Purpose

For research on circadian intraocular pressure (IOP), rebound tonometers are widely used with or without general anesthesia as a non-invasive approach to obtain IOP values. However, whether general anesthesia such as inhalation anesthesia with isoflurane affects the circadian rhythm of IOP and in turn IOP measurements is currently unclear. As such, data reporting IOP values obtained under general anesthesia should be interpreted with caution. The purpose of this study was to evaluate how general anesthesia with isoflurane inhalation affects the circadian rhythm of IOP.

Methods

C57Bl/6J strain mice maintained using a 12h:12h light/dark cycle (lights on and off at ZT0 and ZT12, respectively) were used. IOPs were measured using a rebound tonometer (Icare TonoLab) before and 3, 5, 10, 15, and 30 min after initiating anesthesia in both light and dark phases (ZT 2–6 and ZT 14–18, respectively). Awake IOPs and IOPs at 3 and 5 min after anesthesia initiation were also obtained at ZT5, 8, 11, 14, 17, and 20 to assess IOP diurnal curves under gas anesthesia.

Results

IOP values gradually decreased after anesthesia initiation in both light and dark phases (P < 0.001) and there was no interaction between light/dark phase and anesthesia time (P = 0.88). There was a slight, but not significant, reduction in IOP 3 min after initiating anesthesia (P = 0.23), and significant decreases in IOP occurred at subsequent timepoints (P ≤ 0.001). Both awake and anesthetized mice showed a robust IOP rhythm that reached a peak and trough in the dark and light phase, respectively. Awake IOP levels did not significantly differ from those for anesthetized mice at 3 min after anesthesia initiation at all time points (P ≥ 0.07).

Conclusions

Both awake and anesthetized mice demonstrated a robust circadian rhythm for IOP. Murine IOP showed similar gradual decreases under inhalation anesthesia with isoflurane in both the light and dark phases. IOPs measured using a rebound tonometer within 3 min of initiating isoflurane anesthesia were comparable to awake IOPs, and thus may be useful to monitor the circadian rhythm of IOP in mice.

中文翻译：

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异氟烷吸入麻醉对小鼠眼压昼夜节律的影响

目的

为了研究昼夜节律性眼压（IOP），回弹眼压计广泛用于有或没有全身麻醉的无创方法，以获取IOP值。但是，全身麻醉（例如异氟烷的吸入麻醉）是否会影响IOP的昼夜节律，因此IOP测量目前尚不清楚。因此，应谨慎解释在全身麻醉下获得的报告IOP值的数据。这项研究的目的是评估异氟烷吸入全身麻醉如何影响眼压的昼夜节律。

方法

使用以12h：12h亮/暗周期（分别在ZT0和ZT12处点亮和熄灭）维持的C57Bl / 6J品系小鼠。在明，暗阶段（分别为ZT 2-6和ZT 14-18）开始麻醉之前和之后3、5、10、15和30分钟，使用回弹眼压计（Icare TonoLab）测量IOP。还在ZT5、8、11、14、17和20处获得了麻醉开始后3和5分钟的清醒IOP和IOP，以评估气体麻醉下的IOP日曲线。

结果

麻醉开始后，明，暗阶段的IOP值逐渐降低（P <0.001），明/暗阶段与麻醉时间之间没有相互作用（P = 0.88）。开始麻醉后3分钟，IOP略有降低，但不显着（P = 0.23），在随后的时间点，IOP显着降低（P≤0.001）。处于清醒状态和麻醉状态的小鼠均显示出强大的IOP节律，分别在黑暗和明亮阶段达到峰值和谷值。在所有时间点麻醉开始后3分钟，觉醒的IOP水平与麻醉小鼠的IOP水平没有显着差异（P≥0.07）。

结论

清醒和麻醉的小鼠均表现出强健的IOP昼夜节律。在亮和暗阶段，在异氟烷吸入麻醉下，鼠眼压显示出相似的逐渐降低。在开始异氟烷麻醉后3分钟内使用回弹眼压计测量的IOP与清醒的IOP相当，因此可能有助于监测IOP的昼夜节律。