Pediatric Rattlesnake Envenomations Treated With Crotalidae Equine Immune F(Ab’)₂ Antivenom

Abstract

Objectives Rattlesnake envenomations are uncommon, and the majority occur in adults. Although Crotalidae equine immune F(ab’)₂ antivenom (F(ab’)₂AV; trade name ANAVIP) was introduced in 2018, no pediatric specific studies of F(ab’)₂AV have been reported to date. The objective of this study was to evaluate the clinical performance and adverse effects of F(ab’)₂AV in children. Methods A single-center, retrospective chart review was performed on patients with rattlesnake envenomation presenting to a children's hospital between October 2018 and August 2022. Inclusion criteria were age younger than 18 years and F(ab’)₂AV use. Exclusion criteria were other antivenom use at any time and presentation beyond 24 hours postenvenomation. Demographic characteristics, hemoglobin, platelet count, fibrinogen, international normalized ratio, number of F(ab’)₂AV vials used, infusion-related complications, and clinical outcomes were collected. Results Twenty-six patients, 19 males and 7 females, with a mean age of 7.7 years (0.67 to 16 years) met inclusion criteria. Fourteen (54%) were treated with only the initial 10 vial F(ab’)₂AV doses. Twelve patients were given additional doses with a median additional vials of 10 (4–34 vials; interquartile range, 8.75–12 vials). The median total vials given for all patients was 10 (10–44 vials; interquartile range, 10–20 vials). Two patients developed acute infusion reactions. Both were treated by slowing the infusion rate and with medications (diphenhydramine, corticosteroids). No delayed reactions were noted. No patients required blood products or surgical interventions. After discharge, no complications, recurrent symptoms, return visits, or readmissions were reported. Follow-up by chart review or phone was obtained for 18 patients, and no postdischarge complications were noted. Seven patients had postdischarge hematologic laboratory evaluations and all were normal. Conclusions Although limited by small sample size and postdischarge follow-up, F(ab’)₂AV was well tolerated in our series of pediatric patients, consistent with prior studies of all age groups.