Southern Pacific Rattlesnake bite: a unique clinical challenge.

The Southern Pacific Coast Rattlesnake (Crotalus Helleri) is responsible for most of the snake bites in the coastal area of California from Los Angeles to San Diego. However, Crotalidae polyvalent immune ovine Fab fragments are not made from the venom of C. Helleri. This sheep-derived antivenom is indicated only in moderate snakebite envenomations. Very scant data are available regarding venom-induced thrombocytopenia treated with ovine Crotaline Fab fragments. This is the second reported case of venom-induced thrombocytopenia that followed a "biphasic" pattern with the inability of ovine Crotaline Fab fragments to prevent this toxic effect. This case shows that severe envenomation from Crotalus Helleri associated with a delayed presentation to the Emergency Department does not have a sustained response to the ovine antivenom, and suggests that the use of Wyeth (equine) antivenom may be of greater therapeutic benefit.