Action of Calloselasma rhodostoma (Malayan pit viper) venom on human blood coagulation and fibrinolysis using computerized thromboelastography (CTEG).

The effects of Malayan pit viper (Calloselasma rhodostoma) venom on human blood coagulation and fibrinolysis were studied in vitro using computerized thromboelastography. At low concentrations the venom had a coagulant effect shown by faster onset of the coagulation process (shortened SP and R), faster progress of the clot (increased angle and shortened K), and increased coagulation (TEG) index. The maximum amplitude (MA) was not affected, suggesting that the venom had no apparent effect on platelet function; and clot lysis was similar to that in the controls, suggesting that there was no primary fibrinolytic activity. At higher concentrations the venom had anticoagulant effects, SP and R were progressively shortened, but there was poor/no progress in the clot formed, evident from prolonged or absent K, diminished MA and reduced angle. These results show that C. rhodostoma venom has both coagulant and anticoagulant actions. The coagulant action may be due to Factor X activator predominance at low concentrations, while the anticoagulant action could be due to ancrod action. TEG is able to demonstrate the dual effect of this venom, previously described as a paradox, and may be a useful tool in the diagnosis and monitoring of envenomation patients.