Treatment of envenomation by Echis coloratus (mid-east saw scaled viper): a decision tree.

Envenomation by Echis coloratus causes a transient hemostatic failure. Systemic symptoms, hypotension and evident bleeding are rare, with only one reported fatality. In this paper, we examine the decision to treat victims of Echis coloratus by a specific horse antiserum. The decision model considers the mortality of treated and untreated envenomation, and the side effects of antiserum treatment: fatal anaphylaxis, serum sickness and increased risk of death after a possible repeated exposure to horse antiserum in the future. The results of the analysis are not sensitive to variations in the probability of side effects of antiserum treatment. They are sensitive to variations in the risk of bleeding after envenomation, in the degree of reduction of this risk by antiserum treatment and in the risk of dying after an event of bleeding. Prompt administration of antiserum appears to be the treatment of choice if it reduces the risk of bleeding from 23.6% to 20.3% and if 1.6% or more of the bleeding events are fatal. We conclude that presently available data support antiserum treatment of victims of Echis coloratus who present with hemostatic failure, even though the advantage imparted by this treatment appears to be small.