow fusiform shape with an internal dimension of 8 × 5 × 3 cm and an elastic belt wrapped around the animal securing the device in place. Vital signs were recorded at 30-min intervals. End points included a respiratory rate below 3 breaths/min, oxygen saturation < 80%, or survival to 8 h. Survival to 8 h was analyzed using Fisher's exact test, with p < 0.05 indicating significance. Survival analysis was performed using the Mantel-Cox test to assess time to death with outcomes represented in a Kaplan-Meier Cumulative survival plot.

RESULTS

Five of the six pigs in the treatment group survived 8 h (293-480 min). None of the control pigs survived to 8 h (Fisher's exact p = 0.04), with mean time of respiratory failure 322 min (272-382 min). Survival analysis showed a significant delay in time to event in the treatment group compared to the control group (p = 0.04).

CONCLUSIONS

The LoCC device used in this study delayed the onset of systemic toxicity and significantly increased survival time after artificial truncal envenomation by Eastern coral snake venom.

Compartment syndrome after Bothrops jararaca snakebite: monitoring, treatment, and outcome

OBJECTIVE

To report the outcome of a patient who developed compartment syndrome after Bothrops jararaca snakebite.

CASE REPORT

A 39-year-old male was admitted 5 h after being bitten on the lower right leg. Physical examination revealed tense swelling, ecchymosis, hypoesthesia, and intense local pain that worsened after passive stretching, limited right foot dorsiflexion, and gingival bleeding. The case was classified as moderate/severe and eight vials of bothropic antivenom (AV) were infused 1 h postadmission. The main laboratory findings upon admission were incoagulable blood (incoagulable PT, aPTT, and INR), thrombocytopenia, serum creatine kinase (CK) of 580 U/L (reference value < 170 U/L), and a serum venom level of 33.7 ng/mL (ELISA; cutoff = 2.3 ng/mL). High anterior compartment pressure (60 mmHg) was identified 8 h post bite, with progressively lower pressures after AV administration and limb elevation (36 mmHg; 19 h post bite). However, moderate pain and limited foot dorsiflexion persisted. In addition, there was a progressive increase in serum CK (6,729 U/L; 45 h post bite), as well as marked edema and hemorrhage of the anterior compartment detected by magnetic resonance imaging (MRI) at 48 h post bite. A fasciotomy done after a further increase in intracompartmental pressure (66 mmHg, 57 h post bite) revealed hemorrhage/necrosis of the anterior tibial muscle that subsequently required partial resection. The patient developed a local infection (day 15 post bite) and a permanent fibular palsy.

CONCLUSION

Compartment syndrome is an unusual but severe complication of snakebites. MRI, in conjunction with subfascial pressure measurements, may be useful in the diagnosis of compartment syndrome after snakebites.

Pilot studies of pressure-immobilization bandages for rattlesnake envenomations

STUDY OBJECTIVE

Pressure-immobilization bandages sequester venom in extremities and are recommended for snakebites without local toxicity. Pilot studies were performed to determine the time of onset of toxicity and efficacy of pressure-immobilizations bandages in a porcine model of rattlesnake envenomation.

METHODS

After IACUC approval, anesthetized pigs were injected subcutaneously in a distal hind leg with 200 mg of Crotalus atrox venom. After 1 min, pigs received either a pressure-immobilization bandage (N = 3) or no treatment (N = 3). At 24 h, surviving pigs received antivenin and then the pressure-immobilization bandages were removed. Surviving subjects were followed for 1 week. Chi-square analysis and paired t-test were used.

RESULTS

Pigs with pressure-immobilization bandages survived for 24 h, whereas untreated pigs died at 13.68 +/- 3.42 h (p = 0.014). Surviving pigs walked on the extremity at 7 days. Potassium rose from 4.033 +/- 0.252 at baseline to 17.767 +/- 5.218 mEq/L (p < 0.0001) at time of death in untreated pigs but was normal at 24 h in treated subjects. Widespread tissue necrosis was seen in the untreated group but only local necrosis in the treatment group.

CONCLUSIONS

Pressure-immobilization bandages prevented death from severe C. atrox envenomations with a 24 h delay to treatment. Surviving pigs had recovery of limb use at 1 week.

Epidemiological, clinical and therapeutic aspects of Bothrops asper bites

Bothrops asper inflicts the majority of snakebites in Central America and in the northern regions of South America, mostly affecting young agricultural workers in rural settings. This species is capable of provoking severe envenomings associated with local and systemic manifestations. The main clinical features are: local edema, ecchymoses, blisters, dermonecrosis, myonecrosis, defibrinogenation, thrombocytopenia, systemic bleeding, hypotension and renal alterations. In addition, soft-tissue infection, acute renal failure, compartmental syndrome, central nervous system hemorrhage and, in pregnant women, abortion, fetal wastage and abruptio placentae have been described as complications. Intravenous administration of antivenom constitutes the mainstay in the therapy. Antivenoms composed of either whole IgG or F(ab')(2) fragments, manufactured in Brazil, Colombia, Costa Rica and Mexico, have been tested in controlled clinical trials, and rational protocols for antivenom administration have been developed. In addition to antivenom therapy, a number of ancillary interventions are recommended in the treatment of B. asper bites.

The approach to the patient with an unknown overdose

Toxic overdose can present with various clinical signs and symptoms. These may be the only clues to diagnosis when the cause of toxicity is unknown at the time of initial assessment. The prognosis and clinical course of recovery of a patient poisoned by a specific agent depends largely on the quality of care delivered within the first few hours in the emergency setting. Usually the drug or toxin can be quickly identified by a careful history, a directed physical examination, and commonly available laboratory tests. Once the patient has been stabilized, the physician must consider how to minimize the bioavailability of toxin not yet absorbed, which antidotes (if any) to administer, and if other measures to enhance elimination are necessary.

A Pilot Study of Mechanical Stimulation and Cardiac Dysrhythmias in a Porcine Model of Induced Hypothermia☆

BACKGROUND

Hypothermia is a frequent complication of cold weather exposure and/or wilderness injuries. Anecdotal reports have postulated that patients suffering from acute hypothermia are at significantly increased risk of developing lethal cardiac dysrhythmias secondary to the physical stimulation from moving and transporting patients.

OBJECTIVE

To develop a model to attempt to determine if rough handling and sudden movement can induce lethal cardiac dysrhythmias in a controlled animal study of mild to severe hypothermia.

METHODS

Ten anesthetized swine had continuous cardiac and invasive blood pressure (BP) monitoring. Core body temperature (CBT) was measured with an esophageal probe. Animals were secured to a backboard in a supine position for the duration of the study and their CBT was serially lowered by external cooling measures. At preset intervals (every 3 degrees C lowered from the baseline CBT of 38 degrees C), the animals were lifted via the backboard and rolled 90 degrees to the left and held for 5 seconds and then rolled to the right and held for 5 seconds. After rolling, the swine were lifted via the backboard 6 inches off the surgical table and dropped back onto the table, and after 15 seconds this was repeated at 12 inches. If no signs of dysrhythmia were noted, external cooling was continued. Data were analyzed by tests of proportion on mortality associated with hypothermia and mechanical stimulation. To determine whether hypothermia and mechanical stimulation were independent effects, a one-sided McNemar's test of matched pairs was employed.

RESULTS

No animal developed a dysrhythmia at a CBT > 25 degrees C with or without stimulation. Fifty percent of the animals developed fatal dysrhythmias (3 ventricular fibrillation, 2 asystole) with no stimulation but at CBT <or= 25 degrees C (average CBT 22.7 degrees C). Twenty percent (2/10) developed fatal dysrhythmias (ventricular fibrillation) during mechanical stimulation. For hypothermia, a binomial test of the observed proportion 0.70 (fatality during hypothermia) against a hypothetical proportion of 0 (no fatality in the absence of hypothermia) yielded P < .001 with power = 1.00. For mechanical stimulation, a binomial test of the observed proportion 0.20 (fatality from mechanical stimulation); against a hypothetical proportion of 0 yielded P < .001 with power = 1.00. The test of matched pairs yielded P < .037, indicating that the variables of mechanical stimulation and hypothermia jointly caused mortality.

CONCLUSION

Profound hypothermia induces fatal dysrhythmias both with and without mechanical stimulation in a swine model.

Pressure-Immobilization Bandages Delay Toxicity in a Porcine Model of Eastern Coral Snake (Micrurus fulvius fulvius) Envenomation

STUDY OBJECTIVES

Pressure-immobilization bandages are used in countries where neurotoxic snake envenomations are common. They impede lymphatic egress from the bite site and delay systemic venom toxicity. The effectiveness of these devices has not been evaluated in coral snake envenomations. We investigated the efficacy of pressure-immobilization bandages in delaying the onset of systemic toxicity in a porcine model of coral snake envenomation.

METHODS

A randomized controlled trial of pressure-immobilization bandages was conducted in a university animal care center. Subjects were 12 anesthetized, spontaneously breathing pigs, ranging from 9.1 to 11.4 kg. After injection with 10 mg of Micrurus fulvius fulvius venom in the subcutaneous tissue of the distal foreleg, subjects were randomized to receive no treatment or application of a pressure-immobilization bandage at 1 minute after injection. Treated animals had elastic bandages applied to the extremity and splinting for immobilization. Vital signs and quality of respirations were recorded. Outcome was the onset of respiratory failure or survival to 8 hours. Necropsies and histologic analysis of the envenomation site was performed.

RESULTS

One animal from each group was removed because of the discovery of pre-existing respiratory pathology. Four of 5 pigs in the treatment group survived to 8 hours, but none in the control group survived. Mean time to onset of respiratory compromise was 170.4 +/- 33.3 minutes in the control group. None of the pigs had histologic changes at the envenomation site consistent with ischemia or pressure-related injury.

CONCLUSION

Pressure-immobilization bandages delayed the onset of systemic toxicity in our porcine model of M fulvius envenomation.

Fasciotomy worsens the amount of myonecrosis in a porcine model of crotaline envenomation

STUDY OBJECTIVE

We evaluate the efficacy of fasciotomy or crotaline snake antivenom in reducing myonecrosis.

METHODS

We used a randomized, blinded, controlled acute animal preparation. Twenty anesthetized swine were injected intramuscularly in the anterior tibiales muscle of both hind limbs with 6 mg/kg of Crotalus atrox venom (total of 12 mg/kg of venom per animal). Immediately after venom injection, the right hind limb underwent fasciotomy. Muscle biopsies were obtained from the fasciotomized hind limb at 0, 4, and 8 hours and from the other hind limb at the conclusion of the study (8 hours). In addition, animals received either 8 vials of reconstituted Crotalidae polyvalent immune Fab (ovine) (CroFab; FabAV) or an equal volume of normal saline solution intravenously 1 hour after venom injection. A pathologist blinded to the study determined the percentage of myonecrotic cells in each biopsy. Statistical analysis was performed using repeated measures analysis of variance for compartment pressure. Rank-order methods were used for comparison of myonecrosis between groups.

RESULTS

Biopsies from hind limbs undergoing fasciotomy revealed a progressive increase in the amount of myonecrosis over time (myonecrosis median at 0, 4, or 8 hours [or death]: 0%, 14%, or 14.5%, respectively; P<.001). Comparison of the amount of myonecrosis of biopsies at death or 8 hours revealed that limbs that underwent fasciotomy had significantly more myonecrosis than those that did not (myonecrosis median: 14.5% versus 2.5%, P=.048). No difference was detected in the amount of myonecrosis when FabAV was compared with normal saline solution on final biopsies from either fasciotomy or nonfasciotomy hind limb (myonecrosis median: 10.0% versus 10.0%, P=.64).

CONCLUSION

Fasciotomy significantly worsens the amount of myonecrosis in a porcine model of intramuscular crotaline venom injection. No change in the amount of myonecrosis was detected with the use of FabAV treatment at the dosages used in this animal model.