However, in some patients the impaired hemostasis leads to clinically significant bleeding. 13-15 Although the hematotoxicity may be noted at presentation, it may also develop at any point in the first two weeks following envenomation. Thrombotic events are also possible, but true disseminated intravascular coagulation is incredibly uncommon. Neurotoxicity is not typical of crotalid envenomations but may manifest in bites from some rattlesnakes, including snakes that possess the Mojave toxin and certain populations of the timber rattlesnake. 16,17 Signs may include myokymia, ptosis, dysphagia, and diplopia, but more severe manifestations such as peripheral muscle paralysis and respiratory failure are possible. Uncommon sequelae of crotalid envenomation include myocardial injury, cerebrovascular accident, rhabdomyolysis, and fasciitis. 18,19 Compartment syndrome is a much feared but rarely observed complication of pit viper bites. Venom is typically deposited above the fascia, so the overlying skin and subcutaneous tissue may be swollen and taut while compartment pressures remain normal. However, venom may be injected into the fascia if overlying tissue is particularly thin. Signs may include paresthesias, paralysis, diminished distal pulses, poikilothermia, pallor, and significant pain. Among native pit vipers, rattlesnakes typically cause the most severe envenomations, while copperheads are often considered the least dangerous. Some physicians have suggested that copperhead bites do not require aggressive treatment. However, the potential for serious toxicity from copperheads should not be minimized. A study of copperhead envenomations in the Carolinas found that tissue necrosis was present in 8% of bites, hematologic abnormalities were observed in approximately 30% of patients for whom lab testing was performed, and the median duration of disability in untreated patients was 42 days, with some patients reporting disability one year after the envenomation. 20 Another study found that patients who went untreated took an average of 45 days to recover. 21 Lastly, although death from snakebite is uncommon in the U.S., six fatalities were attributed to copperhead envenomations in the years 1989–2019. 6 Figure 6. Eastern Copperhead (Agkistrodon Contortrix)
immobilization, and localized circumferential compression. These may limit systemic absorption of venom, but they also expose the local tissue to venom for a longer duration. In 2011, multiple toxicology societies issued a joint position statement condemning these interventions whenever tissue damage is expected. 23 An additional consideration is that few people can perform pressure immobilization correctly. In one study, only 13% of applications performed by emergency physicians achieved the correct pressure, and only 5% of layperson applications were successful. 24 Electrical therapy has been proposed to treat snakebites as well as other envenomations. However, there is no evidence that it neutralizes venom. 25 Furthermore, there is ample evidence of harm, including burns, hypopigmentation, and death. 26 Diphenhydramine is also commonly recommended by nonexperts, and several posts encouraging diphenhydramine for snakebites in humans and in pets have gone viral on social media. However, post shares and retweets are not substitutes for evidence. Histamine is not one of the clinically significant venom components in snake envenomation; antagonizing its effects will provide little clinical benefit. Furthermore, diphenhydramine can cause sedation, which may prevent a patient from relaying important medical information to healthcare professionals. Additionally, if people believe that antihistamines are a safe, cheap alternative to antivenom following snakebite they may fail to seek timely medical attention for themselves or a loved one. A recent Reuters news story highlighted the discrepancy between the promotion of diphenhydramine and its actual benefits, and hopefully this will reduce its popularity. 27 The only time antihistamines are helpful following snake envenomation is in the setting of concomitant allergic reaction, which is quite uncommon except in patients who work with snakes regularly. Even then, a serious allergic reaction, that is, anaphylaxis, requires epinephrine; antihistamines do not suffice. Cryotherapy does not appear to offer any benefit and may be harmful to tissue. In a rat study of cold application to the site of envenomation from eastern cottonmouths, there was no improvement compared to control. 28 Other animal studies have indicated that local cooling increased tissue injury without improving mortality. 29 Anecdotally, some snakebite victims report pain relief following cold application. It is reasonable to consider using icepacks briefly, for example, five minutes on for every 15–20 minutes, but prolonged application, as well as direct skin contact, must be avoided. Surgical intervention for snakebites is also contraindicated in the prehospital environment. “Cutting and sucking,” in which an incision is made and then someone uses his or her mouth to “suck” out the venom, confers no benefit and undoubtedly worsens outcomes by causing a bigger wound and potentially introducing mouth flora into the tissue. Excising the affected tissue is also not recommended, as it has not shown to be beneficial and may be harmful and disfiguring. 30 The prehospital intervention for which there seems to be much popularity despite evidence that it is harmful is venom extraction. Various commercially available suction devices promise to remove venom if applied shortly after the envenomation. However, the amount of venom they can remove is negligible. In an animal study using radioactive-labeled mock venom, these instruments removed between 0.04% and 2% of the venom load. 31 Furthermore, these “extractors” can cause harm. In a different animal study, tissue damage was increased following application of the negative pressure device. 32 An editorial summarizing the use of extraction devices concluded that the risks of harm greatly outweigh any benefits and their use should be abandoned. 33 In response to the persistent availability and promotion of this “treatment,” a panel of experts contributed to a report denouncing these devices. 34
Source: Nathan Wells A bite from any pit viper has the potential to be mild, moderate, serious, or even fatal. Because there is such variability in presentation, and also because people frequently misidentify snakes, it is recommended to base treatment decisions on the clinical findings rather than the suspected species. Many interventions have been proposed to treat snakebites in the out-of-hospital environment. Unfortunately, most of these have failed to show benefit, and many have proven to be harmful. Tourniquets were once recommended, but the harm of compromising the arterial blood supply to an affected limb is much greater than any benefit in limiting the spread of venom. Methods of obstructing lymphatic flow have also been proposed, including constriction bands, pressure
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