SNAKEBITES
DAVID WHARTON M.D. FACEP
2013
Objectives
To gain some general information about
snakes
To recognize different types of snake bites
and potential injuries
To discuss different treatment options for
snake envenomation
General Information
Cold blooded (become dormant and seek protected environment in cold weather)
Lay eggs or bear live young
Reach maximum size in two years
Nocturnal feeders
Deaf for air conduction but excellent vibratory sense
Poor vision
excellent sense of smell
20 of 120 species in USA are venomous
Two Venomous Families:
Crotalinae (Pit Vipers
Elapidae (Coral Snakes
General Information on poisonous snakes
Venom present at birth
More than 45,000 snake bites/year
Approx. 8,000 bites from poisonous snakes per year
Fewer than 10 deaths / year from snake bites
About 60% of bites are on the lower and about 40% on
upper extremities
98% of bites are from pit vipers, 1% from Coral Snakes, 1%
exotic snakes
Venom glands are actually an anlage of the parotid gland
Fangs are present in poisonous snakes
Length of the fangs is 5-20 mm
Distance between the fangs:
Small snake < 8 mm
Medium snake 8-12 mm
Large snake > 12 mm
Harmless Snakes
Significance of bite: contaminated puncture wound
Have rows of teeth and may leave imprint
Treatment: Cleansing and Tetanus
Rarely have an allergic reaction
Some "nonpoisonous" snakes in the SW USA may have rear
fangs which can inject some poison but is rather
insignificant in amount and symptoms
POISONOUS SNAKES
Coral SnakeShy, live in dark humid sites (compost piles, wood piles, creek
Black Head
“Red on yellow kill a fellow, red on black venom lack”
Lays eggs
Round pupils, no pits, 2 rows of anal plates
Coral SnakeMay or may not see fang marks
May have minimal local tissue effect
Has to “chew in” the poison
May have delay systemic effect
Toxin is a potent neurotoxin
Coral SnakesNausea and vomiting
Paresthesias at the bite site
Bulbar type paralysis: Ptosis
Miosis / blurred vision
Salivation, swallowing dysfunction
Dysarthria
Respiratory paralysis
Coral Snakebite Treatment
Be more aggressive
Specific Eastern Coral Snake antivenin (Wyeth Labs)
Requires less antivenin (3-6 vials) than rattlesnakes
If bitten by a snake identified as a coral snake, give three
vials prophylactically
Cottonmouth or “Water Moccasin”
Found in permanent aquatic habitats
Will "stand their ground" and often even attack
Shows white moist "cotton" mouth lining
Copperhead"Highland moccasin"
Least potent venom
Most plentiful
Rocky outcroppings in wooded areas
Somewhat sluggish and rely on camouflage to escape detection
Not normally aggressive
RattlesnakesIn Tennessee and Georgia, only the Eastern Diamondback, Timber,
Canebrake and Pigmy rattlesnakes
New rattle each time skin is shed (2-5 times a year)
Some (Diamondback) aggressive while others (Timber) not
Contain 20-30 different peptides and enzymes for immobilization
and digestion
Hematoxic venom
Mojave Rattlesnake
MOJAVE RATTLESNAKE is the most potent and requires
different treatment as it has a neurotoxin (12-16 hours
later) and little local reaction. Found only in SW USA
Number of bites
Location of bites
Species of snake
Size of snake
Age and size of victim
Interference (boot, clothes, etc.)
FACTORS AFFECTING THE SEVERITY OF A SNAKEBITE
25-40 % of bites are “dry bites”
20-30% of bites are mild bites
30-40% of bites are moderate to severe bites
TYPES OF REACTIONS TO SNAKEBITE
Swelling and pain are most common
Hematologic
Bleeding
Neurotoxicity
Systemic Toxicity
TYPES OF REACTIONS TO SNAKEBITE
SWELLING AND PAIN ARE MOST COMMON
TYPES OF REACTIONS TO SNAKEBITE
HEMATOLOGIC
Coagulopathy
Thrombocytopenia
TYPES OF REACTIONS TO SNAKEBITEBleeding
Neurotoxicity—Most common with Mojave Rattlesnake bites
Paresthesias
Fasciculations
Worse case scenario would be respiratory failure
REACTIONS TO SNAKEBITES
Systemic Toxicity
Loss of consciousness
Circulatory collapse
FIRST AID FOR SNAKEBITES
Stay calm with little activity as possible
Get away from the snake
"The Extractor" by Sawyer is very effective for up to 50%
of the venom if used within 1-2 minutes after the bite. It
is not useful if applied after 30 minutes
Kill snake and bring in for identification if it can be done
safely without additional risk to other personnel.
The Wilderness Medical Society's position on field management of snake envenomation:
Incision and suction is not efficacious in any type of the bite, and is not recommended.
There is no evidence that lymphatic constriction bands have any definite treatment value. Most consultants feel they interfere with definitive treatment and result in increased local tissue edema and damage while a few still advocate their use.
Local ice may possibly be detrimental (Russell FE: Snake Venom Poisoning, New York, 1983, Scholium International, Inc.)
There is no evidence that splints or pressure wraps have any value in the first aid treatment of snake envenomation. However, a splint may make the patient more comfortable.
The bottom line in snake bite first aid is to rapidly transport the patient to a medical facility.
DEFINITIVE CARE FOR SNAKEBITES
ABC's of life support, Oxygen
2 Large bore IVs and baseline lab (CBC, Type and screen)
UA, CMP, PT/PTT, fibrinogen)
AMPLE History:
Allergies
Medicines
Past medical history
Last meal
Events of accident: ID snake, time of attack, tx. )
DEFINITIVE CARE FOR SNAKEBITES
Measure circumference at and 10 cm above bite initially
then every 20 minutes for 1-2 hours then hourly
Tetanus and wound care
Broad spectrum antibiotic
Remove constricting bands
Elevate
Call poison control 1-800-222-1222 for questions
Antivenin
Polyvalent for vipers or coral snakes
Best if given within 4 hours; Poor if given after 24 hours
Binds to the antigen of the venom and inactivates it
Crotalidae polyvalent immune Fab (ovine) (CroFab) is
indicated for the management of patients with North
American crotalid evenomation. Early use of CroFab is
advised to prevent clinical deterioration and the
occurrence of systemic coagulation abnormalities
GUIDELINES FOR TREATMENT OF VIPER BITES
GRADES OF SYMPTOMS & SIGNS MEDICAL ANTICIPATORY
POISONING WITHIN 3-4 HOURS MEASURES MEASURES
__________________________________________________________
0 Fang marks, no local Observation
or systemic signs
I Moderate pain, edema, Cleansing, antibiotic T & S blood
MINIMAL 1-6", erythema, debridement, tetanus CBC, UA,
No systemic signs antihistamine clotting studies
II Severe pain, edema As above plus As above, also be
MOD 10"-15", erythema, IV antivenin ready to treat
petechiae, vomiting, in selected cases hemorrhage
fever, weakness
III Widespread pain As above As above, also
SEVEREedema 15"-20 Check electrolytes be ready to
Ecchymosis, systemic coagulation intubate
systemic signs, vertigo antivenin
IV Rapid swelling antivenin in large As above, also
VERY CNS symptoms, doses, blood, clotting watch for cardiac
SEVERESeizure, shock factors arrest, renal failure
HYPERSENSITIVITY REACTION
TREATMENT
Stop antivenin
Epinephrine
Antihistamines
Steroids
Albuterol aerosol
Often can restart slowly if
reaction not severe
CAUSE
Allergy to sheep
Reaction to the papain used
to cleave the antibodies in
the process of making the
antivenin
SNAKEBITES: TREATMENT PLAN
To gain initial control of the envenomation as evidenced
by cessation of swelling and pain
Coagulation studies and platelets trending toward normal
SNAKEBITES: TREATMENT PLAN
Maintenance
2 vials every 6 hours for 3 doses for rattlesnakes
Most of the time no maintenance dose is needed for
copperhead bites
Plan is to decrease local swelling and decrease the
occurrence of late hematologic toxicity
You may need to repeat dosing if swelling restarts or
coagulation studies start worsening but this is a good time to
call poison control for advice as you do not want to be
chasing lab values
Hospital Treatment
Daily Platelets and Protime
Reassessment to be sure swelling and pain better
Give blood products only if bleeding
DO NOT CHASE LAB VALUES
DISCHARGE INSTRUCTIONS
Elevate the injured extremity
Crutches with weight bearing as tolerates
NO NSAIDs
2 weeks of no contact sports, dental work or surgery
Report any bleeding immediately
Repeat CBC and PT 2-3 days and 5-7 days after discharge
IF LATE HEMATOLOGIC TOXICITY OCCURS YOU MAY NEED TO RETREAT
BUT WILL NEED TO CALL POISON CONTROL AT 1-800-222-1222
Delayed serum sickness
Type III IgG/IgM mediated immune complex deposition
Urticaria, fever, arthralgias, myalgias, malaise
Rarely severe
8-10% of patients have this
More common the more vials used
Treat with moderate steroids until symptoms resolve,
then taper over 7-10 days. Also antihistamines if needed.
PITFALLS TO AVOID
Careful to not over diagnose compartment syndrome
Do not chase abnormal labs with blood products
Low platelets or elevated PT responds to antivenin
If significant bleed present, blood products are indicated
Do not give excess antivenin unless indicated
Fasciculations are common but no not need extra antivenin
Decreasing platelets do not need platelets, but may or may
not need extra antivenin
Have a low threshold to intubate anyone with bite near
then head or neck or who is having any angioedema