The time between pre-exposure to VGAs and infliction of bTBI differentially affects the ability of ISO and SEVO to reduce the risk of mortality following bTBI. The MI24 was determined for mixed-sex, 0-7 or 1-8 day old w1118 flies either not exposed to anesthetic (−) or exposed to ISO for 2 hrs prior to infliction of the standard bTBI protocol immediately (A), 1 hr later (B) or 1.5 hrs later (C). Alternatively, the MI24 was determined for mixed-sex, 0-7 or 1-8 day old w1118 flies either not exposed to anesthetic (−) or exposed to SEVO for 2 hrs prior to infliction of the standard bTBI protocol immediately (D), 0.5 hrs later (E), or 1 hr later (F). Error bars represent the 95% Confidence Intervals.