I. Epidemiology: Incidence
A. Total: 45,000 snake bites in U.S. per year
B. Venomous bites: 8000 in U.S. per year
C. Deaths from snake bite in U.S.: 12 or less per year
D. Envonomation occurs in 75% of U.S. poisonous snakebites
II. Etiology: U.S. Poisonous snakes
A. Coral Snakes (Family Elapidae)
1. Nonaggressive snakes of the southern U.S.
2. Transfer venom via chewing instead of injection
B. Pit Vipers or Crotalidae (99% U.S. venomous bites)
1. Rattlesnake (Crotalus or Sisturus genera)
a. Most common poisonous snake in U.S.
b. Potent venom
c. Responsible for 95% of deaths (esp.
2. Cottonmouth, water moccasin (Agkistrodon piscivorous)
a. Aggressive water snakes in Southeastern U.S.
b. Moderately potent venom
3. Copperhead (Agkistrodan contortix)
a. Least potent venom
III. Signs and Symptoms: Pit Vipers (except Mojave rattler)
A. Long movable fangs cause skin puncture marks
B. Venom alters Coagulation Factors, tissue necrosis
1. Immediate pain and burning at bite site
2. Within a few minutes redness and swelling develops
3. Bite site develops a purplish discoloration
C. Generalized symptoms (Hemotoxic effects)
1. Nausea and Vomiting
4. Sweats and chills
5. Metallic or rubbery taste in mouth
D. Systemic complications
1. Disseminated Intravascular Coagulation (DIC)
2. Acute Renal Failure
3. Hypovolemic shock (7% of cases)
1. Not immediately fatal unless envenomation into vein
IV. Signs and Symptoms: Coral Snakes
A. Small fixed fangs cause tiny semicircular scratches
B. Venom contains a Neurotoxin
C. Generalized symptoms may be delayed 1-8 hours
1. Drowsiness, Weakness
2. Paresthesias with numbness at bite site
3. Blurred vision
4. Slurred speech
D. Systemic complications
2. Cardiac arrest or respiratory arrest may occur
V. Management: First Aid in field
A. Get to a medical facility as soon as possible
B. Calm and reassure patient
C. Attempt to identify snake type from a distance
1. Do not try to capture the snake for Identification
D. Do not leave a patient alone
E. Have the patient lie down
F. Immobilize bite area below the level of the heart
G. Remove jewelry or clothing that tighten with swelling
H. Clean the bite area with soap and water
1. Apply antiseptic solution and gauze if available
I. Use a venom extractor device within 5 minutes of bite
1. Do not cut wound or try to suck out venom
2. Use vacuum-suction device to extract venom
3. Venom extractor left in place for 30 minutes
4. Avoid harmful methods (see below) at bite site
J. Low pressure constriction band
1. Indicated if medical assistance is >1 hour away
2. Wrap a band (ACE, belt, sock) 2-3 inches above bite
a. Band should be wide and flat
b. Band applied between bite site and heart
3. Do not cut off arterial circulation
a. Pressure: 20 mmHg
b. Be able to slip a finger between band and skin
4. Leave band in place until medical facility
A. Blood Type and cross match
C. Chemistry panel (e.g. Chem8)
1. Renal Function tests (BUN and Creatinine)
2. Serum electrolytes
3. Serum Glucose
D. Liver Function Tests
E. Coagulation Factors (draw baseline and at 12 hours)
1. Complete Blood Count with Platelet Count
2. Prothrombin Time (PT)
3. Partial Thromboplastin Time (PTT)
5. Fibrin Degradation Products
F. Other studies that may be indicated
1. Electrocardiogram (EKG)
2. Arterial Blood Gas (ABG)
VII. Management: Emergency Department
A. See Snake Antivenin
B. Contact poison control immediately
C. Clean wound
D. Tetanus Toxoid or immune globulin if underimmunized
E. Do not draw blood or start IV in affected extremity
F. Start intravenous fluids
G. Prophylactic antibiotics are not recommended
H. Suspected pit viper bite management
1. Observe asymptomatic patients 12 hours after bite
2. Mark leading edge of bite site swelling q30 minutes
3. Indications for discharge
a. No proximal spread of extremity findings
b. Normal laboratory studies
c. Patient able to return immediately for worsening
I. Suspected coral snake bite management
1. Observe asymptomatic patient for at least 24 hours
2. Requires immediate treatment and antivenin
VIII. Avoid harmful methods
A. Do not cut skin at bite site
B. Fasciotomy is rarely indicated
1. Compartment Syndrome may be controlled by antivenin
2. Only Consider if hourly serial ICP >30 mmHg
C. Do not use electric shock or stun gun at bite site
D. Do not apply tightly constricting tourniquet
E. Do not administer antivenin in the field
1. Risk of Anaphylaxis
A. On coming upon a snake:
1. Slowly and quietly move away, and allow it to escape
2. Do not expect a warning before they strike
a. Most snakes do not hiss or rattle before striking
3. Do not handle any snake (even if snake appears dead)
B. Be alert in areas commonly inhabited by snakes
1. Hiking, picnicking, camping and firewood areas
2. Water areas
3. Tall grass, underbrush, abandoned buildings
4. Piles of logs, rocks, and branches
C. Be careful of areas of decreased visibility
1. Avoid reaching into holes and crevices
2. Avoid jumping over logs and fences
3. Pull logs or rocks toward you when turning over
4. Avoid placing fingers under objects being lifted
D. Prepare for a hike
1. Wear boots and long pants
2. Carry a flashlight for nighttime conditions
3. Hike with a companion
E. Reduce residential risks of snake bite
1. Provide lighting for yard, sidewalks, and patio
2. Keep yard mowed and bushes pruned
3. Keep home free of mice
The Clinical Management of Snake Bites in the South East Asian Region
Conclusions and main recommendations
It is clear that in many parts of the South East Asian region, snake bite is an important medical
emergency and cause of hospital admission. It results in the death or chronic disability of many
active younger people, especially those involved in farming and plantation work. However, the
true scale of mortality and acute and chronic morbidity from snake bite remains uncertain
because of inadequate reporting in almost every part of the region.
To remedy this deficiency, it is strongly recommended that snake bite should be
made a specific notifiable disease in all countries in the South East Asian region.
Snake bite is an occupational disease of farmers, plantation workers, herdsmen, fishermen and
other food producers. It is therefore a medical problem that has important implications for the
nutrition and economy of the countries where it occurs commonly.
It is recommended that snake bite should be formally recognised as an
important occupational disease in the South East Asian region.
Despite its importance, there have been fewer proper clinical studies of snake bite than of almost
any other tropical disease. Snake bites probably cause more deaths in the region than do
Entamoeba histolytica infections but only a small fraction of the research investment in
amoebiasis has been devoted to the study of snake bite.
It is recommended that governments, academic institutions, pharmaceutical,
agricultural and other industries and other funding bodies, should actively
encourage and sponsor properly designed clinical studies of all aspects of snake
Some ministries of health in the region have begun to organise training of doctors and other
medical workers in the clinical management of snake bite patients. However, medical personnel
throughout the region would benefit from more formal instruction on all aspects of the subject.
This should include the identification of medically-important species of snake, clinical diagnosis
and the appropriate use of antivenoms and ancillary treatments.
It is recommended that education and training on snake bite should be included
in the curriculum of medical schools and should be addressed specifically
through the organisation of special training courses and other educational
Community education on snake bite is outside the terms of reference of this publication. However,
it is clear that this is an essential component of any community programme for prevention of
Community education about venomous snakes and snake bite is strongly
recommended as the method most likely to succeed in preventing bites.
Most of the familiar methods for first-aid treatment of snake bite, both western and
quot;traditional/herbalquot;, have been found to result in more harm (risk) than good (benefit). Their use
should be discouraged and they should never be allowed to delay the movement of the patient to
medical care at the hospital or dispensary.
Recommended first-aid methods emphasise reassurance, immobilisation of the
bitten limb and movement of the patient to a place where they can receive
medical care as soon as possible.
Diagnosis of the species of snake responsible for the bite is important for optimal clinical
management. This may be achieved by identifying the dead snake or by inference from the
quot;clinical syndromequot; of envenoming.
A syndromic approach should be developed for diagnosing the species
responsible for snake bites in different parts of the region.
Antivenom is the only effective antidote for snake venom. However, it is usually expensive and in
short supply and its use carries the risk of potentially dangerous reactions.
It is recommended that antivenom should be used only in patients in whom
the benefits of treatment are considered to exceed the risks. Indications for
antivenom include signs of systemic and/or severe local envenoming.
Skin/conjunctival hypersensitivity testing does not reliably predict early or
late antivenom reactions and is not recommended.
It is recommended that whenever possible antivenom should be given by
slow intravenous injection or infusion.
Epinephrine (adrenaline) should always be drawn up in readiness in case of
an early anaphylactic antivenom reaction.
Subcutaneous epinephrine (adernaline) may reduce the incidence of early
antivenom reactions if given immediately before the start of antivenom
When no antivenom is available judicious conservative treatment can in many
cases save the life of the patient.
In the case of neurotoxic envenoming with bulbar and respiratory paralysis
antivenom alone cannot be relied upon to prevent early death from
asphyxiation. Artificial ventilation is essential in such cases. In countries
where neurotoxic envenoming is common
more doctors should be trained to carry out endotracheal intubation and
mechanical ventilators should be available in major hospitals.
Conservative management and, in some cases, dialysis, is an effective
supportive treatment for acute renal failure in victims of Russell’s viper,
saw-scaled viper and sea snake bites.
Fasciotomy should not be carried out in snake bite patients unless or until
haemostatic abnormalities have been corrected, clinical features of an
intracompartmental syndrome are present and a high intracompartmental
pressure has been confirmed by direct measurement.
Last update: 05 October 2005
FIGURE 1. Rattlesnake tail. The rattle is the FIGURE 3. Cottonmouth or water moccasin
hallmark of Crotalus and Sistrurus genera of (Agkistrodon piscivorous).
the Crotalidae (“pit viper”) family of snakes.
FIGURE 2. Copperhead snake (Agkistrodon
tlesnakes, genera Crotalus and Sistrurus (Fig-
ure 1); copperheads, Agkistrodon contortrix
(Figure 2); and cottonmouths, or water moc-
casins, Agkistrodon piscivorous (Figure 3).
These snakes are referred to as pit vipers
because of small, heat-sensitive pits between
the eye and the nostril that allow them to
sense their prey.
Because of their widespread distribution
and relatively potent venom, rattlesnakes are FIGURE 5. Coral snakes (Micrurus species) are
responsible for the majority of fatalities from a less common cause of snakebites in the
snakebites; eastern and western varieties of
diamondback rattlesnakes account
for almost 95 percent of these deaths.3 Bites the family elapidae (Figure 5) are responsible
from copperhead snakes, which are common for a minority of snakebites in the United
in the eastern United States, seldom require States. Native to the deep South, their terri-
antivenin therapy because they have the least tory extends west to Arizona. Coral snakes are
potent venom and a negligible fatality rate. secretive and nonaggressive; they seldom bite
Cottonmouths, or water moccasins, are unless provoked. Their venom is transferred
aggressive semi-aquatic snakes native to the by chewing rather than by injecting. Coral
southeast; they have an intermediate-potency snake bites, although rare, are easy to miss,
venom. Coral snakes of the Micrurus genus in and often present as painless, tiny puncture
1368 AMERICAN FAMILY PHYSICIAN www.aafp.org/afp VOLUME 65, NUMBER 7 / APRIL 1, 2002
wounds with negligible surrounding tissue
change. Because of their widespread distribution and relatively potent
Although exotic snakes account for only a venom, rattlesnakes are responsible for most fatalities from
small percentage of venomous snakebites,7
snakebites in the United States.
the prevalence of these bites is increasing as
the popularity of keeping exotic snakes as
house pets continues to rise.
lation, acute renal failure, hypovolemic shock,
Snake Envenomation and death. Renal failure is a common cause of
Snake venoms can be classified as hemo- delayed mortality from untreated snakebites
toxic (attacking tissue and blood) and neuro- in developing parts of the world. Immediately
toxic (damaging or destroying nerve tissue). life-threatening conditions such as hypoten-
Pit viper snake venoms are hemotoxic, except sion or shock occur in only about 7 percent of
for some Mojave rattlers. Contrary to public envenomations.7
perception, pit viper bites are not immedi- The venoms of coral snakes, exotic elapids
ately fatal unless the venom enters a vein and some Mojave rattlesnakes are neurotoxic
directly. The venom consists of proteins, and usually cause local numbness instead of
polypeptides, and enzymes that cause necro- pain and swelling, with the risk of cranial
sis and hemolysis. Most crotalid venoms nerve palsies, respiratory paralysis, and death.
damage capillary endothelial cells, resulting Symptoms of neurotoxic envenomations are
in third spacing of plasma and extravasation listed in Table 2. Systemic reactions are diffi-
of erythrocytes.8 cult to reverse once they develop.
Pit viper bites classically appear as two fang
punctures (one or three puncture wounds Snakebite First Aid
occur, but rarely) with local swelling and In recent years, first aid measures for
necrosis. Extremity bites are rarely compli- snakebites have been radically revised to
cated by infection and compartment syn- exclude methods that were found to worsen a
drome, and prophylactic fasciotomies often patient’s condition, such as tight (arterial)
do more harm than good.
Clinical effects of snakebites range from
mild local reactions to life-threatening sys- TABLE 2
temic reactions, depending on the species and Symptoms of Snakebite Envenomation
size of the snake involved; the location of the
bite(s); the volume of venom injected; and Hemotoxic symptoms Neurotoxic symptoms
the age, size, and health of the victim. Chil- Intense pain Minimal pain
dren are more likely to suffer significant mor- Edema Ptosis
bidity and mortality because they receive a Weakness Weakness
Swelling Paresthesia (often numb
larger envenomation relative to body size.9
Numbness or tingling at bite site)
Most pit viper bites are painful within five
Rapid pulse Diplopia
minutes and soon display local swelling. Ecchymoses Dysphagia
Symptoms of hemotoxic envenomation are Muscle fasciculation Sweating
listed in Table 2. Significant hypofibrinogen- Paresthesia (oral) Salivation
emia and thrombocytopenia lasting up to two Unusual metallic taste Diaphoresis
weeks may occur after envenomation by Vomiting Hyporeflexia
North American pit vipers.10 Confusion Respiratory depression
Systemic reactions include a syndrome Bleeding disorders Paralysis
similar to disseminated intravascular coagu-
APRIL 1, 2002 / VOLUME 65, NUMBER 7 www.aafp.org/afp AMERICAN FAMILY PHYSICIAN 1369
left in place for 30 minutes.5 Although electric
First-aid measures for snakebite include avoiding excessive shock (often with a stun gun) has been a
activity, immobilizing the bitten extremity, and quickly trans- popular treatment for snakebite in develop-
ing countries, it should be avoided as it is a
porting the victim to the nearest hospital.
potentially hazardous intervention that has
never been shown to be effective.14
An attempt should be made to identify the
tourniquets, aggressive wound incisions, and type of snake from a safe distance; however,
ice. Initial treatment measures should include no attempt should be made to capture or kill
avoiding excessive activity, immobilizing the the snake. Even if the snake is dead, it should
bitten extremity, and quickly transporting the not be picked up with the hands because
victim to the nearest hospital.11 envenomation by reflex biting after death of
A wide, flat constriction band may be the snake has been reported.15
applied proximal to the bite to block only Equine-derived antivenin to snake venom
superficial venous and lymphatic flow (typi- is not recommended for the formularies of
cally, with about 20 mm Hg pressure) and standard emergency medical services because
should be left in place until antivenin therapy, of the potential for life-threatening allergic
if indicated, is begun. One or two fingers reactions from the antivenin and the length of
should easily slide beneath this band, since any time required for reconstitution (up to
impairment of arterial blood flow could 60 minutes).16 As safer products, such as Cro-
increase tissue death. Upper extremities talidae Polyvalent Immune Fab (Ovine; Cro-
should be splinted as close to a gravity-neutral Fab), become more commonplace, antivenin
position as possible, preferably at heart level. administration in the field may become more
No study has shown any benefit in survival feasible, especially in remote areas.
or outcome from incision and suction.11-13
However, a venom extractor can be beneficial Treatment
if applied within five minutes of the bite and Patients with snakebite must be admitted to
an emergency department, where a poison
control center should be contacted immedi-
TABLE 3 ately. Wounds should be cleaned, and admin-
Laboratory Evaluation in Snakebite istration of tetanus toxoid or tetanus immune
globulin should be considered for under-
Complete blood count with platelets Platelet count immunized or nonimmunized patients. Pa-
and differential* Liver function tests tients should be given intravenous fluid, and
Prothrombin time* Bilirubin blood should be drawn from an unaffected
Partial thromboplastin time* Creatine kinase
extremity. Complete recommendations for
Fibrin degradation products* Urinalysis† laboratory evaluations of snakebite are sum-
Blood type and cross match Stool hemoccult marized in Table 3. At least 25 percent of
Serum electrolytes Electrocardiography‡ snakebites do not result in envenomation.
Glucose Arterial blood gas§ Patients with asymptomatic pit viper bites
Blood urea nitrogen
should be observed for at least 12 hours before
discharge.8 When envenomation does occur,
*—Should be performed as soon as possible and repeated within 12 hours.
the leading edge of the swelling should be
†—Including free protein, hemoglobin, and myoglobin.
‡—Suggested for patients older than 50 years and patients with a history of marked, the time of observation recorded, and
heart disease.11 the circumference of the extremity measured
§—Should be tested if any signs or symptoms of respiratory compromise are evident. every 30 minutes.17 If there is no proximal
progression of local signs on the extremity
1370 AMERICAN FAMILY PHYSICIAN www.aafp.org/afp VOLUME 65, NUMBER 7 / APRIL 1, 2002
and no coagulopathy after 12 hours of clinical
observation and serial laboratory examina- Equine-derived antivenin to snake venom has been the main-
tions, a reliable patient can be sent home. stay of hospital treatment for venomous snakebites.
The patient should be given strict instruc-
tions to return to the hospital immediately if
any of the following occurs: increase in pain
or onset of redness or swelling; fever; epi- bites in October 2000; its use is still limited
staxis; bloody or dark urine; nausea or vomit- because of availability and expense, but it is
ing; faintness; shortness of breath; diaphore- likely to soon replace the equine crotalid
sis; or other symptoms except mild pain at the antivenin. A prospective trial using CroFab
bite site.8 Prophylactic antibiotics are usually reports only a 14.3 percent incidence of acute
not recommended, as the occurrence of reaction, and nearly all events were mild to
wound infection following crotalid enveno- moderate.20 Experience with CroFab is still
mation is low (3 percent).18,19 too limited to support the conclusion that
Patients with bites from snakes with neuro- serious allergic reactions like anaphylaxis will
toxic venom should be observed for at least never occur with its administration.
24 hours. A patient with suspected enveno- Eastern coral snakebites require Antivenin
mation by the eastern coral snake needs (Micrurus fulvius). The specific antivenin for
immediate treatment with an appropriate exotic snakebites may be acquired from the
antivenin, and necessary resuscitation mea- Arizona Poison and Drug Information Center
sures should be implemented. (520-626-6016). An antivenin index is avail-
able from the American Zoo and Aquarium
Antivenin Indications and Administration Association (301-562-0777) and the American
Equine-derived antivenin to snake venom Association of Poison Control Centers (800-
has been the mainstay of hospital treatment 222-1222).22 A prescription is required to
for venomous snakebite for 35 years.20 It is obtain U.S. antivenin, and a permit is needed
used to treat approximately 75 percent of the to import antivenin not held domestically.23
venomous snakebites inflicted annually in the Ideally, antivenin is administered within
United States.5 The majority of snakebite vic- four hours of the snakebite, but it is effective
tims in the United States reach a medical for at least the first 24 hours. Physicians
facility within 30 minutes to two hours of should be present for antivenin administra-
being bitten and can be given antivenin at an tion, and epinephrine and antihistamines
early stage.3 (both histamine H1 and H2 receptor blockers)
For rattlesnake, cottonmouth, and copper- should be at the bedside.
head bites, Antivenin (Crotalidae) Polyvalent Performing a skin test with horse serum is a
(ACP) has been the standard available treat- matter of controversy because it delays ther-
ment; however, ACP is known to be highly apy, has itself caused anaphylaxis and serum
allergenic because of its equine origin and sickness,24,25 and has been demonstrated to
may pose a greater risk to the patient than the have a 10 to 36 percent false-negative rate21,26
snakebite.21 In retrospective studies,20 rates for and a 33 percent false-positive rate.21 Some
acute allergic reactions (including hypoten- physicians believe that medicolegal issues
sion and anaphylaxis) after ACP administra- mandate that this test be performed before
tion range from 23 to 56 percent, with even antivenin administration except in extreme
higher rates for delayed serum sickness. emergencies.27 Other physicians bypass skin
The ovine (sheep-derived) antivenin, Cro- testing altogether, relying instead on premed-
Fab, received approval by the U.S. Food and ication with antihistamines and a trial dose of
Drug Administration for treatment of snake- 5 mL of antivenin administered intravenously.
APRIL 1, 2002 / VOLUME 65, NUMBER 7 www.aafp.org/afp AMERICAN FAMILY PHYSICIAN 1371
In the event of a significant skin-test reac- administration. Reconstitution can take up to
tion, antivenin would be reserved for use in 60 minutes and should be initiated immedi-
only the most severe cases and should only be ately when the patient arrives in the emer-
given with careful monitoring, hydration, and gency department. ACP can be reconstituted
premedication with antihistamines.An alterna- by injecting 10 mL of supplied sterile water
tive to skin testing is to premedicate all patients diluent into each vial and swirling (not shak-
who will receive equine antivenin.28 Suggested ing) to mix, or by diluting 10 vials of antivenin
intravenous antihistamine pretreatment is in 1 L of normal saline. The reconstituted
diphenhydramine (Benadryl), in a dosage of 1 antivenin (amount will vary, depending on
mg per kg, and cimetidine (Tagamet), in a amount required) is then diluted in 500 mL of
dosage of 6 mg per kg.8 If signs or symptoms of normal saline or 5 percent dextrose in water,
anaphylaxis develop, the patient should be and a trial dose of 5 to 10 mL is administered
immediately treated with epinephrine and intravenously over five minutes. If no reaction
steroids.8 Unstable patients (i.e., those with occurs, the rate should be adjusted to give up
hypotension, severe coagulopathy, respiratory to 10 vials in the first hour. Additional infu-
distress) must receive antivenin because no sions should be given every two hours until
other treatment can reverse the venom’s effect. signs and symptoms are resolving.
The unpredictable nature of snakebites In contrast, the safer CroFab is given as a
often makes assessment and management large initial dose to control the envenoma-
difficult. Progressive local injury (swelling, tion, and smaller subsequent doses are given
ecchymosis), a clinically evident coagulation as needed. In one study,20 a total of three to 12
abnormality, or systemic effects (hypoten- vials of CroFab were given for initial control,
sion, altered mental status) are strong indica- and additional two-vial doses were given at
tions for antivenin treatment. Withholding six, 12, and 18 hours.
antivenin is recommended in patients with For any eastern coral snake bite with possi-
milder envenomations.21 The decision to use ble envenomation, three to five vials of
antivenin requires a careful analysis of the Antivenin (Micrurus fulvius) should be
risks and benefits. administered immediately. If systemic mani-
festations are present, at least six to 10 vials
ADMINISTRATION OF ANTIVENIN should be administered. One exception is the
Both ACP and CroFab are provided as dry Arizona coral snake (Micruroides), which is
powders and require reconstitution before not associated with human fatality and for
which no antivenin exists.
Immediate hypersensitivity reactions to
any antivenin should be managed with epi-
The Authors nephrine, antihistamines and supportive care
GREGORY JUCKETT, M.D., M.P.H., is associate professor in the Department of Family to protect the respiratory and cardiovascular
Medicine at West Virginia University School of Medicine, Morgantown. He received a systems. Serum sickness, which commonly
medical degree from Pennsylvania State University College of Medicine, Hershey, and a
master’s degree in public health from West Virginia University. He completed a family occurs one to four weeks after administration
medicine residency at the Medical University of South Carolina, Charleston. Dr. Juckett of antivenin, presents with pruritus, urticaria,
is a diplomate in tropical medicine of the American Society of Tropical Medicine and fever, and arthralgias. Serum sickness can be
Hygiene and coordinates the International Travel Clinic at West Virginia University.
successfully treated with systemic steroids.
JOHN G. HANCOX, M.D., is an intern in internal medicine and psychiatry at West Vir-
ginia University School of Medicine, where he received his medical degree. He will begin GRADING THE SEVERITY OF THE BITE
a dermatology residency at Wake Forest University, Winston-Salem, N.C., in July 2002.
A popular scale for grading the severity of
Address correspondence to Gregory Juckett, M.D., M.P.H., West Virginia University
School of Medicine, Robert C. Byrd Health Sciences Center, Morgantown, WV 26506 pit viper bites and estimating the antivenin
(e-mail: firstname.lastname@example.org). Reprints are not available from the authors. dose is presented in Table 4. It is important to
1372 AMERICAN FAMILY PHYSICIAN www.aafp.org/afp VOLUME 65, NUMBER 7 / APRIL 1, 2002
Grading Scale for Severity of Snake Bites
envenomation Presentation Treatment
0. None Punctures or abrasions; some pain or tenderness Local wound care, no antivenin
at the bite
I. Mild Pain, tenderness, edema at the bite; perioral If antivenin is necessary, administer
paresthesias may be present. about five vials.*
II. Moderate Pain, tenderness, erythema, edema beyond the Administration of five to 15 vials
area adjacent to the bite; often, systemic of antivenin may be necessary.
manifestations and mild coagulopathy
III. Severe Intense pain and swelling of entire extremity, Administer at least 15 to 20 vials
often with severe systemic signs and symptoms; of antivenin.
IV. Life-threatening Marked abnormal signs and symptoms; severe Administer at least 25 vials of
*—Because of their less potent venom, grade-I copperhead bites are usually not treated with antivenin.
remember that a patient must have serial measured compartment pressures exceeding
evaluations, because an envenomation that 30 mm Hg. These criteria should be present
appears to be mild on presentation can soon despite elevation of the affected limb and
exhibit the hallmarks of a severe envenoma- administration of 20 vials of antivenin.8 In an
tion. Doses of antivenin must not be reduced animal study,29 the best outcome in subjects
for children or small persons, since the with compartment syndrome was achieved
amount of venom that needs to be neutral- with the administration of antivenin alone. In
ized is the same. a series of 1,257 cases of extremity bites, only
two fasciotomies were necessary.12
Although once popular, surgical interven- Prevention
tion with fasciotomy for venomous snakebite Physicians should educate their patients on
is now reserved for selected rare cases and ways to prevent snakebites, as prevention is
should never be performed prophylactically. far preferable to treatment. Many bites can be
The local and systemic effects of crotaline easily prevented by using common sense. For
venom closely resemble the signs and symp- some precautions against snakebites, see the
toms of compartment syndrome15 and can- accompanying patient information handout on
not be reliably diagnosed in an envenomated page 1377.
patient without directly measuring the com-
partment pressure. The photographs in Figures 1 through 4 were pro-
vided by James G. Arbogast, M.D., West Virginia Uni-
Fasciotomy should only be performed in
versity School of Medicine, and John N. Casto, M.D.
patients with clinical signs and symptoms of is in private practice in Ridgely, WV.
compartment syndrome (i.e., pain on passive
stretch, hypoesthesia, tenseness of compart- The authors indicate that they do not have any con-
ment, and weakness) and hourly, serially flicts of interest. Sources of funding: none reported.
APRIL 1, 2002 / VOLUME 65, NUMBER 7 www.aafp.org/afp AMERICAN FAMILY PHYSICIAN 1373
REFERENCES treatment for rattlesnake envenomation. Ann
Emerg Med 1991;20:659-61.
1. Snyder CC, Knowles RP. Snakebites. Guidelines for 15. Suchard JR, LoVecchio F. Envenomations by rat-
practical management. Postgrad Med 1988;83:52- tlesnakes thought to be dead. N Engl J Med
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1374 AMERICAN FAMILY PHYSICIAN www.aafp.org/afp VOLUME 65, NUMBER 7 / APRIL 1, 2002