Symptoms of venomous snake bites

A snake bite, whether venomous or not, usually causes terror in the victim, often with vegetative manifestations (eg, nausea, vomiting, tachycardia, diarrhea, sweating), which are difficult to distinguish from the systemic manifestations of envenomation.

Bites from non-venomous snakes cause only local symptoms, are usually painful, and leave 2-4 rows of scratches from the snake's upper jaw at the bite site.

Symptoms of poisoning can be local, systemic, coagulopathic, and combinations of these options are also possible depending on the degree of poisoning and the type of snake.

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Pit Viper

Approximately 25% of pit viper bites are dry (do not inject venom) and no systemic manifestations develop. Local symptoms include teeth marks and scratches. If venom has been injected, swelling, erythema, or ecchymosis will develop at the bite site and surrounding tissues within 30-60 minutes. The swelling progresses rapidly and may involve the entire limb within a few hours. Lymphangitis is possible, with further enlargement and soreness of the regional lymph nodes. The temperature in the bite area rises. In moderate to severe poisoning, ecchymosis is characteristic around the bite site within 3-6 hours. The most pronounced ecchymosis develops after bites of green and diamondback rattlesnakes, water pit viper; prairie green rattlesnake, timber rattlesnake, and striped rattlesnake. Less commonly, ecchymosis occurs with copperhead and Mojave rattlesnake bites. The skin around the bite may appear tense and discolored. Bullae, serous or hemorrhagic, with mixed contents usually appear at the bite site within 8 hours. Edema from North American rattlesnake bites is usually limited to the skin and subcutaneous tissues, although in severe envenomations, edema extends into the subfascial tissues, causing compartment syndrome (defined as an increase in intrafascial pressure >30 mm Hg) within an hour. Necrosis develops around the bite site in most cases after rattlesnake envenomation. The effect of the venom on soft tissues reaches its peak within 2-4 days.

Systemic manifestations of envenomation include nausea, vomiting, sweating, restlessness, confusion, spontaneous bleeding, fever, hypotension, and shock. Some rattlesnake bite victims report a rubbery, minty, or metallic taste in the mouth. The venom of most North American pit vipers causes subtle neuromuscular changes, including weakness, paresthesia, and muscle twitching. Some patients may experience mental status changes. Mojave and diamondback rattlesnakes can cause severe neurologic deficits and respiratory distress. Rattlesnake envenomation can cause a variety of coagulation abnormalities, including thrombocytopenia, prolonged INR or PTT, hypofibrinogenemia, elevated fibrin degradation products, or a combination of these abnormalities, producing a disseminated intravascular coagulation (DIC)-like syndrome. In most cases, thrombocytopenia may be asymptomatic or, in the presence of multicomponent coagulopathy, manifest as spontaneous bleeding. Victims with coagulopathy typically present with hemorrhages at the bite site or on mucous membranes, hematemesis and blood in the stool, hematuria, or a combination of these signs. Ht increases rapidly as a result of hemoconcentration. Later, Ht may decrease due to fluid replacement and blood loss from DIC-like syndrome. In severe cases, a rapid decrease in Ht may cause hemolysis.

Coral snake

Pain and swelling are minimal or absent, and are often transient. The absence of local symptoms may be mistaken for a dry bite, contributing to a false sense of security in both patient and physician. Weakness in the bitten limb may become apparent within a few hours. Systemic neuromuscular manifestations may occur after 12 hours and include general weakness and drowsiness; altered consciousness, euphoria, and drowsiness; cranial nerve palsies causing ptosis, diplopia, blurred vision, dysarthria, and dysphagia; increased salivation; muscle flaccidity, respiratory distress, or respiratory failure. By the time the effects of the neurotoxic venom become apparent, they are difficult to prevent and last for 3 to 6 days. Untreated patients may die of respiratory arrest. They require mechanical ventilation.

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