Snakebite%2025%20 August%202004

1. ACTIVITY: Navy Operational Medical Lessons Learned Center
DATE: 25 August 2004
ORIGINATOR: J.W. Rose, M.D., M.P.H., CAPT, MC (FS) (ret)
PHONE: (904) 886-2711
E-MAIL: jwrose@nomi.med.navy.mil
TITLE: SOAP NOTE “TREATMENT FOR SNAKEBITE IN US NAVAL UNITS
DEPLOYED ASHORE AND THE USE OF ANTIVENIN”
Situation: A few US Naval Medical personnel who deployed ashore in Kuwait and Iraq
during Operation Iraqi Freedom, Phase I, observed that “selected USN medical units forward
deployed in direct support of ground combat elements should have venomous snake antitoxin
in order to initiate immediate treatment of venomous snakebites.”
Observation: The US Military Medical Officers and Epidemiologists consulted on this issue
determined it is NOT a good Force Health Protection measure to provide antitoxin (antivenin)
to Hospital Corpsmen and Medics and Level I and II medical care units. All did agree that,
although venomous snakebite have posed a small-to-moderate medical threat to modern
militaries worldwide, the threat can be reduced by medical planning which must include:
• Briefing preventive (snake avoidance) measures before and during deployments to areas in
which venomous snakes live.
• Ensuring personnel are trained and equipped to provide first aid to victims known or
suspected to have been bitten by a venomous snake
• Establishing a dedicated casualty evacuation plan for the area of operations that ensures
known or suspected snakebite victims are rapidly transferred from the field to a ICU-
capable medical treatment facility capable of administering species-specific or polyvalent
antitoxin, if indicated, and diagnosing and treating life-threatening complications of the
venom itself and possible allergic reactions to any antitoxin administered.
A more detailed discussion is in order:
• First, although envenomation can be a life-threatening emergency and the care and
evacuation of victims of poisonous snakebite must be planned for in U.S. Military operations
in areas where poisonous snakes or arthropods are found, poisonous snakebite has not been a
major medical problem for U.S. Forces:
- Per discussions in April 2004, with the Mortality Surveillance Division, Office of the
Armed Forces Medical Examiner, Armed Forces Institute of Pathology (AFIP), in the
U.S. Military, snakebites are not a significant cause of mortality in U.S. active duty
personnel in the continental United States and overseas, and only a rare cause of
hospitalization:
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2. - - There have been no U.S. Military deaths due to snakebite over the last six years,
according to the DOD Mortality Register, which contains detailed cause and manner
of death of all U.S. active duty personnel since 1998.
- - There have been no reported U.S. Military deaths due to snakebite since 1978, as
indicated by the AFIP mortality files, which contain “unusual cases” and all
autopsies performed by Armed Forces Medical Examiner – approximately 1/3 of all
active duty deaths.
- - From 1994 to 2003, four U.S. active duty personnel (two Air Force, two Marine
Corps) were admitted to U.S. Military medial treatment facilities (MTF) for
snakebite (ICD-9 Code: 905.0), as determined by a review of the DOD Medical
Surveillance System.
[Note: The U.S. Military physicians consulted on this issue are “pretty sure that some
bites never make into the DOD Medical Surveillance System.” For instance, one USAF
physician was involved in the treatment of two snakebite injuries at Eglin AFB from
1997-2001: one involved an Army Ranger Instructor bitten by a “Timber Rattler” at the
Ranger Jungle School on the Eglin reservation; the other was an Air Force Combat
Controller who was bitten by his “pet Western Diamondback.” The same physician also
treated an Airman at Brooke Army Medical Center in 2002. The four snakebites
indicated above as being recorded in the DOD Medical Surveillance System could
include these two USAF personnel, but would not include the USA Ranger.]
Likewise, data shows that venomous snakebites have posed a small-to-moderate medical
problem to modern militaries worldwide:
- A retrospective study of soldiers in field units of the Israeli Defense Forces between
the years 1993-1997 reports a yearly rate of 32-52 (mean 43.6) physician visits per
100,000 soldier years for snakebites – and 1370-1729 (mean 1478) physician visits per
100,000 soldier years for arthropod bites. There were no fatal envenomations during the
study period. The paper does not indicate the extent of physician intervention, the
number of evacuations, or the number of bites that required antivenin. The authors do
conclude that poisonous animals pose a significant threat to field soldiers, in that their
bites are painful, often debilitating and potentially life-threatening. [Haviv et al,
“Poisonous Animal Bites in the Israeli Defense Forces,” Public Health Review (Israel)
1998; 26: 237-245.] They and other authors conclude this threat can be reduced by
proper common-sense preventive measures and that such measures should be stressed
during Force Health Protection briefings before and during operations in areas where
poisonous snakes live. The preventive measures advocated include:
- Do not enter snake-infested areas without adequate protective clothing: calf-high
footwear, thick socks and fully-extended pant legs – full-length sleeves rolled down and
gloves only offer partial protection.
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3. - Do not put hands or feet in places that cannot be seen clearly, and do not put them in
places without first looking
- Do not overturn or lift rocks, boulders or fallen branches or trees with unaided
hands; use entrenching tools or sticks or some other tool or use your foot if your ankle
and leg are properly protected; use careful techniques for digging fighting holes and
trenches and filling sandbags
- Do not step over an obstacle (log, bush or boulder) if the other side is not visible;
rather, step on the obstacle and ensure it is safe before stepping down
- Do not sit down before looking around carefully
- Do not put sleeping bags near rocks, rubbish plies or cave entrances
- Do not handle, antagonize or otherwise disturb snakes
- Do not handle freshly killed venomous snakes.
[Murdock et al, “Prevention and Emergency Field Management of Venomous Snakebites
during Military Exercises,” Military Medicine, 1990; 155, 12:587; Ismail and Memish,
“Venomous Snakes of Saudi Arabia and the Middle East; a keynote for travelers,
International Journal of Antimicrobial Agents, 2003, 21: 164-169.]
[Note: One U.S. Military physician stressed that the majority of snakebites in the U.S.
involve young adult males who are bitten while “playing” with the snake. Alcohol is
frequently involved. His experience in “treating more than 50 snakebite victims over the
years has been that most victims (approximately 40 of 50) were intoxicated and messing
with the snake.” His number one rule in preventing snakebites in young active duty
males is: “Don’t Mess With The Snake!”]
• Second, although all bites by poisonous snakes must be considered medical emergencies
until it is proven that envenomation has not occurred, many such bites will prove not to be life
threatening - no envenomation occurs in approximately 20% of documented bites by New-
World pit vipers - rattlesnake, copperhead, water moccasin, and fer-de-lance. An even higher
percentage of bites inflicted by other snake families (e.g., up to 50% for cobras and 75% for
sea snakes) are “dry.” [Harrison’s Principles of Internal Medicine, 15th Edition, 2001; 2616-
2617.] This is due to the circumstances of the bites, which are usually defensive in nature,
and the species of the snake - some having more prominent fangs, or being more aggressive
biters and more likely to envenomate than others. In a one-year (July 1999-July 2000)
prospective study of snake bites in Australia, which has 40% of the world’s neurotoxic snakes
and 23% of all venomous snakes, 70 patients from the general population admitted to the
emergency department with a diagnosis of snake bite, 35 (36%) had no signs of
envenomation; of the remaining 45, only three (4.3%) were considered severe and required
antivenin. [Isbister and Curry, “Suspected Snakebite: One Year Prospective Study of
Emergency Department Presentations,” Emergency Medicine (2003), 15, 160-169.]
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4. [Note: All U.S. Military physicians consulted agree that snakebite in the field must be
considered a medical emergency until it is PROVEN that the bite was a “dry strike” or a
hit from a non-venomous snake; that is, given snakebite in the field, it best to assume
that envenomation has occurred. This DOES NOT mean to give antivenin every time.
Indeed, antivenin should be given only when there are appropriate clinical signs and
symptoms. It DOES mean that “medical planning should include rapid evacuation to a
medical facility with ER or ICU capability where the casualty can be observed for at
least six-to-eight hours in the case of New-World pit viper or Old-World viper bites, and
up to 24 hours for Elipidae family bites (cobras and coral snakes) and Hydrophidae
Family bites (sea snakes).]
• Third, healthy young adults are most likely to survive envenomation – with the likelihood
of survival increasing with proper first aid and rapid transport to a high-level medical
treatment facility where intensive care can be rendered and species-specific antivenin can be
administered safely. In the United States, human mortality in the general population due to
snake envenomation remains low, where 20 of the more than 120 species of snakes are
poisonous:
- In 1994, Gold and Wingert estimated approximately 8,000 poisonous snakebites
annually, resulting in about nine to fifteen fatalities, [“Snake venom poisoning in the
United States: a review of therapeutic practice,” South Med J 1994; 87:579-589.]
- Langley and Morrow (1997) estimated 700-8000 bites per year, resulting in five to
six deaths, [“Deaths resulting from animal attacks in the United States,” Wilderness &
Environmental Medicine 1997; 8:8-16.]
Per Gold and Barish, “The ultimate severity of any venomous snakebite depends on the health
of the person bitten and the quantity and comparative toxicity of the venom injected. These
factors are determined by the size and species of the snake, the number and depth of fang
punctures, and the age, size, and underlying medical condition of the victim.” [“Venomous
Snakebites: current concepts in diagnosis, treatment and management,” Emergency Medical
Clinics of North America, 1992; 249-267.] All studies show that, although the preponderance
of American victims of snakebite are young (between 17-27 years of age), the majority of the
deaths occur in those with systemic disease and in the very young and very old - outside the
U.S. Military active duty age group. Worldwide, there are some 3000 identified species of
snakes, of which some 15% (450) are considered dangerous to humans. However, estimates
of death due to snakebite in general populations are either unavailable or highly unreliable, as
many serious envenomations and deaths occur in medically underserved or non-served
populations and areas.
• Fourth, it is virtually impossible to procure, distribute, and store potent species-specific
antivenin (for the different venomous snakes and arthropods in a given operating area) or
polyvalent antivenin at lower level medical units, forward deployed ashore in direct support of
ground combat elements. Dr. Otten, CAPT, MC, USNR, an Emergency Physician and
Toxicologist, University of Cincinnati, reports that, “In Desert Storm we deployed troops with
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5. antivenin for pit vipers (mostly New World rattlesnake, copperhead, water moccasin, fer-de-
lance), which was worthless because the antivenin was absolutely no good against any of the
snakes found in S.W. Asia.” [Otten, “Scenario Seven: Snakebite,” Wilderness &
Environmental Medicine, Volume 9, 99-103 (1998).]
• Fifth, a definitive diagnosis of snakebite poisoning requires identification of the snake and
signs and symptoms of envenomation. It is essential not to mistake autonomic reactions in
response to the bite for actual envenomation, thereby leading to unwarranted treatment.
[Harrison’s Principles of Internal Medicine, 15th Edition.] Unless the person who is bitten
knows the snake to be non-poisonous (e.g., the North American garter snake or king snake),
the initial symptom of snakebite is usually related to a “terror reaction,” characterized
typically by autonomic discharge: nausea, vomiting, diarrhea, dizziness, fainting, dyspnea,
tachycardia, and cold, clammy skin. Conversely a casualty may enter a stage of lethargy and
withdrawal.
[Note: The U.S. Military physicians who reviewed this paper agreed that such “terror
reactions” to bites by non-venomous snakes usually “sort themselves out early in the
clinical course.” The signs and symptoms characteristic of envenomation by the
families Viperidae (Old-World vipers that include puff adders, desert adders and true
vipers) and Crotalidae (New-World pit vipers such as the rattlesnake, copperhead, and
cottonmouth) result from the primarily hemotoxic effect of the venom: severe pain,
progressive swelling and ecchymosis beginning at the bite site, a metallic taste in the
mouth, ptosis, and thrombocytopenia.
[Note: The Mojave Rattlesnake (Crotalus scutalus) is a particularly dangerous species
for U.S Military personnel in the field in the U.S. Southwest. It is renowned over most
of its range – the desert of California, Nevada and Arizona and Mexico - for its ability to
inflict severe, even fatal, injury without any appreciable degrees if pain or swelling;
patients bitten by the Mojave Rattlesnake often do not exhibit these signs and symptoms
because its venom is more neurotoxic than that of the average pit viper.]
One expert regards bites by Elapids (cobras, mambas, craits, and coral snakes) as “clinically
more interesting,” in that, “Early on, it is difficult to determine if the nausea, dyspnea and
fainting are due to venom or fear. It is important to look for other neurological signs, and, if
any are positive, one must treat for a significant envenomation.”
• Sixth, MEDICAL PLANNING MUST PROVIDE for the rapid transfer of a proven
envenomation victim to a Level III or higher facility that can diagnose, monitor and treat life-
threatening emergencies (multiple organ and system failures) and administer large doses
(many vials) of species-specific or polyvalent antivenin. Planning must also provide for the
distribution to designated higher-level facilities of antivenin from a source approved by the
Commander of the Geographical Command.
[Note: U.S. Military physicians agree, “Yes! Medical planning must include the
capability to get these patients out of the field and to an ICU-capable facility ASAP!]
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6. • Finally, Administration of antivenin is the only effective treatment for moderate to severe
envenomations. Its effectiveness is both dose- and time-related, with its greatest effect
occurring during the first four hours. It is less effective after 12 hours, but has reversed
coagulopathies after 24 hours. [Gold, “Snake Venom Poisoning,” Conn’s Current Therapy,
1167-1170 (1999); Gold and Barish, Emergency Medical Clinics of North America, (1992).]
• Antivenins are derived from the serum of different animals: some countries use horses,
some use goats, others sheep. The original Wyeth Crotalid polyvalent antivenin was made
from horse serum; the newer CroFab Crotalid antivenin is derived from sheep and considered
the safer of the two in that it has a significantly lower incidence of severe allergic reactions.
However, it must be stressed that anyone administering antivenin must be alert to possible
immediate or delayed antivenin-precipitated anaphylactic reactions in 15-25% of patients.
They must also be prepared to deal with serum sickness days after administration of antivenin
which, in a retrospective study of snakebites in Arizona over a five-year period, occurred in
34%, 36%, 88% and 100% cases when patients received fewer than 20, 20 to 29, 30 to 39, or
40 or more vials of polyvalent antivenin respectively to presumed victims of Rattlesnake bites.
[Lo Vecchio et al, “Serum Sickness Following Administration of Antivenin (Crotalidae)
Polyvalent in 181 Cases of Presumed Rattlesnake Envenomation,” Wilderness &
Environmental Medicine, Volume 14, 220-221 (2003).] A snakebite expert at Loma Linda
lost a patient to snakebite last year, despite progressive, appropriate antivenin therapy. The
patient had a cerebral vascular attack (CVA) two days into his course of therapy. It remains
unknown if the CVA was due to the envenomation, the administration of antivenin, or just a
coincidence. Dr. Edward Otten notes, “The problems involved with using antivenin are much
more serious than the benefits of using them in the field.” [Otten, “Scenario Seven:
Snakebite,” Wilderness & Environmental Medicine, 1998, Volume 9, 99-103.]
Analysis/Mission Impact:
• Venomous snakebites do not occur in significant numbers in U.S Military personnel in the
United States or overseas. Many young American males of active duty age are bitten by
poisonous snakes while handling, antagonizing or attempting to kill the animals; in
approximately 50 percent of the cases, the young men have consumed alcohol.
• It is not practical to add species-specific or polyvalent antivenin to the Authorized Medical
Allowance List (AMMAL) of forward-deployed Level I and II medical facilities.
• Although the vast majority of venomous snake - and arthropod - bites sustained by US
Military personnel are not life-threatening, medical support plans for US combat forces should
include:
- Force Health Prevention briefings regarding snake avoidance and snakebite
prevention
- First responder training to evaluate bites to determine if poisoning has occurred, and,
when confronted with envenomation, provide effective first responder (tactical field)
care. The basic elements of first responder aid are:
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7. -- Move the victim and rescuers to a place of safety, keep the casualty as inactive as
possible to limit the systemic spread on venom, and rapidly transport them to
definitive medical care.
-- The injured part (usually a limb) should be immobilized in a functional position
below the level of the heart and a pressure wrap placed proximal to the bite – if it can
be placed within 30 minutes of the bite. The wrap should be just tight enough to
impede lymphatic flow, thereby delaying the systemic absorption and circulation of
the venom - but not so tight to restrict venous or arterial circulation. If placed,
pressure wraps should be left in place until arrival at the treating facility, probably
until after the administration of antivenin.
[Note: Some providers strongly advocate the use of pressure-immobilization techniques
only for snakebites caused by elapid or neurotoxic-predominant species. However, other
providers advocate pressure-immobilization for all venomous snakebites. Current
research projects addressing this issue are expected to be completed soon.]
[Note: Use of the Extractor Pump has been deleted from US SPECOPS protocols after
recent studies showed it is not effective and may, in some cases, cause severe necrosis at
the suction site. ]
-- Potentially constricting items, such as watches, rings, and tight clothing should be
removed prior to the onset of edema.
-- Do not give food, drink or aspirin-containing medicines; analgesia (e.g.,
morphine) may be required
-- During transport from the point of injury to Level I Care (e.g., a Battalion Aid
Station) the casualty must be given supportive care and reassurance that CASEVAC
to definitive care is forthcoming.
- En route care to definitive treatment in a Level III or higher medical facility capable
of administering large amounts of antitoxin and treating its complications and the
venom-induced multiple-organ failure.
- Medical Planning to that includes a tactical CASEVAC plan to support the timely
evacuation as indicated above.
- The source(s), approved by the U.S. Geographic Commander, from which snake and
arthropod antivenin can be provided to the facility where U.S. personnel will be treated
for proven envenomations.
• Excellent sources regarding snakebite during wilderness and military operations are:
- The proceedings of the Wilderness Medical Society workshop “Wilderness Medicine
Scenarios for Military Special Operations,” published as a special issue of “Wilderness
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8. and Environmental Medicine,” Volume 9, Number 2, Scenario Seven, “Snakebite,” 99-
103, (1998).
- Special Operations Forces Medical Handbook, Chapter 17: “Toxicology: Venomous
Snake Bite,” 5/142-5/145, (2001)
- Anderson, “Rattlesnake Bite and the Art of Medicine - Sorting Out Therapies,” Journal
of Special Operations Medicine, Volume 4, Edition 1, 52-57 (2004).
- “Wilderness Medicine,” 4th Edition, Auerbach, editor, (Mosby 2001).
- “Field Guide to Wilderness Medicine,” Auerbach, Donner, and Weiss, (Mosby 2003);
a quick reference “handbook” associated with Auerbach’s Wilderness Medicine
Textbook.
• The initial symptom of most bites in which envenomation occurs is progressively
intensive pain, which commonly starts within five to 30 minutes, with profound envenomation
usually resulting in shorter time of onset of symptoms. Systemic signs and symptoms follow,
including evolving edema and erythema or ecchymoses both proximally and distally as the
venom spreads. Therefore rapid evacuation is required to an MTF which can:
- Treat the significant complications of envenomations - altered mental state,
respiratory problems which can progress to arrest, hemolysis, rhabdomyolysis, and renal
failure
- Administer antitoxin that is species-specific whenever possible and acquired from
approved sources
- Treat potentially life-threatening systemic reactions to antitoxin that occur in 15-25%
of all cases.
• Treatment at a medical facility consists of initial evaluation and definitive care, if
necessary. Initial evaluation includes examination of the injured part of the body, as well as a
full evaluation of the neurologic, cardiovascular, and pulmonary systems. Laboratory
evaluation is vital, including tests of clotting function (whole blood clotting time is sensitive),
renal function, and for hemolysis and rhabdomyolysis. Treatment with antivenom is indicated
for cases where systemic toxicity is present.
• Finally, the treatment of clinically significant venomous snakebites is complicated.
Antivenom should not be administered in the field; it should only be administered in an
intensive care setting, after pre-medication, where hemodynamic and airway emergencies can
be managed. The literature is clear that the adverse effects of antivenin are significant –
including anaphylactic reactions and serum sickness. Note also that bites severe enough to
warrant specific treatment often needed significant amounts of antivenin; the experience from
Arizona showed a mean of 38 vials administered, and 31% received 40 or more vials of
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9. antivenin, There is a very significant risk of immediate effects, and with doses needed to
counteract a severe envenomation the risk of serum sickness approaches unity.
Plans/Recommendations:
1. Medical personnel assigned to U.S. Naval units should conduct Force Health
Prevention briefings regarding snake avoidance and snakebite prevention before and
during operations in areas where poisonous snakes and arthropods live, with emphasis
on the poisonous animals that live in the area of operations.
2. Medical personnel assigned to U.S. Naval units that will operate ashore in areas where
poisonous snakes and arthropods live should be capable of and equipped to administer
effective first responder care to casualties suspected or know to have been
envenomated by a poisonous snake or arthropod.
3. Medical plans should include emergency CASEVAC of envenomation victims to
designated upper Level medical treatment facilities capable of administering intensive
care and administering species-specific antivenin, derived from sources approved by
the Commander of the Geographical Command.
END
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