Mojave rattlesnake envenomation: prolonged neurotoxicity and rhabdomyolysis

Geographic variation in the clinical features of Mohave rattlesnake (Crotalus scutulatus) envenomations reported to the North American Snakebite Registry

The geographic variation of Mohave rattlesnake (Crotalus scutulatus) venom is well established. We reviewed all the Mohave rattlesnake bites reported to the Toxicology Investigators Consortium's North American Snakebite Registry between January 1, 2015 and 12/31/2021. Data reviewed for this study included details regarding the snake encounter, patient demographics, signs and symptoms, treatment, and outcomes. Our objective was to describe the epidemiology, clinical manifestations, and management of Mohave rattlesnake envenomations using prospective data from two geographically distinct sites. There were 20 subjects, including eight nonpregnant females. Ages ranged from seven to 75 years, median age 48. Nine of the bites were managed in Arizona and 11 in California. In Arizona, all envenomated patients had local swelling. None had neurological toxicity. In California, swelling was present in nine patients. Neurological effects were observed in five subjects. Four Arizona patients and one California patient had hypotension requiring treatment. Each site had one patient with thrombocytopenia. An Arizona patient who sustained a bite to the face was intubated. Rhabdomyolysis occurred in two California patients. All envenomated patients received antivenom. Mohave rattlesnakes have the potential to cause significant local and/or systemic toxicity. Neurotoxicity was not observed in envenomations from Mohave rattlesnakes that presumably lack Mohave toxin, but hypotension and gastrointestinal signs were more common than in bites from snakes believed to possess Mohave toxin. Neurological toxicity was limited to paresthesias and fasciculations. Significant skeletal or respiratory muscle weakness was not observed in our study population.

Neurotoxicity Associated With the Southern Pacific Rattlesnake (Crotalushelleri)

The Southern Pacific rattlesnake (Crotalus helleri) is commonly encountered throughout Southern California. Typical toxicity includes tissue injury and hematologic toxicity. However, neurotoxicity is not commonly reported with rattlesnake envenomations, other than infrequently with select species, including the Mojave rattlesnake (Crotalus scutulatus scutulatus). Importantly, clinical neurotoxicity has not been well described with the Southern Pacific rattlesnake, the only rattlesnake in the city of Los Angeles, along with the Southern and coastal regions of Los Angeles County. In this case series, 7 patients envenomated by the Southern Pacific rattlesnake with significant neurotoxicity, including dysarthria, ataxia, and myokymia, are presented. Clinicians practicing in this region should be aware of evolving patterns of toxicity associated with the Southern Pacific rattlesnake.

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.

Retrospective Analysis of the Demographic and Clinical Features of Snake Bites Followed in the Intensive Care Unit

Objective Cases of poisoning due to snake bite are a medical condition that requires an emergency treatment approach, which creates serious health problems that can be seen in our country and all over the world. In the Eastern Anatolia Region, poisoning cases due to the bites of viper snakes, especially from the Viperidae family, are frequently seen. The aim of this study is to examine the bite sites, clinical stages, antivenom needs and doses, changes in blood biochemistry, prognostic characteristics of patients treated in our intensive care unit for snake bites in our region, and to present our regional experience with snake bites. Material and Methods Our study included 44 patients who were treated in the intensive care clinic with the complaint of snake bite between August 1, 2018 and August 1, 2021. Symptoms, bite sites, clinical stages, need and doses of antivenom, length of hospital stay, changes in blood biochemistry and mortality of these patients who were exposed to snake bites were retrospectively investigated. Results A total of 44 patients, 13 female (29.55%) and 31 male (70.45%), aged between 18-72 years, who were followed up due to snake bites, were included in the study. In our study, 1 (2.27%) patients in Stage 0, 18 (40.90%) in Stage 1, 21 (47.7%) in Stage 2 and 4 (9.09%) patients in Stage 3 it was found that he was followed up due to snake bite. While total antivenom (4.33±2.18) vials were given to 10 intoxication cases with stage (0-1), vials of total antivenom were given to 25 (7.65±3.03) intoxication cases with stage (2-3). Conclusion We believe that in addition to antivenom treatment in sufficient doses and in an early time, the first correct intervention to snake bite can prevent problems that may develop after poisoning.

Neutralizing potency and immunochemical evaluation of an anti-Crotalus mictlantecuhtli experimental serum

Snakebite in Mexico is commonly treated with an antivenom which uses Bothrops asper and Crotalus simus venoms as immunogens. Current taxonomic recommendations for the C. simus species complex suggest a novel endemic species from Mexico: Crotalus mictlantecuhtli. The aim of this report was to evaluate the immunogenic properties of C. mictlantecuhtli venom and its potential to generate polyclonal antibodies capable of neutralizing other pitviper venoms. We generated an experimental anti-Crotalus mictlantecuhtli serum, using the rabbit model, to test recognition and neutralizing capacity against the homologous venom as well as venoms from C. atrox, C.basiliscus, C. durissus terrificus, C. scutulatus salvini, C. tzabcan and Ophryacus sphenophrys. Pre-incubation neutralization experiments using our experimental serum showed positive results against venoms containing crotoxin, while venoms from two non-neurotoxic pit-vipers were not neutralized. Rescue experiments in mice showed that, when intravenously injected (i.v.), C. mictlantecuhtli venom is not neutralized by a maximum dose of Antivipmyn® and the experimental serum after 5 min of envenomation, albeit mice envenomated intraperitoneally (i.p.) and rescued i.v. with Antivipmyn® survived even at 50 min after envenomation. Our results highlight the importance of using the highly neurotoxic C. mictlantecuhtli venom to increase antivenom effectiveness against Mexican neurotoxic pitvipers.

Case reports of envenomation and venom composition differences between two Arizona populations of the Southwestern Speckled Rattlesnake, Crotalus pyrrhus (Cope, 1867)

Envenomations by the Southwestern Speckled Rattlesnake (Crotalus pyrrhus) are fairly rare. Previous descriptions in the literature do not include locality, an important factor in the clinical symptoms or syndromes of snakebites resulting from geographic variation in venom composition. Here, we describe two cases of envenoming by C. pyrrhus from two Arizona localities (Tinajas Altas Mountains, Yuma County, and Phoenix Mountains, Maricopa County). Both patients experienced swelling, but neither demonstrated coagulopathy, thrombocytopenia, or hypofibrinogenemia. The Phoenix Mountains patient developed hemorrhagic bullae and tissue damage in his bitten extremity, necessitating the amputation of the distal portion of his middle finger. Treatment for both consisted of medication for pain, isotonic crystalloid, and antivenom therapy with recovery in each case. Based on visual inspection of 1D-gels and RP-HPLC chromatograms, venom samples were largely similar but appeared to differ quantitatively for several toxin families between and within populations.

A Single Mutation Unlocks Cascading Exaptations in the Origin of a Potent Pitviper Neurotoxin

Evolutionary innovations and complex phenotypes seemingly require an improbable amount of genetic change to evolve. Rattlesnakes display two dramatically different venom phenotypes. Type I venoms are hemorrhagic with low systemic toxicity and high expression of tissue-destroying snake venom metalloproteinases. Type II venoms are highly neurotoxic and lack snake venom metalloproteinase expression and associated hemorrhagic activity. This dichotomy hinges on Mojave toxin (MTx), a phospholipase A2 (PLA2) based β-neurotoxin expressed in Type II venoms. MTx is comprised of a nontoxic acidic subunit that undergoes extensive proteolytic processing and allosterically regulates activity of a neurotoxic basic subunit. Evolution of the acidic subunit presents an evolutionary challenge because the need for high expression of a nontoxic venom component and the proteolytic machinery required for processing suggests genetic changes of seemingly little immediate benefit to fitness. We showed that MTx evolved through a cascading series of exaptations unlocked by a single nucleotide change. The evolution of one new cleavage site in the acidic subunit unmasked buried cleavage sites already present in ancestral PLA2s, enabling proteolytic processing. Snake venom serine proteases, already present in the venom to disrupt prey hemostasis, possess the requisite specificities for MTx acidic subunit proteolysis. The dimerization interface between MTx subunits evolved by exploiting a latent, but masked, hydrophobic interaction between ancestral PLA2s. The evolution of MTx through exaptation of existing functional and structural features suggests complex phenotypes that depend on evolutionary innovations can arise from minimal genetic change enabled by prior evolution.

The binding effectiveness of anti-r-disintegrin polyclonal antibodies against disintegrins and PII and PIII metalloproteases: An immunological survey of type A, B and A+B venoms from Mohave rattlesnakes

Snake venoms are known to have different venom compositions and toxicity, but differences can also be found within populations of the same species contributing to the complexity of treatment of envenomated victims. One of the first well-documented intraspecies venom variations comes from the Mohave rattlesnake (Crotalus scutulatus scutulatus). Initially, three types of venoms were described; type A venom is the most toxic as a result of ~45% Mojave toxin in the venom composition, type B lacks the Mojave toxin but contains over 50% of snake venom metalloproteases (SVMPs). Also, type A+B venom contains a combination of Mojave toxin and SVMP. The use of an anti-disintegrin antibody in a simple Enzyme-Linked Immunosorbent Assay (ELISA) can be used to identify the difference between the venoms of the type A, B, and A+B Mohave rattlesnakes. This study implements the use of an anti-recombinant disintegrin polyclonal antibody (ARDPA) for the detection of disintegrins and ADAMs (a disintegrin and metalloproteases) in individual crude snake venoms of Mohave rattlesnakes (Crotalus scutulatus scutulatus) of varying geographical locations. After correlation with Western blots, coagulation activity and LD₅₀ data, it was determined that the antibody allows for a quick and cost-efficient identification of venom types.

Antidote Use in the Critically Ill Poisoned Patient

The proper use of antidotes in the intensive care setting when combined with appropriate general supportive care may reduce the morbidity and mortality associated with severe poisonings. The more commonly used antidotes that may be encountered in the intensive care unit ( N-acetylcysteine, ethanol, fomepizole, physostigmine, naloxone, flumazenil, sodium bicarbonate, octreotide, pyridoxine, cyanide antidote kit, pralidoxime, atropine, digoxin immune Fab, glucagon, calcium gluconate and chloride, deferoxamine, phytonadione, botulism antitoxin, methylene blue, and Crotaline snake antivenom) are reviewed. Proper indications for their use and knowledge of the possible adverse effects accompanying antidotal therapy will allow the physician to appropriately manage the severely poisoned patient.

A case of neurotoxicity following envenomation by the Sidewinder rattlesnake, Crotalus cerastes

INTRODUCTION

North American rattlesnake envenomations typically result in local tissue injury and hematologic derangements. Neurotoxicity is uncommon but when present often manifests as fasciculations and paresthesias. Neurotoxicity following Sidewinder (Crotalus cerastes) envenomation has not been previously reported.

CASE REPORT

A 56-year-old man bitten on the right foot developed painful paresthesias, weakness and fasciculations of the right lower extremity, and involuntary muscle contractions of the anterior thigh. Local tissue effects and hemotoxicity never developed. The patient was discharged 5 days after the bite with resolution of fasciculations but continued to have right-sided weakness. The snake was identified as a Sidewinder, C. cerastes, by the patient and two independent herpetologists.

CONCLUSION

This is the first reported case of a Sidewinder rattlesnake envenomation resulting in neurotoxicity.

Neurotoxicity in snakebite--the limits of our knowledge

Snakebite is classified by the WHO as a neglected tropical disease. Envenoming is a significant public health problem in tropical and subtropical regions. Neurotoxicity is a key feature of some envenomings, and there are many unanswered questions regarding this manifestation. Acute neuromuscular weakness with respiratory involvement is the most clinically important neurotoxic effect. Data is limited on the many other acute neurotoxic manifestations, and especially delayed neurotoxicity. Symptom evolution and recovery, patterns of weakness, respiratory involvement, and response to antivenom and acetyl cholinesterase inhibitors are variable, and seem to depend on the snake species, type of neurotoxicity, and geographical variations. Recent data have challenged the traditional concepts of neurotoxicity in snake envenoming, and highlight the rich diversity of snake neurotoxins. A uniform system of classification of the pattern of neuromuscular weakness and models for predicting type of toxicity and development of respiratory weakness are still lacking, and would greatly aid clinical decision making and future research. This review attempts to update the reader on the current state of knowledge regarding this important issue.

North American poisonous bites and stings

Critters and creatures can strike fear into anyone who thinks about dangerous animals. This article focuses on the management of the most common North American scorpion, arachnid, hymenoptera, and snake envenomations that cause clinically significant problems. Water creatures and less common animal envenomations are not covered in this article. Critical care management of envenomed patients can be challenging for unfamiliar clinicians. Although the animals are located in specific geographic areas, patients envenomed on passenger airliners and those who travel to endemic areas may present to health care facilities distant from the exposure.

North American snake and scorpion envenomations

Envenomations by snakes and scorpions in North America, although uncommon, do occur, and the victims may seek medical treatment. Combined, snake and scorpion encounters result in more than 25,000 calls a year to poison centers. Although some similarities exist with respect to general signs of envenomation and treatment, specific nuances distinguish the medical care to be anticipated and therapies available. Regardless of geographic practice area, exposures will occur that may result in a significant envenomation. This article provides critical care nurses with fundamental knowledge of varied snake and scorpion envenomation presentations and treatments to assist in optimizing patient outcomes.

Neurological effects of venomous bites and stings: snakes, spiders, and scorpions

Snake and spider bites, as well as scorpion sting envenoming, are neglected diseases affecting millions of people all over the world. Neurological complications vary according to the offending animal, and are often directly related to toxic effects of the venom, affecting the central nervous system, the neuromuscular transmission, the cardiovascular system, or the coagulation cascade. Snake bite envenoming may result in stroke or muscle paralysis. Metalloproteinases and other substances (common in vipers and colubrids) have anticoagulant or procoagulant activity, and may induce ischemic or hemorrhagic strokes. The venom of elapids is rich in neurotoxins affecting the neuromuscular transmission at either presynaptic or postsynaptic levels. The clinical picture of scorpion sting envenoming is dominated by muscle weakness associated with arterial hypertension, cardiac arrythmias, myocarditis, or pulmonary edema. These manifestations occur as the result of release of catecholamines into the bloodstream or due to direct cardiac toxicity of the venom. Cerebrovascular complications have been reported after the sting of the Indian red scorpion. Intracranial hemorrhages occur in the setting of acute increases in arterial blood pressure related to sympathetic overstimulation, and cerebral infarctions are related to either cerebral hypoperfusion, consumption coagulopathy, vasculitis, or cardiogenic brain embolism. Three main syndromes result from spider bite envenoming: latrodectism, loxoscelism, and funnel-web spider envenoming. Latrodectism is related to neurotoxins present in the venom of widow spiders. Most cases present with headache, lethargy, irritability, myalgia, tremor, fasciculation, or ataxia. Loxoscelism is caused by envenoming by spiders of the family Sicariidae. It may present with a stroke due to a severe coagulopathy. The venom of funnel-web spiders also has neurotoxins that stimulate neurotransmitter release, resulting in sensory disturbances and muscle paralysis. Proper management of the envenomed patient, including prompt transport to the hospital, correction of the hemostatic disorder, ventilatory support, and administration of antivenom, significantly reduce the risk of neurological complications which, in turn, reduce the mortality and improve the functional outcome of survivors.

Rattlesnake envenomation with neurotoxicity refractory to treatment with crotaline Fab antivenom

INTRODUCTION

Neurotoxicity following rattlesnake envenomation is reported with certain crotaline species. In some instances, crotaline Fab antivenom therapy that effectively halts progression of local tissue edema and hemotoxicity fails to reverse neurologic venom effects.

CASE SERIES

A 50-year-old man presented following a rattlesnake envenomation to the left ring finger. He had swelling and pain in the affected hand and complained of dyspnea and dysphonia. Significant fasciculations were seen in the face, tongue, neck, trunk, and arms. The patient received crotaline Fab antivenom but continued to develop worsening respiratory distress. His respiratory insufficiency requiring ventilatory support appeared related to respiratory muscle incoordination as extremity motor function remained intact. Initial control of local edema progression and hematologic parameters was achieved with antivenom, but diffuse fasciculations involving the entire body worsened despite aggressive antivenom treatment. In another case, a 9-year-old boy was envenomated by a rattlesnake on the left thenar eminence. He presented with pain and swelling up to the forearm and fasciculations of the tongue, face, and upper extremities. The progression of edema was halted at the mid-bicep level and hematologic parameters normalized with crotaline Fab antivenom. However, fasciculations continued for two days despite antivenom treatment.

CONCLUSION

We describe two cases of neurotoxicity following rattlesnake envenomation in which treatment with crotaline Fab antivenom adequately obtained initial control of local swelling and hematologic effects, but neurotoxic venom effects remained refractory to antivenom therapy. This phenomenon is anecdotally recognized following certain crotaline species envenomations.

Envenomations

Numerous types of envenomations may be encountered by health care workers depending on where in North America they work. Clinicians should be familiar with the animals in their region that may lead to envenomation.A rational approach with use of poison center or medical toxicology consultation services ensures that cases are managed appropriately.

Absence of myocardial involvement in children victims of Crotalus durissus terrificus envenoming

The myotoxic activity of the venom of Crotalus durissus terrificus is demonstrable by increased serum levels of the enzymes creatine kinase (CK), lactate dehydrogenase (LD), and aspartate aminotransferase. Serial measurements of CK, LD and their isoenzymes in bite victims showed a pattern similar to that observed in acute myocardial infarction, although the clinical course and electro- and echocardiographic data did not suggest cardiac involvement. These data have raised the hypothesis that crotalid venom preferentially causes damage to type I and/or type IIa fibers, which contain quantities of CK-MB and LD1 similar to those found in cardiac fibers. In order to detect a possible concomitant silent cardiac involvement, seven children with severe crotalid envenoming were studied. Serum troponin I, determined more than once in each patient, were found to be normal. These data demonstrate the absence of cardiac involvement in these patients envenomed by C. durissus terrificus and confirmed the skeletal muscle origin of the elevated CK-MB.

Tumor necrosis factor as a mediator of cardiac toxicity following snake envenomation

OBJECTIVE

To investigate the possible role of tumor necrosis factor in mediating cardiotoxicity following venom injection in a rat.

DESIGN

A randomized controlled experimental study using a Langendorff isolated heart model.

SETTING

Animal laboratory.

SUBJECTS

Adult male Wistar rats.

INTERVENTIONS

The control group (n = 10) was injected with saline only. Each animal in the experimental groups 1-3 (n = 10 each) was injected with Vipera aspis venom 500 microg/kg intramuscularly. Group 1 animals received no additional substance beforehand, group 2 animals were injected intramuscularly with 250 microg of soluble tumor necrosis factor receptor (sTNF-R p55) 15 mins before the venom injection, and group 3 animals were injected intraperitoneally with 40 microg of anti-tumor necrosis factor 60 mins before the venom injection.

MEASUREMENTS AND MAIN RESULTS

Cardiac performances were investigated following envenomation. Cardiac histology and myocardial tumor necrosis factor-RNA concentrations were assessed. Serum tumor necrosis factor concentrations rose and peaked 2 hrs following envenomation. A reduction in peak systolic pressures, maximum and minimum change in pressure over time, time-pressure integral, and coronary flow occurred in the venom-only-injected rats compared with controls, whereas blocking tumor necrosis factor activity prevented the deleterious cardiac effects of the envenomation. No histologic changes or increases in myocardial tumor necrosis factor-RNA concentrations were detected.

CONCLUSION

These results strongly suggest that systemic release of tumor necrosis factor mediates cardiac toxicity following Vipera aspis envenomation.

Neurotoxicity associated with suspected southern Pacific rattlesnake (Crotalus viridis helleri) envenomation

An 18-year-old man was bitten on the hand by a snake he believed to be a Southern Pacific rattlesnake (Crotalus viridis helleri). Within minutes he developed generalized weakness, difficulty breathing, diplopia, dysphagia, and dysphonia. Neurological examination revealed ptosis and decreased motor strength. These symptoms partially improved after administration of Antivenin (Crotalidae) Polyvalent, but the patient continued to have difficulty walking for several days due to weakness. In addition to neurological symptoms, the patient also experienced pain immediately after the bite occurred and rapid swelling of the entire extremity, which extended beyond the shoulder. He complained of a metallic taste in his mouth and developed intense muscle fasciculations of the face, tongue, and upper extremities, which lasted for 2 days and did not improve with antivenin treatment. He exhibited laboratory evidence of coagulopathy and rhabdomyolysis. Although neurotoxins are known to occur in the venom of certain populations of rattlesnakes, only a few clinical reports describing severe neurological symptoms appear in the literature. To our knowledge, this is the first reported case of neurotoxicity associated with a suspected Southern Pacific rattlesnake envenomation.

Antivenom therapy in the Americas

Envenomations are an important cause of injury in the Americas. While supportive care alone may result in an acceptable outcome, antivenom offers a specific therapy that can significantly reduce the injury and symptoms of the envenomation. Antivenoms are hyperimmune sera collected from animals immunised with venom. The antibodies contained in the serum bind and inactive venom components. This leads to cessation or reversal of the toxic effects of the venom. The serum is often processed to increase the level of antibodies directed against venom components and decrease the amount of inactive proteins that may cause allergic reactions. The processing may include precipitation of inactive proteins, chromatographic methods and cleavage of the immunoglobulins to form antibody fragments known as Fab or F(ab)2. In the Americas, antivenoms are produced to treat crotalid and Micrurus snake envenomations. Latrodectus and Loxosceles spider envenomations and Centruroides and Tityus scorpion envenomations. The indications, method of administration and incidence of adverse reactions differ greatly for each antivenom. The adverse effects encountered when using antivenoms are primarily allergic in nature. Anaphylaxis, which may be life threatening, is a major concern. Preparations to treat anaphylaxis must be made before initiating antivenom therapy. Serum sickness is also common with many of the antivenom preparations.

Mojave rattlesnake (Crotalus scutulatus scutulatus) identification

Mojave rattlesnake (Crotalus scutulatus scutulatus) identification has important diagnostic and therapeutic implications. Envenomation by certain populations of Mojave rattlesnakes may cause a different clinical presentation than that caused by other rattlesnakes. Specifically, Mojave rattlesnake envenomation may cause fewer local effects and more neurologic effects (including respiratory difficulty) than are typically seen after bites from other types of rattlesnake. Thus, it is useful for clinicians to distinguish the Mojave rattlesnake from other rattlesnakes in order to prevent underestimation of severe envenomation because of the lack of local tissue injury. Patients suspected to have been bitten by Mojave rattlesnakes may need more aggressive treatment with antivenin as well as more intensive supportive care. In addition, patients suspected to have been bitten by Mojave rattlesnakes should be closely monitored for an extended observation period, as venom effects may be delayed or prolonged. Mojave rattlesnakes may be particularly difficult to distinguish from Western Diamondback rattlesnakes (Crotalus atrox) because of their similarity in appearance and overlapping ranges. The purpose of this report is to provide clinicians with key characteristics which may assist in distinguishing Mojave rattlesnakes from Western Diamondback and other rattlesnakes.

Envenomations

Envenomations are uncommon, challenging causes of critical care admissions. This article describes the diagnosis and treatment of envenomations that cause the most critical care admissions in the United States. Most are caused by the following animals: rattlesnakes, copperheads, cottonmouths, coral snakes, brown recluse spiders, and bark scorpions.

Crotalid snake envenomation

Over 5000 Americans suffer from snake bites annually, and of these, nearly one quarter are from poisonous species. Although these cases are undeniably reported, death appears to occur in only a few cases each year, and often reflects delay in obtaining medical care. Two families of venomous snake indigenous to the United States account for most envenomations: Crotalidae (pit vipers or new world vipers) and Elapidae. This article focuses on the snakes of the Crotalidae family.

Successful treatment of crotalid-induced neurotoxicity with a new polyspecific crotalid Fab antivenom

STUDY OBJECTIVE

To report the effectiveness of a new polyvalent crotalid antivenom on neurotoxicity associated with North American rattlesnake envenomation. Two syndromes of crotalid-induced neurotoxicity have been reported. In severe envenomation by Crotalus scutulatus scutulatus (Mojave rattlesnake), weakness and fasciculations of various muscle groups, including those innervated by cranial nerves, may develop. Occasionally respiratory insufficiency develops. The second neurotoxic effects is myokymia, a type of fasciculation most frequently reported after bites by Crotalus horridus horridus (timber rattlesnake) and Crotalus atrox (Western diamondback rattlesnake). Conventional polyvalent antivenom is often ineffective in the treatment of venom-induced neurotoxicity.

METHODS

We report a case series of three patients envenomated by North American rattlesnakes, one of which was identified as C scutulatus scutulatus. All three patients experienced neurotoxicity with weakness, paresthesias, and dramatic fasciculations, along with other signs and symptoms of crotalid venom poisoning.

RESULTS

The administration of new polyspecific crotalid antivenom made of ovine Fab was successful in immediately and completely reversing neurotoxicity in each of these patients.

CONCLUSION

We report the use of a new antivenom for North American crotalid envenomation that seems to have efficacy in reversing neurotoxicity associated with these bites.

Canebrake rattlesnake envenomation

STUDY OBJECTIVE

To document the clinical presentation and course of consecutive cases of envenomation by the canebrake rattlesnake (Crotalus horridus atricaudatus).

METHODS

The medical care provided all patients envenomated by canebrake rattlesnakes in two institutions was retrospectively reviewed. Particular attention was paid to coagulation abnormalities, serum enzymes, electrocardiographic findings, and treatment with antivenom.

RESULTS

Of the 15 patients, envenomation was judged to be mild in 3, moderate in 6, and severe in 5. In one case envenomation caused death. The clinical course generally predicted the degree of increase in the serum creatinine kinase (CK) level, as well as the amount of antivenom used for treatment. Despite increases in serum CK concentration and frequent increases in the serum CK-MB fraction, we found no evidence of cardiac damage.

CONCLUSION

In envenomation by North American pit vipers, rhabdomyolysis appears to be characteristic of envenomation by the canebrake rattlesnake. We speculate that toxins in the canebrake venom cause skeletal muscle rhabdomyolysis. Physicians caring for victims of canebrake bite should regard marked increases in CK concentration as coming from skeletal, not cardiac, muscle. Good general medical support and antivenom for victims with moderate to severe envenomation appears effective.

Thrombocytopenia following timber rattlesnake envenomation

STUDY OBJECTIVE

To better characterize timer rattlesnake venom--induced thrombocytopenia and coagulopathy and the response to therapy with Antivenin (Crotalidae) Polyvalent.

METHODS

We conducted a retrospective multicenter review of timber rattlesnake envenomation.

RESULTS

We reviewed 18 cases at two institutions. Restoration of normal prothrombin time and partial thromboplastin time was achieved in all cases with antivenom therapy. In contrast, complete reversal of thrombocytopenia was not achieved, despite antivenom therapy.

CONCLUSION

Antivenom (Crotalidae) Polyvalent was less effective in reversing thrombocytopenia than coagulopathy after timber rattlesnake envenomation, suggesting that a component of timber rattlesnake venom persists in the blood despite antivenom therapy. Persistent thrombocytopenia may be due to a venom factor that the antivenom does not neutralize or to inadequate dosing of antivenom. Prompt reversal of thrombocytopenia following treatment of timber rattlesnake envenomation with this antivenom appears unlikely.

Severe toxicity from crotalid envenomation after early resolution of symptoms

Initial observation of a patient who sustained a rattlesnake bite on the hand showed resolution of mild swelling over 3 hours. The patient left the emergency department against medical advice, only to return 12 hours later with severe pain and swelling, as well as a marked coagulopathy. This case illustrates the need for an observation period after crotalid bite, even when the envenomation seems to be minor or when symptoms resolve.

Severe rattlesnake envenomation with anaphylaxis and rhabdomyolysis

A 7-year-old boy presented to the emergency department with severe hypotension and lethargy after a rattlesnake bite. He developed anaphylaxis to antivenom and required intubation, epinephrine, antihistamines, and steroids. Severe rhabdomyolysis and myoglobinuric kidney failure developed over 24 hours, with a peak creatine phosphokinase level of 214,500 units/L. Severe hypocalcemic tetany was treated with replacement therapy. Local wound swelling was never severe and the patient had no coagulopathies. Marked motor weakness improved with antivenom administration. Because of the myotoxic and neurologic effects in the absence of fibrinogenolysis/thrombocytopenia and minimal tissue signs, as well as the similarity to a previously reported case from our area, the envenomation was most likely caused by a Mojave rattlesnake.