Does the aggressive use of polyvalent antivenin for rattlesnake bites result in serious acute side effects?

To determine the incidence and severity of acute side effects from the use of polyvalent antivenin in victims of rattlesnake bites.

We retrospectively reviewed the records of all patients who presented with rattlesnake bites to a university teaching hospital during an 11-year period. From patient medical records, we extracted demographic data, clinical measurements, and outcomes during emergency department evaluation and subsequent hospitalization. Data regarding serum sickness were not collected.

Primary outcome variables were the occurrence of immediate hypersensitivity reaction to antivenin, the type of reaction, permanent disability at hospital discharge, and mortality.

We identified a total of 73 patients with rattlesnake bites during the study period. Bite envenomation was graded as nonenvenomated, 7 patients (10%); mild, 23 patients (32%); moderate, 32 patients (44%); and severe, 11 patients (15%). We identified 65 patients who received antivenin. Antivenin doses ranged from 1 to 30 vials per patient (mean, 12.0 +/- 6.0), for a total of 777 vials. In 43 patients (66%), 10 or more vials of antivenin were given. The mean number of vials of antivenin given to each snakebite grade were as follows: mild, 8.4 (+/-4.0); moderate, 11.8 (+/-5.7); and severe, 18.7 (+/-6.3). No deaths, amputations, or permanent disability from snakebite occurred in the patients receiving antivenin. Acute side effects of antivenin-occurring within the first 6 hours after administration-were seen in 12 patients (18%; 95% confidence interval, 10%-30%). Acute side effects consisted solely of urticaria in all but 1 patient (2%; 95% confidence interval, 0%-8%). This patient had a history of previous antivenin reaction and required a short course of intravenous epinephrine for blood pressure support. No other complications occurred.

The administration of polyvalent Crotalidae antivenin is safe. Acute hypersensitivity, when it occurs, consists solely in most cases of urticaria. Serious side effects are uncommon.