rattlesnake ( C. viridis ). Myotoxins that can cause rhabdomyolysis are found in multiple snake species, including Mojave rattlesnakes. Pit viper venom may also include bradykinin-related peptides that can lead to angioedema and hypotension. Figure 3. Mojave Rattlesnake (Crotalus Scutulatus)
The most consistent finding in crotalid envenomation is local tissue injury, which is present in >95% of cases. Fang marks are not always obvious, and often only one fang is responsible for the envenomation. The distance between puncture wounds is not always a reliable way of estimating the size of the snake. Although a large distance between fang marks suggests that a larger snake was responsible for the bite, fang marks in close proximity do not necessarily mean the snake was small, because pit viper fangs are very mobile and may move toward each other, resulting in a surprisingly small distance between injection sites. Swelling and ecchymosis are usually observed after envenomation and are typically present by the time victims seek medical attention. However, it may take several hours for local findings to appear, and it is imperative to not dismiss a bite as “dry” prematurely. Hemorrhagic blebs are common following bites to the finger but may be seen elsewhere on upper extremities and on lower extremity bites. Figure 5. Hemorrhagic Bleb From Snakebite
Source: Justin Doll Pit vipers are solenoglyphous; they have hollow, mobile, and relatively long fangs capable of delivering venom quite efficiently. Not all crotalid bites result in envenomation. Approximately 10%–15% of bites will be “dry,” meaning no venom is injected. Victims will have a puncture wound and minimal swelling immediately adjacent to the bite site but no other signs or symptoms. Any bruising, swelling beyond the bite site, or systemic symptoms indicate a venom effect. Snakebites are also dynamic, and bites that appear insignificant at first can become increasingly severe over the next few hours. Multiple factors related to both the snake and the victim determine the severity of the envenomation. These may include the species, age, size, and overall health of the snake as well as its diet and the last time it had fed or released venom. The age and health of the patient as well as the location of the bite will also affect the severity. Figure 4. Pit Viper Envenomation
Source: Spencer Greene Systemic toxicity can present in several ways. Nausea, vomiting, tachycardia, and a sensation of impending doom are nonspecific findings and may represent nothing more than anxiety from being bitten. These symptoms often develop within the first hour after being bitten but may be delayed in some patients. However, recurrent vomiting may suggest a significant envenomation, and tachycardia may result from significant third-spacing of fluids. Hypotension may also result from fluid shifts or be one manifestation of a severe envenomation. Cardiovascular collapse and airway swelling may be due to anaphylaxis in patients who have been previously sensitized to snake venom antigens and may also occur in patients with severe envenomations who have never been previously exposed to venom. Rhabdomyolysis can develop in limbs with significant swelling but can also appear independently following bites from snakes with potent myotoxins in their venom. Hematologic toxicity is frequently reported in crotalid envenomation. Many patients have various lab abnormalities (e.g., elevated prothrombin time [PT], thrombocytopenia, and/ or hypofibrinogenemia) without any overt signs and symptoms.
Source: Spencer Greene
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Book Code: RPTTX2024
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