La Vipera sulle mie
Sulle Prealpi Venete ci
sono 3 specie di vipere: la Comune (V. Aspis), il Marasso (V. Berus) e
la vipera dal Corno (V. Ammodytes). Sono abbastanza simili, ma la vipera
dal Corno ha, appunto, un cornetto sul naso che la rende particolare. Il
colore non è sempre uguale. Basta una ricerca in Google immagini per
rendersi conto di come siano varie le livree, dal grigio al marroncino
con varie sfumature.
Il modo migliore per
riconoscere le vipere velenose dai serpenti innocui è la forma del
corpo. Le vipere hanno la coda corta e tozza, i serpenti lunga e
affusolata. La testa delle vipere è ben definita, distinta dal corpo,
tozza e triangolare, schiacciata. La testa dei serpenti innocui è invece
affusolata, meno distinguibile dal corpo. Anche la pupilla è diversa.
Nelle vipere è a fessura, verticale come nei gatti, nei rettili innocui
è tonda. Meglio comunque non avvicinarsi per verificare la pupilla
Le vipere sono comunque corte, sotto il metro, in genere una sessantina
La vipera Comune e quella
del Corno si trovano anche ad alte quote, sopra i 2000 metri. Hanno un
disegno a zigzag sulla schiena, più scuro del resto del corpo, ma che a
volte si distingue molto poco. La Berus è meno tossica e leggermente più
piccola della altre due, ma statisticamente in Europa è quella con più
segnalazioni di morsicature. Piccola ma bastarda
Iniziamo con lo sdrammatizzare. La
Vipera non è un Cobra Reale. E' un animaletto che non ha sicuramente
voglia di passare le sue giornate a caccia di escursionisti, è
relativamente timido, ama starsene al sole a crogiolarsi, o all'ombra a
digerire. Tra il 1980 e il 1984 sono state morse 885 persone, e di
queste solo 3 sono morte. Solamente circa il 4% dei morsi di Aspis non
trattati sono mortali. Inoltre circa il 20% dei morsi di vipera sono
morsi secchi. Secondo il
Notiziario della Società Italiana di Medicina di Montagna l’incidenza
annuale, in Europa, è di 15-20.000 morsicature, con 50 morti per anno
(esclusa la Russia ed i paesi dell’Est).
Nel 1995 sono stati segnalati in Svezia 231 ricoveri per morso di
vipera, di cui il 41% hanno sviluppato sintomi; di questi ultimi solo il
45%, cioè il 18% di tutti i ricoveri, ha richiesto il trattamento con
Linko un articolo, tratto
dal sito Sicurezza in montagna, che mi sembra fra tutti uno dei
migliori. Credo sia la cosa migliore da fare, invece di riportare qui le
informazioni. Tra l'altro il sito è molto ben fato e interessante, vi
invito a visitarlo. Potrà sicuramente esservi utile!!!
Riporto inoltre 3 spezzoni
di articoli molto interessanti. Il primo è tratto dal Journal of
Wilderness Medical Society, Vol. 17, n. 4:
aid for pit viper bite
on pit viper envenomations and their outcomes have led to numerous
changes in the recommended first-aid measures. The old “cut and suck”
method recommended in the 1960s and 1970s and the use of
venom-extraction devices, chill methods, electroshock therapy, and
tourniquets have all been shown to potentially worsen the outcome of a
bite and are now strongly discouraged.
currently recommended that victims of pit viper envenomation be placed
at rest and kept calm and warm. The injured part of the body should be
freed of any constricting jewelry; immobilized with a loose-fitting
dressing; and, if possible, maintained at the level of the heart.
Paramedical attention should be directed toward the maintenance of a
patent airway, administration of oxygen, establishment of intravenous
access in an unaffected limb, and prompt transportation to the nearest
medical facility. Immediate hypersensitivity to venom components is
possible in some victims and may require the use of epinephrine and
antihistamines to lesson its impact. The progression of swelling should
be closely monitored during transport. Marking the advancing edge of the
swelling with a marker at 15- to 20-minute intervals can provide the
treating physician with valuable information on gauging the bite's
Once at a
medical facility, all victims of snakebite should be promptly evaluated.
Aggressive supportive care including pain management, wound care,
updating tetanus prophylaxis, and sometimes antivenom therapy are often
required with cases involving moderate to severe envenomation. The
decision to administer antivenom should be made on a case-by-case basis
and only by a qualified physician. Factors considered in this decision
should include the snake species involved in the incident, the
progression of local effects, signs of systemic poisoning, laboratory
findings, and the victim's hypersensitivity status. The only antivenom
approved by the Food and Drug Administration for North American crotalid
bites that is currently being manufactured is CroFab (Protherics—Altana
division of Savage Laboratories, Melville, NY). CroFab is a polyvalent,
ovine-derived Fab product that is prepared against the venoms of 4 North
American pit vipers: the western diamondback rattlesnake, the eastern
diamondback rattlesnake, the Mohave rattlesnake, and the cottonmouth.
Experimental studies and clinical case reports have shown this antivenom
product to have activity against the venoms of a wide range of New World
pit vipers. Although uncommon, adverse reactions including immediate
hypersensitivity reactions and serum sickness are still possible with
Fab-based antitoxin products and need to be considered and monitored for
in-patients treated with CroFab. Consultation with a medical
toxicologist at a regional poison control center (National Hotline
(800)222-1222) is recommended for the treatment of any pit viper
Anche il secondo è tratto
dal Journal of Wilderness Medical Society, Vol. 18, n. 3:
Venomous Snakebite in Mountainous Terrain:
Prevention and Management
Jeff J. Boyd, MBBS, UIAGM;
Giancelso Agazzi, MD; Dario Svajda, MD; Arthur J. Morgan, MBBCh;
Silvia Ferrandis, MD; Robert L. Norris, MD
From the Mineral Springs
Hospital, Banff, Canada (Dr Boyd); the Italian Alpine Club
Medical Commission, Colzate, Italy (Dr Agazzi); the Mountain
Rescue Medical Commission, Pozega, Croatia (Dr Svajda); the
Mountain Club of South Africa National Rescue Committee,
Pretoria, South Africa (Dr Morgan); the Hospital Comarcal
del Pallars, Tremp, Spain (Dr Ferrandis); and the Stanford
University Medical Center, Stanford, CA (Dr Norris)
1 Continuing Medical Education credit for WMS member physicians
is available for this article. Go to
wms.org/cme/cme.asp?whatarticle;eq1831 to access the test
prevention and management of venomous snakebite in the world's
mountains present unique challenges. This paper presents a
series of practical, clinically sound recommendations for
management of venomous snakebite in a mountain environment. The
authors performed an extensive review of current literature
using search engines and manual searches. They then fused the
abundant knowledge of snakebite with the realities of remote
first aid and mountain rescue to develop recommendations. A
summary is provided of the world's most troublesome mountain
snakes and the mechanisms of toxicity from their bites.
Preventive measures are described. Expected symptoms and signs
are reviewed in lay and medical terms. A review of currently
recommended first-aid measures and advanced medical management
for physicians, paramedics, and other clinicians is included.
Venomous snakebites in mountainous environments present unique
challenges for management. This paper offers practical
recommendations for managing such cases and summarizes the
approach to first aid and advanced management in 2 algorithms.
Key Words: snakebite, rescue,
mountaineering, elapid, viper, antivenom, first aid
medical emergencies in mountainous terrain demands unique measures
to deal with limited on-scene resources; communication and
transportation difficulties; ongoing environmental stresses on
victims, rescuers, equipment, and supplies; and protecting the
patient from hazards inherent in mountain rescue. Standard
preparation and training are oriented towards the injuries resulting
from mechanical trauma that constitute the majority of mountain
emergencies. There is a need, however, for mountain travelers (“mountaineers”)
and mountain rescuers to have a working knowledge of unusual
emergencies, such as snakebite, both to prevent such injuries and to
initiate appropriate management when necessary.
snakes are found in a number of mountain habitats, and bites
occasionally occur in remote mountain settings. Management of such
bites involves a wide spectrum of priorities. General prevention and
management are comprehensively described in first-aid manuals and in
emergency medicine textbooks. Such texts are rarely available at the
scene during a mountain rescue, and communication links to obtain
outside advice may not be available in remote areas or if
communications fail. For these reasons, the Medical Commissions of
the International Committee for Alpine Rescue (ICAR) and the
International Mountaineering and Climbing Federation (UIAA MEDCOMS)
have compiled the core knowledge and recommendations presented in
articles were located by searching Pub Med, EMBASE, and Google
Scholar using the phrase “snake bite” and similar terms. In addition,
appropriate reference textbooks were hand searched. The search
returned more than 3500 references that were then examined for
relevance and current content. From these references, the
recommendations found herein were developed.
snakes inhabit the foothills and mountains of all the continents
except Antarctica. Terrestrial snakes that are of most concern in
the mountains are from the families Viperidae (vipers and pit vipers)
only approximately 15% of the 3000 species of snakes are considered
dangerous to human beings. Of venomous snakebites reported in the
United States, it is estimated that significant envenomation occurs
in only 80% of pit viper bites and 75% of coral snake bites. In
other regions of the world, nonenvenomations or “dry bites” also
occur with regularity. The case fatality rate from pit viper bites
in the United States has improved from 5 to 25% in the nineteenth
century to 2.6% with the advent of critical care and to 0.28% with
the introduction of antivenom. Similarly, in South Africa and Europe,
the case fatality rate is currently reported as 0.3%. However, in
developing countries, case fatality rates are reported to be
considerably higher, with Nepal reporting a fatality rate of 27% in
Mechanisms of toxicity and symptoms and signs
important for those venturing into wilderness environments to learn
the patterns of effects for the snake species found in their
destinations. Snake venoms, particularly viperid venoms and
necrotizing elapid venoms, contain many enzymes and other toxins (low–molecular
weight polypeptides) that disrupt cellular processes, resulting in
vascular damage and tissue destruction (eg, muscle cell disruption ;obrhabdomyolsis;cb).
This results in tissue loss and release of potassium into the
circulation. If potassium levels rise high enough (hyperkalemia),
this may cause heart irregularities (dysrhythmias). Muscle
destruction also releases protein (myoglobin) into the circulation,
and this can result in kidney damage (acute renal failure). Vascular
damage allows leakage of fluid into the tissues, resulting in
peripheral edema, pulmonary edema, hypovolemia, and metabolic
acidosis. Other toxins disrupt the coagulation process. Some promote
coagulation and result in diffuse intravascular clotting that can,
rarely, result in heart attacks (coronary artery thrombosis) or
strokes. More commonly, snake venoms result in the consumption of
blood-clotting factors and may produce incoagulable blood and
excessive bleeding at essentially any site (eg, bleeding in and
around the brain [intracranial hemorrhage]).
components, especially in many of the elapids, can also poison the
nervous system, causing numbness and muscle weakness, including
weakness of the muscles of respiration leading to respiratory
failure. Cardiac toxins can result in poor pumping of the heart (myocardial
depression), as well as direct rhythm irregularities (eg, atrial
fibrillation, atrioventricular block, ventricular tachycardia or
can cause early cardiovascular collapse (syncope, shock,
cardiopulmonary arrest), notably in bites from European vipers
(Vipera species), Australian brown snakes (Pseudonaja pecies), and
some rattlesnakes. Early collapse may be due to fainting (neurogenic
syncope), direct cardiac toxins, or severe allergic (anaphylactic or
general, vipers tend to cause significant local effects (pain,
swelling, bruising, and tissue necrosis) due to cellular and
coagulopathic toxins, although they may also cause systemic effects,
including bleeding, shock, and cessation of breathing in severe
envenomations. A few viperid species, such as certain populations of
the Mohave rattlesnake (Crotalus scutulatus), have neurotoxic
components in their venoms that can cause significant neurological
dysfunction in the absence of impressive local findings.
elapid venoms are predominantly neurotoxic and tend to cause fewer
local effects. These snakes may cause paralysis (through either pre-
or postsynaptic neurotoxins). Early findings after significant bites
by these snakes tend to involve cranial nerve abnormalities (eg,
eyelid drooping [ptosis], difficulty speaking [dysarthria]) but may
progress to disruption of breathing (respiratory failure). Some
elapids, such as the Australian common tiger snake (Notechis
scutatus) and eastern brown snake (Pseudonaja textilis), can cause
clotting problems, resulting in widespread bleeding. Other elapids,
such as Asian and African cobras, can cause significant local injury
and severe necrosis. Spitting cobras (certain Naja sp) and rinkhals
(Hemachatus haemachatus) can accurately spit venom into the eyes of
a victim from a distance of up to 2.5 meters. This causes severe
conjunctival irritation and produces temporary or permanent
impairment of vision. Systemic envenomation does not follow isolated
ocular exposure to spitting cobra venom.
generalities aside, every snakebite is different. There are
countless variables involved in any particular incident including
the species and health of the snake, the health of the victim,
environmental conditions, and the care rendered. Thus, with a
suspected venomous snakebite, the caregiver must be vigilant for the
onset of a varied and complex sequence of outcomes; local changes,
bleeding, neurological dysfunction, renal failure, cardiovascular
collapse, and respiratory distress being among the most important.
application of preventive measures during rescue and other
operations can reduce the risk of snakebite even in areas with a
high density of venomous snakes. Before going into a new area,
gather as much information about the local snakes as possible,
including color photographs of indigenous species to be used for
identification purposes. This will promote appropriate preventive
behaviors, dictate what emergency equipment and supplies should be
carried, and direct the most appropriate management should a bite
occur. Clinicians traveling with expeditions to remote ranges should
develop a snakebite management plan that considers limited logistics,
methods of evacuation, and access to antivenom resources. Preventive
measures should include wearing adequate protective clothing such as
long baggy trousers, long boots or gaiters, and thick socks when
traveling in areas where venomous snakes may be encountered. Baggy (bloused)
clothing provides some barrier protection and may reduce the depth
of penetration if a bite occurs.
walking, always scan the path ahead and look around carefully before
squatting or sitting down. Probe ahead of you with a walking stick
before entering an area with an obscured view of your feet. If
preparing to step over a log, scan the other side before proceeding.
Avoid putting hands into areas where snakes may be hiding, such as
in long grass, under rocks or logs, in trees, or on rock ledges.
Gloves add a degree of protection. Be aware of snakes even in
vertical places (eg, on ledges or in fissures while climbing) or in
the water (eg, while canyoneering).
snake is seen, no attempt should be made to approach, capture, or
kill it. Many bites occur to victims attempting to move or kill a
snake. If a snake has been killed, it should not be handled because
recently killed snakes possess a reflex biting mechanism for some
time after their death, and fatalities have occurred in victims
bitten by decapitated snake heads. In addition, venom remains active
in dead snakes for long periods and can result in envenomation if a
person is penetrated by a fang while handling the specimen.
torch or flashlight at night when walking, and never go about with
bare feet. Do not sleep in the open or in poorly sealed
accommodations in areas where snakes are common, and do not put
sleeping bags near rocks, cave entrances, or rubbish piles.
Carefully check your sleeping bag, boots, and other equipment before
recommendations for managing venomous snakebites are based on
limited studies, and these recommendations should, therefore, be
considered guidelines only.
the victim and witnesses may reveal useful identification
Digital photography of the snake using zoom settings may be helpful,
but the snake should be approached only if it is safe to do so. A
snake's effective striking range is approximately half its body
length. The remains of a killed snake, if needed for identification,
are best maneuvered into a thick receptacle (eg, heavy rucksack)
with a stick or trekking pole. Because all US pit vipers are
adequately covered by crotalid antivenoms available in this country,
precise species identification of US pit vipers is not necessary. It
is important in other regions of the world to carefully identify the
snake, because antivenoms in these regions may be species specific.
Being able to differentiate a venomous snake from a nonvenomous
snake is certainly worthwhile, because a bite by a harmless snake
should not necessarily end an outing.
Safety, basic life support, victim
comfort, secondary survey
Initial considerations for first
aid should follow standard approaches and incorporate safety, basic
comfort of the victim, and a targeted secondary survey.
Cardiopulmonary resuscitation may be lifesaving and immediately
necessary in snakebite that produces early collapse. Prolonged
rescue breathing may be necessary.
Evaluate bite, remove constrictions
The bite should be examined, and
the leading edge of swelling marked indelibly with a line, along
with the time of the observation in order to track progression. The
circumference of the limb at a marked site above the wound can also
be noted. If local effects progress, re-mark the perimeter with the
time and measure the circumference every 30 minutes or more
frequently if advancing quickly. Rings, watches, and constricting
clothing should be removed to avoid a tourniquet effect as swelling
Do no harm
Incision, excision, heat, ice,
cryotherapy, poultices, topical chemicals or herbals, electrical
shocks, alcohol, or stimulants offer no benefit and may worsen
Mechanical suction not recommended
Recent evidence indicates that
mechanical suction devices do not extract venom, may impair natural
oozing of venom from the bite, and may increase tissue damage.
Their use is, therefore, not recommended.
The bite site should not be
manipulated, although a simple, dry dressing can be applied.
Constriction bands and tourniquets
Constriction bands and tourniquets
have never been found to improve outcome and should be avoided
because of their inherent risk of worsening local tissue damage.
Pressure immobilization (PI) is now
recommended in many regions of the world for non-necrotizing elapid
snakebites because it reduces absorption of these neurotoxic venoms
into the central circulation.
To apply pressure immobilization, a broad elastic or crepe bandage
or a torn item of clothing is bound from the distal portion of the
bitten limb firmly up over the bite site, at similar pressures as
for a severely sprained ankle. The bandage is then wrapped up the
extremity as far as possible and the limb is splinted or placed in a
sling . For PI to be effective, the pressures achieved by the wrap
must be within a narrow range (approximately 40–70 mm Hg). Pressures
outside of this range are ineffective and may actually enhance venom
spread. Use of a splint or sling is also required for the technique
to work, and the victim must be carried from the location. Pressure
immobilization should not be used if the offending snake's venom is
of a necrotic variety, as with most vipers, pit vipers, and certain
Asian and African cobras, due to the risk of worsening local venom
effects. When used, PI should be left in place until the patient
reaches definitive care and antivenom, if indicated, is started.
Definitive proof of efficacy of this technique or ability of
rescuers to apply it remains lacking.
Whether or not PI is to be used,
apply a splint to the limb to reduce pain, swelling, and bleeding,
and keep the victim at rest as much as possible.
Acetaminophen (paracetamol) will
give pain relief, but avoid aspirin and anti-inflammatory agents (eg,
ibuprofen), which may worsen bleeding.
If transport times are long and an
intravenous line is not running, allow the victim to take clear
liquids (but no solids) as long as there is no nausea or vomiting.
The first responder should obtain
expert advice and begin rescue logistics as early as possible by
contacting the most appropriate local emergency dispatch center,
emergency department, and/or poison center. Most rescues are
initiated using modern wireless communications,
and mountaineers are encouraged to carry wireless devices
appropriate to the region. Mobile cell phones that use code division
multiple access (CDMA) technology have greater ranges (up to 70 km)
than global system for mobile (GSM) phones (limited to 35 km), and
analogue modes give greater range than these CDMA and GSM digital
modes. Hand-held programmable radios may be useful in areas with
repeater networks that allow emergency access. Satellite phones are
the only option in many remote mountain ranges. Intervening
obstacles, such as mountains and canyon walls, impair all wireless
communications and may render them useless.
rescue has become common, although this may require a ground team to
first get the victim to a suitable location for slinging or hoisting.
Attempting to sling or hoist through trees is hazardous. Helicopter
operations are limited by availability, fuel capacity, geography,
weather, and visibility.
team requirements will be influenced by such factors as the need for
ground evacuation and first aid and medical management on scene and
during transport. Rescue breathing may be required for many hours or
even days when evacuation is delayed, especially after serious
neurotoxic elapid envenomation.
Eye exposure to spitting cobra
Irrigate the eyes extensively with
water or saline for 15 to 20 minutes.
Transport should not be
significantly delayed by any first-aid measure.
ADVANCED MEDICAL TREATMENT
section is intended for qualified clinicians and presumes that all
appropriate measures in the first-aid section have been instituted.
Baseline physical examination
The physical examination should be
targeted and brief with special attention to the bite area, as well
as the cardiovascular, pulmonary, and neurological systems to obtain
a baseline assessment.
Monitor vital signs, key physical
findings (eg, soft-tissue swelling, evidence of neurotoxicity), and
cardiac rhythm and oximetry when available.
Ideally, at least 2, large-bore
intravenous lines should be started to provide access for fluid and
antivenom administration as needed. In a mountain wilderness setting,
it is not unusual for victims to be somewhat volume depleted from
physical activity and reduced fluid intake. This can compound
venom-induced hypotension. It is, therefore, prudent to provide
hydration to the victim prior to or during transport as long as
there is no contraindication to doing so. If hypotension occurs, the
victim should receive intravenous physiologic crystalloid
resuscitation (20 mL per kg, repeated as necessary). Intraosseous
access is an alternative if the victim is in shock and an
intravenous line cannot be established. Fluids administered through
an intraosseous line may need to be given under pressure. A blood
pressure cuff can be wrapped around the fluid bag and inflated to a
pressure that achieves an adequate flow rate.
Oxygen should be administered
according to the clinical condition and availability.
Local pain may be severe,
especially after most viperid and some elapid bites, and may require
parenteral opiates. Alternatively, ketamine has been advocated for
analgesia in wilderness settings54
and for mountain rescue,55
although its use has not been studied in snakebites.
Advanced life support interventions
Early collapse after a snakebite (within
minutes) could be due to venom toxicity or an anaphylactic or
anaphylactoid reaction. Such patients should be managed with
intravenous fluid boluses, intramuscular epinephrine (0.01 mL/kg of
1:1000 solution up to 0.5 mL), antihistamines, and steroids,
in addition to antivenom, as soon as possible (see later).
Intramuscular injections should be avoided in a coagulopathic
patient if possible, but, if necessary, concentrated direct pressure
should be applied to the site to prevent hematoma formation.
Alternatively, if cardiovascular collapse is severe, epinephrine may
be administered cautiously intravenously according to advanced life
support guidelines for anaphylaxis. Likewise, cardiac dysrhythmias
should be managed according to advanced life support guidelines.
If the patient develops respiratory
distress, ventilations may need to be supported using a
bag-valve-mask, mouth-to-mask, or mouth-to-mouth technique.
Definitive control of the airway is obtained via placement of a
cuffed endotracheal tube below the vocal cords, generally via direct
laryngoscopy, but this should be done with great care to avoid
traumatizing the airway and causing additional bleeding and swelling.
The use of sedating and paralytic agents (rapid sequence intubation)
may be needed. If, however, it is predicted that securing the airway
will be difficult, it may be best to perform intubation under direct
visualization with the patient lightly sedated but not paralyzed (ie,
awake intubation). In the wilderness setting, if airway equipment is
very limited, the availability of an endotracheal tube and stylet
may allow securing the airway of an apneic victim by the digital or
tactile technique. As a last resort, if the need for a secured
airway exists and the patient cannot be intubated from above the
cords, a surgical airway (cricothyrotomy) is needed, although this
can be especially challenging if the victim is coagulopathic. In
bites to the head or neck, as might occur in a person climbing up a
rock face, airway management should be considered early, before
severe edema and coagulopathy develop.
All currently available snake
antivenoms are heterologous serums produced by injecting laboratory
animals (generally horses or sheep) with the venoms of snakes for
which the product is intended. Antivenoms are relatively specific
for the venoms for which they are protective, and there is little to
no cross-protection against venoms of unrelated snakes. All
heterologous serums carry a risk of inducing acute adverse reactions,
typically anaphylactic or anaphylactoid in nature, or delayed serum
Field administration of antivenom
The decision as to whether or not
to carry antivenom on wilderness excursions must be made based on
several factors. These include the risk of snakebite (based on snake
population densities and the practicality of preventive measures),
the logistics related to evacuation (transportation availability,
access to definitive care, etc), the availability of equipment and
expertise to administer antivenom and deal with potential
complications, and the financial resources of the team. In
well-equipped and adequately staffed expeditions to remote regions,
having antivenom immediately available might prove beneficial,
because the sooner antivenom is given after a significant bite, the
more effective it will be.
In elapid envenomations, for example, neurotoxicity, once
established, may not be reversible with antivenom and the
consequences, including respiratory failure, may persist for weeks.
Administering antivenom in such bites at the earliest sign of
toxicity may prevent the need for prolonged intubation and
mechanical ventilation. Although the ability of antivenom to prevent
local tissue damage after necrotizing bites is suspect, any benefit
of the antiserum in this regard is clearly dependent on getting it
on board within the first hour after the bite, a requirement that
can only be met if antivenom is available in the field.
a qualified rescue team may consider carrying antivenom to a
snakebite victim in the field in circumstances in which rescue may
be prolonged, if the bite appears severe, and if snake
identification allows the appropriate choice of antivenom. Field
transport of antivenom must always ensure appropriate storage
conditions, as detailed in the manufacturer's product insert.
on the quality of the product used, acute anaphylactic or
anaphylactoid reactions may develop in 5 to 80% of patients given
antivenom. Field antivenom therapy should, therefore, only be
contemplated when a qualified clinician is on scene and when all
equipment and drugs are available to manage an anaphylactic or
anaphylactoid reaction (ie, definitive airway drugs and equipment,
intravenous supplies, epinephrine, antihistamines, and
administration should generally proceed according to the
manufacturer's product insert, which may need to be translated into
the physician's native language before embarking on an expedition or
rescue. The insert provides information regarding the species
covered by the product and dosage recommendations. It may be prudent,
whenever possible, to confirm recommended dosing and redosing
intervals with a physician knowledgeable about the use of the chosen
antiserum, because antivenom product inserts produced by some
manufacturers may contain misleading or erroneous recommendations.
Antivenom should only be given intravenously (or intraosseously).
The total dose to be given should be placed into an intravenous bag,
and the infusion should be started slowly for the first several
minutes. If no reaction occurs, the rate is increased to get the
total dose in within 1 to 2 hours.
pretesting for potential allergy to antivenom, although occasionally
recommended by manufacturers, is unreliable, delays antivenom
administration, and should be omitted.
possible that acute anaphylactic or anaphylactoid reactions to
antivenom will be prevented or blunted by expanding the victim's
intravascular volume with crystalloid and by pretreating with
standard doses of intravenous antihistamines (H1 and H2 blockers)
and, when the risk of reaction is felt to be particularly high,
subcutaneous epinephrine. The efficacy of prophylactic
antihistamines is controversial. Caution must be used if pretreating
with epinephrine in a patient with coagulopathy, because
epinephrine-induced hypertension could increase the risk of
intracranial hemorrhage. Whether or not pretreatment is used, these
drugs must be immediately available to intervene if an acute
Anticholinesterase trial for
The anticholinesterase drugs,
edrophonium and neostigmine, may reverse the effects of snake venoms
with postsynaptic neurotoxins, such as some cobras (eg,
Naja sp) and
Australian death adders ( Acanthophis sp). It is reasonable to
administer a test dose of an anticholinesterase drug in any victim
of snakebite who is demonstrating clear neurological dysfunction (eg,
ptosis). Patients should be pretreated with atropine (adults: 0.5 mg
intravenously; children: 0.02 mg/kg body weight; minimum 0.1 mg).
After this, edrophonium (0.25 mg/kg intravenously; maximum 10 mg) or
neostigmine (0.025– 0.08 mg/kg intravenously; maximum 2.5 mg) is
given. If after 5 minutes there is clear improvement in neurological
function, the patient should receive additional neostigmine at a
dose of 0.01 mg/kg, up to 0.5 mg intravenously every 30 minutes as
needed until recovery occurs. Atropine should also be redosed
periodically as indicated by significant bradycardia, especially
with hypotension. Anticholinesterase therapy may reverse
neurotoxicity to a degree such that intubation and ventilatory
support are not required, making extraction from the mountain much
easier. Care must be taken to closely monitor the victim, however,
during such therapy and evacuation for any evidence of cholinergic
crisis, to ensure that neurotoxicity is not progressing and to
victim clearly bitten by a venomous snake should be immediately
evacuated from the field to definitive medical care, regardless of
whether or not there are early findings of envenomation. Once
definitive care is reached, all victims with clear evidence of venom
toxicity must be admitted for at least 24 hours, even if antivenom
is not required. In the United States, victims who are asymptomatic
for 6 to 8 hours after a pit viper bite can be discharged home with
instructions to return if they develop any delayed signs or symptoms.
In other regions of the world, even asymptomatic patients should be
admitted to hospital for 24 hours of observation, given the
potential delay in onset of venom toxicity.
article is intended to provide mountaineers, first responders, and
rescue clinicians with a working knowledge of snakebite in the
mountains. Readers are encouraged to seek more extensive information
regarding the indigenous snakes of the regions they will be visiting
or in which they provide rescue support and to develop specific
management and evacuation plans before they leave on their next trip
into the mountains.
Il terzo articolo è preso dalla
National Library of Medicine, e redatto dall'Università della
California, dipartimento di Medicina d'Emergenza.
Suction for venomous
snakebite: a study of "mock venom" extraction in a human model.
Department of Emergency Medicine, University Medical Center, University
of California, San Francisco, Fresno 93702, USA. firstname.lastname@example.org
We determine the percentage of mock venom recovered by a suction device
(Sawyer Extractor pump) in a simulated snakebite in human volunteers.
mock venom (1 mL normal saline solution, 5.0 mg albumin, 2.5 mg
aggregated albumin) radioactively labeled with 1 mCi of technetium was
injected with a curved 16-gauge hypodermic needle 1 cm into the right
lateral lower leg of 8 supine male volunteers aged 28 to 51 years. The
Sawyer Extractor pump was applied after a 3-minute delay, and the blood
removed by suction was collected after an additional 15 minutes. A 1991
Siemens Diacam was used to take measurements of the radioactive counts
extracted and those remaining in the leg and body.
RESULTS: The "envenomation
load," as measured by mean radioactivity in the leg after injection, was
89,895 counts/min. The mean radioactivity found in the blood extracted
in the 15 minutes of suction was 38.5 counts/min (95% confidence
interval [CI] -33 to 110 counts/min), representing 0.04% of the
envenomation load. The postextraction leg count was less than the
envenomation load by 1,832 counts/min (95% CI -3,863 to 200 counts/min),
representing a 2.0% decrease in the total body venom load.
CONCLUSION: The Sawyer
Extractor pump removed bloody fluid from our simulated snakebite wounds
but removed virtually no mock venom, which suggests that suction is
unlikely to be an effective treatment for reducing the total body venom
burden after a venomous snakebite.