Clinical predictors of tissue necrosis following rattlesnake envenomation

Rattlesnake envenomation (RSE) causes edema, hemotoxicity and tissue necrosis. Necrosis may result in permanent disability.

To study patient-related factors associated with tissue necrosis after Crotalus envenomation.

Prospective cohort study of patients admitted to the Medical Toxicology service with diagnosis of RSE between April 2011 and November 2014. Inclusion criteria were age ≥18 years and upper extremity (UE) envenomation site. Primary outcome was tissue necrosis, including dermonecrosis, manifesting as bullae. Secondary outcome was amputation.

77 subjects, age 18 to 88 years, met inclusion criteria. Rattlesnake species was unknown in most cases. All received Fab antivenom. 62 (82%) had a digital envenomation. 31 (40.3%) had necrosis. Necrotic area ranged from 0.1 cm² to 14 cm². Procedural interventions, (superficial debridement, dermotomy, surgical exploration, and operative debridement of devitalized tissue) occurred in 25 (32.5%). Five (6.5%) underwent dermotomy and 6 (7.8%) operative debridement. No amputations were performed. Patients with cyanosis on presentation had increased risk of developing necrosis (11/12; RR 2.98 95% CI 1.99-4.46). Ecchymosis on presentation was also associated with increased risk of necrosis (24/32; RR 4.04 95% CI 2.08-7.86). Patients with social or regular ethanol use were more likely to develop necrosis than those without (28/53; RR 4.23 95% CI 1.42-12.6). Regular cocaine use was associated with increased risk of operative debridement (4/6; RR 9.13 95% CI 2.33-35.8). A nonsignificant risk of operative debridement occurred with tobacco use (RR 1.14 95%CI 0.99-1.31 p = 0.09). Time to antivenom did not correlate with risk of necrosis.

UE RSE patients who presented with cyanosis, ecchymosis or history of ethanol use were at increased risk of developing necrosis. Cocaine use was associated with increased risk of operative debridement.