There was no statistically significant difference in body weight and age among all rats (P > 0.05). The blood/gas partition coefficient of HFIP at 37 °C was measured to be 421.9 ± 40.7.
Blood free HFIP and sevoflurane concentrations in three groups of rats
The three groups of rats showed similar trends of sevoflurane concentration in blood over time during anesthesia, but the changes in the 1.5MAC group were more stable and the blood sevoflurane concentration basically reached equilibrium(Figure 1). The rate of ascending and descending of free HFIP concentration in the blood of the three groups of rats after anesthesia was similar, with a trend of increasing and then decreasing with the extension of anesthesia time, with a peak at 1 hour of anesthesia (P < 0.05)(Table 1). However, when the concentration of sevoflurane increased to 1.5 MAC, the free HFIP in blood showed a decreasing trend and each time corresponding point decreased to below 1.0 MAC group (P < 0.05)(Figure 2).
Table1 Comparison of free HFIP concentration in blood of SD rats among the three groups
Group
|
No. of cases
|
0.5h
|
1.0h
|
1.5h
|
2.0h
|
0.5 MAC
|
4
|
0.064 ± 0.002
|
0.077 ± 0.002 ‡
|
0.067 ± 0.006‡
|
0.061 ± 0.005
|
1.0 MAC
|
4
|
0.075 ± 0.002†
|
0.112 ± 0.008†‡
|
0.084 ± 0.010†‡
|
0.077 ± 0.011†
|
1.5 MAC
|
4
|
0.048 ± 0.002
|
0.070 ± 0.007‡
|
0.060 ± 0.006‡
|
0.053 ± 0.006
|
MAC = minimum alveolar concentration.
†P < 0.05 versus values of the 0.5-MAC group and 1.0-MACgroup.
‡P < 0.05 versus values of the previous anesthesia time.
Figure 1. The changes of hexaflfluoro-isopropanol (HFIP) in the blood. The trends of free HFIP concentration in blood during anesthesia were similar in the three groups of rats. After the rats received sevoflurane anesthesia, HFIP rapidly began to accumulate in the blood, and the peak HFIP concentration was reached after 1 hour of anesthesia, after which it slowly decreased. Among them, the HFIP concentrations in the 1.0 MAC group were higher than those in the other two groups at all time points.
Figure 2. The changes of sevoflurane in the blood. The concentration of sevoflurane in the blood of the three groups of rats increased gradually with anesthesia duration and eventually reached equilibrium slowly. Among them, the blood sevoflurane concentrations in the 1.5-MAC group were higher than those in the other two groups at all time points
Effects of 1.0 MAC sevoflurane anesthesia on behavioral studies during the awakening period in rats after various durations of anesthesia
We established a rat model of sevoflurane anesthesia by inhalation of 1.0 MAC in this study, and through the behavioral testing of anesthetized rats after 0 h, 0.5 h, 1 h, 1.5 h, and 2 h, it was found that ( Figure 3A), compared with the 0h group, the 4 groups of rats in the 0.5 h, 1 h, 1.5 h, and 2 h groups showed an increase in the number of feces discharged in the open field area, and the difference was statistically significant; and in the analysis of the rat's The analysis of the distance and time of crossing the center area revealed that the rats in the 4 groups of 0.5 h, 1 h, 1.5 h as well as 2 h showed an increase in the time and distance in the center area with statistically significant differences; and the group of 1 h showed an increase in the time and distance of entering the center area compared to the groups of 0.5 h, 1.5 h as well as 2 h, and the differences were statistically significant ( Figure 3C, 3D, and 3E).
Figure 3. 1.0MAC sevoflurane anesthesia after different periods of time in rats with abnormal behavior during the awakening period; A. Trajectory diagram of mouse open field experiment; B. the amount of feces excreted by the open field mice; C. Distance traveled by open field mice in the central area; D. Time spent in the central region of the open field experimental mice. * P< 0. 05,** P< 0. 01,*** P<0. 001, ns P > 0. 05.
Neuroinflammation in rat cortex and hippocampus after different durations of 1.0 MAC sevoflurane anesthesia
Immunohistochemical staining of IBA1 in the cerebral cortex, hippocampal CA1 and CA3 of rats after 0.5 h, 1 h, 1.5 h, and 2 h of sevoflurane anesthesia showed (Figure 4A, 4C, 4D, and 4E) a relative increase in the cytosol of microglial cells, and an increase in their number, with a statistically significant difference suggesting that neuroinflammation was occurring, and in the 1 h group compared to the 1.5 h and 2 h groups, a relative increase in the cytosol of microglial cells and an increase in the number of synapses was the most significant in the cortical, hippocampal CA1 and The most significant increase in the number of microglia in the cortex, CA1 and CA3 regions of the hippocampus and a significant increase in the number of synapses, the difference was statistically significant, compared to 0.5 h, in the cortex microglia appeared to be similar changes, the difference was not statistically significant, and in the hippocampus there was a statistically significant difference in the number of microglia. The results of GFAP immunohistochemical staining of astrocytes in each group showed (Figure 4B, 4C, 4D and 4E) that astrocytes in the cerebral cortex and CA3 area of rats after 0.5 h, 1 h, 1.5 h and 2 h of sevoflurane anesthesia showed hypertrophy of cytosol and protrusions, and increased in number, with a statistically significant difference, when compared with the 0 h group of rats. The increase in the number of astrocytes in the CA1 area of the hippocampus in the 1.5 h and 2 h groups was similar to that in the 0 h group, and the difference was not statistically significant. And compared with the 0.5 h, 1.5 h and 2 h groups, the most significant increase in the number of glial cells in the cerebral cortex, hippocampal CA1 and CA3 of rats in the 1 h group. The above results suggest that regardless of the duration of sevoflurane anesthesia, it induces neuroinflammation in cognitively related brain regions such as the cortex and hippocampus, but the neuroinflammatory activation was most pronounced within 1h of anesthesia.
Figure 4. 1.0MAC sevoflurane anesthesia for different lengths of nerve inflammation in rat cortex and hippocampus ; A. Immunohistochemical detection of IBA1; B. GFAP immunohistochemistry test; C-E. Immunohistochemistry was used to detect the expression levels of IBA1 and GFAP in the CA1 and CA3 regions of the rat cortex, hippocampus, and the statistical analysis. * P<0. 05, ** P< 0. 01, *** P<0. 001, ns P >0. 05。