Comparison of heart rate variability, hemodynamic, metabolic and inflammatory parameters in various phases of decompansatory hemorrhagic shock of normal and vagotomized conscious male rats.

Background: Heart rate variability (HRV) analysis has shown promise as a valuable complementary tool for clinical assessment in trauma cases. This study aims to evaluate the utility of HRV in monitoring different severities of hemorrhagic shock (HS) and its correlation with traditional hemodynamic and metabolic parameters.

Methods: Male Sprague-Dawley rats were divided into different experimental groups, including those with and without vagotomy, and were exposed to different classes of decompensatory HS. To induce varying severities of HS, volume resuscitation was delayed by gradually returning 0%, 20%, or 50% of the shed blood volume at the end of the compensation phase, referred to as 0% DFR, 20% DFR, and 50% DFR class, respectively. Hemodynamic parameters were monitored, and HRV was calculated. Levels of TNF-α and IL-10 were determined in lung tissue at the end of the experiments. Correlations between HRV, hemodynamic parameters, inflammatory gene expression and arterial blood gas variables were evaluated.

Results: HRV showed increased power of the low-frequency (LF) and respiratory sinus arrhythmia (RSA) in all groups during the hypotension phase of HS (Nadir 1). Subdiaphragmatic vagotomy blunted the increase in the LF component in the Nadir 1. After volume resuscitation, systolic blood pressure (SBP), RSA and LF returned to baseline in the 0% DFR and 20% DFR classes. However, animals in 50% DFR class exhibited a reduced SBP and LF and lower pH. Notably, strong correlations were found between LF and SBP as well as tissue hypoperfusion markers. The expression of TNF-α in the lung was increased in all HS groups, while this gene expression was significantly higher in the vagotomized animals.

Conclusion: The alterations in HRV components were found to be significantly correlated with the hemodynamic and metabolic status of the animals, while showing no association with inflammatory responses. Additionally, the intervention of subdiaphragmatic vagotomy significantly impacted both HRV components and inflammatory responses. Collectively, these findings suggest the potential of HRV components for the assessment of the presence and severity of HS.