Research Study: Late hemotoxicity following North American rattlesnake envenomation
1.) Research Title:
Late hemotoxicity following North American rattlesnake envenomation treated with crotalidae immune F(ab’)2 (equine) antivenom and crotalidae immune polyvalent Fab (ovine) antivenom reported to the North American Snakebite Sub-registry.
2.) What We Know/What Authors Wanted to Know:
Is crotalidae immune F(ab’)2 (equine) antivenom (Fab2AV) better than crotalidae immune polyvalent Fab (bovine) antivenom (FabAV) in preventing late hemotoxicity in patients who have been bitten and envenomated by rattlesnakes?
a.) Fab2AV has shown promise in a phase 3 RCT and was associated with less late hemotoxicity than FabAV.
b.) The purpose of this study was to retrospectively compare the occurrence of late hemotoxicity in rattlesnake bite patients treated with Fab2AV vs. FabAV.
3.) Research Hypothesis
Rattlesnake bite patients treated with Fab2AV would have less late hemotoxicity events than similar patients who were treated with FabAV.
4.) Project Description
Patient records were obtained and analyzed from the ToxIC North American Snake Bite Registry (created by the American College of Medical Toxicology) from January 1, 2019 to December 31, 2020. Various data were pulled from the registry and compared including demographics, treatments, indicators of hemotoxicity (such as platelets, fibrinogen, etc.), late hemotoxicity in follow up visits, delayed bleeding events.
5.) Project Findings
94 patients were included in the study- 49 received Fab2AV and 45 received FabAV. 50 additional patients received both Fab2AV and FabAV and their cases were reviewed separately. Fab2AV patients received an average of 18 vials of antivenom while FabAV patients received an average of 12 vials. Thrombocytopenia was the most common indicator of late hemotoxicity, and 4% of the Fab2AV patients had late hemotoxicity, while 42% of the FabAV patients had late hemotoxicity.
6.) Importance/Conclusion
The data supports the evidence that Fab2AV is associated with less late hemotoxicity than FabAV in the treatment of patients who have been bitten and envenomated by rattlesnakes. This could lead to less repeat hospitalizations, decrease hospital length-of-stay, and prevent late bleeding events. This also supports a decreased need for continued follow-up (from a late hemotoxicity perspective) in patients treated with Fab2AV as opposed to those treated with FabAV.
This study supports the previous evidence in the phase 3 clinical trial and supports the hypothesis that Fab2AV is superior to FabAV in the prevention of late hemotoxicity following rattlesnake envenomation.
The next steps include further studies enrolling larger numbers of patients, as well as comparing the efficacy of Fab2AV and FabAV in the treatment and prevention of other complications of rattlesnake envenomation such as neurotoxicity, hypersensitivity, etc. In addition, studies investigating the clinical benefits of preventing late hemotoxicity, such as patient quality of life and days out of the hospital, as well as weighing the potential savings (decreased LOS, decreased recurrent hospitalizations) would help inform which antivenom should be selected for rattlesnake bite patients.
Link to article:
https://pubmed.ncbi.nlm.nih.gov/35261320/
Author: Gabriel Padilla, MD is a current third-year emergency medicine resident at Brown Emergency Medicine Residency.
Faculty Reviewer: Michelle Myles, MD is an assistant professor and clinician educator at Brown Emergency Medicine.
Citation:
Spyres MB, Padilla GK, Gerkin RD, et al. Late hemotoxicity following North American rattlesnake envenomation treated with crotalidae immune F(ab')2 (equine) antivenom and crotalidae immune polyvalent Fab (ovine) antivenom reported to the North American Snakebite Sub-registry. 2022 Clin Toxicol (Phila) 2022;60(7):838-842. doi:10.1080/15563650.2022.2042550