the snake. The bite occurred through her tennis shoe. Upon arrival in the ED, symptoms were described as “mild” consisting of erythema and swelling of involved the toe.
What poisonous snake species are found in Northern California?
In Northern California only one poisonous snake species is found in the wild: the Northern Pacific rattlesnake (Crotalus oreganus). This pit viper has brown to green coloring, a triangular head, thin neck, and relatively heavy body. The presence of a rattle indicates a poisonous snake, however absence of arattle does not necessarily exclude a snake from being venomous. Juvenile rattlesnakes may onlyhave a button and adult snakes may lose their rattles traumatically.
What are the symptoms of rattlesnakeenvenomation?
Envenomation causes three types of toxicity: Local/tissue toxicity, hemotoxicity, and/or neurotoxicity. Local symptoms include pain, swelling, redness, bruising, and frank tissue necrosis. Hemotoxicity causes defibrination (decreasing fibrinogen) and/or thrombocytopenia either of which may result in clinical bleeding. Neurotoxicity is less prominent in Northern Pacific rattlesnake envenomation, but clinically results in local to diffuse muscle fasciculations. Although death from rattlesnake bite is unusual, lifethreatening envenomation may occur with strikes to the head or neck, intravascular venom deposition, or with anaphylactoid reactions to venom.
Initial field treatment includes immobilization and rapid transport to a facility that has antivenom. Paramedics are encouraged to start IV lines, give fluids, and administer analgesia. As many as 20% of rattlesnake bites are non-envenomated (or “dry bites”). Patients who develop symptoms of envenomation will do so within 8 hours of being bitten. Those with envenomation symptoms (as described above) should be treated with rattlesnake antivenom. The antivenom preparation that is currently in use is Crotalidae Polyvalent Immune Fab (CroFab). This is an ovine (sheep) based Fab antivenom developed using the venom from 4 North American crotaline species. CroFab is administered intravenously to control the symptoms of envenomation.
Thorough follow-up care, including physical therapy is also important to ensure good functional outcome.
What is the role of surgical therapy for rattlesnake envenomation?
Prophylactic surgical treatment is NEVER indicated for rattlesnake envenomation. This practice was reported in the past, but has never demonstrated to be of benefit. Early surgical debridement is more likely to cause harm to the patient’s functional outcome than benefit. Debridement of necrotic tissue should be performed 1-2 weeks after the initial bite once final wound appearance has been delineated.
Compartment syndrome after envenomation is extremely rare. Cases of suspected compartment syndrome, should be managed with aggressive antivenom therapy and serial pressure measurements. Fasciotomy is almost never necessary.
Our Experience
Our Experience
Our experience with N. Pacific rattlesnake bite has leads us to recommend prompt initiation of antivenom therapy at the first signs of envenomation (tissue toxicity, abnormal coag studies, and/or
neurotoxicity). Proper dosing is important to ensure effectiveness and appropriate use of this expensive
medication. Since the warm weather and snake season are here, we expect to start seeing rattlesnake bites. A KPNC Toxicologist is always on call to help manage these unusual cases.
Bonus Question: True or False…. “Baby rattlesnakes are more poisonous than adults.”
False. The common notion that baby rattlesnakes are more poisonous than fully grown snakes may have some kernel of truth. In fact juvenile snake venom is more toxic by volume, however adult snakes deliver much more volume. For example, juvenile prairie rattlesnakes have venom shown to be 2-3 times more potent, but the adult snake strikes deliver 17x more venom. The only known predictor of envenomation severity is snake size...larger snakes deliver more venom!
No comments:
Post a Comment