A trend of platelet indices in patients with green pit viper toxin

The green pit viper (Trimeresurus albolabris and Trimeresurus macrops) is a common venomous snake in Thailand. The green pit viper venom has major effects on the hematologic system. The venom is found to have a thrombin-like effect in vitro but cause a defibrination syndrome in vivo. Unlike other pit viper snakes (such as Malayan pit viper and Russel's pit viper), the venomous effect on red blood cells is rarely mentioned. Clinical features of venomous snake bites vary from asymptomatic to fatal bleeding. In this study, an attempt was made to discern hematologic parameters in green pit viper envenomation and to characterize the changes in blood cells. The study included data from 40 patients who were hospitalized at the King Chulalongkorn Memorial Hospital during 1995 to 1999 and 40 normal, healthy subjects as control. Concerning platelet determination, significantly decreased (p < 0.05) total platelet count and mean platelet volume (MPV) were demonstrated in envenomous blood. The changes in blood cells may be partly due to the effect of green pit viper toxin on the platelet morphology. However, the explanation of this phenomenon requires further investigation for the specific pathophysiology. The components of green pit viper venom that have these hematologic effects in humans are interesting and should be further identified.