There are more than 2,700 species of snakes worldwide, about 600 venomous snakes and 50 species in China. There are about 10 common venomous snakes in China, including five-step snake, crab snake, branded iron head, bamboo leaf green, golden-ringed snake, silver-ringed snake, sea snake, long-nosed sea snake, cobra, king cobra and pit viper. They are common in rural and coastal areas in the south of China, mostly occurring in outdoor activities, and are more common in April and October, with bites to the extremities. Every year, 100,000 people are bitten by venomous snakes in China, 73% of whom are young and middle-aged, and the mortality rate of snakebite is 5% to 10%. Venomous snakes have venomous glands in their mouths, which are connected by detoxification ducts to the basal sheaths of the venomous teeth. The venom secreted by the venom gland is injected into the body by the venom tooth, and then flows centripetally into the blood along the lymphatic vessels, after which it flows to all tissues and organs of the body, causing systemic symptoms of poisoning, a process that takes about 30 min. In the body, snake venom is mainly destroyed by phagocytosis of the reticuloendothelial system and the immune function of the body, and the liver plays a very important role in the detoxification process; only about 1/3 of snake venom is excreted by the kidneys. Clinical features 1. Clinical manifestations due to neurotoxicity: commonly seen in bites of golden-ringed snakes, silver-ringed snakes, cobras, pit vipers, sea snakes, etc. Local manifestations: local wound reaction is light, mild numbness, no exudate, no redness or swelling, no pain. Systemic manifestations: The skeletal muscles are flaccidly paralyzed, firstly, the head and neck, eye muscles are damaged, presenting drooping eyelids, and diplopia may also occur; the facial muscles are damaged, showing difficulty in opening the mouth and swallowing, and the teeth are closed, and then the respiratory muscles are damaged, resulting in respiratory difficulty or even respiratory arrest. The poisoned person feels dizziness, drowsiness, salivation, nausea, vomiting, hearing loss, and even urinary and fecal incontinence, and in severe cases, there are twitching of the limbs, pain and other abnormal feelings in the whole body, and in critical cases, coma. The main cause of death: respiratory failure, but the survivors often have no sequelae. 2. Clinical manifestations due to blood poisoning: commonly seen in bites of viper, five-step snake, pit viper, bamboo leaf green, branded iron head, cobra, etc. Local manifestations: severe swelling, spreading to the proximal end, showing skin erythema, blisters, blood blisters, with tissue necrosis and bleeding, severe pain in the wound, which may be accompanied by lymphangitis, lymphadenitis, swollen and painful lymph nodes in the nearby area. Systemic manifestations: skin and mucous membrane hemorrhage, manifested as widespread skin hemorrhagic spots, nasal hemorrhage, blood oozing from the teeth and eyes, etc. Visceral bleeding manifests as hemoptysis, vomiting blood, blood in the stool or urine, and vaginal bleeding in women. Hemolytic xanthogranuloma and hemoglobinuria may also occur. The above factors may lead to shock and even damage to all major organs of the body, for example, pulmonary embolism in thrombosis, liver steatosis leading to abnormal liver function, cardiac steatosis with bleeding, myocardial fracture and interstitial edema, which may lead to cardiac arrhythmia, heart failure, and abnormal electrocardiogram, and renal epithelial cell detachment and necrosis in the kidney, which may lead to renal failure. Main causes of death: organ hemorrhage, circulatory failure. Survivors often have local and related system sequelae. 3, mixed toxin injury: cobra, king cobra, pit viper and other bites can often appear at the same time the clinical manifestations of neurotoxicity and blood circulation toxicity. The clinical features are rapid onset, local and systemic symptoms are more obvious.