Crotalus atrox Venom Exposed to Carbon Monoxide Has Decreased Fibrinogenolytic Activity In Vivo in Rabbits.

Envenomation by haemotoxic enzymes remains a significant source of human morbidity and mortality worldwide, with administration of long-acting or multiple doses of antivenom first-line therapy. However, coagulopathy can still occur and recur. Of interest, it has been recently demonstrated that direct, isolated exposure of snake venom enzymes with fibrinogenolytic activity to carbon monoxide (CO) abrogates venom-mediated loss of coagulation in human plasma. These observations of CO inhibition of venom fibrinogenolytic activity were subsequently repeated in rabbit whole blood. This study sought to translate these findings in an in vivo rabbit model of envenomation with fibrinogenolytic Crotalus atrox venom. Sedated rabbits were intravenously administered C. atrox venom (400 μg/kg) pre-exposed to 0 or 1000 μM carbon monoxide-releasing molecule-2 (CORM-2) in vitro. Arterial whole-blood samples demonstrated that compared to pre-envenomation values, the CORM-2-naïve venom significantly prolonged the onset of coagulation, decreased the velocity of clot growth and decreased clot strength as determined by thromboelastography an hour after venom injection. In contrast, CORM-2 pre-exposure prevented or attenuated C. atrox venom effects on coagulation kinetics. Future studies to determine whether rabbits injected with such venom subcutaneously/intramuscularly can have consequent coagulopathy abrogated by injection of carbon monoxide-releasing molecules into the 'bite site' are justified.