Fatal rattlesnake envenomation in Arizona: 1969-1984

Ruthenium-based antivenom attenuates Crotalus atrox venom mediated coagulopathy in rabbits

BACKGROUND

The Western diamondback rattlesnake ( Crotalus atrox ) is a medically important venomous snake in the Southwestern United States, injuring humans, and their companion animals. The goals of this investigation were to utilize a rabbit model of subcutaneous envenomation to assess Crotalus atrox venom coagulopathy and determine the efficacy of a ruthenium-containing antivenom (RA) in attenuating it.

METHODS

Sedated New Zealand White rabbits had viscoelastic measurements of whole blood coagulation kinetics obtained from ear artery samples. Crotalus atrox venom (4 mg/kg) was injected subcutaneously and changes in coagulation determined over three hours and compared to samples obtained prior to envenomation. Other rabbits had site-directed RA injected 5 min after venom injection.

RESULTS

A significant decrease in the velocity of clot growth and thrombus strength was observed in animals injected with venom alone. Site-directed administration of RA resulted in no change in coagulation over the 3 h following venom injection. The interaction of antivenom administration and time was significantly different in the cases of clot growth velocity and strength.

CONCLUSIONS

A novel rabbit model was used to define the toxicodynamic profile of coagulopathy of Crotalus atrox venom and demonstrate the efficacy of RA. Future investigation is planned involving other medically important venoms and RA administration.

Pulmonary effects and complications of snakebites

This review is on the pulmonary complications of snakebites, which can have fatal consequences. We identified three common themes as reported in the literature regarding envenomation: generalized neuromuscular paralysis affecting airway and respiratory muscles, pulmonary edema, and pulmonary hemorrhages or thrombosis due to coagulopathy. Respiratory paralysis and pulmonary edema can be due to either elapid or viper bites, whereas pulmonary complications of coagulopathy are exclusively reported with viper bites. The evidence for each complication, timeline of appearance, response to treatment, and details of pathophysiology are discussed.

North American snake envenomation in the dog and cat

Snake envenomation can be a cause of significant morbidity in dogs and cats in North America. Being familiar with the venomous snakes in your area and understanding the mechanisms of action of their venom will allow for successful treatment of envenomation cases. Treatment of snake envenomation revolves around supportive care in mild to moderate cases and venom neutralization with antivenom in severe cases. Dogs and cats envenomated by North American snakes have a good prognosis if treated appropriately.

AAPCC database characterization of native U.S. venomous snake exposures, 2001-2005

BACKGROUND

Differences in victim demographics, clinical effects, managements, and outcomes among native viperid (rattlesnake, copperhead, and cottonmouth) and elapid (coral snake) species have not been systematically characterized.

METHODS

The database of the American Association of Poison Control Centers from 2001 through 2005 was analyzed.

RESULTS

Between 2001 and 2005, there were 23,676 human exposures (average = 4,735/year) to native venomous snakes in the United States reported to U.S. poison centers in all states except Hawaii: 98% were to viperid snakes and 2% to elapids. Overall, 77% of victims were male, 70% were adults >20 years, and 12% were aged less than 10 years. Sixty-five cases involved pregnant women, with rattlesnake bites resulting in moderate or greater effects in over 70%. The overall hospital admission rate was 53%. Outcomes were generally more severe with rattlesnake and copperhead envenomations and in children <6 years of age. The fatality rate of reported cases was 0.06%.

CONCLUSIONS

Native U.S. venomous snakebite results in considerable morbidity and mortality. Rattlesnake and copperhead envenomations, and those in children <6 years of age, produce the most severe outcomes, but coral snakebites result in similar hospital admission rates.

Syncope, massive aspiration, and sudden death following rattlesnake bite

Fatalities following rattlesnake bite are rare in the United States, usually occur some hours following the bite, and are generally secondary to direct venom effects. We report a patient with acute syncope and subsequent massive aspiration resulting in airway obstruction and rapid death following a probable Northern Pacific rattlesnake (Crotalus oreganus oreganus) bite.

Prospective study of morbidity associated with snakebite envenomation

BACKGROUND

The morbidity associated with snakebite envenomation has not been well documented.

METHOD

Using a standardized questionnaire all patients with snakebite reported to a regional poison center during the year 2001 were followed after hospital discharge by telephone until resolution of symptoms.

RESULTS

One hundred and twenty-eight snakebite cases were reported, of which 16 (12.5%) were lost to follow-up and 31 (24.2%) reported no progression of symptoms beyond puncture and were deemed "dry bites." Eighty-one (63.3%) patients were followed for the duration of symptoms. Age ranged from 1 to 86 years with a mean of 32 years. There were 64 males (79%). The snakes were identified as copperhead (n = 57), unidentified venomous (n = 17), timber rattlesnake (n = 6), and cottonmouth (n = 1). All patients were initially evaluated in a hospital emergency department of which 51 were admitted. Nine patients received antivenin. Of the 37 patients who had a job, 33 lost a mean of 14 days of work (SD +/- 18.1). Mean duration of edema was reported as 11.4 days (S.D +/- 12). Recurrent edema frequently occurred with limb activity. Pain was scored on a scale of 1 to 10, with a mean score of 4.8 (SD +/- 2.7). Mean duration of pain was reported as 7.8 days (SD +/- 6.4). Thirty patients required accommodation for ambulation including crutches (n = 11), limp (n = 11), and no shoes or loose shoes (n = 14). Of the 26 patients bitten on the hand or finger, duration of reduced function persisted for a mean of 14.3 days (SD +/- 10.4) and reduction of hand strength persisted for a mean of 22 days (SD +/- 25.5). Five patients had poorly healing wounds at the bite site which persisted from 14 to 77 days with a mean of 45 days (SD +/- 22.8)

CONCLUSION

In this study snakebite resulted in significant duration and extent of morbidity in a majority of patients.

Effects of a negative pressure venom extraction device (Extractor) on local tissue injury after artificial rattlesnake envenomation in a porcine model

OBJECTIVES

To determine if a commercially available negative-pressure venom extraction device (Extractor) reduces local tissue injury after artificial rattlesnake envenomation in a porcine model.

METHODS

We prospectively studied 10 pigs using a crossover design. After the pigs were anesthetized, 25 mg Crotalus atrox venom was injected obliquely with a 22-gauge needle 7 mm deep into subcutaneous tissues proximal to the ventral hind hoof. Pigs were randomized to receive either the Extractor (applied 3 minutes following envenomation and left in place for 30 minutes) or no Extractor. The protocol was repeated 14 days later by using the alternate treatment group and opposite hind leg for each animal. We measured leg circumference at standardized locations on the hoof, foreleg, and thigh at baseline and then 1, 2, 3, 4, 5, 6, 24, 48, 72, and 96 hours following venom injection. Maximal changes in circumference at 6 hours were compared using the paired t test. Minimum residual swelling at up to 96 hours was similarly compared.

RESULTS

Maximal 6-hour swelling was similar with and without the Extractor: the hoof difference with the Extractor was -0.1% (95% CI = -3.4% to 3.2%, P = .95), foreleg difference was 0.3% (95% CI = -4.1% to 4.7%, P = .88), and thigh difference was -2.8% (95% CI = -10.0% to 4.4%, P = .40). Minimum residual swelling at up to 96 hours was also similar with and without the Extractor: hoof difference with the Extractor was 1.2% (95% CI = -5.6% to 8.0%, P = .70), foreleg difference was 0.6% (95% CI = -3.7% to 4.9%, P = .76), and thigh difference was 0.3% (95% CI = -2.4% to 3.0%, P = .81). A circular lesion identical in size and shape to the Extractor suction cup, which later necrosed and resulted in tissue loss, developed where the device had been applied in 2 animals. No such lesions occurred in legs not treated with the Extractor.

CONCLUSION

No benefit was demonstrated from Extractor use for artificial rattlesnake envenomation in our animal study. The skin necrosis noted in 2 Extractor-treated extremities suggests that an injury pattern may be associated with the device.

Epidemiology and hospital course of rattlesnake envenomations cared for at a tertiary referral center in Central Arizona

OBJECTIVE

To describe the demographics and primary inpatient treatment of victims of rattle-snake bites (RSBs) referred to a teritiary referral poison treatment center in central Arizona, and to compare the frequency of local tissue complications and hematologic toxicity during hospitalization in children with those for adults.

METHODS

This was a chart review of patients diagnosed as having RSB by a toxicology service between July 1994 and April 2000. Data collected included: age, sex, date, bite location, time to and length of hospitalization, time to and amount of antivenin, serial hematologic studies, and inpatient complications.

RESULTS

Of 241 patients admitted, 236 charts met inclusion criteria. The majority of RSB victims were male (81%). Children (< or =13 years) represented 22%. Most RSBs (78%) occurred between April and September. Mean time (+/-SEM) to presentation was 1.7 +/- 0.2 hours. Antivenin was administered to 77% of patients, with an average (+/-SEM) of 28.5 +/- 0.9 vials administered. Hematologic abnormalities included: coagulopathy (60%), hypofibrinogenemia (49%), and thrombocytopenia (33%). No statistically significant difference in the above parameters was detected between upper- and lower-extremity envenomations, or between children and adults. Immediate antivenin reactions occurred in 36% of patients. Hemorrhagic bullae formation occurred in 22%, occurring most frequently in upper extremities. Operative procedures were required in 3.4% of patients. Hospitalization averaged 2.5 +/- 0.1 days. There was no fatality.

CONCLUSIONS

In Arizona, RSB victims were typically adult males with upper-extremity bites. Hematologic abnormalities were common. Local tissue complications were more common with upper-extremity envenomations. No statistically significant difference was detected in frequency of hematologic disorders or local tissue complications when children were compared with adults.

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.

Mojave rattlesnake envenomation in southern California: a review of suspected cases

To clarify whether Mojave rattlesnake (Crotalus scutulatus scutulatus) envenomations occurring in California cause typical crotalid tissue effects, pain, edema, and ecchymosis, we reviewed charts of snakebite victims at a tertiary care teaching hospital and a moderate-size community hospital. Forty-two patients were bitten within the range of Mojave rattlesnakes. Eight snakes were identified as Mojave rattlesnakes (group 1); of these, four were confirmed by experts in snake identification (group 1a). Fifteen patients were reported bitten by other rattlesnake species (group 2), and in 19 envenomations the species was unknown (group 3). Seventy-five percent of patients in group 1 were reported to have local edema at the envenomation site compared with all of the patients in group 2. Ecchymosis was found in 25% of group 1 patients and 73% of group 2 patients. Pain was documented in only 12% of group 1 and 67% of group 2 victims. Neurotropic events, many severe, were found in 75% of group 1 patients compared with 7% of those in group 2. Although this study does not have the power to justify statistical evaluation, C. scutulatus envenomations do appear inclined to less tissue reaction. A disturbing trend toward severe neurotropic manifestations was also suggested in presumed Mojave rattlesnake envenomations.

Mojave rattlesnake envenomation: prolonged neurotoxicity and rhabdomyolysis

An 11-year-old girl presented to the emergency department with hypoventilation and shock after being bitten by a Mojave rattlesnake. Intubation was required, and she improved rapidly after fluid resuscitation and antivenom administration. She was extubated four hours after envenomation and did well. The patient subsequently developed increased weakness and cranial nerve paresis and required reintubation for respiratory failure at 30 hours after envenomation despite administration of 30 vials of antivenom. She improved after administration of additional antivenom and was extubated ten hours later. Twenty-four hours after envenomation, signs of rhabdomyolysis were noted with myoglobinuria and a creatine phosphokinase level of 96,400 units/L. Myoglobinuric renal failure was treated with mannitol, hydration, and alkalinization of the urine. The patient's renal and neurological functions improved steadily during the following three to four days. Neurotoxic and myotoxic effects of Mojave venom are known to occur but are not well documented in human beings. Recognition of potential complications from envenomation such as respiratory paralysis and rhabdomyolysis with myoglobinuric renal failure is critical.

The legitimacy of rattlesnake bites in central Arizona

Previous authors have classified poisonous snake bites as being legitimate or illegitimate, depending on whether the victim was taking unnecessary risks with a snake before being bitten. We reviewed medical records of 86 consecutive rattlesnake bite victims cared for at a single medical center to determine legitimacy of snake bites. A bite was considered illegitimate if, before being bitten, the victim recognized an encounter with a snake but did not attempt to move away from the snake. A legitimate bite was said to have occurred if a person was bitten before an encounter with a snake was recognized or was bitten while attempting to move away from a snake. The study group was made up of 75 male (87.2%) and 11 female (12.8%) victims. Seventy-four percent were 18 to 50 years old, and 15% had been bitten previously. Only 43.4% of all bites were considered legitimate, and pet (captive) snakes accounted for almost one third of all illegitimate bites. The ingestion of alcoholic beverages was associated with 56.5% of illegitimate bites versus 16.7% of legitimate bites (P less than .001). While 74.4% of bites were to upper extremities, only 27% of upper extremity bites were legitimate. All bites to the lower extremity were legitimate (P less than .001). Of 14 individuals bitten by pet snakes, all were men and 64.3% were under the influence of alcohol at the time of the bite.(ABSTRACT TRUNCATED AT 250 WORDS)