Tumescent contravenom: murine model for prehospital treatment of Naja naja neurotoxic snake envenomation.

BACKGROUND: Snake envenomation is a neglected global health problem. There is a need for a prehospital treatment of neurotoxic snakebite that prolongs survival and allows time for a victim to reach a hospital for antivenom therapy. Tumescent epinephrine consists of a large volume of dilute epinephrine (2 mg/l) injected subcutaneously. It functions as "contravenom" by causing capillary vasoconstriction and delaying venom absorption.

METHODS: A murine model of neurotoxic envenomation using lidocaine as a surrogate for neurotoxic snake venom was first developed in a pilot study. A lethal dose of lidocaine was injected subcutaneously into control and treatment groups. Mice in the treatment group were then treated with a tumescent infiltration of dilute epinephrine in saline, while control mice either received no treatment or tumescent infiltration with saline alone. The experiment was repeated using lethal doses of neurotoxic Naja naja cobra venom. The main end-points were survival rate and survival time.

RESULTS: None of the control mice survived a lethal (LD100 ) dosage of subcutaneous lidocaine. Mice given an LD100 of subcutaneous lidocaine and treated immediately with tumescent epinephrine had 80% survival. Following LD50 doses of Naja naja venom, 50% of control mice survived, while 94% survived when treated immediately with tumescent epinephrine (P < 0.01). All animals died following LD100 doses of Naja naja venom, but survival was significantly prolonged (P < 0.0001) by immediate tumescent epinephrine.

CONCLUSIONS: Tumescent epinephrine, when given immediately after toxin injection, improves survival rates in mice following neurotoxic doses of lidocaine or Naja naja cobra venom.