Evolution of venom antigenaemia and antivenom concentration in patients bitten by snakes in Uruguay.

In this work we describe the first study carried out in Uruguay of venom antigenaemia and antivenom concentration in patients bitten by snakes. Between 50 and 70 snake bite accidents per year are caused in Uruguay by 2 species: Rhinocerophis alternatus and Bothropoides pubescens. The patients are treated with a specific polyvalent antivenom. Gaining insight on the evolution of venom antigenaemia and antivenom concentration in patients is important to improve treatment protocols. Blood samples of 29 patients were analysed to determine venom and antivenom concentrations at different times. Venom was detected in 18 of 19 samples before antivenom administration, with a mean concentration of 57 ng/mL. Most of the patients received 4 or 8 vials to neutralize the venom effects. Only one patient needed a total of 16 vials. He showed a severe envenomation and needed supplementary amounts of antivenom after the fifth day of the snake bite accident to reach normal clotting parameters. Antivenom concentrations were determined at 12 h, 24 h and 15 days after antivenom administration. It was found a faster antivenom decrease between 12 and 24 h than to 24 h to 15 days. This was explained by a different clearance mechanism in each period. In the first phase, the cause would be the neutralization of venom present in the blood whereas in the second phase it would be due to unbound antivenom elimination.