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Introduction: In 2023, a group of experts proposed that a definition of major bleeding in pharmaceutically anticoagulated patients be used in all snakebite trials. This includes bleeding that results in death, is life-threatening, causes chronic sequelae, or consumes major healthcare resources, including bleeding into a major area or hemoglobin concentration decrease ≥20 g/L. We hypothesized that a decline in hemoglobin concentration ≥20 g/L is common but rarely clinically significant in our population of Arizona rattlesnake bite patients., Methods: Poison center records of rattlesnake bites in humans from 2018 through 2022 were retrospectively reviewed and assessed for major bleeding by the above criteria., Results: Four hundred and eighty-one patients met the inclusion criteria, of whom 265 (55.1%) had a hemoglobin concentration decrease ≥20 g/L. No patients died, and there was no evidence of bleeding into a critical organ. Three patients (1.1%) received blood transfusions. A decrease in hemoglobin concentration ≥20 g/L was 100% sensitive for identifying the major bleeding-associated outcomes; however, specificity was only 45.2%. Measures of healthcare utilization and chronic sequelae were somewhat higher in patients with a decrease in hemoglobin concentration ≥20 g/L., Discussion: Laboratory manifestations of hemotoxicity were common in this population, but hemorrhage was rare. While over half of patients met the major bleeding criterion of a decline in hemoglobin concentration ≥20 g/L, only 1.1% had bleeding that was potentially life-threatening as measured by receipt of a red blood cell transfusion. None died or had bleeding into a critical area. While nonspecific for major bleeding, a drop in hemoglobin concentration correlated with worse envenomation severity: these patients received more vials of antivenom, had a higher medical bill, a longer hospital stay, and were less likely to report full recovery at 90 days., Conclusions: A decrease in hemoglobin concentration ≥20 g/L should not be used as evidence of major bleeding for Arizona rattlesnake envenomation studies, but it may have a role as an indirect marker of envenomation severity.

Introduction: Rattlesnake ( Crotalus spp ., Sistrurus spp.) bites in the southwestern United States are associated with significant morbidity. This study aims to describe 25 years of rattlesnake encounters reported to the Arizona Poison and Drug Information Center to identify vulnerable populations and circumstances where encounters occur to create public education to reduce future bites., Methods: Cases of suspected rattlesnake encounters in Arizona reported to the Arizona Poison and Drug Information Center between 1999 and 2023 were analyzed to identify populations and circumstances associated with encounters., Results: A total of 3,808 cases were analyzed overall and by age subgroups. Most encounters occurred in men (69.9%), during the evening (16:00-21:59; 49.2%), in summer (41.9%), and close to home (38.2%). Most bites occurred to the lower extremity (51%). Children 0 to 12-years-old have more encounters than those 13-years-old and older in rural zip codes (27.7% versus 14.8%; P  = 0.005), during spring (31.8% versus 22.3%; P  = 0.0005), and during the evening (64.4% versus 48.1%; P  < 0.001)., Discussion: Rattlesnakes are encountered when rattlesnake and human behavior patterns overlap. Many people spend time outside during evening hours in the summer, and valuable resources like food, water, and shelter can be found near houses where humans spend much of their time. Most age groups have similar encounter circumstances but encounters among children 0 to 12-years-old differ in time of day, season, and urbanization level than encounters of those 13-years-old and older. Limitations of this study include underreporting of encounters, incomplete case details, potential reporting bias, potential snake misidentification, and geographic coverage of the poison center., Conclusion: Prevention of rattlesnake bites by reducing encounters is the most effective way to reduce suffering and healthcare costs. Future steps include creating and disseminating targeted public health education using the data collected.