When a snake bites.

Primary care physicians may be required to treat snake-bitten patients and must differentiate between venomous and nonvenomous snakes. The chief distinguishing characteristics of venomous snakes are fangs and a single row of subcaudal anal plates. The physiologic effects of snake venom are on the cardiovascular, hematologic, and neurovascular systems. The snake-bitten patient first needs supportive treatment and stabilization. Then, the physician must establish whether envenomation has occurred, grade it, and monitor edema around the bite. Local treatment, broad-spectrum antibiotics, and tetanus prophylaxis should be used for all envenomation grades. The decision to administer antivenin therapy should be made on clinical grounds and the envenomation grade. Its use, however, can lead to anaphylaxis and anticomplement reactions.