Desflurane impairs outcome of organotypic hippocampus slices in an in vitro model of traumatic brain injury

<b>Abstract</b>Decreasing mortality and disability after traumatic brain injury is a significant medical challenge. Desflurane, a widely used volatile anesthetic has proven to be neuroprotective in a variety of <i>in vitro</i> and in vivo models of ischemic brain injury. The aim of this study was to prove that desflurane reveals its neuroprotective properties in an<i> in vitro</i> model of traumatic brain injury. Organic hippocampal slice cultures were prepared from brains of 5-7 day old C57/BL6 mice pups. After 14 days of culture the slices were exposed to a focal mechanical trauma and thereafter incubated with three different concentrations of desflurane (2, 4 and 6 vol %) for 2, 24 and 72 hours. Cell injury was assessed with propodium iodide. Our results showed that after two hours of desflurane exposure no significant change in trauma intensity was observed. However in the group without traumatic brain injury, a concentration of 2% and 4% desflurane could reduce the trauma intensity significantly in comparison to the group without desflurane and trauma. Incubating with 4% desflurane for 24 hours doubled the trauma intensity in comparison to the trauma control group and further increased after 72 hours of incubation. Furthermore, a dose-dependent increase of trauma intensity after 24 hours exposure was observed. In conclusion, our results suggest that a general neuroprotective attribute of desflurane in an <i>in vitro</i> model of traumatic brain injury was not observed.<br><b>Figure 1 Trauma intensity of TBI organic hippocampal slice cultures incubated with various concentrations of desflurane for 2 hours </b>After 2-hour incubation, cell death was stained using fluorescence images. Trauma intensity of the different groups is shown in relation to trauma intensity of mechanical traumatized slices after an incubation with 5% CO2, 21% O2,74% N2 for2 hours. Significant differences to the trauma no desflurane group are marked with *. There was no significant reduction in trauma intensity at the groups with mechanical trauma (P &gt; 0.05). In the group without TBI, a concentration of 2% desflurane (*P = 0.033) and 4% desflurane (*P =0.004) reduced the trauma intensity significantly in comparison to the group without desflurane and trauma. For each group an average of 80 with a minimum of 56 slices where analyzed.<br><b>Figure 2 Trauma intensity of TBI organic hippocampal slice cultures incubated with various concentrations of desflurane for 24 hours</b>After 24-hour incubation, cell death was stained using fluorescence images. Trauma intensity of different groups is shown in relation to trauma intensity of traumatized slices after an incubation with 5% CO2, 21% O2,74% N2 for 2 hours. Significant differences compared with the positive control group after two hours of incubation (Trauma without desflurane) are marked with *. Important significant differences between the groups after 24h incubation are also marked with * on the top of the figure. After 24 hours of incubation the trauma intensity tripled as compared to the trauma intensity after 2 hours of incubation. In the group without TBI the increase of trauma intensity rises also from 2% desflurane (*P = 0.000) to 6% desflurane (*P = 0.000). For the trauma group a significant increase of trauma intensity was observed at 4% desflurane (*P = 0.006) and 6% desflurane (*P = 0.000). For each group an average of 73 with a minimum of 62 slices were analyzed.<br><b>Figure 3 Trauma intensity of TBI organic hippocampal slice cultures incubated with concentration of 4% desflurane for 2, 24 and 72 hours.</b>In summary on this figure slices were exposed to a concentration of 4% desflurane and to 5% CO2, 21% O2, 74% N2 (trauma no desflurane) for 2-72 hours. Trauma intensity of the different groups is shown in relation to trauma intensity of traumatized slices after an incubation without desflurane for 2 hours. Significant differences compared with the trauma no desflurane after two hours of incubation are marked with *. After 2 hours of incubation, there was no significant difference between the trauma no desflurane group and the trauma group with 4% desflurane (P = 0.273). After 24 hours, an increase to the double trauma intensity at the trauma group without desflurane was observed. Incubating with 4% desflurane after trauma led to an increase of trauma intensity to the four-fold. Finally after 72 hours the trauma intensity represents without desflurane and with 4% desflurane in the trauma group. For each group an average of 94 with a minimum of 73 slices where analyzed.<br>