Viscoelastic testing is improved following antivenom treatment in rattlesnake-envenomated equids

To characterize coagulopathies before and after antivenom administration in rattlesnake-envenomated equids.

Client-owned envenomated equids treated with antivenom at Colorado State University (2023 to 2024). Rattlesnake bite severity score (RBSS), platelet count, prothrombin time, activated thromboplastin time, D-dimers, antithrombin, and viscoelastic testing variables were assessed before and after antivenom administration. Paired comparisons of hemostatic variables between admission and approximately 24 hours, and correlation analysis with RBSS, were performed. Length of hospitalization (LOH) and outcome were recorded.

Seven acutely envenomated equids. Admit median (IQR) RBSS was 7 (4 to 7) out of 13. At admission, coagulopathies were present in all animals. Most common findings were thrombocytopenia, increased D-dimers, abnormal amplitude at 20 minutes (A20), and abnormal maximum clot firmness (MCF) on viscoelastic testing. On the day following admission, RBSS [3 (1 to 3)], A20 (admit, 15.8 ± 10; recheck, 26.4 ± 5), and MCF (admit, 18.7 ± 9.5; recheck, 28.8 ± 6) were improved. Significant correlations were found between RBSS and platelet count (ρ = -0.68; n = 12), activated thromboplastin time (ρ = 0.64; n = 14), A20 (r = -0.70; n = 14), and MCF (ρ = -0.56; n = 14). Median LOH was 2 days. The mortality rate was 0%.

Coagulopathies are common in rattlesnake-envenomated equids, and viscoelastic testing allows for identification and monitoring of qualitative disorders.

Antivenom administration may mitigate venom's effects, reduce LOH, and improve outcomes.