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Venomous Snakebite

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Venomous Snakebite R Johnson MBBS MRCS DTM&H Five Venomous Snake Families Viperidae: N.American pit vipers (rattlesnakes, copperheads, mocassins), Asian pit vipers ... – PowerPoint PPT presentation

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Title: Venomous Snakebite


1
Venomous Snakebite
  • R Johnson MBBS MRCS DTMH

2
Five Venomous Snake Families
  • Viperidae N.American pit vipers (rattlesnakes,
    copperheads, mocassins), Asian pit vipers,
    African and Asian vipers and adders
  • Elapidae cobras, kraits, mambas, coral snakes,
    Laticauda seasnakes of Tropics, Sub-Tropics
  • Hydrophidae seasnakes, Australasian venomous
    snakes
  • Colubridae mostly non-venomous but includes
    rear-fanged boomslang, vine snakes, mole vipers,
    Japanese yamakagashi, Asian keelback
  • Actractaspididae burrowing asps of Africa

3
Elapid-mamba
Non-venomous python
Pit viper
Rear fanged boomslang
Fang Types
4
Venomous snake behaviour
  • The majority of bites do not lead to envenomation
  • First bite is often a warning
  • Juvenile snakes more dangerous
  • Few snakes are aggressive they are more scared
    of us
  • People to not drop dead in seconds!!!
  • Many bites associated with alcohol or trying to
    tease or kill the snake
  • 98 of U.S. snakebite due to pit vipers but
    exotic envenomations are becoming common as well
  • Coral snakes seldom bite but can be very dangerous

5
UK experience
  • One indigenous venomous snake
  • Vipera berus (adder)
  • 75-100 bites per year
  • Last fatality 1975
  • Estimated 2000 dangerous snake pets
  • 15-20 bites per year
  • Most bites on the hand whilst picking up snake

6
Pit Viper Fang Apparatus
7
Most dangerous U.S. snake
Diamond Back Rattlesnakea pit viper
8
Pitviper Fangs and Ridges
9
Elapid
Arizona Coral Snake
Red touch yellow, kill a fellow red touch black,
fear may lack (in U.S.A.)
10
Red touch Black fear may lack only works north
of Mexico City
11
Pit Vipers
  • Large thick-bodied snakes with triangular head
  • Heatsensing pit
  • Elliptical pupils
  • Single row of scales past the anal plate
  • Rattleif a rattlesnake!
  • Venom digests tissue and induces hemolysis and
    possible later kidney failure

12
Pit Viper
N.A. Non-venomous
13
Two Venom Types Hemolytic (Vipers)and Neurotoxic
(Elapids)
  • Most Vipers and Pit vipers have a hemolytic or
    tissue-destroying digestive type of venom that
    causes immediate local pain and swelling
    (exceptions some Mojave rattlesnakes are
    neurotoxic)
  • Most Elapids and Hydrophids (seasnakes) have a
    neurotoxic venom that produces little if any
    local symptomshowever cranial nerve palsies and
    respiratory arrest may follow (exception
    spitting cobra bites will destroy tissue )

14
Pit Viper Venom
  • Enzyme cocktail complex mixture of enzymes and
    small molecular weight peptides
  • Purpose is to immobilize and predigest prey,
    defense is secondary
  • Constituents proteolytic enzymes, thrombin,
    collaginase, hyaluronidase, phospholipase AB,
    crotamine (causes tetany), croactin, convulsin,
    gyroxin
  • 25 bites are dry 25 minimal 50 will be OK
  • Same antivenin used for all U.S. pit vipers
    rattlesnakes, copperheads and cottonmouths

15
Bothrops Envenomation Hemolytic/Proteolytic
16
Symptoms of Viper Envenomation
  • Swelling
  • Pain searing or burning
  • Fang marks 1-4
  • Ecchymoses
  • Vomiting
  • Fasciculations
  • Paresthesias
  • Increased bleeding
  • Blood blisters/blebs
  • Lymphadenitis
  • Metallic taste
  • Arrhythmias
  • Seizures
  • Shock
  • Coagulopathy (DIC)
  • Thrombocytopenia
  • Tetany
  • Coma
  • Death (usually takes days)

17
Measure Compartment Pressures but Never do
prophylactic fasciotomy!
Bad outcome often results
18
Check the Urine!!! Viper victims often survive
the initial bite only to walk in and later die of
renal failure
Myoglobinuria due to tissue destruction can cause
renal shutdown
19
Fatal Bite in a Toddler from Eastern Diamondback
Charleston, S.C.
20
Diamondback Rattlesnake Fang Marks
21
Vein penetration documented
22
The Culprit Diamond Back Rattlesnake
23
First Aid in Snakebite
  • Calm and reassure victim
  • Remove rings, watches, tight clothes
  • Dont catch or kill snake--second bite likely
  • Dont cut fang marks or suck out with mouth
  • May use Sawyer-type venom extractor within 3m
    (leave on for 30m)
  • May use constriction band (no tourniquet)
  • Dont use ice or electric shock
  • TRANSPORT ASAP TO HOSPITAL (phone and car keys
    most important emergency equipment)
  • Best not to administer antivenin in field
    setting!!!!!
  • No role for prophylactic antibiotics!

24
Elapid First Aid Compression/Immobilization
25
Snake Bite Investigations
  • FBC with platelets
  • Urinalysis
  • ABG
  • PT/PTT/fibrinogen (repeat w/in 12h)
  • UE/ creatinine
  • Liver function tests
  • Glucose
  • ECG
  • Type and Cross
  • Creatinine kinase

26
Polyvalent Antivenin
  • Antivenin (Crotalidae) polyvalent rattlesnake,
    copperhead, cottonmouth
  • Horse serum antibodies to venom
    sheep (ovine) antivenin should be safer
  • Dangerousgive only under controlled situations
    where anaphalaxis can be managed
  • Expect serum sickness later treat with
    prednisolone
  • If necessary, use enough (5 vials for grade I,
    5-15 for grade II, 15-20 for grade III)
  • Dose not reduced for children!
  • Expensive 200/vial

27
Antivenin Administration
  • Best w/in 4h but effective for at least 24h and
    possibly up to 72h with coagulopathy
  • Only give IV with physician in attendance and
    adrenaline and antihistamines available at
    bedside
  • If antivenin to be given, first skin test with
    horse serum kit unless pt in extremis. If ()
    give only if true threat to life/limb and then
    pre-medicate with hydrocortisone IV and
    chlorphenaramine IV
  • If negative, still consider pre-medication w/
    chlorphenaramine IV and Cimetidine 300 mg IV

28
Antivenin Administration
  • Reconstitute by injecting 10ml sterile water
    diluent to each vial and swirling (takes time)
  • Always get informed consent from pt or family if
    possible
  • Reconstituted antivenin vials are added to 500 ml
    NS or D5W then trial dose of 5-10 ml given over 5
    minutes epinephrine(11000) .3cc should be taped
    to IV bag just in case
  • If no reaction, adjust rate to give up to 10
    vials in 1st hour w/ additional infusions every
    2h until sign/sx resolving common error too
    little, too late
  • Fasciotomy rarely required with proper care

29
Serum Sickness
  • Expect 1-4 weeks after antivenin administration
    whatever the dose
  • Sx itching, urticarial rash, fever, arthralgias
  • Rx oral prednisolone therapy 60-80 mg with taper
    every 4 days
  • Many physicians anticipate serum sickness and
    discharge on steroids rather than waiting for it
    to develop

30
CroFab Antivenin
  • Purified sheep antigen-binding fragment
  • Compared to equine IgG antivenom
  • More effective
  • Fewer and less severe adverse effects
  • No anaphylaxis reported to date
  • Currently approved only for rattlesnake bites
  • Cost 4600 to 14,000 (4 to 18 vials)

31
Contacts for help
  • Arizona Poison Control 1-602-626-6016
  • Good current source of information on exotic
    antivenin availability
  • Herpetologists available for consultation
  • Royal Veterinary College, London Tel 44 (0)20
    7468 5000
  • Liverpool School of Tropical Medicine 44(0)151
    705 3100
  • Nearest zoo will keep antivenins for the snakes
    in its collection

32
Neurotoxic Envenomations
  • Elapids and Hydrophidsvenom attacks nervous
    system and kills by respiratory arrest (hard to
    reverse)
  • Some snake venoms (e.g. cobra) are intermediate
    and are also hemotoxic causing severe local
    reactions like pit vipers
  • Minimal local reaction for most elapids (dont
    wait for swelling to use antivenin!)
  • Rapid onset of neurologic symptoms ptosis,
    respiratory paralysis, death
  • Fist Aid immobilization and compression dressing
  • Swab wound for venom antigen ID (Australia)
  • Antivenin administration very soon

33
Ptosis due to krait bite (neurotoxic)
34
Coral Snake (Micrurus) Bites
Red touch yellow, kill a fellow red touch black,
fear may lack
  • Elapid bites rare since snake is secretive/shy
  • Local symptoms absentsystemic neurologic
    symptoms will develop first and will be difficult
    to reverse
  • Treat likely eastern coral bites with Micrurus
    antivenin immediatelybite is unimpressive
  • 3-5 vials if no signs or symptoms
  • 6-10 vials if systemic symptoms exist

35
Spitting Cobra of Africa
36
Large Constrictors can kill never wrap a
constrictor around your neck!
Non-Poisonous Snakes can also kill
37
Snakebite Prevention
  • Wear protective clothing and boots
  • Avoid drugs and alcohol with snakes
  • Watch where you step and place your hands
  • Avoid tall brush and undergrowth
  • Leave snakes alone, dont pick up dead snake or
    even a snake head (reflex bites)
  • Dont keep venomous snakes as pets
  • Dont walk after darkif you do, use a flashlight

38
Ha! Aint a rattler, Jake. You got one of them
maraca players down your bagand hes probably
more scared than you.
39
Spider Bites/ scorpion stings
  • No native spiders of importance
  • Occasional pet spider bites
  • Most only mildly venomous
  • Treat like bee sting
  • Local measures ice packs, analgesia and topical
    anaesthetic agents
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