Continuous intravenous midazolam infusion for Centruroides exilicauda scorpion envenomation

Study objective: We sought to describe the effects of continuous intravenou s midazolam infusion as therapy for severe bark scorpion (Centruroides exil icauda) envenomation. Methods: A retrospective chart review from July 1, 1993, through January 1, 1998, identified all patients treated at a university hospital with Intern ational Classification of Diseases, Ninth Revision, codes 989.5 (toxic effe ct of venom) or E905.2 (scorpion sting causing poisoning). By using standar dized collection forms, data were extracted from the medical record of ever y patient who had a grade III or IV envenomation and was treated with a con tinuous intravenous midazolam infusion. Results: Our search identified 104 patients; 34 had grade III or IV envenom ation. Of these, 33 were treated in the ICU with continuous intravenous mid azolam infusion. Median patient age was 4 years (range, 1 to 68 years). Mid azolam dosage was adjusted to induce a light sleep state to control agitati on and involuntary motor activity. The median amount of midazolam resulting in the first recorded decrease in agitation and involuntary motor activity was 0.30 mg/kg (range, 0.03 to 1.76 mg/kg). This first evidence of clinica l improvement was recorded as 1.00 hour (median), with a range of 0.00 to 3 .75 hours. The initial midazolam infusion rate was 0.10 mg.kg(-1).h(-1) (me dian), with a range of 0.01 to 0.31 mg.kg(-1).h(-1). The maximal midazolam infusion rate was 0.30 mg.kg(-1).h(-1) (median), with a range of 0.06 to 1. 29 mg.kg(-1).h(-1). The median time until the maximal midazolam infusion ra te was 2.5 hours (range, 0.00 to 8.50 hours). The median duration of infusi on was 9.50 hours (range, 4.25 to 20.50 hours). The median length of stay i n the ICU was 15.17 hours (range, 6.0 to 28.0 hours), and 85% of patients w ere discharged directly home. All patients had resolution of abnormal motor activity and agitation during their midazolam infusion. Transient hypoxemi a without: evidence of end-organ dysfunction was documented in 4 patients d uring midazolam therapy. Conclusion: A continuous intravenous midazolam infusion can be a safe, effe ctive, and readily available treatment option for patients with grade III o r IV C exilicauda envenomation.