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