European viper envenomings: Assessment of Viperfav™ and other symptomatic treatments

Abstract

The treatment of European viper envenomings is based on IV antivenom infusions. Viperfav™ contains purified F(ab′)₂ fragments of equine antibodies, and a 4 ml vial can neutralize 500–1000 mouse LD50 of Vipera aspis, V. ammodytes and V. berus venoms and is known to be safe and efficient. Assessments of Viperfav™ (dosage and timing of infusions) and of symptomatic treatments such as low-molecular-weight heparin (LWHM), corticosteroids and the routine use of antibiotic therapy have not as yet been reported. Objectives. The objective was to compare the efficacy and safety of Viperfav™ as a function of the time to infusion and to assess other symptomatic treatments given for European viper bites such as antibiotics, corticosteroids and LWMH. Methods. A prospective case review study of viper envenomings treated with Viperfav™ was compiled by the Angers Poisons Centre. The endpoints chosen were as follows: duration of hospital stay, complications (haematoma, infection) and persistent functional discomfort on day 15. Statistical studies were based on multivariate data analysis (MVA). Results. 268 moderate or severe envenomings (Grades II and III) recorded in adults and children between 1999 and 2009 were included in the study. A time to the Viperfav™ infusion < 10 h after the bite (179 patients vs. 72) significantly reduced the incidence of haematomas (OR 2.3; p < 0.006), functional discomfort (OR 3.7; p < 10 - 4) and length of hospital stay (OR 2.1; p < 0.03). Multiple doses of Viperfav™ (2 or 3 vials in 22 patients vs. 246 treated with 1 vial) did not improve the selected endpoints. Routine antibiotic therapy was prescribed in 102 patients (vs. 166 patients without) and no significant difference was seen with respect to the endpoints. Moreover, no local or systemic infections were recorded in the non-antibiotic group. Corticosteroids were prescribed in 36 patients (vs. 232 without) but they did not significantly improve the endpoints or oedema. LMWH in 32 patients (vs. 236 without) increased the length of hospital stay (OR 3.2; p < 0.009 and the level of significantly persistent functional discomfort at day 15 (OR 3.7; p < 0.003). Conclusions. A single infusion of Viperfav™ (one vial) was effective whatever the grade of envenomation, and multiple doses did not improve the outcome. Viperfav™ was most effective when given soon (< 10h) after envenoming. The routine use of antibiotic therapy was not necessary. Corticosteroids did not improve the endpoints selected, and we do not recommend the use of LMWH as this increased persistent functional discomfort and the length of hospital stay.

Keywords:

• Snakes etc
• Antivenins