Nonpoisonous snakes sometimes leave an imprint of their two rows of teeth, but the wounds should lack fang puncture marks The dramatic signs of crotalid envenomation are derived primarily from the victim’s hypovolemic state, bleeding diathesis and neuromuscular dysfunction Table 90.23 outlines the more notable physical signs and symptoms Coral snake Coral snakes leave unimpressive local signs but can neurologically cripple their prey The bite may have one or two punctures, at most to mm apart, and other small teeth marks Extremity paresthesias and weakness are often reported initially Over several hours, generalized malaise, nausea, fasciculations, and weakness develop insidiously Other symptoms include ptosis, diplopia, dysarthria, and dysphagia Physical examination may reveal bulbar dysfunction and generalized weakness Respiratory failure may ensue Triage Pit viper The airway, breathing, and circulation of the patient must be addressed before attending to the snakebite ( Fig 90.22 ) The first priority of prehospital care of the snakebite victim is rapid transport to a medical facility All activities in the field must be tempered by the fact that time is of the essence Without delaying transport, the wound should be cleaned with soap and tap water or with an antiseptic solution It is important to approach the patient with reassurance and to place him or her at rest The affected extremity should be stripped of any constricting jewelry or clothing and immobilized in a position of function below the level of the heart to decrease systemic spread of venom The patient should be kept warm and not allowed to have anything by mouth FIGURE 90.22 Management of pit viper bite a Complete blood cell count, platelet count, prothrombin time, partial thromboplastin time, urinalysis, type and hold; in moderate or severe cases, add fibrinogen, arterial blood gases, electrolytes, blood urea nitrogen, and creatinine b Seldom need antivenin; exceptions with large snakes and small children Tourniquets, inadvertently tightened for prolonged full vascular occlusion, have created more problems than they have solved and therefore cannot be recommended for prehospital care In experienced hands, however, a constriction band that obstructs lymph and venous flow can be valuable when a long transport is anticipated (longer than 30 to 60 minutes) The band should be at least cm wide and placed to 10 cm proximal to the wound (proximal to the nearest joint if the wound is nearby) The constriction should be loose enough to admit a finger and preserve good distal arterial pulses Vigilant observation for adequate perfusion is necessary because of progressive edema; the constriction band should be shifted to remain proximal to the swelling To be effective, the band must be applied initially within hour of the pit viper bite It may be removed when antivenin therapy is started Incision and suction (extractors) of the pit viper wound is no longer advised The usefulness of extractors can be supported only if applied within minutes of the bite and even then, recovery of venom is variable in the laboratory setting Animal studies not demonstrate an increase in survival In the rare situation in which skilled personnel and supplies are at the scene and a long transport is expected, it is reasonable to allow one or two attempts at IV access Many authorities also suggest capturing or killing the snake for later verification, but again, prudence dictates that time not be wasted and that an inexperienced person not risk the bite of an agitated snake If the snake arrives in the ED, treat it with respect—decapitated snakes can bite reflexively for up to hour Management If the history and physical examination on arrival in the ED are consistent with a venomous snakebite, immediate laboratory evaluation and IV access are indicated A CBC, coagulation studies, platelet count, urinalysis, and blood crossmatching should be obtained, as blood may be difficult to crossmatch after massive hemolysis In moderate or severe poisoning, analyses of serum electrolytes, BUN, creatinine, liver function tests, creatine kinase, fibrinogen, and ABG are also indicated Hemolysis, anemia, thrombocytopenia, hypofibrinogenemia, prolonged bleeding times, and metabolic acidosis all may be seen in severe poisoning Repeat the laboratory studies every hours to ensure no significant changes occur For patients with complaints of chest pain, a 12-lead ECG, a chest radiograph, and troponin levels should be ordered Patients require serial comprehensive neurologic examinations If there is a concern for a hemorrhagic cerebrovascular accident, a noncontrast CT scan of the head should be obtained Similarly, when intra-abdominal bleeding is suspected with the presence of abdominal tenderness or distention, clinicians may consider an abdominal ultrasound or CT scan Therapy will be based on the clinician’s overall grading of venom toxicity Local and systemic manifestations, as well as laboratory findings, weigh heavily in this judgment The clinical pattern may change as the venom’s effects unfold and frequent reassessment is crucial The physician should measure and record the circumference of the injured extremity at the leading point of edema and 10 cm proximal to this level every 30 minutes for hours, then at least every hours for a total of 24 hours Table 90.24 is derived from a grading system suggested by the Scientific Review Subcommittee of the American Association of Poison Control Centers Any prehospital care (e.g., extremity immobilization) should be rechecked If an occluding tourniquet is inappropriately present, the physician should place a more proximal constriction band and then cautiously remove the tourniquet, being prepared to respond therapeutically to a systemic release of venom The older antivenin Crotalidae polyvalent (AVCP; Wyeth-Ayerst Pharmaceuticals) is no longer available; it was derived from horse serum and was highly antigenic It has been replaced by CroFab, which was licensed in 2000 and is a polyclonal, polyvalent Fab affinity purified antivenin (FabAV; CroFab Protherics Medicines Development Ltd.) derived from sheep It has significantly fewer adverse reactions than seen with AVCP CroFab is effective for rattlesnake and cottonmouth/water moccasin envenomations As copperhead venom was not used in the development of CroFab, its efficacy in copperhead envenomizations is unclear, especially in patients only with minor local symptoms and without systemic effects In 2018 mercury was removed from the CroFab manufacturing process due to concerns of potential toxicity For maximal venom binding, the antivenin should be given within to hours of the snake bite The benefits of antivenin administration after 12 hours are questionable, and antivenin use generally is not indicated after 24 hours (an exception may be continued coagulopathy) The dosage regimen for CroFab is different than AVCP As unbound CroFab may be cleared before venom emerges from tissue deposits, CroFab is given either on a fixed schedule or on a sliding scale Relative contraindications for use include known hypersensitivity to papain, papaya, or CroFab It is unknown whether CroFab can harm the fetus when administered to a pregnant woman Its use during pregnancy should be discussed with the regional Poison Control Center For patients receiving CroFab, an initial dose of four to six vials is given over hour Pediatric patients should receive the same CroFab dose as adults as the antivenom is dosed according to the amount of venom injected rather than body weight Skin testing is not needed for CroFab Each vial is reconstituted with 18 mL of normal saline, and then all vials are mixed with normal saline to create a final volume of 250 mL The infusion should be started slowly, at a rate of 25 to 50 mL/hr for 10 minutes, while observing for allergic reaction The rate should be increased so the 250 mL is given over hour If mild allergic manifestations develop, the infusion should be stopped and diphenhydramine (1 to mg/kg IV) ... 2000 and is a polyclonal, polyvalent Fab affinity purified antivenin (FabAV; CroFab Protherics Medicines Development Ltd.) derived from sheep It has significantly fewer adverse reactions than... Control Center For patients receiving CroFab, an initial dose of four to six vials is given over hour Pediatric patients should receive the same CroFab dose as adults as the antivenom is dosed according