Venomous Snake Bites in Taiwan

Abstract

There are six kinds of poisonous snakes with epidemiological significance in Taiwan. Three species induce hemorrhagic symptoms (Trimeresurus mucrosquamatus, Trimeresurus stejnegeri, and Deinagkistrodon acutus), two species induce neurotoxic symptoms (Naja atra and Bungarus multicinctus) and one species induces hemorrhagic and neurotoxic symptoms (Vipera russelii formosensis). The hemorrhagic venom causes disorders of the clotting cascade such as prolonged bleeding, primary fibrinolysis and disseminated intravascular coagulopathy. The neurotoxic venom provokes respiratory distress from weakened respiratory muscles, blurred vision, diplopia, dysarthria, dysphagia, dysphonia and paralysis of muscles of the extremities. Mixed envenomation manifests as a combination of these neurotoxic and hemorrhagic effects as well as rhabdomyolysis and acute renal failure. Identification of the snake species is important if antivenom is to be used. Therefore, guidelines for snakebite identification based on clinical symptoms and laboratory analysis are important to improve the clinical diagnosis of snakebites. In Taiwan, Trimeresurus stejnegeri bites are the most common and Deinagkistrodon acutus the least common. Aggressive antivenom treatment can reduce the mortality rate for snakebites, but for Bungarus multicinctus bites, additional measures such as maintaining the patient's airway and supporting ventilation are vital. Patients with dry bites or bites with no envenomation should be observed for at least 6-12 hours. The emergency physician should determine the severity of envenomation and predominating venom activity before deciding on the type, dosage and duration of antivenin treatment. The history of exposure, local effects and systemic syndromes of envenomation, progression of symptoms and signs, and laboratory data obtained in the emergency department should guide decisions about antivenom therapy. The dosage most toxicologists use for treating pediatric patients with snakebites is the same as that for adults. In general, 6-12 vials of antivenom against neurotoxic venom are used for Naja atra bites and two vials are used for Bungarus multicinctus. One vial of antivenom against hemotoxic venom is used for both Trimeresurus stejnegeri and Trimeresurus mucrosquamatus bites. Two vials of anti-Deinagkistrodon acutus are used for Deinagkistrodon acutus bites and 2-4 vials of anti-Vipera russelli formosensis are used for Vipera russelli formosensis bite. During the infusion, the blood pressure, level of consciousness and skin reaction should be monitored. The varied clinical manifestations of snake bite must be considered for effective management. Ready availability and appropriate use of antivenom, close monitoring of patients and the institution of ventilatory support all help reduce mortality.