Finally, it is essential to remember to not transport the snake to the hospital, whether dead or alive. Bringing a live snake to the emergency department (ED) is obviously potentially dangerous to patients, staff, and visitors. It is also potentially dangerous to the snake, which may get killed or relocated to an unfamiliar neighborhood, which will ultimately lead to its premature death. Bringing a dead snake is also dangerous. Dead snakes can still envenomate, typically for about 30–45 minutes after the fatal injury, but the record is approximately 8.5 hours. A man in South Dakota died following a bite from a decapitated prairie rattlesnake. 35 Other patients have suffered significant nonfatal envenomations from decapitated snakes. 36 The best treatment for snakebites in the prehospital environment is to arrange for quick, safe transport to an appropriate medical facility. The closest hospital may not be the best destination if the staff lacks the resources and/or expertise to manage an envenomation. If the patient is unstable (e.g., there is airway compromise or hypotension), they should be transported to the closest hospital. However, if the patient has only local findings, longer transport to a snakebite expert may result in faster and more appropriate treatment, which in turn results in a quicker and more complete recovery. If the snake can be safely and quickly photographed, that may influence treatment decisions, particularly if it can be quickly identified as nonvenomous. However, as mentioned previously, many nonexperts misidentify snakes, so it is essential to consult someone with herpetological expertise. Transport should not be delayed to photograph the snake, because the actual snake never needs to be visualized. Pit viper envenomation is ultimately a clinical diagnosis, and a healthcare professional familiar with snakebites should be able to distinguish a crotalid envenomation from a coral snake envenomation and from a bite from a nonvenomous snake by physical examination. Airway patency must be ensured. Ensure adequate oxygenation and ventilation. Intravenous fluids should be given judiciously; pit viper bites can result in significant third-spacing, leading to hypoperfusion. It is important to maintain euvolemia, but excessive fluid administration can potentially exacerbate the local tissue edema. Epinephrine should not be used routinely in snakebite management but may be necessary in patients with fluid-refractory hypotension. Analgesia should also be provided. Intravenous opioids are preferred, but subdissociative ketamine is also effective. Nonsteroidal anti-inflammatory drugs (NSAIDs) are not recommended because of their potential hematologic effects. Nausea may develop from analgesics or from the envenomation itself, and nonsedating antiemetics may be required. Constrictive clothing and jewelry should be removed. Mark the leading edge of tenderness every 15 minutes. Circumferential measurements of the affected limb are no longer recommended because of poor intra- and inter-rater reliability. Immobilize the affected extremity and position it correctly. Although it was previously believed that the affected limb should be kept below heart level following pit viper envenomations, this is now contraindicated, because this will aggravate local swelling and tissue injury. Most crotalids envenomations will present with only local tissue swelling, and the affected limb should be elevated to 45°–60°. Elevating the limb will not significantly affect systemic venom absorption but will prevent the venom from accumulating in the extremity and will reduce the hydrostatic pressures that can exacerbate tissue swelling and subsequent tissue injury. Furthermore, patients report symptomatic improvement with elevation.
Figure 7. Proper Elevation of Snakebite
Source: Spencer Greene Because snakebites can progress rapidly, it is essential to constantly reassess the patient. If there is any decompensation, the patient should be transported to the nearest facility capable of stabilizing the patient. Once the patient has arrived at the hospital, definitive care may ensue. Airway, breathing, and circulation must be reassessed. Ensure adequate analgesia and symptomatic treatment. Morphine appears to cause greater histamine release, which could exacerbate swelling and mimic allergic phenomenon, so hydromorphone and fentanyl are preferable. Proper positioning will also help alleviate pain. Elevate and gently immobilize the envenomed limb without causing any constriction. If a tourniquet was placed in the prehospital environment, it should not be rapidly removed, because that could allow all the accumulated venom to enter the systemic circulation at once. Instead, loosen it slowly over a period of time equal to how long it has been present and ensure good intravenous access in case the patient requires resuscitation. A full assessment of the snakebite patient includes laboratory studies, including PT, fibrinogen, serum electrolytes, blood urea nitrogen (BUN), creatinine, and complete blood count (CBC). The partial thromboplastin time (PTT) and D-dimer do not provide any additional information and are not typically required. Rotational thromboelastometry and thromboelastography are not readily available in many healthcare settings, and their role in the evaluation of snakebite patients is unclear. Routine measurement of serum creatine kinase (CK) is not obligatory. However, in patients with known or suspected rhabdomyolysis, serial levels should be obtained. Radiographic studies are similarly not necessary in most patients but may be considered if there is suspicion for a retained foreign body or to evaluate end-organ damage. The affected extremity should be monitored for progression of swelling and tenderness. Evaluation of neuromuscular strength is recommended for envenomations from suspected neurotoxic species. The negative inspiratory force is a sensitive test for respiratory muscle strength and can be performed at the bedside by a respiratory therapist. Serial dynamometry is a simple, noninvasive method of assessing skeletal muscle strength. Continuous end-tidal carbon dioxide monitoring and serial negative inspiratory force measurements can identify any respiratory muscle weakness. The definitive treatment for snake envenomations is antivenom, and each patient should be assessed individually to determine if antivenom is indicated. There are currently two FDA-approved antivenoms for North American pit viper envenomations. Crotalidae Polyvalent Immune Fab Ovine (CroFab, henceforth referred to as FabAV) was first studied in 1993 and has been commercially available since 2000. 37 It is made by immunizing different flocks of sheep with the venom of one of five crotalid species: Western diamondback rattlesnake, eastern diamondback rattlesnake ( C. adamanteus ), Mojave rattlesnake,
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Book Code: RPTTX2024
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