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Snake Envenomation, Rattle: Differential Diagnoses & Workup

Author: Sean P Bush, MD, FACEP, Professor of Emergency Medicine, Loma Linda University School of Medicine; Consulting Staff, Envenomation Specialist, Department of Emergency Medicine, Loma Linda University Medical Center
Contributor Information and Disclosures

Updated: Jul 24, 2008

Differential Diagnoses

Bee and Hymenoptera Stings
Scorpion Envenomations
Bites, Animal
Snake Envenomations, Coral
Bites, Insects
Snake Envenomations, Moccasins
Cellulitis
Snake Envenomations, Mohave Rattle
Lizard Envenomations
Spider Envenomations, Brown Recluse
Necrotizing Fasciitis
Spider Envenomations, Tarantula

Workup

Laboratory Studies

  • Coagulopathy commonly occurs with rattlesnake envenomation, although clinical bleeding is uncommon. Defibrination and/or thrombocytopenia most often characterize snakebite coagulopathy. Defibrination is manifested by low serum fibrinogen, elevated prothrombin time, and elevated fibrin split products (FSP). Venom-induced thrombocytopenia may exist in association with or independently of defibrination. Abnormal coagulation parameters may last for a week or more. Recurrence of coagulopathy after resolution with antivenom has been reported.
    • Complete blood count (CBC) with differential
    • Platelets
    • Prothrombin time
    • Activated partial thromboplastin time
    • Fibrinogen
    • Type and screen
    • Urinalysis
  • Rhabdomyolysis may occur from severe envenomation but is best described after canebrake (Crotalus horridus atricaudatus) and Mohave (Crotalus scutulatus) rattlesnake envenomations. Rhabdomyolysis may lead to myoglobinuric renal failure and subsequent electrolyte abnormalities, such as hyperkalemia, hypokalemia, or hypocalcemia.
    • Creatine kinase (CK)
    • Electrolytes
    • Blood urea nitrogen (BUN), creatinine
    • Calcium
    • Phosphorus
    • Urinalysis
  • For respiratory difficulty, consider arterial blood gases (ABGs), although arterial puncture should be avoided if a severe venom-induced coagulopathy develops.
  • Obtain laboratory and other diagnostic data on a case-by-case basis. Factors to consider may include severity of envenomation, physician preference, and cost.

Imaging Studies

  • Plain radiographs may depict teeth or fangs retained in the wound.
  • Consider a head CT if the patient has a headache or altered level of consciousness (ALOC) with a severe coagulopathy.

Other Tests

  • Obtain an electrocardiogram (ECG), if indicated.
  • Skin testing
    • Skin testing is not necessary before administering Crotaline Fab antivenom (CroFab) therapy. Skin testing is described below for educational purposes or for the unusual case in which a practitioner determines it is indicated.
    • Intracutaneous injection of 0.02-0.03 mL of a 1:10 dilution of horse serum or antivenom is recommended in the Antivenin (Crotalidae) Polyvalent package insert.
      • A positive test result is manifested by the development of a wheal within 5-30 minutes.
      • However, skin testing is very unreliable. False-positive and false-negative test results may occur.
      • Using antivenom (further diluted to 1:100), rather than the horse serum control that is supplied, may increase the sensitivity and specificity of the test.
      • Skin testing may be considered useful in variably predicting immediate hypersensitivity in cases of moderate envenomation when it is uncertain whether the need for antivenom outweighs the risk of anaphylaxis.
      • Skin testing may sensitize individuals at risk for future exposures to antivenom, or it may precipitate anaphylaxis.
      • If antivenom is clearly indicated, it should be started as described below, without waiting to conduct a skin test.

Procedures

  • Central venous or interosseous access may need to be obtained. However, avoid placing a central line in a noncompressible site (eg, internal jugular) because of the risk of bleeding from venom-induced coagulopathy.
  • Fasciotomy may be indicated if measured compartment pressures remain persistently and severely elevated despite adequate antivenom. CroFab has been shown to limit the decrease in perfusion pressure associated with compartment syndrome.
    • Compartment syndrome may manifest subjectively, with complaints of increasing pain, and objectively, with tenderness on passive muscle stretch, a rock hard feel to the compartment or a diminished capillary refill.
    • True compartment syndrome is rare following snakebite, even in patients with severe edema, because most envenomations are believed to be subcutaneous.
    • Myonecrosis has been shown to occur from direct myotoxicity, even after fasciotomy of the affected compartment.
    • Distinguishing compartment syndrome from the effects of envenomation may be difficult. Similar to compartment syndrome, rattlesnake envenomation may cause a bluish discoloration of the skin or pallor (because of subcutaneous bruising), severe swelling, paresthesias, and pain. If effects are only caused by envenomation and the patient does not have compartment syndrome, capillary refill is normal and compartmental pressure is not elevated.

More on Snake Envenomation, Rattle

Overview: Snake Envenomation, Rattle
Differential Diagnoses & Workup: Snake Envenomation, Rattle
Treatment & Medication: Snake Envenomation, Rattle
Follow-up: Snake Envenomation, Rattle
Multimedia: Snake Envenomation, Rattle
References
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References

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  4. Bronstein AC, Spyker DA, Cantilena LR Jr, Green J, Rumack BH, Heard SE. 2006 Annual Report of the American Association of Poison Control Centers' National Poison Data System (NPDS). Clin Toxicol (Phila). Dec 2007;45(8):815-917. [Medline].

  5. Burgess JL, Dart RC. Snake venom coagulopathy: use and abuse of blood products in the treatment of pit viper envenomation. Ann Emerg Med. Jul 1991;20(7):795-801. [Medline].

  6. Burgess JL, Dart RC. Snake venom coagulopathy: use and abuse of blood products in the treatment of pit viper envenomation. Ann Emerg Med. Jul 1991;20(7):795-801. [Medline].

  7. Bush SP. Snakebite suction devices don't remove venom: they just suck. Ann Emerg Med. Feb 2004;43(2):187-8. [Medline].

  8. Bush SP, Green SM, Laack TA, Hayes WK, Cardwell MD, Tanen DA. Pressure immobilization delays mortality and increases intracompartmental pressure after artificial intramuscular rattlesnake envenomation in a porcine model. Ann Emerg Med. Dec 2004;44(6):599-604. [Medline].

  9. Bush SP, Green SM, Moynihan JA, Hayes WK, Cardwell MD. Crotalidae polyvalent immune Fab (ovine) antivenom is efficacious for envenomations by Southern Pacific rattlesnakes (Crotalus helleri). Ann Emerg Med. Dec 2002;40(6):619-24. [Medline].

  10. Bush SP, Hegewald KG, Green SM, Cardwell MD, Hayes WK. Effects of a negative pressure venom extraction device (Extractor) on local tissue injury after artificial rattlesnake envenomation in a porcine model. Wilderness Environ Med. Fall 2000;11(3):180-8. [Medline].

  11. Bush SP, Jansen PW. Severe rattlesnake envenomation with anaphylaxis and rhabdomyolysis. Ann Emerg Med. Jun 1995;25(6):845-8. [Medline].

  12. Bush SP, Wu VH, Corbett SW. Rattlesnake venom-induced thrombocytopenia response to Antivenin (Crotalidae) Polyvalent: a case series. Acad Emerg Med. Feb 2000;7(2):181-5. [Medline].

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  17. French WJ, Hayes WK, Bush SP, Cardwell MD, Bader JO, Rael ED. Mojave toxin in venom of Crotalus helleri (Southern Pacific Rattlesnake): molecular and geographic characterization. Toxicon. Dec 1 2004;44(7):781-91. [Medline].

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  22. Langley RL, Morrow WE. Deaths resulting from animal attacks in the United States. Wilderness Environ Med. 1997;8:8-16.

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  25. Offerman SR, Bush SP, Moynihan JA, Clark RF. Crotaline Fab antivenom for the treatment of children with rattlesnake envenomation. Pediatrics. Nov 2002;110(5):968-71. [Medline].

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  29. Watson WA, Litovitz TL, Klein-Schwartz W, Rodgers GC Jr, Youniss J, Reid N, et al. 2003 annual report of the American Association of Poison Control Centers Toxic Exposure Surveillance System. Am J Emerg Med. Sep 2004;22(5):335-404. [Medline].

  30. Watson WA, Litovitz TL, Klein-Schwartz W, Rodgers GC Jr, Youniss J, Reid N, et al. 2003 annual report of the American Association of Poison Control Centers Toxic Exposure Surveillance System. Am J Emerg Med. Sep 2004;22(5):335-404. [Medline].

  31. Wingert WA, Chan L. Rattlesnake bites in southern California and rationale for recommended treatment. West J Med. Jan 1988;148(1):37-44. [Medline].

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Further Reading

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Keywords

rattlesnake, rattlesnake bite, rattlesnake venom, rattlesnake envenomation, Crotalus species, Sistrurus species, rattle snake envenomation, pit vipers

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Contributor Information and Disclosures

Author

Sean P Bush, MD, FACEP, Professor of Emergency Medicine, Loma Linda University School of Medicine; Consulting Staff, Envenomation Specialist, Department of Emergency Medicine, Loma Linda University Medical Center
Sean P Bush, MD, FACEP is a member of the following medical societies: American College of Emergency Physicians, International Society on Toxicology, Society for Academic Emergency Medicine, and Wilderness Medical Society
Disclosure: Protherics Consulting fee Consulting; Nycomed (formerly Fougera) Grant/research funds Speaking and teaching; Rare Disease Therapeutics Grant/research funds Research; Bioclon Grant/research funds Research

Medical Editor

Robert L Norris, MD, Associate Professor, Department of Surgery; Chief, Division of Emergency Medicine, Stanford University Medical Center
Robert L Norris, MD is a member of the following medical societies: American College of Emergency Physicians, American Medical Association, California Medical Association, International Society of Toxinology, Society for Academic Emergency Medicine, and Wilderness Medical Society
Disclosure: Nothing to disclose.

Pharmacy Editor

John T VanDeVoort, PharmD, Regional Director of Pharmacy, Sacred Heart & St. Joseph's Hospitals
John T VanDeVoort, PharmD is a member of the following medical societies: American Society of Health-System Pharmacists
Disclosure: Nothing to disclose.

Managing Editor

James Steven Walker, DO, MS, Clinical Professor of Surgery, Department of Surgery, University of Oklahoma Health Sciences Center
James Steven Walker, DO, MS is a member of the following medical societies: American Academy of Emergency Medicine, American College of Emergency Physicians, American College of Osteopathic Emergency Physicians, and American Osteopathic Association
Disclosure: Nothing to disclose.

CME Editor

John D Halamka, MD, MS, Associate Professor of Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center; Chief Information Officer, CareGroup Healthcare System and Harvard Medical School; Attending Physician, Division of Emergency Medicine, Beth Israel Deaconess Medical Center
John D Halamka, MD, MS is a member of the following medical societies: American College of Emergency Physicians, American Medical Informatics Association, Phi Beta Kappa, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

Chief Editor

Jonathan Adler, MD, Attending Physician, Department of Emergency Medicine, Massachusetts General Hospital; Division of Emergency Medicine, Harvard Medical School
Jonathan Adler, MD is a member of the following medical societies: American Academy of Emergency Medicine and Society for Academic Emergency Medicine
Disclosure: eMedicine.com, Inc. Consulting fee Consulting

 
 
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