Snake bites
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Snake bites. Hussein Unwala Dr. Ingrid Vicas February 4, 2010. Objectives. Identifying Venomous Snakes Signs of Envenomation Treatment of Presumed Snakebites. Identifying the Pit Viper. Prairie rattlesnake - coiled and rattling Longest fangs 3-4 cm Significant local tissue destruction.

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Snake bites

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Snake bites

Snake bites

Hussein Unwala

Dr. Ingrid Vicas

February 4, 2010



  • Identifying Venomous Snakes

  • Signs of Envenomation

  • Treatment of Presumed Snakebites

Identifying the pit viper

Identifying the Pit Viper

Prairie rattlesnake coiled and rattling longest fangs 3 4 cm significant local tissue destruction

Prairie rattlesnake - coiled and rattlingLongest fangs 3-4 cmSignificant local tissue destruction

Hey doc is this snake poisonous

“Red on Yellow Kills a Fellow”

Hey Doc! Is This Snake Poisonous?

Identifying Coral Snakes

Sonoran Coral Snake

Hey doc is this snake poisonous1

Hey Doc! Is This Snake Poisonous?

“Red on Black, Venom Lack”

Milk Snake - nonvenomous

Is the patient envenomated

Is the patient Envenomated?

  • Characteristics of a Venomous Snakebite

    • # strikes

    • Depth of envenomation

    • Size of snake

    • Potency/amount of venom injected

    • Size/health of victim

    • Location of bite

So how does this venom work

So how does this venom work?

  • “mosaic of antigens”

    • Proteolytic enzymes, procoagulants/anticoagulants, cardiotoxins, hemotoxins, neurotoxins

  • Venom is both circulating and tissue-fixed

    • Thus, anti-venom can halt progression, but won’t reverse clinical findings

  • What clinical signs are present

    What Clinical Signs are Present?

    • Local Reactions

    What clinical signs are present1

    What Clinical Signs are Present?

    • Systemic Signs

      • Venom travels via lymph/superficial veins to enter circulation

        • Mild: weakness, malaise, nausea, restlessness

        • More Severe: confusion, abdominal pain/V/D, tachycardia, hypotension, blurred vision, salivation, metallic taste in mouth

        • Rare: DIC, MODS

        • In some envenomations, neurotoxins predominate

        • Anaphylaxis

    What lab findings might you expect

    What Lab Findings might you expect?

    • Platelets 10-50,000

    • Fibrinogen approaches Zero

    • PT, PTT immeasurably high

      • The majority of patients have no clinical bleeding!

    Okay now what

    Okay, now what?

    • Observing asymptomatic patients

      • 8-12 hours, if skin broken, and unable to ID snake

    • Pressure immobilization?

      • Do not occlude venous+arterial flow!

      • Broad, firm, constrictive wrap at 50-70mmHg

      • NOT recommended for NA pit viper envenomations

    • Venom Removal?

      • No benefit of negative pressure venom extraction

    Okay now what1

    Okay, now what?

    • Delineate extent of edema, measure diameter of extremity

    • Look for any signs of clinical bleeding

    • Labs initially, then q 4-6 h

    • Tetanus

    • Analgesia/Anxiolysis

    What about antivenom

    What About Antivenom?

    • First line therapy for moderate-severe envenomations

    • CroFab : ovine-derived Fab fragment

      • Fewer hypersensitivity reactions vs equine derived

      • Infused IV in 4-6 vials reconstituted in NS

        • Initiated at slow rate; if no signs of anaphylactoidrx, then rate is increased to complete the infusion over 1 hour

        • If progressive limb swelling, thrombocytopenia, coagulopathy, dose repeated prn

        • Once symptoms controlled, maintenance doses of 2 vials q 6h x 3 doses



    • Initial routine use of tissue excision, fasciotomy, or “exploration and debridement” not recommended

    • Surgical debridement usually done 3-6 days post envenomation

    Other management points

    Other Management Points

    Low rates (0-3%) of wound infections

    No rationale for routine use of corticosteroids or anthistamines

    Careful followup of patients who received CroFab

    recurrence phenomenon

    serum sickness, delayed type hypersensitivity

    Fetal loss may be as high as 43% for bites during pregnancy

    Avoid any activity where risk of bleeding increased!!

    What about exotic snakes

    What about exotic snakes?

    • Efforts should be made to identify snake

    • Once snake identified, antivenom should be obtained

      • Local zoos, poison centers, snake collector

    • Give antivenom if signs of envenomation (ie fang marks!)

    • Compression immobillization of entire extremity



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