Use of polyvalent equine anti-viper serum to treat delayed coagulopathy due to suspected Sistrurus miliarius streckeri envenomation in two children.

BACKGROUND

Western Pygmy Rattlesnake (WPR) envenomation reportedly causes refractory and persistent coagulopathy when treated with CroFab® (Crotalidae Polyvalent Immune Fab). We report two cases where polyvalent equine anti-viper serum (AntivipmynTRI®) was used to treat recurrent coagulopathy in children.

CASE DETAILS: The first patient was a 16-month-old male who was bitten by a confirmed WPR. The patient received a total of 18 vials of CroFab®. His labs normalized, swelling gradually improved, and the child was discharged to home. On day 5, the child returned to the emergency department with a great deal of inguinal tenderness. Labs were obtained and the child's INR was >13.1, while the fibrinogen was <60 mg/dL and the d-dimer was 11.72 mg/L. A decision was made to administer Antivipmyn TRI®, and the child received a total of 10 vials. Lab values significantly improved: INR 1.2, fibrinogen 93 mg/dL, and d-dimer 4.21 mg/L. The second patient was a 20-month-old male who presented following snake envenomation. The child was administered a total of 22 vials of CroFab® over approximately 70 h following envenomation. Physical exam continued to improve, however, lab results showed an increasing INR 1.98, decreasing platelet count 124 × 103 per μL, fibrinogen <60 mg/dL, and d-dimer >20 ug/mL. A total of 15 vials of Antivipmyn TRI® were administered to this patient. Following this administration, labs and clinical exam both significantly improved. Labs revealed INR 1.16, fibrinogen 110 mg/dL, d-dimer 3.2 mg/L and platelet count 215 × 103/μL.

DISCUSSION: CroFab® is still the first-line treatment for children bitten by a WPR, but in some cases patients develop a recurrent coagulopathy. The rapid response demonstrated by Antivipmyn TRI® leads us to conclude that this is a potential therapy for this clinical situation.