Rattlesnake bites and surgical decompression: results using a laboratory 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.

Clinical aspects of snakebite envenoming and its treatment in low-resource settings

There is increasing recognition of the public health importance of snakebite envenoming. Worldwide annual incidence is likely to be 5 million bites, with mortality exceeding 150 000 deaths, and the resulting physical and psychological morbidity leads to substantial social and economic repercussions. Prevention through community education by trained health workers is the most effective and economically viable strategy for reducing risk of bites and envenoming. Clinical challenges to effective treatment are most substantial in rural areas of low-resource settings, where snakebites are most common. Classic skills of history taking, physical examination, and use of affordable point-of-care tests should be followed by monitoring of evolving local and systemic envenoming. Despite the profusion of new ideas for interventions, hyperimmune equine or ovine plasma-derived antivenoms remain the only specific treatment for snakebite envenoming. The enormous interspecies and intraspecies complexity and diversity of snake venoms, revealed by modern venomics, demands a radical redesign of many current antivenoms.

Snakebite: When the Human Touch Becomes a Bad Touch

Many issues and complications in treating snakebite are a result of poor human social, economic and clinical intervention and management. As such, there is scope for significant improvements for reducing incidence and increasing patient outcomes. Snakes do not target humans as prey, but as our dwellings and farms expand ever farther and climate change increases snake activity periods, accidental encounters with snakes seeking water and prey increase drastically. Despite its long history, the snakebite crisis is neglected, ignored, underestimated and fundamentally misunderstood. Tens of thousands of lives are lost to snakebites each year and hundreds of thousands of people will survive with some form of permanent damage and reduced work capacity. These numbers are well recognized as being gross underestimations due to poor to non-existent record keeping in some of the most affected areas. These underestimations complicate achieving the proper recognition of snakebite’s socioeconomic impact and thus securing foreign aid to help alleviate this global crisis. Antivenoms are expensive and hospitals are few and far between, leaving people to seek help from traditional healers or use other forms of ineffective treatment. In some cases, cheaper, inappropriately manufactured antivenom from other regions is used despite no evidence for their efficacy, with often robust data demonstrating they are woefully ineffective in neutralizing many venoms for which they are marketed for. Inappropriate first-aid and treatments include cutting the wound, tourniquets, electrical shock, immersion in ice water, and use of ineffective herbal remedies by traditional healers. Even in the developed world, there are fundamental controversies including fasciotomy, pressure bandages, antivenom dosage, premedication such as adrenalin, and lack of antivenom for exotic snakebites in the pet trade. This review explores the myriad of human-origin factors that influence the trajectory of global snakebite causes and treatment failures and illustrate that snakebite is as much a sociological and economic problem as it is a medical one. Reducing the incidence and frequency of such controllable factors are therefore realistic targets to help alleviate the global snakebite burden as incremental improvements across several areas will have a strong cumulative effect.

Algorithmic approach to the prevention of unnecessary fasciotomy in extremity snake bite

BACKGROUND

In the literature, there is a lack of a consensus about the occurrence of the compartment syndrome due to the snake bites. There are different concepts for the surgical treatment of the threshold value of the chamber pressure. There are many different classifications and assessment criteria for the snakebites.

PURPOSE

There is not any appropriate classification in order to the assessment of extremity snake bites while making a decision for fasciotomy. We aimed to standardize the follow-up and decision making to perform fasciotomy with a new classification system for the snakebites using objective data.

PATIENTS AND METHODS

The data of all patients were recorded prospectively between 2006 and 2011. A total of 97 patients (64 male, 33 female) with a mean age of 30.94±14.04 were followed-up. During the evaluation of the patients, we used a new classification system that was improved for the extremity bites. We classified the patients due to their signs into four groups as for the classification system.

RESULTS

40 patients with compartment like symptoms were carefully followed for 48-72h, and only three patients required fasciotomy where full recovery was achieved in 37 patients. Coverage of the defects was performed with full thickness skin grafting in 4 patients and cross finger flap in two patient. In two patients, the defects were located on the palmar aspect of the thumb. Thus, we applied Kite flap for skin coverage. Reverse dorsal digital artery flap was performed in eight patients and dorsal interosseous metacarpal flap in six patients. Four patients underwent an amputation. Two patients had web reconstruction due to first web contracture.

CONCLUSIONS

We present a large series of snake bite injuries and propose a classification and treatment recommendations. Fasciotomy should only be done while the measurement of intra-compartment pressure is above 55mmHg as snakebite can mimic the compartment syndrome.

LEVEL OF EVIDENCE

III-IV.

A Multidisciplinary Approach with Hyperbaric Oxygen Therapy Improve Outcome in Snake Bite Injuries

Aim:

Snakebite injuries are common in tropical India among those who are involved in outdoor activities. These injuries results in cellulitis, gangrene at the bite area, bleeding manifestations, compartment syndrome, regional lymphadenopathy, septicemia, hypotension, and disseminated intravascular coagulation (DIC) resulting in significant morbidity and mortality. The purpose of this study is to share our experience of multidisciplinary approach in the management of snakebite injuries of the extremities with various treatment modalities including hyperbaric oxygen (HBO) therapy, surgical debridement, and soft tissue reconstruction to provide an effective treatment for snake bite injuries.

Methods:

The study was conducted in the Department of Plastic Surgery, during the period October 2012–December 2014, wherein all the patients who were admitted with snakebite injuries were enrolled and the patients treated in plastic surgery department were included into the study. Out of total 766 patients, there were 323 patients treated with anti snake venom (ASV) and 29 died among the treated patients; 205 patients belonged to pediatric age group.

Results:

Out of 112 patients referred to Department of Plastic Surgery, 50 cases presented with cellulitis, 24 patients with compartment syndrome, and 38 patients were referred for the management of soft tissue cover over the extremities. Among 112 patients, 77 involved the lower extremity and 35 the upper extremity.

Conclusion:

Multidisciplinary approach including hyperbaric oxygen (HBO) therapy improves outcome in the management of snakebite injuries of the extremities.

Predictors of the development of post-snakebite compartment syndrome

Background

To identify the factors associated with the development of post-snakebite compartment syndrome (PSCS) in snakebite patients and to analyze the clinical prognosis of these patients.

Methods

We retrospectively reviewed the medical records of patients who presented to our institution with snakebites from March 2009 to December 2012. The clinical data, hospital course and outcome were all recorded.

Results

A total of 136 patients were included in the present study. Nine patients developed PSCS and underwent fasciotomy. Relative to the non-PSCS group, the PSCS group demonstrated a significant increase in the white blood cell count (WBC, p = 0.006), segment form (Seg, p ≤ 0.001), aspartate aminotransferase level (AST, p = 0.002) and alanine aminotransferase level (ALT, p = 0.008). Elevated WBC count and AST level were identified as independent risk factors for PSCS (p = 0.028 and 0.037, respectively) in a multivariate analysis.

Conclusions

Snakebite patients have a high likelihood of developing locoregional complications such as PSCS. Symptomatic snakebite patients should be observed for at least 48 h, and increased WBC counts and AST levels are risk factors for PSCS.

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.

Commissioned article: management of exotic snakebites

Exotic (foreign or non-native) snakes, including venomous species, are becoming increasingly popular pets in Western countries. Some of them are kept illegally (as defined by the UK Dangerous Wild Animals Act of 1976). There is a large international market for such animals, with contraventions of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). In the UK, several other European countries and the USA the reported numbers of bites by venomous exotic snakes, although small, are increasing but still underestimate the occurrence of these occasionally fatal events because of the victims' reluctance to seek medical care. Victims are predominantly young men who have been drinking alcohol. Bites may be intentionally provoked. In Europe, the species most often involved are cobras, green mambas, American pit vipers particularly rattlesnakes, African adders, vipers and Asian green pit vipers. To illustrate the special problems involved, case histories are presented of bites by exotic species in the UK and of bites abroad, where patients were repatriated for treatment. In view of the relative rarity and diversity of these cases, expert advice must usually be sought. These requests should include information about the species thought to have been responsible and the history and timing of the evolution of envenoming. Sources of advice and antivenom are discussed together with recommendations for appropriate first aid and emergency treatment while this is being awaited. Respiratory and cardiovascular resuscitation may be required and when systemic or severe local envenoming develops, specific (equine or ovine) antivenom is indicated.

The management of pit viper envenomation of the hand

Snakebites are common among the rural population of developing countries. The severity of venomous snakebites depends on several factors, including the location of the bite, the amount of venom injected, and the effectiveness of the initial therapy. Snakebites frequently occur in the extremities with approximately two thirds of envenomations occurring in the upper extremities. In this study, we presented 12 cases of hand reconstruction after Vipera snakebites and discussed how to minimize functional loss and maximize hand rehabilitation. Twelve patients bitten by Vipera between 2001 and 2006 were included in this study. Groin flaps were performed in three cases, full-thickness grafts in two cases, thenar flaps in three cases, and cross finger flaps in three cases. With medical management, spontaneous healing occurred in one case. We prefer to use flaps on the volar site of the hand and, if the bone is not exposed, full-thickness grafts on the dorsal site of the hand. We also recommend starting rehabilitation of the hand early.

Snake Bite: Pit Vipers

Pit vipers are the largest group of venomous snakes in the United States and are involved in an estimated 150,000 bites annually of dogs and cats. The severity of any pit viper bite is related to the volume and toxicity of the venom injected as well as the location of the bite, which may influence the rate of venom uptake. The toxicity of rattlesnake venom varies widely. It is possible for pit vipers' venom to be strictly neurotoxic with virtually no local signs of envenomation. Venom consists of 90% water and has a minimum of 10 enzymes and 3 to 12 nonenzymatic proteins and peptides in any individual snake. The onset of clinical signs after envenomation may be delayed for several hours. The presence of fang marks does not indicate that envenomation has occurred, only that a bite has taken place. Systemic clinical manifestations encompass a wide variety of problems including pain, weakness, dizziness, nausea, severe hypotension, and thrombocytopenia. The victim's clotting abnormalities largely depend upon the species of snake involved. Venom induced thrombocytopenia occurs in approximately 30% of envenomations. Many first aid measures have been advocated for pit viper bite victims, none has been shown to prevent morbidity or mortality. Current recommendations for first aid in the field are to keep the victim calm, keep the bite site below heart level if possible, and transport the victim to a veterinary medical facility for primary medical intervention. The patient should be hospitalized and monitored closely for a minimum of 8 hours for the onset of signs of envenomation. The only proven specific therapy against pit viper envenomation is the administration of antivenin. The dosage of antivenin needed is calculated relative to the amount of venom injected, the body mass of the victim, and the bite site. The average dosage in dogs and cats is 1 to 2 vials of antivenin.

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.

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.

Resolution of compartment syndrome after rattlesnake envenomation utilizing non-invasive measures

Western diamondback rattlesnake envenomation is usually managed by administration of neutralizing antivenom. The development of compartment syndrome is a rare complication that has sparked considerable debate regarding medical vs. surgical management. We report a case of compartment syndrome resulting from a rattlesnake envenomation, which responded to large doses of neutralizing antivenom given concomitantly with mannitol and hyperbaric oxygen. This regimen obviated the need for surgical fasciotomy and its associated morbidity.

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.

David R. Boyd lecture in trauma care and emergency medical systems: "The surgical complications of toxins."

Toxins have had major roles in our societies for thousands of years. Interactions between surgeons, both generalists and subspecialists, and those caring for poisoned patients have been extensive throughout history. The advancement of the science of toxicology, the development of regional poison control centers, the development of emergency medicine, and the development of the subspecialty of medical toxicology have led to more appropriate and creative interactions between medical toxicologists, emergency physicians, and surgeons. This article will review the diverse interfaces between the medical toxicologist and the surgeon.

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.

Snakes and snakebite in Central America

This review treats the general biology, taxonomy, distribution and venom apparatus of the venomous snakes of Central America. Consideration has been given to the chemistry, pharmacology and immunology of the venom, and particular attention is dispensed to the clinical problem, including the treatment, of envenomations by these reptiles.

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.

Venomous snake bite: current concepts of treatment

The optimal treatment of venomous snake-bites remains controversial. Because of the variables involved in treatment, an ideal, prospective clinical trial likely will never be done. The purpose of this article is to review the available treatment methods and outline the treatment methods preferred in our institution for crotalidae envenomation.

Snake envenomation. Incidence, clinical presentation and management

Snake envenomation is a major cause of death and disability in the developing countries, particularly India and Southeast Asia. Species variation in venom components, yield, and lethality leads to quite different clinical presentations and mortality. Venomous snakes are divided into 5 families. Bites of the Viperidae, Crotalidae and Colubridae usually cause primarily local effects and bleeding; the Elapidae most commonly cause neurological symptoms, particularly paralysis; while the Hydrophidae cause paralysis and myolysis. Venoms are complex mixtures of enzymes, peptides and metalloproteins. 26 enzymes have been identified, and 10 of those are found in most venoms. Components have been identified that act as procoagulants, anticoagulants, hyaluronidases, RNases, DNases, postsynaptic toxins and presynaptic toxins. Other peptides induce capillary leak syndrome, haemolysis and shock. The clinical results of envenomation vary widely, and there may be no envenomation with a bite. Syndromes reported include oedema, haemolysis, shock, bleeding, pituitary failure, renal failure, myonecrosis, and combinations of the above. First aid measures that have been proposed include tourniquets, constricting bands, tight crepe bandages, incision and suction, cryotherapy, and high voltage electric shock. None of these has been shown to be effective except usage of a crepe bandage for Australian elapid bite. Tourniquets or cryotherapy, if used for extended periods may lead to gangrene. The most important first aid measure is rapid transport to comprehensive medical care. There is some controversy about medical treatment in the United States, but less in other countries. Supportive measures routinely required include intravenous fluids, tetanus prophylaxis and antibiotics. Anticholinergics may be useful in elapid bite. Intubation and ventilation may be necessary. Unproven surgical approaches include excision of envenomated tissues and fasciotomy. The former is disfiguring, the latter should be reserved for those patients with demonstrated increased intracompartmental pressure. More than 100 antivenins are produced by about 36 laboratories worldwide. The products are effective, but carry a high risk of serum sickness and a lesser risk of anaphylaxis. A more effective and less reactive product is under development.

Wound care of spider and snake envenomations

Venomous bites and stings are numerous but severe local tissue damage is uncommon. Venoms may be simple substances or complex mixtures of many poorly characterized components whose interactions are still not fully understood. The best studied example of a dermonecrotic venom is that produced by the brown recluse spider (Loxosceles reclusa). Rattlesnake envenomation also causes significant wound injuries. Many spider and snake envenomation management modalities are controversial and the evidence is mounting against the use of a number of these treatments.

Severe myonecrosis in a fatal case of envenomation by the canebrake rattlesnake (Crotalus horridus atricaudatus)

Severe myonecrosis was found at autopsy in a fatal case of envenomation by Crotalus horridus atricaudatus. The degree and extent of rhabdomyolysis were independent of the site of muscle sampling, being no more advanced at the site of envenomation. We conclude that myonecrosis was not enhanced by increased interstitial pressure.

The effect of antivenin on intramuscular pressure elevations induced by rattlesnake venom

The dose of an antivenin required to neutralize a clinical case of venom poisoning, as well as determining the timing or need to initiate antivenin treatment, is frequently difficult to objectively ascertain. In this study, venom from the southern Pacific rattlesnake, Crotalus viridis helleri, was injected into 29 dog hind limb anterolateral compartments. A solution of C. v. helleri venom (15 mg/ml) was prepared using dessicated venom and saline; 0.2 ml were injected sub-fascially so that each of the compartments received 3 mg of venom. In one group no antivenin was given, in a second group four vials of antivenin were administered i.v. 1 hr post-injection, and in the final group eight vials of antivenin were administered i.v. 1 hr following venom injection. In all groups intracompartment pressures, limb girth and surface temperature were measured at regular intervals over the first 48 hr. In the group receiving eight vials of antivenin the intracompartment pressure reached a peak mean pressure of 49 mm Hg at 2 - 4 hr, and then rapidly fell. In those treated with none or four vials the pressure rose to 70 and 60 mm Hg, respectively, and remained elevated over the first 24 hr. The difference between the former and latter two groups is statistically significant. The findings indicate that the intracompartmental pressure, and presumably destructive damage of the venom, can be controlled by adequate levels of i.v. antivenin. Intracompartmental pressure measurements should be considered as an adjunct in the monitoring and decision-making processes for the treatment of patients bitten by rattlesnakes.