Heart rate variability and pulmonary dysfunction in rats subjected to hemorrhagic shock

Fateme Khodadadi,Aminollah Bahaoddini,Farzaneh Ketabchi,Alireza Tavassoli

doi:10.1186/s12872-020-01606-x

Abstract

BackgroundThe 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.MethodsMale 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.ResultsIn 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.ConclusionsThe 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.

Highlights

The activity of autonomic nervous system and its association with organ damage have not been entirely elucidated in hemorrhagic shock
It has been indicated that the compensatory responses to hemorrhagic shock depends on the integrity of afferent fibers of the vagus nerve originated from the arterial baroreceptors [2, 6, 7]
During the In-Com phase of the hemorrhagic shock (HS) group, mean arterial blood pressure (MAP) was maintained in the normal range, whereas heart rate (HR) increased significantly

Summary

Introduction

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. The mechanisms of different phases of compensation in hemorrhagic shock have not been fully elucidated far. It has been indicated that the compensatory responses to hemorrhagic shock depends on the integrity of afferent fibers of the vagus nerve originated from the arterial baroreceptors [2, 6, 7]. Little attention has been devoted about the role of subdiaphragmatic vagus nerve in the compensatory mechanisms of class II hemorrhagic shock yet. A few studies have addressed HRV in evaluating the autonomic activity in the early and compensatory phases of hemorrhagic shock [11, 12]

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