Background: Crotalus viridis viridis, commonly known as the Prairie Rattlesnake (PR), is responsible for nearly all Crotalus envenomations in the Northern Great Plains of the United States. A paucity of literature exists regarding PR envenomations. A review of data from a single poison center (PC) is presented to augment current knowledge.
Methods: A retrospective review of all cases of humans envenomated by PRs reported to a PC from 2006 to 2010 was performed. Data recorded included age, site of bite, clinical effects (local and systemic), CroFab R administration and duration of hospitalization.
Results: 45 total cases of PR exposures were identifi ed with 39 included in the final analysis. 6 cases were excluded due to inconsistent data. All patients survived. Twelve (31%) patients were pediatric (ages 4-13 y), and 27 (69%) were adults (ages 18-76 y). The site of the bite was the upper extremity in 12 cases (31%) and the lower extremity in 27 cases (69%). Isolated local effects were described in 10 patients (20%). Commonly reported local effects included edema (n 32, 82%), pain (n 24, 62%), ecchymosis (n 19, 49%), erythema (n 10, 26%), paresthesias (n 2), and bullae (n 2). Systemic effects were reported in 29 patients (74%). The most commonly reported systemic effects included thrombocytopenia (n 10, 26%), hypofibrinogenemia (n 8, 20%), hypotension (n 7, 18%), and gastrointestinal effects such as vomiting (n 6) and nausea (n 4). Additional systemic effects included coagulopathy (n 4), tachycardia (n 4), peri-oral paresthesias (n 5), and significant airway associated complications such as oropharyngeal swelling (n 4), tongue swelling (n 3), lip edema (n 1), and angioedema (n 1). Intubation was required in 6 patients (15%). Diaphoresis (n 3), fecal incontinence (n 1), diarrhea (n 1), and rash/hives (n 1) were also observed. CroFab R was administered to 33 patients (85%); the average number of CroFab R vials administered per patient was 14 (range 3-30). Thirty-six patients (92%) were admitted to the hospital with an average stay of 4.6 days.
Conclusion: Similar to other Crotalus species, Prairie rattlesnake envenomations result in hematological disturbances. However, the risk of airway compromise from oropharyngeal swelling appears to be an important consideration in the envenomation profile and subsequent treatment. This case series of PR envenomations demonstrates that significant morbidity may occur but mortality is rare. This is consistent with the relative mid-strength LD 50 of Prairie rattlesnake venom of 2.1 mg/kg as compared to other Crotalus species such as the Mojave (Crotalus scutulatus , 0.24 mg/kg LD 50) and Western diamondback (Crotalus atrox, 5.0 mg/kg LD 50).