Crotalid envenomation: the southern Arizona experience

Venomous Snake and Spider Bites in Pregnancy

Importance

Venomous snake and spider bites are relatively rare in the Unites States and even more so in the pregnant population. However, the impact of a venomous bite, also known as an envenomation, can be serious in a pregnant patient. Thus, providers in endemic and high-risk areas must be familiar with the management of envenomation in the pregnant population.

Objective

The purpose of this article is to review the current literature on the most common snake and spider envenomations in the United States, the effects of envenomation on maternal and fetal health, and the management of envenomation in pregnancy.

Evidence Acquisition

Original research articles, review articles, and guidelines on snake and spider envenomation were reviewed.

Results

Snake envenomation carries higher risks of maternal morbidity and fetal morbidity and mortality than spider envenomation. Although the data are limited, current literature suggests that both snake and spider antivenom can be used in the pregnant population without significant adverse outcomes. However, the risks of an adverse hypersensitivity reaction with antivenom administration should be weighed carefully with the benefits.

Conclusions and Relevance

The use of antivenom therapy in the symptomatic envenomated pregnant population is likely safe with the appropriate monitoring and follow-up. Knowledge of the indications for antivenom therapy and proper escalation of care are vital to optimizing maternal and fetal outcomes. More research is needed to determine the effects of both envenomation and antivenom therapy on the pregnant patient and their fetus.

Snake Bite Management: A Scoping Review of the Literature

Background:

Around the world, snake bite envenomation remains an underreported human health hazard. Envenomation can cause local and systemic complications, especially when there is a lack of antivenom availability. Although there are established guidelines regarding snake bite management acute care, there is a paucity of data regarding surgical intervention and the plastic surgeon’s role treating this unique patient population.

Methods:

A review was conducted identifying relevant published articles involving snake bite management and treatment in PubMed and EMBASE.

Results:

One hundred ten articles were identified and 77 met inclusion criteria. Snake bite envenomation can result in complications that are dependent upon a variety of variables. The literature has shown the best field treatment to be timely transportation to the nearest medical facility, along with antivenom administration. The cytotoxic, hemotoxic, and neurotoxic effects of venom can cause a variety of local soft tissue and systemic complications. Surgical interventions such as fasciotomies, wound debridements, skin grafts, and tissue flaps may be necessary in these patients to optimize functional and aesthetic outcomes. Disparities in access to care in resource limited settings are discussed.

Conclusions:

Global health disparities and insufficient antivenom distribution create an inequality of care in snake bite patients. Plastic surgeons have an important role in managing acute and chronic complications of snake bite envenomations that can lead to improved patient outcomes.

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.

Copperhead Envenomation Resulting in a Rare Case of Hand Compartment Syndrome and Subsequent Fasciotomy

Copperhead bites account for nearly 40% of all snakebites in the United States. Although common, these bites are rarely severe, and most are treated with supportive care and antivenom. We describe the first reported case of a copperhead envenomation resulting in a hand compartment syndrome with measured elevated compartment pressures that necessitated fasciotomy of the hand. Our case underscores the importance of vigilance in the diagnosis and management of copperhead envenomation.

Treating venomous snakebites in the United States: a guide for nurse practitioners

This article discusses the current, evidence-based guidelines for managing venomous snakebites indigenous to the United States. A review of common varieties of venomous snakes, venom effects, risk factors for snakebites, and management strategies are presented to assist nurse practitioners in caring for snakebite victims.

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.

Snakebite Survivors Club: retrospective review of rattlesnake bites in Central California

OBJECTIVE

We investigated clinical patterns of crotaline envenomation presenting to a tertiary-care academic hospital in Central California over a 10-year period.

METHODS

An IRB-approved, retrospective chart review was conducted on all patients diagnosed with snakebite from December 2000 to December 2010. Data abstracted: demographics, anatomic location of bite, comorbid conditions and intoxicants, length of stay, antivenom dose, laboratory results, and complications or procedures.

RESULTS

There were 46 snakebite cases admitted over the study period. Five were "dry bites"; the remaining cases (41/46) received antivenom. There was a male predominance (83% male victims). Upper extremity bites were more common (32/41 upper vs 10/42 lower extremity). One victim sustained bilateral bites to the hands. Thirty-five patients (85%) were admitted, with an average length of stay 2.12 days. The longest hospitalization was 15 days. There were no fatalities. The average time from bite to ED presentation was 2 h 44 min. Bites occurred during every month except November, with the majority occurring during spring and summer months and peaking in June (12/42 cases). Most bites occurred in the hours between noon and 8 pm. The amount of antivenom given ranged from 2 to 35 vials (average, 9 vials). Interfacility transfers were common in our study population: thirteen (32%) patients were transferred into our emergency department for a higher level of care, and 3 (7%) were transferred out (two because of insurance requirements, and one for higher level of Pediatric ICU care). There were no surgical interventions in our study group. Intoxication did not appear to play a major role in this population as only 3 patients (7%) were found to be acutely intoxicated: one with cannabis and amphetamines, 1 with alcohol, and 1 with opioids.

CONCLUSIONS

In Central California, crotaline envenomations occurred mainly in adult males. Dry bites, or bites not requiring antivenom administration, were uncommon, comprising only 10% of bites in this study population. Contrary to popular and clinical beliefs, substance abuse and/or alcohol intoxication did not appear to play a role in the majority of patients in this study. Care providers and snakebite specialists should be aware that snakebite patients are often transferred between facilities, a finding that may be useful in designing future first aid protocols and research. We hope these findings add concrete data and help correct some common misconceptions about snakebites in Central California.

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.

Management of venomous snakebite injury to the extremities

Pit vipers (subfamily Crotalinae) are responsible for most venomous snakebites in the United States. The mixture of proteins with cytotoxic, proteolytic, and/or neurotoxic enzymes in snake venom varies by species. Treatment in the field consists of safe identification of the species of snake and rapid transport of the patient to the nearest health care facility. Swelling, bruising, and systemic symptoms are seen following snakebite. Most patients respond to elevation of the affected extremity and observation. Some require the administration of antivenin. Crotalidae Polyvalent Immune Fab (Ovine) (CroFab, BTG International, West Conshohocken, PA) antivenin is safe and effective for the management of local and systemic effects of envenomation. Rarely, compartment syndrome may develop in the affected limb because of edema and tissue necrosis. Close monitoring of the extremity via serial physical examination and measurement of compartment pressure is a reliable method of determining whether surgical intervention is required.

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.

Sensationalistic journalism and tales of snakebite: are rattlesnakes rapidly evolving more toxic venom?

Recent reports in the lay press have suggested that bites by rattlesnakes in the last several years have been more severe than those in the past. The explanation, often citing physicians, is that rattlesnakes are evolving more toxic venom, perhaps in response to anthropogenic causes. We suggest that other explanations are more parsimonious, including factors dependent on the snake and factors associated with the bite victim's response to envenomation. Although bites could become more severe from an increased proportion of bites from larger or more provoked snakes (ie, more venom injected), the venom itself evolves much too slowly to explain the severe symptoms occasionally seen. Increased snakebite severity could also result from a number of demographic changes in the victim profile, including age and body size, behavior toward the snake (provocation), anatomical site of bite, clothing, and general health including asthma prevalence and sensitivity to foreign antigens. Clinical management of bites also changes perpetually, rendering comparisons of snakebite severity over time tenuous. Clearly, careful study taking into consideration many factors will be essential to document temporal changes in snakebite severity or venom toxicity. Presently, no published evidence for these changes exists. The sensationalistic coverage of these atypical bites and accompanying speculation is highly misleading and can produce many detrimental results, such as inappropriate fear of the outdoors and snakes, and distraction from proven snakebite management needs, including a consistent supply of antivenom, adequate health care, and training. We urge healthcare providers to avoid propagating misinformation about snakes and snakebites.

Characteristics of patients transported by an aeromedical service for acute toxicologic emergencies: a 5-year experience

INTRODUCTION

Aeromedical services are used routinely in the prehospital and interhospital transfer of patients with trauma, neurosurgical, cardiac, and other conditions requiring specialized care. The use of aeromedical transport in patients with acute toxicologic emergencies is not well described. We sought to investigate and describe the characteristics of patients transported by our aeromedical service.

SETTING

The study was performed at an urban critical care transport service operating both ground and aeromedical units and transporting an average of 3,362 patients per year during the study period.

METHODS

Charts from the 5-year period of 2000 to 2004 for which a toxicologic emergency was coded as the primary diagnosis were identified and reviewed by the authors. Data abstracted included age, sex, toxin(s) involved, treatment rendered at the scene/bedside and en route by the transport team, and additional data (electrocardiogram [ECG] findings, serum levels) when appropriate.

RESULTS

One hundred thirty-three patients were transported (for a total of 135 transports). Most (82%) were transported by air. Carbon monoxide was the most common toxic exposure, accounting for 16% of all transports. Fifty-seven percent of the patients were intubated, with 11% intubated by the flight crew. Antidotes were administered in 40 patients, with naloxone and bicarbonate being the most common.

CONCLUSION

Acute toxicologic emergencies accounted for a small percentage of total transports. The most common additional intervention by flight crews was endotracheal intubation. Identification of common poisonings encountered by flight crews may assist services in developing education and quality assurance programs.

Surgical implications of snakebites

OBJECTIVE

Snakebites are a common problem in the pediatric age group. Local complications such as necrosis and compartment syndrome threaten limb survival even after control of systemic manifestations. Few recommendations exist about the nature and timing of surgical treatment.

METHODS

A retrospective review of all children with snakebites presenting to the hospital was undertaken over a 6-year period. Records were reviewed with special emphasis on the type of surgical lesions seen and the treatment offered and their results.

RESULTS

44 of the 58 children required some form of local therapy. In the majority conservative treatment was successful. 28% of the patients needed debridement for local necrosis, and only 5 needed a skin graft, with good functional results over a period of 1 to 45 days. One child underwent an above knee amputation. Patients who required surgical intervention received significantly more vials of antivenin.

CONCLUSION

Local complications of snakebite are frequent, but can be managed conservatively. Delayed excision of the resultant local necrosis is associated with good outcomes. The need for fasciotomy is rare.

Surgical issues in the poisoned patient

Some toxicologic emergencies require immediate or urgent surgical intervention in addition to routine medical care. The EP must be familiar with the indications for operative care, even though many of these poisonings and exposures are relatively rare. The EP must also be knowledgeable regarding the various means of surgical decontamination that are available, including temporary cardiopulmonary bypass. Finally, a high level of vigilance must be maintained for patients who have delayed presentation and fulminant organ failure necessitating early involvement of the transplantation team.

Presentation and Treatment of Venomous Snakebites at a Northern Academic Medical Center

Poisonous snakebites are relatively rare in the United States. The incidence of venomous snakebites is comparatively high in the southern states compared with the northern states and reports of these accidents from northern states is particularly uncommon. We report the experience with treatment of venomous snakebites at the University of Michigan over a 25-year period from 1976 to 2001. Six cases were identified and are described in detail. All patients were male and all were bitten in the upper extremity by pit vipers. One patient suffered a moderate envenomation and was treated with antivenin. Four other cases of mild envenomation occurred and two of these cases required antivenin therapy. One case was considered to represent a “dry” bite and required only 24-hour observation. There were no severe envenomations and no mortalities. On short-term follow-up all patients recovered without sequelae. This report demonstrates that venomous snakebites can be treated effectively at low-volume centers.

Role of surgical intervention in the management of crotaline snake envenomation

Crotaline venoms produce various toxic effects. Although these are most commonly treated with specific antivenoms, surgical management of snakebite has also been practiced for many years. Surgical approaches to pit viper envenomation include incision or excision of the bite site, fasciotomy, and digit dermotomy. The evidence regarding each of these procedures is sparse; however, incision or excision of the bite site are difficult to advocate. Fasciotomy and digit dermotomy may be appropriate in carefully selected patients.