Short-term outcomes after Fab antivenom therapy for severe crotaline snakebite.
OBJECTIVE
We seek to determine the short-term outcomes associated with the use of Crotalidae polyvalent immune Fab (ovine) (CroFab; FabAV) therapy for severe crotaline snake envenomation and to better define the incidence of hypersensitivity reactions associated with FabAV use.


METHODS
We conducted a multicenter observational case series study of patients who received FabAV at 17 US hospitals in 2002 to 2004. A 7-point score incorporating local, systemic, and hematologic venom effects was used to grade envenomation severity before and after FabAV therapy. The primary outcome for response to therapy was the change in overall envenomation severity after FabAV administration. The primary safety outcomes were the rates of immediate hypersensitivity reactions and serum sickness.


RESULTS
The outcome-evaluable population included 209 patients, of whom 28 had severe envenomation. All severely envenomated patients improved after receiving FabAV. The median severity scores of severely envenomated patients were 5 (interquartile range [IQR] 5 to 5) before FabAV, 1 (IQR 1 to 2) at the last FabAV loading dose, and 1 (IQR 0 to 1) at the last clinical observation. The proportion of patients with progressive pain, progressive swelling, cardiovascular effects, respiratory effects, neurologic effects, gastrointestinal effects, coagulopathy, and thrombocytopenia all improved after FabAV therapy. The safety population included 247 patients. Immediate hypersensitivity reactions were reported in 6.1% (95% confidence interval 3.4% to 9.8%) of patients. Serum sickness was reported in 5% (95% confidence interval 0.6% to 17%) of patients with a minimum of 6 days of follow-up after the last dose of FabAV.


CONCLUSIONS
FabAV therapy is associated with clinical improvement in severe crotaline snake envenomation. Immediate hypersensitivity and serum sickness rates may be less than described in the FabAV prescribing information.
Rocky Mountain Poison and Drug Center, Denver Health and Hospital Authority, CO, USA. eric.lavonas@rmpdc.org
Eric J
EJ
Lavonas
Jamie
J
Kokko
Tammi H
TH
Schaeffer
Sara L
SL
Mlynarchek
Gregory M
GM
Bogdan
Richard C
RC
Dart
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D000997:Antivenins / Q000009:adverse effects / Q000627:therapeutic use*; D002648:Child; D002675:Child, Preschool; D003435:Crotalid Venoms / Q000037:antagonists & inhibitors; D005260:Female; D006801:Humans; D006967:Hypersensitivity / Q000209:etiology; D007223:Infant; D008297:Male; D008875:Middle Aged; D012720:Severity of Illness Index; D012909:Snake Bites / Q000628:therapy*; D013997:Time Factors; D016896:Treatment Outcome; D017819:Viperidae; D055815:Young Adult
D000997:Antivenins; D003435:Crotalid Venoms