Hemodynamic Changes In Response Research Articles

Depth-Specific Hypoxic Responses to Spreading Depolarizations in Gyrencephalic Swine Cortex Unveiled by Photoacoustic Imaging.

Spreading depolarizations (SDs) are a marker of brain injury and have a causative effect on ischemic lesion progression. The hemodynamic responses elicited by SDs are contingent upon the metabolic integrity of the affected tissue, with vasoconstrictive reactions leading to pronounced hypoxia often indicating poor outcomes. The stratification of hemodynamic responses within different cortical layers remains poorly characterized. This pilot study sought to elucidate the depth-specific hemodynamic changes in response to SDs within the gray matter of the gyrencephalic swine brain. Employing a potassium chloride-induced SD model, we utilized multispectral photoacoustic imaging (PAI) to estimate regional cerebral oxygen saturation (rcSO2%) changes consequent to potassium chloride-induced SDs. Regions of interest were demarcated at three cortical depths covering up to 4mm. Electrocorticography (ECoG) strips were placed to validate the presence of SDs. Through PAI, we detected 12 distinct rcSO2% responses, which corresponded with SDs detected in ECoG. Notably, a higher frequency of hypoxic responses was observed in the deeper cortical layers compared to superficial layers, where hyperoxic and mixed responses predominated (p < 0.001). This data provides novel insights into the differential oxygenation patterns across cortical layers in response to SDs, underlining the complexity of cerebral hemodynamics post-injury.

Intraoperative pediatric electroencephalography monitoring - an updated review.

Intraoperative electroencephalography (EEG) monitoring under pediatric anesthesia has begun to attract increasing interest, driven by the availability of pediatric-specific EEG monitors and the realization that traditional dosing methods based on patient movement or changes in hemodynamic response often lead to imprecise dosing, especially in younger infants who may experience adverse events (e.g., hypotension) due to excess anesthesia. EEG directly measures the effects of anesthetics on the brain, which is the target end-organ responsible for inducing loss of consciousness. Over the past ten years, research on anesthesia and computational neuroscience has improved our understanding of intraoperative pediatric EEG monitoring and expanded the utility of EEG in clinical practice. We now have better insights into neurodevelopmental changes in the developing pediatric brain, functional connectivity, the use of non-proprietary EEG parameters to guide anesthetic dosing, epileptiform EEG changes during induction, EEG changes from spinal/regional anesthesia, EEG discontinuity, and the use of EEG to improve clinical outcomes. This review article summarizes the recent literature on EEG monitoring in perioperative pediatric anesthesia, highlighting several of the topics mentioned above.

Effect of chronic kidney disease induced calcification on peripheral vascular perfusion using near-infrared spectroscopic imaging.

Low-cost techniques that can detect the presence of vascular calcification (VC) in chronic kidney disease (CKD) patients could improve clinical outcomes. In this study, we established a near-infrared spectroscopy-based imaging technique to determine changes in peripheral hemodynamics due to CKD-induced VC. Mice were fed a high-adenine diet with either normal or high levels of phosphate to induce CKD with and without VC, respectively. The mice tail was imaged to evaluate hemodynamic changes in response to occlusion. The rate of change in oxyhemoglobin in response to occlusion showed a statistically significant difference in the presence of VC in the mice.

Ultrafast longitudinal imaging of haemodynamics via single-shot volumetric photoacoustic tomography with a single-element detector.

Techniques for imaging haemodynamics use ionizing radiation or contrast agents or are limited by imaging depth (within approximately 1 mm), complex and expensive data-acquisition systems, or low imaging speeds, system complexity or cost. Here we show that ultrafast volumetric photoacoustic imaging of haemodynamics in the human body at up to 1 kHz can be achieved using a single laser pulse and a single element functioning as 6,400 virtual detectors. The technique, which does not require recalibration for different objects or during long-term operation, enables the longitudinal volumetric imaging of haemodynamics in vasculature a few millimetres below the skin's surface. We demonstrate this technique in vessels in the feet of healthy human volunteers by capturing haemodynamic changes in response to vascular occlusion. Single-shot volumetric photoacoustic imaging using a single-element detector may facilitate the early detection and monitoring of peripheral vascular diseases and may be advantageous for use in biometrics and point-of-care testing.

The effect of combined ultrasound-guided transverse thoracic muscle plane block and rectus sheath plane block on the peri-operative consumption of opioids in open heart surgeries with median sternotomy

ABSTRACT Background Patients undergoing heart surgery with a midline sternotomy typically get intravenous opioids as their primary form of post-operative pain management. Due to its possible drawbacks, regional neuraxial anesthesia is still controversial. There have been reports on the impact of rectus sheath plane (RSP) block in conjunction with ultrasound-guided transverse thoracic muscle plane (TTP) block on postoperative pain following sternotomy. Aim Of The Study The efficiency of combining TTP and RSP blocks in lowering the targeted patients’ perioperative requirement for opioids, minimizing opioid adverse effects, and attaining a potential Fast-Tract Extubation. Patients And Methods 50 patients undergoing open cardiac surgery via median sternotomy were randomly assigned to one of two groups in this randomized, prospective, comparative trial. Group (B) got combined ultrasound-guided TTP and RSP blocks, while Group (S) received saline in the same planes before to the incision. Results There was no significant difference between the groups for the demographic information, postoperative opioid consumption, or VAS pain scores, however there was a very significant difference between the groups for intraoperative opioid intake and time to extubation. Conclusion Combining TTP and RSP blocks has improved fast-track extubation, decreased hemodynamic changes in response to surgical stress, and decreased intraoperative opioid usage. The blocks directed by routine pain score evaluation did not, however, have a significant impact on postoperative opioid use.

Clonidine premedication was better in preventing hemodynamic response changes post laryngoscopy and endotracheal intubation compared to fentanyl premedication

Background: Airway control under general anesthesia can be performed using laryngoscopy and endotracheal intubation. Laryngoscopy and endotracheal intubation produce mechanical and chemical stimuli that increase sympatho-adrenergic activity, causing an increased hemodynamic response. Various pharmacological and non-pharmacological methods have been used to reduce the response of hemodynamic changes in laryngoscopy and endotracheal intubation, such as fentanyl and clonidine. This study aimed to compare the effectiveness of fentanyl and clonidine in reducing hemodynamic response changes after laryngoscopy and endotracheal intubation. Methods: A double-blind randomized clinical trial was conducted on 48 elective surgery patients in the Surgical Installation of Dr. Kariadi General Hospital and Diponegoro National Hospital Semarang who were planned for laryngoscopy and endotracheal intubation procedures. Subjects were randomized and divided into 2 groups. Group 1 was administered with 2 µg/kgBW intravenous fentanyl premedication and group II was administered with 1 µg/kgBW intravenous clonidine premedication 5 minutes before the laryngoscopy and endotracheal intubation procedure. At baseline and at 1, 3, and 5 minutes after laryngoscopy and endotracheal intubation, the systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), and heart rate (HR) were recorded simultaneously. Results: Both fentanyl and clonidine could maintain SBP, DBP, MAP, and HR within normal range. However, clonidine premedication seemed to be better in preventing hemodynamic response changes post-laryngoscopy and endotracheal intubation compared to fentanyl premedication. Clonidine premedication showed lower SBP, DBP, and MAP, but not HR, at the 1st and 3rd-minute post laryngoscopy and endotracheal intubation in comparison with fentanyl premedication (p&lt;0.05). Conclusion: If confirmed by further findings, clonidine premedication may be preferable to prevent hemodynamic changes after laryngoscopy and endotracheal intubation.

Emotional modulation of cortical activity during gum chewing: A functional near-infrared spectroscopy study.

Distinct brain regions are known to be associated with various emotional states. Cortical activity may be modulated by emotional states that are triggered by flavors during food intake. We examined cortical activity during chewing with different flavors and assessed the emotional modulation of cortical activity using multichannel near-infrared spectroscopy. Thirty-six right-handed volunteers participated in this crossover trial. The participants experienced positive and negative emotions from chewing flavorful (palatable) or less flavorful (unpalatable) gums, respectively for 5 min. Participants rated the taste, odor, and deliciousness of each gum using a visual analog scale. Bilateral hemodynamic responses in the frontal and parietal lobes, bilateral masseter muscle activation, and heart rate were measured during gum chewing. Changes in all measured data during gum chewing were also evaluated. The ratings of the tastes and odors of each gum significantly differed among the participants (P < 0.001). Hemodynamic response changes were significantly elevated in the bilateral primary sensorimotor cortex during gum-chewing, in comparison to resting. The difference in hemodynamic responses between palatable and unpalatable gum conditions was detected in the left frontopolar/dorsolateral prefrontal cortex. Muscle activation and heart rate were not significantly different between different gum types. Our findings indicate that differential processing in the left prefrontal cortex might be responsible for the emotional states caused by palatable and unpalatable foods.

Reliability of bioreactance-derived hemodynamic monitoring during simulated sustained gravitational transitions induced by short-arm human centrifugation.

Precise, sensitive, and non-invasive estimates of stroke volume index (SVI) would facilitate clinical decision making and tracking of cardiorespiratory fitness in space. Thoracic electrical bioreactance (TEBR) is capable of providing valid SVI estimates on Earth; however, its reliability in response to simulated sustained gravitational transitions is unknown. Ten healthy male subjects underwent short-arm human centrifugation (SAHC) equivalent to 1g and 1.5g at their center of mass along the z-axis (gz) for 10min each (first 5min: passive; last 5min: active, leg press movements), interspersed by periods without centrifugation (µg). The TEBR-based device Starling™ SV was used to estimate SVI during the five distinct passive gz phases. Precision of SVI measurements and sensitivity to hemodynamic changes induced by simulated gz transitions were determined. Overall SVI precision was very high (coefficient of variation=3.6%), whereas mean sensitivity to SVI changes was satisfactory (sensitivity index=75%). This study shows that the TEBR-based device Starling™ SV is precise and sensitive to hemodynamic changes in response to simulated sustained gz transitions induced by SAHC. Thus, it may be a suitable non-invasive hemodynamic monitor during human spaceflight. Further evaluation of Starling™ SV against a reference method in simulated microgravity is warranted.

The effect of remifentanil on hemodynamic response to laryngeal mask airway insertion in induction of anesthesia with propofol fentanyl or propofol ketamine in cataract surgery

Background. Induction of general anesthesia may cause hemodynamic instability. Remifentanil is often prescribed to suppress the hemodynamic response to anesthesia. The aim of this study was to investigate the effect of remifentanil on hemodynamic response to induction of anesthesia with propofol fentanyl or propofol ketamine and laryngeal mask airway (LMA) insertion. Methods. This double-blind randomized clinical trial study was performed on 44 candidates for cataract surgery in Feyz Hospital, Isfahan, Iran from March to June 2020. Patients were randomly assigned into two groups using random allocation software. The first group received 1 mcg/kg fentanyl and the second group received 0.5 mg/kg ketamine. Also, both groups received 1 mg/kg propofol and 0.5 mcg/kg remifentanil intravenously. Hemodynamic parameters were measured and recorded at study times, and the results were analyzed statistically. Results. The mean age (P=0.199), weight (P=0.050), height (P=0.9), and frequency distribution of gender (0.763) and American Society of Anesthesiologists (ASA) score (0.069) were not significantly different between the two groups. Systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP) in fentanyl group were significantly lower than the ketamine group immediately before LMA insertion, as well as 1, 3, and 5 minutes after LMA insertion (P &lt;0.050). In addition, the mean heart rate (HR) in the fentanyl group decreased significantly at different time (P&lt;0.001), but no significant difference was observed in ketamine group (P=0.056). In addition, the mean HR did not differ significantly between the two groups in any of the follow-up times (P&gt;0.050). Conclusion. Intravenous administration of remifentanil in induction of anesthesia with propofol-ketamine and propofol-fentanyl reduced changes in hemodynamic responses to LMA insertion. This hemodynamic stability was increased by adding remifentanil to the propofol-ketamine combination. Practical Implications. Remifentanil is associated with weakening of hemodynamic responses to LMA insertion in induction of anesthesia with propofol and ketamine or propofol and fentanyl; this effect can be associated with safety in cardiac patients.

Effect of meal intake for evaluating hepatic artery by Doppler ultrasonography in liver transplants: Does fasting matter for screening hepatic artery due to hemodynamic changes in splanchnic circulation?

The aim of this study is to assess the utility of fasting on Doppler ultrasonography findings of hepatic artery in liver transplants. Liver transplant patients without vascular abnormalities were prospectively evaluated between December 2017 and January 2020. Doppler sonography was used to describe hemodynamic changes in response to a standard meal. The diameter, peak systolic velocity, blood flow, resistive index (RI) of the main hepatic artery and portal vein peak velocity were measured. The mean hepatic arterial diameter of 44 patients was higher in the fasting group (4.5mm) than in the postprandial group (3.3mm) (p<.05). The mean hepatic arterial blood flow decreased (from .276 to .127 L/min) and hepatic arterial RI increased (from .66 to .71) following meal ingestion (p<.05). Hepatic arterial velocity was significantly lower and portal venous velocity was higher after oral intake. Meal ingestion has an important effect on hepatic artery Doppler features in liver transplants. Therefore, Doppler ultrasound evaluation should be considered after appropriate fasting due to postprandial responses of liver transplant.

Oscillator decomposition of infant fNIRS data.

The functional near-infrared spectroscopy (fNIRS) can detect hemodynamic responses in the brain and the data consist of bivariate time series of oxygenated hemoglobin (oxy-Hb) and deoxygenated hemoglobin (deoxy-Hb) on each channel. In this study, we investigate oscillatory changes in infant fNIRS signals by using the oscillator decompisition method (OSC-DECOMP), which is a statistical method for extracting oscillators from time series data based on Gaussian linear state space models. OSC-DECOMP provides a natural decomposition of fNIRS data into oscillation components in a data-driven manner and does not require the arbitrary selection of band-pass filters. We analyzed 18-ch fNIRS data (3 minutes) acquired from 21 sleeping 3-month-old infants. Five to seven oscillators were extracted on most channels, and their frequency distribution had three peaks in the vicinity of 0.01-0.1 Hz, 1.6-2.4 Hz and 3.6-4.4 Hz. The first peak was considered to reflect hemodynamic changes in response to the brain activity, and the phase difference between oxy-Hb and deoxy-Hb for the associated oscillators was at approximately 230 degrees. The second peak was attributed to cardiac pulse waves and mirroring noise. Although these oscillators have close frequencies, OSC-DECOMP can separate them through estimating their different projection patterns on oxy-Hb and deoxy-Hb. The third peak was regarded as the harmonic of the second peak. By comparing the Akaike Information Criterion (AIC) of two state space models, we determined that the time series of oxy-Hb and deoxy-Hb on each channel originate from common oscillatory activity. We also utilized the result of OSC-DECOMP to investigate the frequency-specific functional connectivity. Whereas the brain oscillator exhibited functional connectivity, the pulse waves and mirroring noise oscillators showed spatially homogeneous and independent changes. OSC-DECOMP is a promising tool for data-driven extraction of oscillation components from biological time series data.

Hemodynamic Changes in Response to Hyperacute Spinal Trauma in a Swine Model.

Acute spinal cord injury (ASCI) is a devastating event that can have severe hemodynamic consequences, depending on location and severity of the lesion. Knowledge of hyperacute hemodynamic changes is important for researchers using porcine models of thoracic ASCI. The goal of this study was to determine the hyperacute hemodynamic changes observed after ASCI when using pigs as their own controls. Five Yucatan gilts were anesthetized, and a dorsal laminectomy performed at T10-T12. Standardized blunt trauma was applied for 5 consecutive min, and hemodynamic variables were collected 5 min before ASCI, and at 2, 4, 6, 8, 10, 20, 30, 60, 80 and 120 min after ASCI. Arterial blood gas samples were collected at 60 min and 10 min before, and at 30 min and between 120 and 240 min after ASCI. Parametric data were analyzed using a mixed effects model with time point as the fixed factor and subject as the random factor. We found no effect on heart rate, pulse pressure, SpO₂, EtCO₂, and respiratory rate between baseline and timepoints after ASCI. Diastolic arterial pressure, mean arterial pressure, and systolic arterial pressure fell significantly by 18%, 16%, and 15%, respectively, at 2 min after ASCI. However, none of the decrements in arterial pressures resulted in hypotension at any time point. Heart rate did not change significantly after ASCI. Blood glucose progressively increased to 50% above baseline between 120 and 240 minutes after ASCI. Low thoracic ASCI caused a consistent and statistically significant but clinically minor hyperacute decrease in arterial pressures (-15%) that did not produce hypotension or metabolic changes suggestive of tissue hypoperfusion. Our findings using this model suggest that mean arterial pressures should be maintained above 85 mm Hg prior to spinal trauma in order to avoid hypotensive states after ASCI.

Fetal Hemodynamic Response to Anemia in Early Gestation: UsingHemoglobin Bart's Disease as a Study Model.

To assess fetal hemodynamic changes in response to anemia in early gestation, using fetal Hb Bart's disease as a study model. A prospective study was conducted on pregnancies at risk for fetal Hb Bart's disease at 12-14 weeks of gestation. Fetal hemodynamics were comprehensively assessed by 2Dultrasound, Doppler velocity, and cardio-STIC just prior to the invasive procedure for diagnosis. The various hemodynamic parameters of the affected and unaffected fetuses were compared. Of 56 fetuses at risk, 17 had Hb Bart's disease and 39 were unaffected. The right and combined ventricular cardiac outputs (CO) were significantly higher in the affected fetuses (0.993 vs. 1.358; p < 0.001 and 1.010 vs. 1.236; p < 0.001, respectively), whereas the left CO tended to be higher but not significantly (1.027 vs. 1.113; p = 0.058). Cardiac dimensions, middle-cerebral artery peak systolic velocity, Tei index, and isovolemic contraction time were significantly increased, while the global sphericity index was significantly decreased. Interestingly, cardiac preload, ventricular wall thickness, shortening fraction, isovolemic relaxation time, and fetal heart rate were unchanged. Four fetuses had hydropic changes, but all cardiac functions were normal. Fetal anemia induces hypervolemia and increases cardiac output to meet the tissue oxygen requirement, resulting in an increase in size without hypertrophy, volume load without pressure load, and a decrease in the globular sphericity index. The heart works very well but works harder, especially systolic ventricular load. Hydrops fetalis due to anemia appears not to be caused by heart failure as previously believed but rather by volume load with high vascular permeability at least in early pregnancy.

Hemodynamic changes in response to excitatory and inhibitory modulations by transcranial magnetic stimulation at the human sensorimotor cortex

Abstract Transcranial magnetic stimulation (TMS) can non-invasively induce excitatory or inhibitory neural activity depending on the stimulation parameters. However, the neurophysiological basis for both kinds of modulation remains elusive. Here, with a controlled dosage over the 30-s interval, we elicited excitatory and inhibitory modulations over the human primary motor cortex (M1) with TMS bursts of high (10-Hz and 30-Hz; HF) and low frequency (0.5-Hz; LF), respectively, and took functional magnetic resonance images (fMRI) and electromyography (EMG) recordings simultaneously. We used a customized 8-channel head coil array to integrate with an MRI-compatible TMS coil connected to the stimulator on a 3T MRI scanner. Images were prescribed to cover the left M1. Each TMS-fMRI run consisted of five 30-second “TMS on” and 30-second “TMS off” blocks. One of five types of TMS stimuli was administered in the “TMS-on” block: 0.5-Hz, 10-Hz-3-pulses-per-burst (ppb), 10-Hz-5-ppb, 30-Hz-3-ppb, and 30-Hz-5-ppb. In each TR (2s), images were acquired between 0 and 1 s after the start of each volume acquisition, and TMS pulses were delivered during the MRI silent period. EMG responses were calculated the peak-to-peak amplitudes from the time interval between 20 and 40 ms after the TMS onset. Image pre-processing and General Linear Model were performed using SPM12. Excitatory and inhibitory modulations were evidenced by changes in EMG responses to the HF and LF stimulation, respectively. Significantly increased fMRI signal at M1 was only detected under excitatory HF TMS but not during inhibitory LF TMS. The supplementary motor area (SMA) had significant fMRI signal changes after both TMS. The topology of the activated M1 and SMA matched the activated sensorimotor network during voluntary movement. These findings demonstrated the asymmetric hemodynamic responses to excitatory HF and inhibitory LF TMS modulations with region-dependent relationships between the local fMRI signal changes and TMS dosage over different time scales. Keywords: Transcranial magnetic stimulation, Functional magnetic resonance imaging, Primary motor cortex, Frequency

High-speed functional photoacoustic microscopy using a water-immersible two-axis torsion-bending scanner

Optical-resolution photoacoustic microscopy (OR-PAM) can provide functional, anatomical, and molecular images at micrometer level resolution with an imaging depth of less than 1 mm in tissue. However, the imaging speed of traditional OR-PAM is often low due to the point-by-point mechanical scanning and cannot capture time-sensitive dynamic information. In this work, we demonstrate a recent effort in improving the imaging speed of OR-PAM, using a newly developed water-immersible two-axis scanner. Driven by water-compatible electromagnetic actuation force, the new scanning mirror employs a novel torsion-bending mechanism to achieve fast 2D scanning. The torsion scanning along the fast-axis works in the resonant model, and the bending scanning along the slow-axis operate at the quasi-static mode. The scanning speed and scanning range along the two axes can be independently adjusted. Steered by the two-axis torsion-bending scanning mirror immersed in water, the focused excitation light and the generated acoustic wave can be confocally aligned over the entire imaging area. Thus, a high imaging speed can be achieved without sacrificing the detection sensitivity. Equipped with the torsion-bending scanner, the high-speed OR-PAM system has achieved a cross-sectional frame rate of 400 Hz, and a volumetric imaging speed of 1 Hz over a field of view of 1.5 × 2.5 mm2. We have also demonstrated high-speed OR-PAM of the hemodynamic changes in response to pharmaceutical and physiological challenges in small animal models in vivo. We expect the torsion-bending scanner based OR-PAM will find matched biomedical studies of tissue dynamics.

Two-layer spatial frequency domain imaging of compression-induced hemodynamic changes in breast tissue

.Significance: Longitudinal tracking of hemodynamic changes in the breast has shown potential for neoadjuvant chemotherapy (NAC) outcome prediction. Spatial frequency domain imaging (SFDI) could be suitable for frequent monitoring of shallow breast tumors, but strong sensitivity to superficial absorbers presents a challenge.Aim: We investigated the efficacy of a two-layer SFDI inverse model that accounts for varying melanin concentration in the skin to improve discrimination of optical properties of deep tissue of the breast.Approach: Hemodynamic changes in response to localized breast compression were measured in 13 healthy volunteers using a handheld SFDI device. Epidermis optical thickness was determined based on spectral fitting of the model output and used to calculate subcutaneous optical properties.Results: Optical properties from a homogeneous model yielded physiologically unreasonable absorption and scattering coefficients for highly pigmented volunteers. The two-layer model compensated for the effect of melanin and yielded properties in the expected range for healthy breast. Extracted epidermal optical thickness was higher for higher Fitzpatrick types. Compression induced a decrease in total hemoglobin consistent with tissue blanching.Conclusions: The handheld SFDI device and two-layer model show potential for imaging hemodynamic responses that potentially could help predict efficacy of NAC in patients of varying skin tones.

Prefrontal Cortex Involvement during Dual-Task Stair Climbing in Healthy Older Adults: An fNIRS Study.

Executive function and motor control deficits adversely affect gait performance with age, but the neural correlates underlying this interaction during stair climbing remains unclear. Twenty older adults (72.7 ± 6.9 years) completed single tasks: standing and responding to a response time task (SC), ascending or descending stairs (SMup, SMdown); and a dual-task: responding while ascending or descending stairs (DTup, DTdown). Prefrontal hemodynamic response changes (∆HbO2, ∆HbR) were examined using functional near-infrared spectroscopy (fNIRS), gait speed was measured using in-shoe smart insoles, and vocal response time and accuracy were recorded. Findings revealed increased ∆HbO2 (p = 0.020) and slower response times (p < 0.001) during dual- versus single tasks. ∆HbR (p = 0.549), accuracy (p = 0.135) and gait speed (p = 0.475) were not significantly different between tasks or stair climbing conditions. ∆HbO2 and response time findings suggest that executive processes are less efficient during dual-tasks. These findings, in addition to gait speed and accuracy maintenance, may provide insights into the neural changes that precede performance declines. To capture the subtle differences between stair ascent and descent and extend our understanding of the neural correlates of stair climbing in older adults, future studies should examine more difficult cognitive tasks.

Application of dynamic contrast enhanced ultrasound in the assessment of kidney diseases.

Many forms of acute and chronic disease are linked to changes in renal blood flow, perfusion, vascular density and hypoxia, but there are no readily available methods to assess these parameters in clinical practice. Dynamic contrast enhanced ultrasound (DCE-US) is a method that provides quantitative assessments of organ perfusion without ionising radiation or risk of nephrotoxicity. It can be performed at the bedside and is suitable for repeated measurements. The purpose of this review is to provide updates from recent publications on the utility of DCE-US in the diagnosis or assessment of renal disease, excluding the evaluation of benign or malignant renal masses. DCE-US has been applied in clinical studies of acute kidney injury (AKI), renal transplantation, chronic kidney disease (CKD), diabetic kidney disease and to determine acute effects of pharmacological agents on renal haemodynamics. DCE-US can detect changes in renal perfusion across these clinical scenarios and can differentiate healthy controls from those with CKD. In sepsis, reduced DCE-US measures of perfusion may indicate those at increased risk of developing AKI, but this requires confirmation in larger studies as there can be wide individual variation in perfusion measures in acutely unwell patients. Recent studies in transplantation have not provided robust evidence to show that DCE-US can differentiate between different causes of graft dysfunction, although it may show more promise as a prognostic indicator of graft function 1 year after transplant. DCE-US can detect acute haemodynamic changes in response to medication that correlate with changes in renal plasma flow as measured by para-aminohippurate clearance. DCE-US shows promise and has a number of advantages that make it suitable for the assessment of patients with various forms of kidney disease. However, further research is required to evidence its reproducibility and utility before clinical use can be advocated.

Cardiopulmonary Hemodynamic Profile Predicts Mortality After Transcatheter Tricuspid Valve Repair in Chronic HeartFailure.

This study was designed to assess hemodynamic changes in response to transcatheter tricuspid valve edge-to-edge repair (TTVR) and to identify hemodynamic predictors associated with mortality. Severe tricuspid regurgitation (TR) is associated with high mortality. TTVR effectively alleviates heart failure symptoms, but comprehensive hemodynamic characterization of patients undergoing TTVR is currently lacking. This international, multicenter study included 236 patients undergoing TTVR. Data from clinical assessment, echocardiography, intraprocedural right heart catheterization, and noninvasive cardiac output measurement were analyzed. Hemodynamic predictors for mortality were identified using linear Cox regression analysis and were used for stratification of patients with subsequent analysis of survival time. Patients (median age 78 years, 53% women) were symptomatic (89% in New York Heart Association functional class III or IV) because of severe TR (grade≥3+ in 100%). TTVR significantly reduced TR at discharge (grade≥3+ in 16%; p<0.001), with a corresponding 19% reduction of the right atrial v wave (21mmHg vs. 16mmHg; p<0.001) and an improvement in cardiac output (from 3.5 to 4.0 l/min; p<0.01). Invasive mean pulmonary artery pressure, transpulmonary gradient, pulmonary vascular resistance, and right ventricular stroke work were significant predictors of 1-year mortality (p<0.05 for all). Hemodynamic stratification by mean pulmonary artery pressure and transpulmonary gradient best predicted 1-year survival (p<0.001). Although patients with pre-capillary dominant pulmonary hypertension showed an unfavorable prognosis (1-year survival 38%), patients without or with post-capillary pulmonary hypertension had favorable outcome (1-year survival 92% or 78%, respectively). Invasive assessment of cardiopulmonary hemodynamic status predicts survival after TTVR. Invasivehemodynamic characterization may help identify patients profiting most from TTVR.

Hemodynamic response varies across tactile stimuli with different temporal structures.

Tactile stimuli can be distinguished based on their temporal features (e.g., duration, local frequency, and number of pulses), which are fundamental for vibrotactile frequency perception. Characterizing how the hemodynamic response changes in shape across experimental conditions is important for designing and interpreting fMRI studies on tactile information processing. In this study, we focused on periodic tactile stimuli with different temporal structures and explored the hemodynamic response function (HRF) induced by these stimuli. We found that HRFs were stimulus‐dependent in tactile‐related brain areas. Continuous stimuli induced a greater area of activation and a stronger and narrower hemodynamic response than intermittent stimuli with the same duration. The magnitude of the HRF increased with increasing stimulus duration. By normalizing the characteristics into topographic matrix, nonlinearity was obvious. These results suggested that stimulation patterns and duration within a cycle may be key characters for distinguishing different stimuli. We conclude that different temporal structures of tactile stimuli induced different HRFs, which are essential for vibrotactile perception and should be considered in fMRI experimental designs and analyses.