for bites by
United States & Canadian Rattlesnakes
(Crotalus species)

In the event of an actual or probable bite from a U.S. or Canadian rattlesnake, execute the following first aid measures without delay.


  1. Make sure that the responsible snake or snakes have been appropriately and safely contained, and are out of danger of inflicting any additional bites.


  1. Immediately call for transportation.



  1. 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.

  2. 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.

  3. 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.

  4. DO NOT remove the constricting band until the victim has reached the hospital and is receiving Antivenom.

  5. Have the Wyeth Crotalidae Polyvalent Antivenom ready for the emergency crew to take with the victim to the hospital. Give them the following:

    1. the available antivenom (at least 10 vials)
    2. the accompanying instruction (Protocol) packet
    3. 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
United States & Canadian Rattlesnakes
(Crotalus species)

The bite of rattlesnakes is rarely fatal. Victims will usually complain of pain at the bite site and swelling may be evident. Tremendous local tissue destruction can ensue. Prompt medical therapy avoids this problem. Please read the attached and respond appropriately.

  1. First Aid:

    1. Apply constricting band if not already present, proximal to bite on arms, legs, hands, or feet.

    2. Transport to a medical center emergency or trauma service.

  2. Medical Management:

    1. 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.

    2. Observe for Signs and Symptoms of Envenomation.

    3. If signs or symptoms are present, perform the following:

      1. Apply intradermal skin test.

      2. Administer Lactated Ringers intravenously at a

        rate of 200 cc/hour. Obtain appropriate blood and urine laboratory data.

      3. Wait 20 minutes.

      4. Reconstitute 5 vials of antivenom in 50 cc Lactated Ringers.

      5. 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.

      6. Monitor signs, symptoms, and laboratory data and

        administer additional aliquots of 5 vials of antivenom as needed to neutralize signs and symptoms. Average treatment is 15 vials (range 0-40 vials).

      7. 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.

      8. 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
United States & Canadian Rattlesnakes
(Crotalus species)

This person has received a bite and probable envenomation from a rattlesnake. There are several species of rattlesnakes within the United States and Canada, envenomation by all of which will be covered by this protocol. Those snakes which are indigenous to Mexico, Central America, and South America, whose ranges do not overlap into the United States, will be covered in separate protocols. Fatalities in modern times are infrequent. The venom can produce a wide spectrum of clinical manifestations, including local tissue destruction, cardiovascular collapse, coagulopathy, and with some species neurotoxic and neuromuscular symptoms.

Please read and execute the following procedures without delay.

  1. 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.

  2. Make sure that at least 20 vials of Crotalidae Polyvalent Antivenom (Wyeth) are available. This antivenom contains the necessary fractions to neutralize the venoms of all United States and Canadian rattlesnakes.

  3. If the patient has been envenomated, the initial treatment is 5 to 10 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:

The specific signs and symptoms which may manifest in a patient who has been envenomated will vary in presence and in severity, depending on several factors noted in the General Considerations below. The time course of development will also vary considerably from case to case. The following list of signs and symptoms represent a general compilation enumerated from a series of 100 cases of rattlesnake envenomation (Russell, 1983). Not all of the symptoms will necessarily develop, even with severe envenomation.

Sign or Symptom Frequency
Pain 65-95/100

Swelling, Edema 74/100

Weakness 72/100

Sweating and or Chills 64/100

Numbness, tingling
(circumoral, lingual, scalp, feet, etc.)

Pulse rate changes 60/100

Faintness, dizziness 57/100

Ecchymosis 51/100

Nausea and/or vomiting 48/100

Blood pressure changes 46/100

Numbness, tingling in the affected part 42/100

Decreased blood platelets 42/100

Fasciculations 41/100

Vesicles or boli 40/100

Regional lymph adenopathy 40/100

Respiratory rate changes 40/100

Increased blood clotting time 39/100

Decreased hemoglobin 37/100

Thirst 34/100

Change in body temperature 31/100

Local tissue necrosis 27/100

Abnormal electrocardiogram 26/100

Glycosuria 20/100

Increased salivation 20/100

Spearing of red cells 18/100

Cyanosis 16/100

Proteinuria 16/100

Hematemesis, hematuria, melena 15/100

Unconsciousness 12/100

Blurring of vision 12/100

Muscle contraction 6/100

Increased blood platelets 4/ 25

Swollen eyelid 2/100

Retinal hemorrhage 2/100

Convulsions 1/100

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). However with rattlesnake envenomation, fang marks are invariably present and are generally seen on close examination. Bleeding may persist from the fang wounds. The presence of fang marks does not always indicate envenomation; rattlesnakes when striking in defense will frequently elect not to inject venom with the bite, resulting in a dry bite (i.e. no envenomation). Manifestations of signs and symptoms of envenomation is necessary to confirm the diagnosis of snake venom poisoning.

Medical Management:

  1. Admit patient to an emergency or trauma service and call the consultant identified by the Poison Control Center.

  2. Begin a peripheral intravenous infusion (18 gauge catheter) of Lactated Ringers Solution at the rate of 250 cc/hr.

  3. Draw blood from the contralateral arm, and collect urine for the following laboratory tests. Mark STAT.

    1. Type and Cross Match TWO units of whole blood.

    2. CBC with differential and platelets.

    3. Coagulation Parameters:

      1. Prothombin Time (PT)
      2. Partial Thromboplastin Time (PTT)
      3. Fibrinogen levels
      4. Fibrin Degradation Products

    4. Serum Electrolytes, BUN/Creatinine, Calcium, Phosphorus.

    5. Lactate Dehydrogenase (with Isoenzyme analysis). Isoenzyme analysis may indicate multiple targets of venom components which may dictate further management.

    6. Urinalysis (Macroscopic and Microscopic Analysis).

      Must include analysis for:

      1. Free Protein
      2. Hemoglobin
      3. Myoglobin

    7. Electrocardiogram (Sinus Tachycardia would be expected).

    8. Intermittent or indwelling Foley Catheter to monitor

      urine output may be necessary in the conscious, impaired patient.

    9. Additional tests as needed or indicated by the patient's hospital course.

    10. 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.

  4. OBSERVE PATIENT CLOSELY for signs and symptoms of envenomation, which usually manifest between 15 minutes and two hours after the bite occurred.

    1. 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).

      1. 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).

    2. If signs and symptoms still fail to manifest, continue CLOSE observation of the patient for an additional 12 to 24 hours.

  5. IF ANY SIGN OR SYMPTOM becomes apparent or has been noted during the course of treatment, begin Antivenom Therapy as follows:

    1. Patients manifesting severe symptoms or who 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.

    2. If the patient is exhibiting envenomation, inject intracutaneously the skin test sample included in the antivenom package, sufficient to raise a small weal.

    3. 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.

    4. 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 untoward responses.

    5. 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. Vigorously 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.

    6. Administer the diluted antivenom intravenously over a period of 10 minutes for the first vial (1 cc/minute).

    7. 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 rate.

    8. After 10 minutes of antivenom administration, the constricting band may be removed.

    9. Assuming that the patient is tolerating the infusion well, additional antivenom may be given at a rate of 1 vial every 5-10 minutes. The first 5 vials should be given over the first hour of treatment.

  6. 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.

    1. Hematologic symptoms may present as Disseminated Intravascular Coagulopathy, and are treated essentially as other DICs.

    2. Neurological symptoms: If the patient is suspected of having been bitten by the Mojave rattlesnake (Crotalus scutulatus), the patient may develop neurological symptoms including respiratory obstruction or failure which must be treated as an immediate emergency. The neurologic symptoms, as others, should be improved by antivenom. If breathing becomes impaired, respiratory assistance may be necessary, and intubation and ventilation may be appropriate adjuncts in certain clinical settings. Secretions may become copious, necessitating suctioning.

  7. 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 thoroughly in Lactated Ringers, transfer the solution to an IV piggyback setup, and deliver over a period of 5-10 minutes per vial. Most bites today are treated with 15 to 20 vials of antivenom. The range is 5 to 40 vials.

  8. It is advisable to check periodic serum and urine analyses during therapy as outlined above.

  9. 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.

General Considerations:

  1. It is important that the patient be placed at rest, kept warm, and avoid unnecessary movement.

  2. 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.

  3. Neurotoxic symptoms: In the United States one species of rattlesnake, the Mojave Rattlesnake (Crotalus scutalatus), is known to produce a clinical picture with predominantly neurotoxic symptoms. The onset and progression of the symptoms may be rapid and subtle. In addition, they are more rapidly reversed in their early stages than when fully developed. It may be necessary to wake the patient and perform a brief neurologic check every hour or so to assure that breathing and other vital functions are not impaired. Carefully note the progression of respiratory paralysis which may be present. Be prepared to intubate and ventilate as necessary.

    Other rattlesnake species in the United States may have neurotoxic components in their venom. However generally speaking, these are at low levels and do not usually manifest significant clinical symptoms.

  4. Compartment Syndrome: It should be noted that fascial compartment syndrome in rattlesnake envenomations is very rare. Limbs may swell significantly, but rarely involve specific fascially bound compartments. If however the logistics of the bite raise a high index of suspicion for Compartment Syndrome, monitoring with a Wick Catheter or appropriate pressure devices may be necessary. Fasciotomy is rarely if ever recommended in these patients.


The following references are recommended for further indepth reading. This material includes case histories, guidelines, and recent findings in crotalus literature. These should be read only after treatment has begun, and the patient is in stable status.

  1. Russell, F.E.: Snake Venom Poisoning. Scholium International, Inc. Great Neck, New York, 1983.

  2. Parrish, H.M.: Incidence of treated snakebite in the United States. Public Health Rep. 81: 269-276, 1966.

  3. Russell, F.E., Cawlson, R.W., Wainschel, J., Osborne, A.H.: Snake venom poisoning in the United States. JAMA 233: 341-344, 1975.

  4. Schmidt, K.P. and Inger, R.F.: Living Reptiles of the World. New York: Doubleday & Company 1957.

  5. Gans, C., Bellairs, A. and Parsons, T. (Eds.): Biology of the Reptilia, Volume 1. London: Academic Press. 1969

  6. Phelps, T.: Poisonous Snakes. Poole, Dorset: Blandford Press. 1981

  7. Klauber, L.M.: Rattlesnakes, Volume I. Berkeley: University of California Press. 1972

  8. Klauber, L.M.: Rattlesnakes, Volume II. Berkeley: University of California Press. 1972

  9. Klauber, L.M.: Rattlesnakes. Berkeley: University of California Press. 1982

  10. Minton, S.A., and Minton, M.R.: Venemous Reptiles. New York: Scribner's Sons. 1969

  11. Bronstein, A.C., Russell, F.E., Sullivan, J.B.: Negative pressure suction in the field treatment of rattlesnake bite victims.

  12. Davidson, T.M.: Intravenous Rattlesnake Envenomation. West J Med, 148: 45-47, 1988.

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