Which lab studies are performed in the evaluation of snakebite?

Updated: Apr 09, 2021
  • Author: Spencer Greene, MD, MS, FACEP, FACMT, FAAEM; Chief Editor: Joe Alcock, MD, MS  more...
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Answer

Patients with possible snakebite envenomation should have the following laboratory tests performed:

  • Complete blood cell count
  • Basic metabolic profile
  • Prothrombin time
  • Fibrinogen value
  • Creatine kinase value

Patients with systemic toxicity may warrant additional testing, including liver function tests, urinalysis, blood type and crossmatch, and venous blood gas analysis. Rotational thromboelastometry and thromboelastography are not readily available in many healthcare settings but may have a greater role in evaluating patients for hematotoxicity in the future.

Routine measurement of D-dimer and fibrin split products is not necessary because the results do not change management.

Hematologic toxicity is frequently observed following crotalid envenomation. It may be present on arrival or it may develop after several days. Specific laboratory abnormalities may include the following:

  • Coagulopathy (prothrombin time >15 seconds)
  • Hypofibrinogenemia (fibrinogen < 150 mg/dL)
  • Thrombocytopenia (platelet count < 150 x 10 3/µL)

In general, copperhead envenomations are associated with the least hematotoxicity. In a study of copperhead envenomations in Virginia, only 14% of copperhead envenomations had any type of hematologic toxicity. [39] A similar percentage of patients developed thrombocytopenia in a study conducted in the Carolinas, although coagulopathy and hypofibrinogenemia were observed in 24% and 63% of patients, respectively. [38]

Coagulopathy was observed in 19% of patients in a multicenter study of cottonmouth envenomations. [40]

Hematologic toxicity was seen in 76% of patients with rattlesnake envenomations. In the same population, 24% of patients had late hematotoxicity. In a study of high-risk snakebite victims, late coagulopathy was present in 32% of subjects. [25, 41]


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