IMMEDIATE FIRST AID
for bites by
(Lachesis muta muta)
In the event of an actual or probable bite from a Lachesis muta muta, execute
the following first aid measures without delay.
- Make sure that the responsible snake or snakes have been appropriately
and safely contained, and are out of danger of inflicting any additional
- Immediately call for transportation.
- Keep the victim calm and reassured. Allow him or her to lie flat and
avoid as much movement as possible. If possible, allow the bitten limb to
rest at a level lower than the victim's heart.
- Identify the bite site, looking for fang marks, and apply the Sawyer Pump
extractor with the largest cup possible over the bite site. If there are two
or more fang marks noted on the limb, apply the pump extractor over at least
one fang mark. If more than one pump extractor is available, they may be
applied to the additional fang marks.
(See the attached copy from "First Aid for Snakebite" by Dr. S.K.
- Immediately wrap a large constricting band snugly about the bitten limb
at a level just above the bite site, ie. between the bite site and the heart.
The constricting band should be as tight as one might bind a sprained ankle,
but not so tight as to constrict blood flow.
- DO NOT remove the constriction band until the victim has reached the
hospital and is receiving antivenom.
- Have the Wyeth Crotalidae Polyvalent Antivenom ready for the emergency
crew to take with the victim to the hospital. Give them the following:
- the available antivenom (at least 20 vials)
- the accompanying instruction (Protocol) packet
- the victim's medical packet (if available)
DO NOT cut or incise the bite site.
DO NOT apply ice to the bite site.
Summary for Human Bite
(Lachesis muta muta)
The bite of Lachesis muta muta can be fatal. It is one of the largest and most
dangerous snakes in South America. Victims will usually complain of pain at
the bite site and swelling may be evident. Significant local tissue
destruction can ensue, along with a substantial coagulopathy. Victims may also
experience additional symptoms which are unique. These include abrupt
hypotension, decreased heart rate, intense colic, and bloody diarrhea. Prompt
medical therapy avoids these problems.
Please read the attached and respond appropriately.
- First Aid:
- Apply constricting band if not already present, proximal to bite on arms,
legs, hands, or feet. Apply suction with the Sawyer Pump extractor for 10-20
minutes. Rest the extremity below the patient's heart.
- Transport to a medical center emergency or trauma service.
- Medical Management:
- Call your local Poison Control Center, or the San Diego Regional Poison
Control Center (800 876-4766). They should locate a consultant to help you
treat this patient.
- Observe for Signs and Symptoms of Envenomation.
- If signs or symptoms are present, perform the following:
- Apply intradermal skin test.
- Administer Lactated Ringers intravenously at a rate of 200 cc/hour.
Obtain appropriate blood and urine laboratory data.
- Wait 20 minutes.
- Reconstitute 5 vials of Wyeth Crotalidae Polyvalent antivenom in 50
ccLactated Ringers (10 ml/vial). e. If no reaction to intradermal skin test,
administer antivenom by intravenous infusion 1 vial (10 cc) every 5-10 minutes.
The constriction band can be removed after the first vial has been infused.
One should anticipate using 20-40 vials for moderate to severe bites.
- Monitor signs, symptoms, and laboratory data and administer additional
aliquots of 5 vials of antivenom as needed to neutralize signs and symptoms at
a rate of 1 vial (10 cc) every 5-10 minutes.
- If patient is allergic to horse serum, administer 1 gram Solu-Medrol IV
push, wait 30-45 minutes, and then begin intravenous antivenom. Be prepared to
administer Benadryl and epinephrine.
- In case of intravenous envenomation, administer antivenom IV push, 1 vial
every 1 minute, until symptoms improve then continue by intravenous infusion
until signs and symptoms are titrated.
for bites by
(Lachesis muta muta)
This person has received a bite and probable envenomation from a Lachesis muta
muta. It is one of the largest and most dangerous snakes in South America.
Even though this snake has large fangs, delivers large amounts of venom, and
has an aggressive nature, few human bites have been recorded because of its
nocturnal nature. Envenomation presents predominately with edema, pain,
hematologic, abdominal, and cardiovascular manifestations. Dizziness and
blistering wounds can also be present. In severe envenomations, peripheral
circulatory collapse and bloody diarrhea may manifest.
Please read and execute the following procedures without delay.
- A constricting band should be in place proximal to the bite site. If
present, leave in place, if not apply a penrose drain as if for venipuncture.
This retards venom absorbtion. DO NOT remove until the patient has
arrived at the hospital and is receiving the antivenom.
- Make sure that at least 20 vials of Crotalidae Polyvalent Antivenom
(Wyeth) are present with the patient. This antivenom contains the necessary
fractions to neutralize the venoms of all Central and South American species of
- If the patient has been envenomated, the initial treatment is 5 to 40
vials of intravenous antivenom. Envenomation is diagnosed by the presence of
characteristic signs and symptoms. Necessary information follows and is
organized in sections:
- Signs and Symptoms of Envenomation
- Medical Management
- General Considerations
- Special Considerations
Signs and Symptoms of Envenomation:
- These signs and symptoms will usually manifest earliest, though their
development will vary considerably from case to case. Not all of these will
necessarily occur, even with severe envenomation.
- Edema & Pain
- Hemorrhage (gingival, wound, rectal)
- Blister formation around wound site
- Abdominal pain (intense colic)
- Bloody diarrhea
- Hypotension (diastolic & systolic)
- Diminished heart sounds
- Brief loss of consciousness
- Blurry vision
- General: The above symptoms can manifest within 5 hours after
envenomation. Pain and edema usually begins within the first few minutes after
the bite. The symptoms can be divided into four categories.
- Local: Edema, pain, and blister formation around the bite site.
- Cardiovascular: Diastolic and systolic hypotension, bradycardia,
diminished heart sounds, brief loss of consciousness, blurry vision, and
- Abdominal: Intense colic, vomiting, and bloody diarrhea.
- Hematology: Hemorrhage (wound, rectal, gingival).
- Local Symptoms: Though pain and edema are the major local manifestations,
hemorrhage around the bite site and local blister formation is common. Tissue
necrosis is seen less frequently. Local and scattered discoloration of skin can
- Hematology: Generally Lachesis venom consumes prothrombin and fibrinogen.
This results in a DIC type coagulopathy with an increase in coagulation and
bleeding times. Fibrinogen levels and sedimentation rates are generally
decreased. White blood cell counts may elevate and hematocrit decrease, but
cell morphology is usually within normal limits.
- Physical Exam: Abdomen - painful abdomen on palpation with hyperactive
bowel sounds on percussion. Cardiovascular - decreased heart sounds with
bradycardia. Extremity - pain to touch and manipulation, with blood oozing
from the wound site.
- Fang Marks: Fang marks may be present as one or more well defined
punctures, as a series of small lacerations, or scratches, or there may not be
any noticeable or obvious markings where the bite occurred. The absence of
fang marks does not preclude the possibility of a bite (especially if a
juvenile snake is involved). The presence of fang marks does not always imply
that envenomation occurred. Multiple bites inflicted by a single snake are
also possible, and should be noted if present. WATCH THE PATIENT CLOSELY.
- Severe Envenomation: One or more of the following clinical pictures can
1. Hypotension and decreased heart rate secondary to peripheral circulatory
2. Intense colic with bloody diarrhea.
- Admit patient to an emergency of trauma service and call the consultant
identified by the Poison Control Center.
- Begin a peripheral intravenous infusion (18 gauge catheter) of Lactated
Ringers Solution at the rate of 250 cc/hr.
- Draw blood from the contralateral arm, and collect urine for the following
laboratory tests. Mark STAT.
- Type and Cross Match TWO units of whole blood.
- CBC with differential and platelets.
- Coagulation Parameters:
- Prothrombin Time (PT)
- Partial Thromboplastin Time (PTT)
- Fibrinogen levels
- Fibrin Degradation Products
- Serum Electrolytes, BUN/Creatinine, Calcium, Phosphorus.
- Lactate Dehydrogenase (with Isoenzyme analysis). Isoenzyme analysis may
indicate multiple targets of venom components which may dictate further
- Urinalysis (Macroscopic and Microscopic Analysis). Must include analysis
- Free Protein
- Electrocardiogram. Place patient on continuous cardiac monitoring.
- Intermittent or indwelling Foley Catheter to monitor urine output may be
necessary in the conscious impaired patient.
- Additional tests as needed or indicated by the patient's hospital
- It may be necessary or practical to repeat some of the above serum and
urine tests periodically over the hospital course to monitor the effects of
antivenom therapy or to detect late changes in laboratory values.
- OBSERVE PATIENT CLOSELY for signs and symptoms of envenomation which
usually manifest between 15 minutes and two hours after the bite occurred.
- If NONE of the signs or symptoms have been noted after two hours, there is
a possibility that the patient received a dry bite (no venom injected).
- Remove the constricting band, watching carefully for any changes in the
patient's status. If any changes occur, assume the patient has been
envenomed, and prepare to give antivenom immediately (as directed below).
- If signs and symptoms still fail to manifest, continue CLOSE observation of
the patient for an additional 12 to 24 hours.
- IF ANY SIGN OR SYMPTOM becomes apparent or has been noted during the course
of treatment, begin antivenom therapy as follows:
- Patients manifesting severe symptoms or are suspected of having an
intravenous injection of venom should be treated immediately with antivenom and
should not undergo skin testing. Corticosteroid adjuncts may facilitate the
delivery of rapid infusion. One should use the dilutions below, but infuse at
a rate of 1 vial (10 cc) per minute.
- If the patient is exhibiting signs of envenomation, inject intracutaneously
the skin test sample included in the antivenom package, sufficient to raise a
- The skin test should be read after 15 minutes, but it is wise to check the
test area and observe the patient constantly during the period following the
injection. If there is no evidence of erythema or vesicular response, the test
should be considered negative.
- A positive test IS NOT a contraindication to giving antivenom, but should
alert the clinician that the rate at which the antivenom is delivered and/or
the use of corticosteroids may need to be adjusted to control potential
- Assuming that the above skin testing precautions have been done,
reconstitute the contents of 5 vials of Wyeth Crotalidae Polyvalent Antivenom
in Lactated Ringers Solution. Gently shake the vials to assure that the
contents are thoroughly mixed, and that there is a minimum of undissolved
particles. Transfer the dissolved solution via a syringe to an IV piggyback
setup with a volumetric regulator. Make sure that there are no undissolved
particles in the solution transfer.
- Administer the diluted antivenom intravenously over a period of 10 minutes
for the first vial (1 cc/minute).
- Should any signs of ALLERGY/ANAPHYLAXIS (e.g. coughing, dyspnea, urticaria,
itching, increased oral secretions, etc.) develop, immediately discontinue the
administration of antivenom and treat symptoms with Corticosteroids,
Epinephrine, Benadryl, Atarax, and/or other Antihistamines as necessary. As
soon as the patient is stabilized, continue the antivenom infusion at a slower
- After 10 minutes of antivenom administration, the constricting band may be
- Assuming that the patient is tolerating the infusion well, additional
antivenom may be given at a rate of one vial per 5-10 minutes. The first 5
vials should be given over the first hour of treatment.
- Antivenom Therapy is the mainstay of treatment for rattlesnake
envenomation. Many of the symptoms are ameliorated or entirely eliminated by
the antivenom alone. Other symptoms will require additional modalities of
therapy to correct.
- Cardiovascular symptoms are usually seen in severe envenomations. They
usually present as hypotension, decreased heart rate, and diminished heart
sounds. Patients should be treated for peripheral circulatory collapse by
continuing peripheral I.V. infusion of Lactated Ringers about 250 cc/hr and
administering vasopressors and volume expanders.
- Intense colic and bloody diarrhea is seen in severe envenomations. It may
necessitate use of antispasmodics and/or blood transfusions.
- If significant limb swelling occurs, orthopaedic evaluation with
intracompartment and subcutaneous tissue pressure measurements can be obtained.
Surgical debridement or fasciotomy is very rarely if ever indicated.
- Hematologic symptoms may present as a Disseminated Intravascular
Coagulopathy, and are treated as other DICs.
- It is important to keep venom neutralization current and continuous. The
best method to accomplish this is to keep a close watch on the patient's
status. If the present condition does not improve, or should it worsen for any
reason, additional antivenom should be administered. Give all additional
antivenom in 5 vial increments. Again, dilute the antivenom 1 to 10 in
Lactated Ringers, transfer the solution to an IV piggyback setup, and deliver
over a period of 5-10 minutes per vial. One should anticipate using 5-40 vials
for moderate to severe bites.
- It is advisable to check periodic serum and urine analyses during therapy
as outlined above.
- It is always best to keep the patient in an Intensive Care setting until
free of major symptoms for 24 hours. The patient should be observed in the
hospital for at least 24 hours after the major symptoms abate.
- It is important that the patient be placed at rest, kept warm, and avoid
- Symptom variability: As noted above, the variability of symptoms in
rattlesnake envenomation can be great. It is important to note the continual
progression of symptoms throughout the course of therapy, and give additional
antivenom as necessary to titrate these symptoms.
- Fluid management is very important in snakebite cases. The patient
should be well hydrated and a brisk urine output maintained.
- Morphine is CONTRAINDICATED because of its tendency to suppress respiration.
Alcohol should also be avoided.
- In cases which Circulatory Shock remains uncorrected by antivenom
therapy, plasma volume expanders and/or vasopressor agents may be given with
- In cases of intense colic, the use of antispasmodics may be considered.
- If the patient remains oligouric, dialysis should be considered early.
- Tetanus prophylaxis should be current.
- Antibiotics are NOT recommended prophylactically.
- Local Tissue Damage: Prompt delivery of antivenom following the bite may
lessen the extent of local tissue damage, although some evidence suggests that
certain antivenoms have less efficacy in ameliorating or protecting against the
local action of Lachesis venom. This latter statement should not be held as a
contraindication to the use of antivenom in those Lachesis bites in which local
- Multiple Bites: It is possible for Lachesis to deliver more than one bite
in a single attack and thus may inject a large volume of venom. If there is
evidence that such an attack occurred (i.e. history or multiple bite sites),
twice the initial dose of antivenom should be given (i.e. 10 vials over 70-100
minutes at the rate of one vial per 5-10 minutes). Always watch closely for
signs of allergic response; if they occur, treat appropriately and with slow
infusion rate. Give all subsequent doses in 5 vial increments at a rate of 1
vial per 5-10 minutes as necessitated by the presence of continued signs and
- Severe Envenomations: If the patient shows severe signs of envenomation,
particularly if early after the bite, treat as a multiple bite, administering
10 vials of antivenom over the first 70-100 minutes. Give all subsequent doses
in 5 vial increments at a rate of 1 vial/5-10 minutes as necessitated by the
presence of continued signs and symptoms.
The following references are recommended for further indepth reading. This
material includes case histories, guidelines, and recent findings in South
American literature. These should be read only after treatment has begun and
the patient is in stable status.
- Wyeth Crotalidae Polyvalent Antivenom: Wyeth Laboratories. Lyophilized
polyvalent Anti-snake venom: Directions of Use (Package insert with
Antivenom). January 1984.
- Silva, J.: Accidentes Humanos por Las Serpientes de los Generos Bothrops y
Lachesis. Mem. Inst. Butantan. 44/45: 403-423, 1980/81.
- Ayerbe, S., Paredos, A., Galves, D.A.: Estudio Retrospectivo Sobre
Ofidiotoxicosis en el Departamento del Cauca. Caud Med. Pop. (Columbia) 40-2:
- Ayerbe, S., Otero, L.M., Galves, D., Paredes, A., Vasquez, A.: Estudio
Retrospectivo Sobre Ofidiotoxicosis en el Departamento del Cauca. Cuadernos de
Medicina Popayan (Columbia) 2(3), November 1977.
- Barrantes, A., Solis, V., Bolanos, R.: Alteracion de los Mechanisimos de la
Coagulacion en el Envenenamiento por Bothrops asper (Terciopelo). Toxicon 23.
No. 3, 399-407, 1985.
- Marinkelle, C.J.: Accidents by Venemous Animals in Columbia. Industrial
Medicine and Surgery. 35:11, 988-992, 1966.
- Morre, G.M., Dewling, H., Minton, S.A., Russell, F.E.: Poisonous Snakes of
the World. U.S. Government Printing Office, Washington, D.C., 1968.
- Russell, F.E.: Snake Venom Poisoning. Scholium International, Inc. Great
Neck, New York, 1983.
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