The green pit viper is an important venomous snake in Thailand. Symptoms following a bite range from asymptomatic to severe. The venom has both thrombin-like effects and platelet aggregating activity, causing systemic bleeding in severe cases due to hypofibrinogenemia and thrombocytopenia.
Symptoms:
(1) local: edema, ecchymosis around the wound, blisters and necrosis
(2) systemic: bleeding, typically from mucosal surfaces
Symptom severity grading:
(1) severe: systemic bleeding observed, which can be fatal
(2) moderate: either prolonged venous clotting time > 15 minutes or platelet count < 150,000 per µL
(3) mild: neither venous clotting time prolonged nor thrombocytopenia present
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Complication
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Increased Risk
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Decreased Risk
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systemic bleeding
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prolonged venous clotting time and thrombocytopenia
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no evidence of bleeding by 24 hours after bite
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bite away from fingers or toes (nondigital)
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wound necrosis
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presence of blisters
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prolonged venous clotting time
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bite involving fingers or toes (digital)
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secondary infection
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blisters
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antivenin allergy
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positive skin test
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Antivenin:
(1) Allergy may be missed by skin testing, although a positive skin test is a good indication that an allergy is present.
(2) About 2% of recipients develop a severe allergic reaction.
(3) Since most bites do not result in a systemic coagulopathy, antivenin should not be routinely administered. It should only be given only in severe cases when evidence for coagulopathy is present.
