Department of Biology, College of Sciences, Shiraz University, Shiraz, Iran.
Department of Pathology, Fasa University of Medical Sciences, Fasa, Iran.
BMC Cardiovasc Disord. 2020 Jul 11;20(1):331. doi: 10.1186/s12872-020-01606-x.
The activity of autonomic nervous system and its association with organ damage have not been entirely elucidated in hemorrhagic shock. The aim of this study was to investigate heart rate variability (HRV) and pulmonary gas exchange in hemorrhagic shock during unilateral subdiaphragmatic vagotomy.
Male Sprague Dawley rats were randomly assigned into groups of Sham, vagotomized (Vag), hemorrhagic shock (HS) and Vag + HS. HS was induced in conscious animals by blood withdrawal until reaching to mean arterial blood pressure (MAP) of 40 ± 5 mmHg. Then, it was allowed to MAP returning toward the basal values. MAP and heart rate (HR) were recorded throughout the experiments, HRV components of low (LF, sympathetic index), high (LH, parasympathetic index), and very low (VLF, injury index) frequencies and the LF/HF ratio calculated, and the lung histological and blood gas parameters assessed.
In the initial phases of HS, the increase in HR with no change in MAP were observed in both HS and Vag + HS groups, while LF increased only in the HS group. In the second phase, HR and MAP decreased sharply in the HS group, whereas, only MAP decreased in the Vag + HS group. Meanwhile, LF and HF increased relative to their baselines in the HS and Vag + HS groups, even though the values were much pronounced in the HS group. In the third phase, HR, MAP, LF, HF, and the LF/HF ratio were returned back to their baselines in both HS and Vag + HS groups. In the Vag + HS group, the VLF was lower and HR was higher than those in the other groups. Furthermore, blood gas parameters and lung histology indicated the impairment of gas exchange in the Vag + HS group.
The sympathetic activity is predominant in the first phase, whereas the parasympathetic activity is dominant in the second and third phases of hemorrhagic shock. There is an inverse relationship between the level of VLF and lung injury in vagotomized animals subjected to hemorrhagic shock.
自主神经系统的活动及其与器官损伤的关系在失血性休克中尚未完全阐明。本研究旨在探讨单侧膈下迷走神经切断后失血性休克时心率变异性（HRV）和肺气体交换的变化。
雄性 Sprague Dawley 大鼠随机分为假手术（Sham）、迷走神经切断（Vag）、失血性休克（HS）和迷走神经切断+失血性休克（Vag+HS）组。在清醒动物中通过放血将平均动脉血压（MAP）降至 40±5mmHg 诱导 HS，然后允许 MAP 恢复至基础值。整个实验过程中记录 MAP 和心率（HR），计算 HRV 的低频（LF，交感神经指数）、高频（LH，副交感神经指数）和极低频（VLF，损伤指数）成分，以及肺组织学和血气参数。
在 HS 的初始阶段，HS 和 Vag+HS 组均观察到 HR 增加而 MAP 无变化，而 LF 仅在 HS 组增加。在第二阶段，HS 组 HR 和 MAP 急剧下降，而 Vag+HS 组仅 MAP 下降。同时，HS 和 Vag+HS 组的 LF 和 HF 相对于基线增加，尽管 HS 组的数值更为明显。在第三阶段，HS 和 Vag+HS 组的 HR、MAP、LF、HF 和 LF/HF 比值均恢复至基线水平。在 Vag+HS 组，VLF 较低，HR 高于其他组。此外，血气参数和肺组织学表明，在失血性休克的迷走神经切断动物中，气体交换受损。
在失血性休克的第一阶段，交感神经活动占主导地位，而在第二和第三阶段，副交感神经活动占主导地位。在失血性休克的迷走神经切断动物中，VLF 水平与肺损伤呈负相关。
