Subcutaneous Crotaline Fab antivenom for the treatment of rattlesnake envenomation in a porcine model.
BACKGROUND
This study was designed to investigate whether the local, subcutaneous injection of Crotaline Fab antivenom (CroFab) at the rattlesnake envenomation site would result in less extremity edema when compared to intravenous (i.v.) antivenom infusion alone.


METHODS
This is a randomized, three-arm laboratory experiment using a porcine model. Each animal was anesthetized, intubated, and maintained on mechanical ventilation. About 6 mg/kg of Crotalus atrox venom was injected subcutaneously at the hock of the right hind leg. Animals were then randomized to immediately receive subcutaneous and i.v. antivenom (SC/IV), i.v. antivenom only, or saline control. SC/IV animals received two vials of CroFab subcutaneously at the envenomation site and two vials intravenously. IV animals received four vials of CroFab intravenously. Limb edema was tracked by serial circumference and volumetric measurements over an 8-h period. Limb circumference was measured at four pre-determined locations hourly. Limb volume was measured by a water displacement method at baseline, 4, and 8 h.


RESULTS
Twenty-six animals were randomized to the three treatment groups. The SC/IV and IV arms included nine animals each. Two animals in the SC/IV group died suddenly during the study, leaving seven animals for data analysis. There were eight controls. Increasing limb edema was observed in all groups. No differences were detected in limb circumferences or limb volumes between control and either treatment arms.


CONCLUSIONS
In this porcine model of crotaline envenomation, no differences in limb edema were found between animals treated with SC/IV or IV CroFab when compared to saline controls.
Offerman
Steven R
SR
Department of Emergency Medicine, Kaiser South Sacramento, Sacramento, CA 95823, USA. steve.offerman@gmail.com
Barry
J David
JD
Richardson
William H
WH
Tong
Tri
T
Tanen
Dave
D
Bush
Sean P
SP
Clark
Richard F
RF
D000818:Animals; D000997:Antivenins / Q000008:administration & dosage / Q000627:therapeutic use*; D003435:Crotalid Venoms / Q000008:administration & dosage; D004195:Disease Models, Animal; D007140:Immunoglobulin Fab Fragments; D007128:Immunoglobulin Fragments / Q000008:administration & dosage / Q000627:therapeutic use*; D015552:Injections, Intralesional; D007275:Injections, Intravenous; D007279:Injections, Subcutaneous; D008297:Male; D011897:Random Allocation; D012909:Snake Bites / Q000188:drug therapy* / Q000276:immunology; D013552:Swine; D016896:Treatment Outcome
D000997:Antivenins; D003435:Crotalid Venoms; C431183:Crotalidae Polyvalent immune Fab; D007140:Immunoglobulin Fab Fragments; D007128:Immunoglobulin Fragments