Central α-adrenergic mechanisms regulate human sympathetic neuronal discharge strategies.

The present study investigated the impact of central α-adrenergic mechanisms on sympathetic action potential (AP) discharge, recruitment and latency strategies. We used the microneurographic technique to record muscle sympathetic nerve activity and a continuous wavelet transform to investigate postganglionic sympathetic AP firing during a baseline condition and an infusion of a α-adrenergic receptor agonist, dexmedetomidine (10 min loading infusion of 0.225 µg kg; maintenance infusion of 0.

Physiologic validation of the Compensatory Reserve Metric obtained from pulse oximetry: A step toward advanced medical monitoring on the battlefield.

Background: The Compensatory Reserve Metric (CRM) provides a time sensitive indicator of hemodynamic decompensation. However, its in-field utility is limited because of the size and cost-intensive nature of standard vital sign monitors or photoplethysmographic volume-clamp (PPG VC ) devices used to measure arterial waveforms. In this regard, photoplethysmographic measurements obtained from pulse oximetry may serve as a useful, portable alternative.

Comparing the compensatory reserve metric obtained from invasive arterial measurements and photoplethysmographic volume-clamp during simulated hemorrhage.

Purpose: The compensatory reserve metric (CRM) is a novel tool to predict cardiovascular decompensation during hemorrhage. The CRM is traditionally computed using waveforms obtained from photoplethysmographic volume-clamp (PPG), yet invasive arterial pressures may be uniquely available. We aimed to examine the level of agreement of CRM values computed from invasive arterial-derived waveforms and values computed from PPG-derived waveforms.

Non-invasive biomarkers for detecting progression toward hypovolemic cardiovascular instability in a lower body negative pressure model.

Occult hemorrhages after trauma can be present insidiously, and if not detected early enough can result in patient death. This study evaluated a hemorrhage model on 18 human subjects, comparing the performance of traditional vital signs to multiple off-the-shelf non-invasive biomarkers. A validated lower body negative pressure (LBNP) model was used to induce progression towards hypovolemic cardiovascular instability.

Arthroscopic assisted brachial plexus catheter placement: an alternative to the percutaneous interscalene approach.

Background: Brachial plexus catheter placement at the interscalene level is beneficial for shoulder analgesia but presents logistical challenges due to the superficial nature of the plexus at this level, increased patient movement in the neck, and therefore higher likelihood for catheter dislodgement.

Methods: Patients requiring shoulder arthroscopy and suprascapular nerve decompression were identified. Under arthroscopic guidance, a catheter was placed percutaneously into the scalene medius muscle next to the suprascapular nerve and the upper trunk of the brachial plexus.

Towards a Lightweight Classifier to Detect Hypovolemic Shock.

Predicting the ability of an individual to compensate for blood loss during hemorrhage and detect the likely onset of hypovolemic shock is necessary to permit early clinical intervention. Towards this end, the compensatory reserve metric (CRM) has been demonstrated to directly correlate with an individual's ability to maintain compensatory mechanisms during loss of blood volume from onset (one-hundred percent health) to exsanguination (zero percent health). This effort describes a lightweight, three-class predictor (good, fair, poor) of an individual's compensatory reserve using a linear support-vector machine (SVM) classifier.

Aging in females is associated with changes in respiratory modulation of sympathetic nerve activity and blood pressure.

Sympathetic nerve activity (SNA) is tightly coupled with the respiratory cycle. In healthy human males, respiratory modulation of SNA does not change with age. However, it is unclear how this modulation is affected by age in females.

Sympathetic transduction to blood pressure during euglycemic-hyperinsulinemia in young healthy adults: role of burst amplitude.

Insulin acts centrally to stimulate sympathetic vasoconstrictor outflow to skeletal muscle and peripherally to promote vasodilation. Given these divergent actions, the "net effect" of insulin on the transduction of muscle sympathetic nerve activity (MSNA) into vasoconstriction and thus, blood pressure (BP) remains unclear. We hypothesized that sympathetic transduction to BP would be attenuated during hyperinsulinemia compared with baseline.

Quantifying muscle blood flow: a transformative breakthrough in the science of human exercise physiology.

Over 50 years ago, John Wahren and Lennart Jorfeldt published a manuscript in Clinical Science where they detailed a series of studies of leg blood flow during exercise. They used a novel approach to indicator dye dilution: continuous arterial infusions of dye using venous samples. This technique allowed them to describe for the first time the fundamental relationships between large muscle group exercise, muscle blood flow, and pulmonary and muscle oxygen uptake.

Creating a Practical Transformational Change Management Model for Novel Artificial Intelligence-Enabled Technology Implementation in the Operating Room.

Objective: To identify change management (CM) strategies for implementing novel artificial intelligence and similar novel technologies in operating rooms and create a new CM model for future trials and applications inspired by the abovementioned strategies and established models.

Methods: Key phases of technology implementation were defined, and strategies for transformational CM were created and applied in a recent CM experience at our institution between October 15, 2020 and October 15, 2021. We appraised existing CM models and propose the newly created model.

The relationship between muscle sympathetic nerve activity and systemic hemodynamics is altered in women with uterine fibroids.

Women with uterine fibroids (UF), benign tumors of the myometrium, have a higher prevalence of hypertension than women without UF. The cause for this relationship is unclear. Muscle sympathetic nerve activity (MSNA) is a regulator of arterial blood pressure, and it is possible that variations in MSNA predispose women with UF to develop hypertension.

AI-Enabled Advanced Development for Assessing Low Circulating Blood Volume for Emergency Medical Care: Comparison of Compensatory Reserve Machine-Learning Algorithms.

The application of artificial intelligence (AI) has provided new capabilities to develop advanced medical monitoring sensors for detection of clinical conditions of low circulating blood volume such as hemorrhage. The purpose of this study was to compare for the first time the discriminative ability of two machine learning (ML) algorithms based on real-time feature analysis of arterial waveforms obtained from a non-invasive continuous blood pressure system (Finometer) signal to predict the onset of decompensated shock: the compensatory reserve index (CRI) and the compensatory reserve metric (CRM). One hundred ninety-one healthy volunteers underwent progressive simulated hemorrhage using lower body negative pressure (LBNP).

Influence of locomotor muscle group III/IV afferents on cardiovascular and ventilatory responses in human heart failure during submaximal exercise.

The purpose of this study is to determine the influence of locomotor muscle group III/IV afferent inhibition on central and peripheral hemodynamics at multiple levels of submaximal cycling exercise in patients with heart failure with reduced ejection fraction (HFrEF). Eleven patients with HFrEF and nine healthy matched controls were recruited. The participants performed a multiple stage [i.

Role of the arterial baroreflex in the sympathetic response to hyperinsulinemia in adult humans.

Muscle sympathetic nerve activity (MSNA) increases during hyperinsulinemia, primarily attributed to central nervous system effects. Whether peripheral vasodilation induced by insulin further contributes to increased MSNA via arterial baroreflex-mediated mechanisms requires further investigation. Accordingly, we examined baroreflex modulation of the MSNA response to hyperinsulinemia.

Impact of Pharmacologically Left Shifting the Oxygen-Hemoglobin Dissociation Curve on Arterial Blood Gases and Pulmonary Gas Exchange During Maximal Exercise in Hypoxia.

Stewart, Glenn M., Troy J. Cross, Michael J.

The Oxygen Cascade During Exercise in Health and Disease.

The oxygen transport cascade describes the physiological steps that bring atmospheric oxygen into the body where it is delivered and consumed by metabolically active tissue. As such, the oxygen cascade is fundamental to our understanding of exercise in health and disease. Our narrative review will highlight each step of the oxygen transport cascade from inspiration of atmospheric oxygen down to mitochondrial consumption in both healthy active males and females along with clinical conditions.

Pulmonary Complications in Esophagectomy Based on Intraoperative Fluid Rate: A Single-Center Study.

Objectives: Esophagectomy is associated with significant morbidity and mortality. The authors assessed the relationship between intraoperative fluid (IOF) administration and postoperative pulmonary outcomes in patients undergoing a transthoracic, transhiatal, or tri-incisional esophagectomy.

Design: Retrospective cohort study (level 3 evidence).

A Novel Method to Measure Transient Impairments in Cognitive Function During Acute Bouts of Hypoxia.

Exposure to low oxygen environments (hypoxia) can impair cognitive function; however, the time-course of the transient changes in cognitive function is unknown. In this study, we assessed cognitive function with a cognitive test before, during, and after exposure to hypoxia. Nine participants (28 4 yr, 7 women) completed Conners Continuous Performance Test (CCPT-II) during three sequential conditions: 1) baseline breathing room air (fraction of inspired oxygen, Fo₂ 0.

Locomotor muscle group III/IV afferents constrain stroke volume and contribute to exercise intolerance in human heart failure.

Key Points: Heart failure patients with reduced ejection fraction (HFrEF) exhibit severe limitations in exercise capacity ( peak). One of the primary peripheral mechanisms suggested to underlie exercise intolerance in HFrEF is excessive locomotor muscle group III/IV afferent feedback; however, this has never been investigated in human heart failure. HFrEF patients and controls performed an incremental exercise test to volitional exhaustion to determine peak with lumbar intrathecal fentanyl or placebo.

Respiratory muscle work influences locomotor convective and diffusive oxygen transport in human heart failure during exercise.

Introduction: It remains unclear if naturally occurring respiratory muscle (RM) work influences leg diffusive O transport during exercise in heart failure patients with reduced ejection fraction (HFrEF). In this retrospective study, we hypothesized that RM unloading during submaximal exercise will lead to increases in locomotor muscle O diffusion capacity (D O ) contributing to the greater leg VO .

Methods: Ten HFrEF patients and 10 healthy control matched participants performed two submaximal exercise bouts (i.