In vitro evaluation of canine whole blood with the addition of Crotalus atrox (Western Diamondback Rattlesnake) venom and antivenom using thromboelastography

Abstract

Objectives: To compare the efficacy of 2 equine-origin antivenom products on correction of coagulation abnormalities noted on thromboelastography (TEG) caused by Crotalus atrox venom in vitro. Design:Prospective in vitro controlled study.Setting: Veterinary teaching hospital. Animals: Six healthy dogs.Interventions: Blood from each dog was used for 4 separate kaolin-activated TEG analyses: A negative control (blood-saline) and positive control (blood-Crotalus atrox venom) were used to assess the dog's normal coagulation and the effect of venom on TEG parameters. Thromboelastographic analyses were then run with blood, venom, and either Argentinian or North American antivenom. All TEG analyses from each dog were compared for efficacy. Measurements and Main Results:The mean R values between the North American antivenom and negative controls were not significantly different (P = 0.681), but were significantly different (P = 0.024) between the Argentinian antivenom and negative controls. The mean fibrinolysis values measured 30 minutes after maximum amplitude achieved between the North American antivenom and negative controls were not significantly different (P = 0.198), but were significantly different (P < 0.001) between the Argentinian antivenom and negative controls. The mean K values between the Argentinian antivenom and negative controls were not significantly different (P = 0.274), but were significantly different (P = 0.043) between the North American antivenom and negative controls. Conclusions:The North American antivenom normalized time to clot formation and fibrinolysis, while the Argentinian antivenom normalized rate of clot formation. Further studies in naturally envenomated patients are necessary to determine if these in vitro results would translate into different clinical outcomes.Abbreviations: F(ab')2, antigen-binding fragments formed after pepsin digestion; Fc, fragment crystallizable region of antibody; K, kinetic time; LY30, fibrinolysis measured 30 minutes after MA achieved; LY60, fibrinolysis measured 60 minutes after MA achieved; MA, maximum amplitude; R, reaction time; TEG, thromboelastography; VICC, venom-induced consumptive coagulopathy.