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<< Diagnosis And Management Of North American Snake And Scorpion Envenomations

ED Management And Stabilization

Initial Stabilization

Upon arrival in the ED, whether by ambulance or by personal vehicle, a rapid assessment of the patient should obviously include an evaluation of airway, breathing, and circulation. Barring a situation in which these are compromised and need to be addressed immediately, the initial stabilization of a snakebite victim includes many of the interventions that are recommended for the field providers.

Obtain an initial set of vital signs, place the patient on continuous cardiac, BP, and pulse oximetry monitoring (on an unaffected extremity), remove constrictive clothing and jewelry, establish intravenous access, and draw blood for labs including tubes for a type and screen and coagulation studies. Supplemental oxygen can be given on a case-by-case basis. Use a SharpieŽ or surgical marker to mark and time the leading edge of erythema. Also, mark two to three sites above the bite as locations for serial measurement of limb circumference.

Once a clinically significant envenomation has been identified, rapidly begin the process of obtaining the appropriate antivenom and begin the mixing process, and/or arrange for rapid transfer of the patient to a facility capable of handling snake envenomations.

Patients with significant envenomations will have considerable pain both from the local cytotoxic effects of the venom and the diffuse muscle fasciculations caused by the neurotoxins and myotoxins in Crotalid venom. It is acceptable to give narcotics and benzodiazepines for comfort while antivenom is being prepared except in the cases of a coral snake, Mojave rattlesnake, or Eastern Diamondback rattlesnake envenomation where the neurotoxic effects of the venom can result in severely impaired mental status. There are no good, evidence-based recommendations in the literature for choice of drugs or dosing. NSAIDs should be avoided due to their antiplatelet effects potentially worsening venominduced coagulopathy.

 History

Once the patient arrives in the ED, key pieces of information pertaining to the snakebite itself must beascertained; see Table 4. Ask the patient about symptoms that may indicate a significant envenomation; particularly pain, numbness, nausea, tingling around the mouth, metallic taste, muscle cramps or fasciculations, dyspnea, diplopia, or dizziness.4,14-15,18-28 Additionally, ascertain the traditional components of a patient history including a comprehensive review of any co-morbid medical conditions (particularly cardiac disease and coagulopathy), a list of current medications, allergies (especially to papain or papaya based extracts, latex, and horse-based or sheep-based products), the time of last oral intake and the patient's tetanus status. Obtaining the history should not interfere with the initiation of treatment in the critically ill or clinically deteriorating patient.



Physical Exam

Focus the initial physical exam on the evaluation of the ABCs and provision of adequate resuscitation. Once the adequacy of all elements of the primary survey is established and the steps outlined in the initial stabilization are completed, the evaluation of the bite site can commence. As mentioned, onefourth of snakebites are dry. Examine the site of the bite for fang marks or scratches and consider the possibility of other types of animal bites or injuries if the diagnosis of a snake envenomation is in doubt.

Pay particular attention to any local signs of envenomation, i.e. edema, petechiae, ecchymosis, or bullae formation.18 Document circumferential measurements at several sites above and below the bite site.16 Mark a line at the site of each measurement to ensure accurate reproducibility. Repeat these measurements every 15 to 30 minutes during the course of treatment. Also, mark and time the edge of the swelling to serve as an index of local progression.4

Focus the remainder of the physical exam primarily on the cardiovascular, pulmonary, and neurologic systems. Patients may be hypotensive due to third space losses and hemorrhage. Initial treatment for hypotension is intravenous isotonic fluids.28 The neurologic exam becomes particularly important in severe envenomations, especially in cases of Mojave rattlesnake, coral snake, or non-native/exotic envenomations where altered mental status and neurologic impairment can be a significant and often delayed feature of the envenomation.18

Diagnostic Studies

The number and type of recommended diagnostic studies in a patient with a snake envenomation varies throughout the snakebite literature. However, the majority of authors agree that a core group of tests is indicated: A baseline complete blood count (CBC) with platelet count, coagulation studies including prothrombin time, partial-thromboplastin time, activated partial-thromboplastin time, fibrinogen level, fibrin split products (fibrin degradation products), basic electrolytes, blood urea nitrogen, serum creatinine, and urinalysis. Patients bitten by an unknown species with no evidence of toxicity require, at a minimum, coagulation studies which are necessary for the grading of the envenomation. Various sources also recommend obtaining an electrocardiogram, a specimen for type and screen or type and crossmatch for blood products (as crossmatch may be more difficult following the administration of antivenom), liver function tests, total creatine kinase, serum myoglobin, arterial blood gases, and chest radiography.4,14-15,18,28 This second set of tests can be ordered judiciously on a case-by-case basis, taking into account severity of the envenomation and co-morbid disease. Grading severity of envenomations will be discussed in detail in the next section.

Compartment pressures: The other diagnostic test that can be performed in selected cases is the measurement of compartment pressures. Most envenomations involve only subcutaneous deposition of venom. In the rare intramuscular envenomation, compartment syndrome may develop but it is often impossible to distinguish the symptoms of compartment syndrome (classically the 5 "P's:" pain out of proportion, pallor, parasthesia, paralysis, and pulselessness) from the symptoms of a significant envenomation. Formerly, fasciotomy was the recommended treatment for snakebites with suspected compartment syndrome, but current review suggests a more conservative treatment plan involving serial Stryker measurement for compartment pressures.

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Last Modified: 08/17/2017
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