Development of a decerebrate model for investigating mechanisms mediating viscero-sympathetic reflexes in the spinalized rat

Data analysis protocol for early autonomic dysfunction characterization after severe traumatic brain injury

Background

Traumatic brain injury (TBI) disrupts normal brain tissue and functions, leading to high mortality and disability. Severe TBI (sTBI) causes prolonged cognitive, functional, and multi-organ dysfunction. Dysfunction of the autonomic nervous system (ANS) after sTBI can induce abnormalities in multiple organ systems, contributing to cardiovascular dysregulation and increased mortality. Currently, detailed characterization of early autonomic dysfunction in the acute phase after sTBI is lacking. This study aims to use physiological waveform data collected from patients with sTBI to characterize early autonomic dysfunction and its association with clinical outcomes to prevent multi-organ dysfunction and improving patient outcomes.

Objective

This data analysis protocol describes our pre-planned protocol using cardiac waveforms to evaluate early autonomic dysfunction and to inform multi-dimensional characterization of the autonomic nervous system (ANS) after sTBI.

Methods

We will collect continuous cardiac waveform data from patients managed in an intensive care unit within a clinical trial. We will first assess the signal quality of the electrocardiogram (ECG) using a combination of the structural image similarity metric and signal quality index. Then, we will detect premature ventricular contractions (PVC) on good-quality ECG beats using a deep-learning model. For arterial blood pressure (ABP) data, we will employ a singular value decomposition (SVD)-based approach to assess the signal quality. Finally, we will compute multiple indices of ANS functions through heart rate turbulence (HRT) analysis, time/frequency-domain analysis of heart rate variability (HRV) and pulse rate variability, and quantification of baroreflex sensitivity (BRS) from high-quality continuous ECG and ABP signals. The early autonomic dysfunction will be characterized by comparing the values of calculated indices with their normal ranges.

Conclusion

This study will provide a detailed characterization of acute changes in ANS function after sTBI through quantified indices from cardiac waveform data, thereby enhancing our understanding of the development and course of eAD post-sTBI.

Time and frequency domain analysis of physiological features during autonomic dysreflexia after spinal cord injury

Introduction

Autonomic dysreflexia (AD) affects about 70% of individuals with spinal cord injury (SCI) and can have severe consequences, including death if not promptly detected and managed. The current gold standard for AD detection involves continuous blood pressure monitoring, which can be inconvenient. Therefore, a non-invasive detection device would be valuable for rapid and continuous AD detection.

Methods

Implanted rodent models were used to analyze autonomic dysreflexia after spinal cord injury. Skin nerve activity (SKNA) features were extracted from ECG signals recorded non-invasively, using ECG electrodes. At the same time, blood pressure and ECG data sampled was collected using an implanted telemetry device. Heart rate variability (HRV) features were extracted from these ECG signals. SKNA and HRV parameters were analyzed in both the time and frequency domain.

Results

We found that SKNA features showed an increase approximately 18 seconds before the typical rise in systolic blood pressure, indicating the onset of AD in a rat model with upper thoracic SCI. Additionally, low-frequency components of SKNA in the frequency domain were dominant during AD, suggesting their potential inclusion in an AD detection system for improved accuracy.

Discussion

Utilizing SKNA measurements could enable early alerts to individuals with SCI, allowing timely intervention and mitigation of the adverse effects of AD, thereby enhancing their overall well-being and safety.

Chronic Pain-Associated Cardiovascular Disease: The Role of Sympathetic Nerve Activity

Chronic pain affects many people world-wide, and this number is continuously increasing. There is a clear link between chronic pain and the development of cardiovascular disease through activation of the sympathetic nervous system. The purpose of this review is to provide evidence from the literature that highlights the direct relationship between sympathetic nervous system dysfunction and chronic pain. We hypothesize that maladaptive changes within a common neural network regulating the sympathetic nervous system and pain perception contribute to sympathetic overactivation and cardiovascular disease in the setting of chronic pain. We review clinical evidence and highlight the basic neurocircuitry linking the sympathetic and nociceptive networks and the overlap between the neural networks controlling the two.

CORP: Practical tools for improving experimental design and reporting of laboratory studies of cardiovascular physiology and metabolism

The exercise consisted of: 1) a short survey to acquire baseline data on current practices regarding the conduct of animal studies, 2) a series of presentations for promoting awareness and providing advice and practical tools for improving experimental design, and 3) a follow-up survey 12 mo later to assess whether practices had changed. The surveys were compulsory for responsible investigators (n = 16; paired data presented). Other investigators named on animal ethics applications were encouraged to participate (2017, total of 36 investigators; 2018, 37 investigators). The major findings to come from the exercise included 1) a willingness of investigators to make changes when provided with knowledge/tools and solutions that were relatively simple to implement (e.g., proportion of responsible investigators showing improved practices using a structured method for randomization was 0.44, 95% CI (0.19; 0.70), P = 0.003, and deidentifying drugs/interventions was 0.40, 95% CI (0.12; 0.68), P = 0.010); 2) resistance to change if this involved more personnel and time (e.g., as required for allocation concealment); and 3) evidence that changes to long-term practices ("habits") require time and follow-up. Improved practices could be verified based on changes in reporting within publications or documented evidence provided during laboratory visits. In summary, this exercise resulted in changed attitudes, practices, and reporting, but continued follow-up, monitoring, and incentives are required. Efforts to improve experimental rigor will reduce bias and will lead to findings with the greatest translational potential.NEW & NOTEWORTHY The goal of this exercise was to encourage preclinical researchers to improve the quality of their cardiac and metabolic animal studies by 1) increasing awareness of concerns, which can arise from suboptimal experimental designs; 2) providing knowledge, tools, and templates to overcome bias; and 3) conducting two short surveys over 12 mo to monitor change. Improved practices were identified for the uptake of structured methods for randomization, and de-identifying interventions/drugs.Listen to this article's corresponding podcast at https://ajpheart.podbean.com/e/experimental-design-survey-training-practical-tools/.