- See:
necrotizing fascitis
- Discussion:
-
snake bite resources
- snake types:
- pit vipers (crotaline) which include rattlesnakes, cottonmouths, and copperheads;
- crotalus (rattlesnakes)
- agkistrodon (copperheads, water moccasins)
- micrurus (coral snakes)
- Epidemiology:
- 15% of the approximately 3000 species of snakes worldwide are considered harmful to humans
- 1998-2001 – AAPCC reports annual average 6000 snakebites
2000 of which were from venomous snakes
- true incidence - 7000-8000 bites by venomous snakes resulting in 5-6 deaths per year
- eastern and western diamondback rattlesnakes account for most fatalities
- Deaths typically in children, elderly, and those either not receiving antivenom,
receiving antivenom after significant delay or inadequate quantities
- Victims typically are male between 17-27 y.o.
- 98% of bites are on the extremities
- most bites occur between April and September
- alcohol intoxication is a major factor (70%)
- Envenomation:
- Implies that enough venom introduced to cause local or systemic signs
- 25% of all pit viper bites are “dry”, 50% of all coral snake bites
- Snake parts should not be handled directly, or handled with care– the bite reflex in recently killed/decapitated snakes remains intact
- Definitive diagnosis requires positive identification of the snake and clinical manifestations of envenomation
- 20% of snake bites in US are non-poisonous
- Pharmacology of Snake Bites:
- Chemically complex mixture of proteins, peptides and enzymes
- Designed to immobilize, kill, and digest prey
- Highly stable – resistant to temp changes, drying, drugs
- Bind to multiple receptor sites
- Lethal components – smaller LMW polypeptides
- Quantity, lethality and composition varies with species, age, geography, time of year
- Damage to endothelial cells of vascular walls, causing blebs in the endothelium, dilating the perinuclear space, and breaking down the plasma membrane
- Affect almost every organ system – esp. CV, heme, respiratory, nervous
- Work Up:
- serial measurements of vital signs especially BP for minimum of 8 hours (note delayed response to venom);
- laboratory data: a minority of patients will require
pRBC transfusion,
FFP, or even platlets;
- H and H
- platlet count
-
PT/PTT (need to rule out consumptive coagulopathy);
- creatine kinase
- urinalysis
-
Dart Severity Scoring:
- grade 0: no envenomation. fang marks and minimal pain.
- grade I:
- minimal envenomation. fang marks, pain, 1 to 5 inches of edema and erythema in 1st 5 hours;
- no systemic symptoms;
- grade II:
- moderate envenomation. fang marks, pain, 6-12 inches of edema in first 12 hours;
- systemic symptoms may be present along with rapid progression of signs from grade I.
- may have bleeding from bite site;
- grade III:
- severe envenomation. fang marks, pain, edema greater than 12 inches in first 12 hours.
- systemic symptoms, including coagulation defects;
- signs of grade I and II envenomation appear in rapid progression;
- grade IV:
- very severe envenomation. local reaction develops rapidly.
- edema may involve ipsilateral trunk. ecchymoses, necroses, and blebs develop.
- potential for compartment syndrome;
- Treatment Considerations:
- US national hotline: national hotline at 800-222-1222
- bleeding disorders
-
compartment syndrome
-
infection
- antivenom:
- antivenoms are directed against two main groups: crotaline (pit vipors) and coral snakes
- antivenom (CroFab; FabAV) composed of purified Fab specific to indigenous snake species
- Fab molecules have a shorter half-life than IgG molecules and may allow recurrence of venom effects, if additional doses are not administered (systemic
effects may reoccur hours or even days after treatment);
- Fab preparation has produced fewer acute or delayed (serum sickness) allergic reactions;
-
indications for treatment:
- most indicated for systemic symptoms, but in some cases, it may be used for rapidly advancing local symptoms;
- worsening local injury (eg, swelling, ecchymosis);
- clinically important coagulation abnormality, or systemic effects (eg, hypotension, altered mental status);
- be aware that over use of antivenom will lead to cases of
anaphylaxis;
- antivenom is composed of purified Fab specific to indigenous snake species
- Fab preparation has produced fewer acute or delayed (serum sickness) allergic reactions;
- dosage: adequate dosage will reverse systemic effects (usually 8-12 vials);
-
complications:
-
anaphylaxis
- overall rate of serum sickness after the administration of FabAV is about 15 percent;
Bacteriology of rattlesnake venom and implications for therapy.
Bacteriology of human and animal bite wounds.
The efficacy of tourniquets as a first-aid measure for Russell's viper bites in Burma.
Tourniquet application after cobra bite: delay in the onset of neurotoxicity and the dangers of sudden release.
Crotalid Envenomation: The Southern Arizona Experience. JT. Tokish et al. Jour. Orthop Trauma. Vol 15. No 1. p 5-9.
Rattlesnake Bites in Children:Antivenin Treatment and Surgical Indications
Initial Experience with Crotalidae Polyvalent Immune Fab (Ovine) Antivenom in the Treatment of Copperhead Snakebite Lavonas et al. Ann Emerg Med. 2004:43:200-206.
Pediatric snakebites: lessons learned from 114 cases
