Fig 9. Caffeine reduced burst suppression caused by deep anesthesia (≥ 1.2% Isoflurane).

In A, a representative raw EEGs from a rat in saline and caffeine experiments. Isoflurane at 2% caused significant burst suppression. Caffeine at 37.5 mg/kg reduced the burst suppression caused by deep anesthesia. Caffeine also led to the shift to high frequency in EGG at a higher concentration of isoflurane. The EEG patterns before RORR were similar in both saline and caffeine experiments. The horizontal lines represent examples of suppression. The small arrows (↓) point to 60 cycles on the EEG. The horizontal lines represent examples of suppression. In B, burst suppression ratio (BSR) was calculated. Each epoch length was 1 minute. BSR of 1 indicated no electrical activity while a ratio of 0 showed no suppression. The graph started 2 minutes before caffeine or saline injection and ended after the burst suppression disappeared. The chart represents an averaged number of 6 rats in both saline and caffeine (37.5 mg/kg) experiments. Caffeine reduced the BSR after the injection. The burst suppression was also reduced as isoflurane was dialed down in saline experiments. The burst suppression ratio was calculated with the formula, BSR = (total time of suppression/epoch length) x 100%. Two members of our group performed this calculation independently. ↓ represents the time of saline ($S$) or caffeine ($\text{C}$) injection. Comparisons were made at each time point between saline and caffeine experiments. A repeated-measures ANOVA model was fit with condition (saline vs caffeine) and time as repeated factors. There was evidence for a time by condition interaction (Green-Geisser adjusted p = 0.0003). Subsequently saline versus caffeine comparisons (Bonerroni adjusted) gave the following: no significant difference from times (t) of 2 min or less; t = 3 (**p<0.01), t = 4 (**p<0.01), t = 5 (****p<0.0001), t = 6 (***p<0.001), t = 7 (*p<0.05) and no significant difference from 8 to 19 min (n = 6).