injuries poisoning
Snakebites
Symptoms and Signs of Snakebites
A snakebite, whether from a venomous or nonvenomous snake, usually causes terror, often with autonomic manifestations (eg, nausea, vomiting, tachycardia, diarrhea, diaphoresis), which may be difficult to distinguish from systemic manifestations of envenomation. Nonvenomous snakebites cause only local injury, usually pain and 2 to 4 rows of scratches from the snake’s upper jaw at the bite site. Symptoms and signs of envenomation may be local, systemic, or a combination, depending on degree of envenomation and species of snake. Treatment can occur, particularly in snake handlers who have been previously sensitized. About 25% of pit viper bites are dry (venom is not deposited), and no systemic symptoms or signs develop. 1 fang marks and scratches. If envenomation has occurred, edema and erythema at the bite site and in adjacent tissues occur, usually within 30 to 60 minutes. Oozing from the wound suggests envenomation. Edema can progress rapidly and may involve the entire extremity within hours. Lymphangitis and enlarged, tender regional lymph nodes may develop; temperature increases over the bite area. In Severity of envenomation , ecchymosis is common and may appear at and around the bite site within 3 to 6 hours. Ecchymosis is most severe after bites by Eastern and western diamondbacks Cottonmouths Prairie, Pacific, and timber rattlesnakes The skin around the bite may appear tense and discolored. Bullae—serous, hemorrhagic, or both—usually appear at the bite site within 8 hours. Edema resulting from North American rattlesnake envenomations may be severe but is usually limited to dermal and subcutaneous tissues, although severe envenomation rarely causes edema in subfascial tissue, causing Compartment Syndrome (defined as compartment pressures Ecchymosis is less common after copperhead and Mojave rattlesnake bites. Systemic manifestationsof envenomation can include nausea, vomiting, diarrhea, diaphoresis, anxiety, confusion, spontaneous bleeding, fever, chest pain, difficulty breathing, paresthesias, hypotension, and shock. Some patients with rattlesnake bites experience a rubbery, minty, or metallic taste in their mouth. The venom of most North American pit vipers causes minor neuromuscular conduction changes, including generalized weakness and paresthesias and muscle fasciculations. Some patients have alterations in mental status. Venom of Mojave and eastern diamondback rattlesnakes may cause serious neurologic deficits, including respiratory depression. Anaphylaxis can cause systemic symptoms immediately. Rattlesnake envenomationsmay induce various coagulation abnormalities, including thrombocytopenia, prolongation of prothrombin time (PT, measured by the INR [international normalized ratio]) or activated partial thromboplastin time (PTT), hypofibrinogenemia, elevated fibrin degradation products, or a combination of these disorders, resembling a disseminated intravascular coagulation (DIC)-like syndrome. Thrombocytopenia is usually the first manifestation and may be asymptomatic or, in the presence of a multicomponent coagulopathy, cause spontaneous bleeding. Patients with coagulopathy typically hemorrhage from the bite site or from venipuncture sites or mucous membranes, with epistaxis, gingival bleeding, hematemesis, hematochezia, hematuria, or a combination. A rise in hematocrit (Hct) is an early finding secondary to edema and hemoconcentration. Later, Hct may fall as a result of fluid replacement and blood loss due to DIC-like syndrome. In severe cases, hemolysis may cause a rapid fall in Hct. Pain and swelling may be minimal or absent and are often transitory. The absence of local symptoms and signs may erroneously suggest a dry bite, producing a false sense of security for both patient and clinician. Suspect envenomation with all bites caused by venomous snakes, even if there are no signs of envenomation soon after the bite. Weakness of the bitten extremity may become evident within several hours. Systemic neuromuscular manifestations may be delayed for 12 hours and include weakness and lethargy; altered sensorium (eg, euphoria, drowsiness); cranial nerve palsies causing ptosis, diplopia, blurred vision, dysarthria, and dysphagia; increased salivation; muscle flaccidity; and respiratory distress or failure. Once the neurotoxic venom effects manifest, they are difficult to reverse and may last 3 to 6 days. Untreated, respiratory muscle paralysis may be fatal. 