Thursday, 5 June 2014

Snake bites in China: the medical consequences

by Michael Woodhead
Living in Australia, I am naturally extremely wary of snakes, given that this continent has many of the world's most venomous and aggressive varieties - often living in your back yard. Aussies know that if you get bitten by a snake you need to use pressure immobilisation and get help - quick. But what about China? What are the chances of being bitten by a snake and how dangerous are they?
A new report of snake bites from  Hainan gives some idea of what might happen. In a review of more than 1000 cases of snake bites, Dr Shuang Jiebo and colleagues from the 425 PLA Hospital in Sanya, found that the vast majority were caused by pit vipers (46% - aka Trimeresurus stejnegeri) or cobras (40%). Most of the bites occurred in summer (April-Sept) in young males, typically farmers or fishermen, and the bites were mostly on the legs or arms. According to the article the pit viper venom contains a potent haemotoxin, but is not usually fatal:
"The wound usually feels extremely painful, as if it had been branded with a hot iron, and the pain does not subside until about 24 hours after being bitten. Within a few minutes of being bitten, the surrounding flesh dies and turns black, highlighting the puncture wounds. The wound site quickly swells, and the skin and muscle become black due to necrosis."
The Hainan doctors found that most of the wound sites of pit viper bite victims showed swelling, and the skin and muscle became black due to necrosis. In contrast, the cobra venoms are mainly neurotoxic, hemotoxic and cardiotoxic. "The cobra bite is extremely painful and the swelling appears immediately. Other symptoms may include drowsiness, nausea, vomiting, abdominal pain, mental alertness and respiratory failure. "
In their review, about a third of snake bites caused mild envenomation, and only 11% resulted in severe envenomation, which meant a longer hospital stay - often a week or more. Only 1% of patients died, and these tended to be due to bites by sea snakes or King Cobras.
Treatment outcomes were better when patients received prompt treatment - and the researchers also claimed that "Sheyao" traditional medicine was a good remedy for snake bites. This is said to contain  toad skin, centipede, and 'humifuse euphorbia' herb as well as paris polyphylla.
"Prevention, pre-hospital management (first aid) and the importance of the early transfer to the hospital should be emphasized," they concluded. 

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