Environmental Dermatology

What’s Eating You? Dusky Pigmy Rattlesnake Envenomation and Management

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The dusky pigmy rattlesnake (Sistrurus miliarius barbouri) is a pit viper (Crotalidae family) along with diamondback rattlesnakes, water moccasins, and copperheads. Although it is a small snake, it is responsible for envenomations requiring hospitalization. We present the case of a 54-year-old man who was bitten in the left index finger with onset of coagulopathy successfully treated with crotalidae polyvalent immune fab (CPIF) antivenom.

Practice Points

  • Avoid icing, cutting, and suctioning a snakebite wound or using tourniquets.
  • Immobilize and elevate the affected extremity and seek medical attention immediately for early initiation of antivenom treatment.
  • Remove rings or constrictive items in the event of swelling.


 

References

Rattlesnakes are pit vipers with a rattle attached to the tip of the tail and facial pits located between the eyes and nose with a special organ that detects heat energy (infrared light) and is used for hunting prey. There are 2 genera of rattlesnakes, Sistrurus (3 species) and Crotalus (23 species). 1 The pigmy rattlesnake belongs to the Sistrurus miliarius species that is subdivided into 3 subspecies: the Carolina pigmy rattlesnake (Sistrurus miliarius miliarius), the Western pigmy rattlesnake (Sistrurus miliarius streckeri ), and the dusky pigmy rattlesnake (Sistrurus miliarius barbouri ). 1 The dusky pigmy rattlesnake is found in South Carolina, southern Georgia, southern Alabama, southeastern Mississippi, and Florida. 2 It is the most abundant venomous snake in Florida. 3 Its rattle is barely audible, and it is an aggressive small snake ranging in length from 38 to 56 cm. 4 Its venom is hemorrhagic, causing tissue damage but not containing neurotoxins. 4 Although bites can be painful, resulting in localized necrosis and rare loss of digits, it is unlikely for bites to be fatal given the snake’s small fangs, small size, and amount of envenomation. However, bites on children may require hospitalization. The venom contains proteins, polypeptides, and enzymes. 5 One such peptide, barbourin, inhibits a transmembrane receptor that plays a role in platelet aggregation. 6

We report a case of a 54-year-old man who was bitten on the left index finger by a dusky pigmy rattlesnake. We describe the clinical course and successful treatment with crotalidae polyvalent immune fab (CPIF) antivenom.

Case Report

A 54-year-old man presented to the emergency department with a rapidly swelling and erythematous left hand following a snakebite to the left index fingertip while weeding in his yard (Figure 1). The patient was able to kill the snake with a shovel and photograph it, which helped identify it as a dusky pigmy rattlesnake (Figure 2). Vitals on presentation included a blood pressure of 161/98, pulse oximeter of 99%, temperature of 36.4°C, pulse of 84 beats per minute, and respiratory rate of 16 breaths per minute.

Figure 1. Clinical appearance of a snakebite on the left index fingertip.

Figure 2. Dusky pigmy rattlesnake (Sistrurus miliarius barbouri).

Given the poisonous snakebite, the patient was admitted to the intensive care unit. Laboratory test results at admission revealed the following values: platelet count, 235,000/µL (reference range, 150,000–450,000/µL); fibrinogen, 226.1 mg/dL (reference range, 185–410 mg/dL); fibrin degradation products, less than 10 µg/mL (reference range, <10 µg/mL); glucose, 145 mg/dL (reference range, 74–106 mg/dL). The remainder of the complete blood cell count and metabolic panel was unremarkable. His blood type was O Rh+. Radiography of the left second digit did not show any fractures, dislocations, or foreign object.

After consulting with the Tampa General Hospital Florida Poison Information Center, 6 vials of CPIF antivenom in 250 mL of sodium chloride initially were infused intravenously, followed by 2 additional vials each at 6, 12, and 18 hours. Serial laboratory test results revealed white blood cell counts of 13,600, 10,000, 6800, 6100, and 6800/µL at 4, 15, 43, 65, and 88 hours postadmission, respectively. Platelet counts were 222,000, 159,000, 116,000, 99,000, and 129,000/µL at 4, 15, 43, 65, and 88 hours postadmission, respectively. The hemoglobin level was 14.8, 13.1, 13.8, 13.7, and 14.3 g/dL at 4, 15, 43, 65, and 88 hours postadmission, respectively. Other laboratory test results including prothrombin time (10.0 s), fibrinogen (226.1 mg/dL), and fibrin degradation products (<10 µg/mL) at 4 hours postadmission remained within reference range during serial monitoring.

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