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

Objective To determine the incidence and severity of acute side effects fro m the use of polyvalent antivenin in victims of rattlesnake bites. Design W e retrospectively reviewed the records of all patients who presented with r attlesnake bites to a university teaching hospital during an 11-year period . From patient medical records, we extracted demographic data, clinical mea surements, and outcomes during emergency department evaluation and subseque nt hospitalization. Data regarding serum sickness were-not collected. Outco me measures Primary outcome variables were the occurrence of immediate hy p ersensitivity reaction to antivenin, the type of reaction, permanent disabi lity at hospital discharge, and mortality. Results We identified a total of 73 patients with rattlesnake bites during the study period. Bite envenomat ion 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 vi als per patient (mean, 12.0 +/-6.0), for a total of 777 vials. In 43 patien ts (66%), 10 or more vials of antivenin were given. The mean number of vial s 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, amput ations, or permanent disability from snakebite occurred in the patients rec eiving antivenin. Acute side effects of antivenin-occurring within the firs t 6 hours after administration-were, seen in 12 patients (18%; 95% confiden ce interval, 10%-30%). Acute side effects consisted solely of urticaria in all but I patient (2%; 95% confidence interval, 0%-8%). This patient had a history of previous antivenin. reaction and required a short course of intr avenous epinephrine for blood pressure support. No other complications occu rred. Conclusion The administration of polyvalent Crotalidae antivenin is s afe. Acute hypersensitivity, when it occurs, consists solely in most cases of urticaria. Serious side effects are uncommon.