scholarly journals The Effects of Hypocapnia on Brain Tissue Pulsations

2020 ◽  
Vol 10 (9) ◽  
pp. 614
Author(s):  
Meshal Alharbi ◽  
Poppy Turner ◽  
Jonathan Ince ◽  
Mitsuhiro Oura ◽  
Kelechi U. Ebirim ◽  
...  
Keyword(s):  
Heart Rate ◽  
Brain Tissue ◽  
Cerebral Autoregulation ◽  
Tissue Doppler ◽  
Arterial Blood ◽  
Starting Point ◽  
Volunteer Study ◽  
Healthy Volunteer Study ◽  
Carbon Dioxide Levels ◽  
The Impact

Hypocapnia is known to affect patients with acute stroke and plays a key role in governing cerebral autoregulation. However, the impact of hypocapnia on brain tissue pulsations (BTPs) is relatively unexplored. As BTPs are hypothesised to result from cerebrovascular resistance to the inflow of pulsatile arterial blood, it has also been hypothesised that cerebral autoregulation changes mediated by hypocapnia will alter BTP amplitude. This healthy volunteer study reports measurements of BTPs obtained using transcranial tissue Doppler (TCTD). Thirty participants underwent hyperventilation to induce mild hypocapnia. BTP amplitude, EtCO2, blood pressure, and heart rate were then analysed to explore the impact of hypocapnia on BTP amplitude. Significant changes in BTP amplitude were noted during recovery from hypocapnia, but not during the hyperventilation manoeuvre itself. However, a significant increase in heart rate and pulse pressure and decrease in mean arterial pressure were also observed to accompany hypocapnia, which may have confounded our findings. Whilst further investigation is required, the results of this study provide a starting point for better understanding of the effects of carbon dioxide levels on BTPs. Further research in this area is needed to identify the major physiological drivers of BTPs and quantify their interactions with other aspects of cerebral haemodynamics.

Abstract 328: Hemodynamic Comparison of Zucker Diabetic Fatty Rats to Their Lean Littermates After Asphyxial Cardiac Arrest

Circulation ◽  
2018 ◽  
Vol 138 (Suppl_2) ◽  
Author(s):  
Claudius Balzer ◽  
Franz Baudenbacher ◽  
Michele M Salzman ◽  
William J Cleveland ◽  
Susan Eagle ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Cardiac Arrest ◽  
Ejection Fraction ◽  
Ischemia Reperfusion ◽  
Diabetic Rats ◽  
Arterial Blood ◽  
Zucker Diabetic Fatty Rats ◽  
Zdf Rats ◽  
The Impact

Patients with metabolic syndrome are at higher risk for cardiac arrest (CA), and also have worse neurologic outcome after CA related to their comorbidities (e.g., Type 2 Diabetes Mellitus [T2DM]). Using Zucker Diabetic Fatty (ZDF) rats as a new and relevant model with common comorbidities for CA and cardiopulmonary resuscitation (CPR), we hypothesized that T2DM is associated with a lower chance for return of spontaneous circulation (ROSC) and/or a worse outcome regarding heart function after asphyxial CA compared to their lean littermates. Two groups of rats (8 ZDF, 7 lean) were monitored for 37±2 weeks. The rats were anesthetized and intubated; heart rate was monitored by subcutaneous ECG needles. Femoral artery and vein were cannulated for continuous blood pressure measurement and delivery of fluids and medications, respectively. Before ventilation was stopped to initiate asphyxial CA, rocuronium was given. After 8 minutes of CA, ventilation was re-initiated with FiO 2 1.0, epinephrine and sodium-bicarbonate were administered, and pneumatic chest compression were started with 200 compressions per minute. Chest compressions were stopped when a systolic blood pressure of 120 mmHg was achieved. During 4 hours of observation, vital parameters were closely monitored, blood gases were measured, and ejection fraction (EF %) was assessed with ultrasound. Data are mean ± SD. Statistics: Unpaired student’s t-test (two-tailed), α.05. At baseline, ZDF rats showed significantly higher blood glucose levels (504±52 vs 174±14 mg/dl) compared to their lean littermates. All ZDF and lean rats achieved ROSC, and measurements taken directly after ROSC and after the first hour showed no relevant differences. After four hours, there was no difference in heart rate between ZDF and lean rats. However, diabetic rats had a significantly higher mean arterial blood pressure (142±24vs. 107±19 mmHg) and ejection fraction (42±16%vs 20±8%) compared to their lean littermates. The hypothesis that ROSC-rate in diabetic rats would be lower could not be proven. Conversely, the ZDF rats showed a significantly higher blood pressure related to an increased EF%. Further analysis in this study will focus on the impact of T2DM on cardiac and neurological ischemia-reperfusion injury.

Prenatal exercise and cardiovascular health (PEACH) study: impact of acute and chronic exercise on cerebrovascular hemodynamics and dynamic cerebral autoregulation

2021 ◽  
Author(s):  
Rachel J. Skow ◽  
Lawrence Labrecque ◽  
Jade A. Rosenberger ◽  
Patrice Brassard ◽  
Craig D. Steinback ◽  
...  
Keyword(s):  
Exercise Training ◽  
Gestational Age ◽  
Cerebral Autoregulation ◽  
Acute Exercise ◽  
Controlled Trial ◽  
Moderate Intensity ◽  
Chronic Exercise ◽  
Arterial Blood ◽  
The Impact ◽  
Dynamic Cerebral Autoregulation

We performed a randomised controlled trial measuring dynamic cerebral autoregulation (dCA) using a sit-to-stand maneuver before (SS1) and following (SS2) an acute exercise test at 16-20 weeks gestation (trimester 2; TM2) and then again at 34-37 weeks gestation (third trimester; TM3). Following the first assessment, women were randomised into exercise training or control (standard care) groups; women in the exercise training group were prescribed moderate intensity aerobic exercise for 25-40 minutes on 3-4 days per week for 14±1weeks. Resting seated mean blood velocity in the middle cerebral artery (MCAvmean) was lower in TM3 compared to TM2 but not impacted by exercise training intervention. dCA was not impacted by gestational age, or exercise training during SS1. During SS2, dCA was altered such that there were greater absolute and relative decreases in mean arterial blood pressure (MAP) and MCAvmean, but this was not impacted by the intervention. There was also no difference in the relationship between the decrease in MCAvmean compared to the decrease in MAP (%/%), or the onset of the regulatory response with respect to acute exercise, gestational age, or intervention; however, rate of regulation was faster in women in the exercise group following acute exercise (interaction effect, p=0.048). These data highlight the resilience of the cerebral circulation in that dCA was well maintained or improved in healthy pregnant women between TM2 and TM3. However, future work addressing the impact of acute and chronic exercise on dCA in women who are at risk for cardiovascular complications during pregnancy is needed.

Esmolol: effects on isoprenaline- and exercise-induced cardiovascular stimulation in conscious dogs

1990 ◽  
Vol 68 (10) ◽  
pp. 1322-1328 ◽  
Author(s):  
G. Fischer ◽  
J. G. Grohs ◽  
G. Raberger
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Diastolic Blood Pressure ◽  
Treadmill Exercise ◽  
Diastolic Pressure ◽  
Left Ventricular ◽  
Concomitant Increase ◽  
Arterial Blood ◽  
Exercise Induced ◽  
The Impact

Esmolol, a recently developed ultra-short acting β-adrenoceptor blocking agent, was evaluated in 12 conscious chronically instrumented dogs with intact autonomic reflexes. The significance of its β1-adrenoceptor selectivity was examined at various cardiovascular activation levels established by either incremental isoprenaline infusion or graded treadmill exercise. The observed parameters were heart rate, systolic and diastolic arterial blood pressure, left ventricular dp/dtmax, and left ventricular end-diastolic pressure. Intravenous infusion of esmolol (25 and 250 μg∙kg−1∙min−1) led to a dose-dependent reduction of the isoprenaline-induced increase in positive dp/dtmax. The concomitant increase in heart rate was suppressed to a lesser extent. Characteristically of a β1-selective agent, esmolol had only a slight effect on the isoprenaline-induced reduction in diastolic blood pressure. The impact of esmolol on exercise-induced hemodynamic activation was much smaller. Exercise-induced increase in positive dp/dtmax was more sensitive to β-adrenoceptor blockade than the concomitant increase in heart rate. Diastolic blood pressure was not influenced significantly. β-Adrenoceptor blockade was virtually reversed within 20 min of discontinuation of esmolol infusion.Key words: esmolol, β1-adrenoceptor selectivity, dogs, treadmill exercise, isoprenaline stimulation.

Levels of Sustainable Aerobic Workload in Dialysis Patients

1998 ◽  
Vol 21 (7) ◽  
pp. 391-397 ◽  
Author(s):  
E.M. Capodaglio ◽  
G. Villa ◽  
D. Jurisic ◽  
A. Salvadeo
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Chronic Hemodialysis ◽  
Step Test ◽  
Aerobic Performance ◽  
Subjective Ratings ◽  
Test Protocol ◽  
Physiological Variables ◽  
Arterial Blood ◽  
Starting Point

The aerobic performance of a heterogeneous group of 89 ambulatory medically stable patients on chronic hemodialysis was studied to define individual levels of the most acceptable metabolic workload. The patients performed a step test protocol (3 steps) with a cycle ergometer. Each step (25 Watt) lasted 6 min. Heart rate (HR), oxygen consumption (VO2), ventilation (VE), respiratory exchange ratio (RER), blood pressure (BP) and subjective ratings of dyspnea (CRd) and fatigue (CRf) levels were monitored throughout the test. The test was continued to exhaustion or to values of systolic arterial blood pressure (SABP) >240 mmHg, heart rate (HR) ≥ 85% max, or ST changes in ECG. In eleven patients (12.5% of the whole group) the test was interrupted within the first two minutes of exercise. In the remaining 78 patients, the maximum workload sustained for at least 3 min (MSW) was 25 Watts for 43 (48.5%), 50 Watts for 27 (30%), and 75 Watts for 8 (9%) patients. Performance was affected in a statistically significant manner by the subjects’ anagraphic age, but not by their dialytic age, hemoglobin (Hb) level or weight. Individual levels of tolerable workload were estimated for 60% of the group from the stability of physiological variables during 3 min, and from subjective ratings at a “moderate” level. This level corresponded to an average of 3.5±0.9 METs, at 60% of the HRmax, with a mean BP of 167±21/98±14 mmHg. This could become a safe starting point for a program of physical retraining.

scholarly journals Relationship Between Baroreflex and Cerebral Autoregulation in Patients With Cerebral Vasospasm After Aneurysmal Subarachnoid Hemorrhage

2022 ◽  
Vol 12 ◽  
Author(s):  
Agnieszka Uryga ◽  
Nathalie Nasr ◽  
Magdalena Kasprowicz ◽  
Karol Budohoski ◽  
Marek Sykora ◽  
...  
Keyword(s):  
Subarachnoid Hemorrhage ◽  
Cerebral Vasospasm ◽  
Cerebral Autoregulation ◽  
Cerebral Blood Flow Velocity ◽  
Aneurysmal Subarachnoid Hemorrhage ◽  
Linear Regression Analysis ◽  
Inverse Correlation ◽  
Arterial Line ◽  
Arterial Blood ◽  
The Impact

Introduction: Common consequences following aneurysmal subarachnoid hemorrhage (aSAH) are cerebral vasospasm (CV), impaired cerebral autoregulation (CA), and disturbance in the autonomic nervous system, as indicated by lower baroreflex sensitivity (BRS). The compensatory interaction between BRS and CA has been shown in healthy volunteers and stable pathological conditions such as carotid atherosclerosis. The aim of this study was to investigate whether the inverse correlation between BRS and CA would be lost in patients after aSAH during vasospasm. A secondary objective was to analyze the time-trend of BRS after aSAH.Materials and Methods: Retrospective analysis of prospectively collected data was performed at the Neuro-Critical Care Unit of Addenbrooke's Hospital (Cambridge, UK) between June 2010 and January 2012. The cerebral blood flow velocity (CBFV) was measured in the middle cerebral artery using transcranial Doppler ultrasonography (TCD). The arterial blood pressure (ABP) was monitored invasively through an arterial line. CA was quantified by the correlation coefficient (Mxa) between slow oscillations in ABP and CBFV. BRS was calculated using the sequential cross-correlation method using the ABP signal.Results: A total of 73 patients with aSAH were included. The age [median (lower-upper quartile)] was 58 (50–67). WFNS scale was 2 (1–4) and the modified Fisher scale was 3 (1–3). In the total group, 31 patients (42%) had a CV and 42 (58%) had no CV. ABP and CBFV were higher in patients with CV during vasospasm compared to patients without CV (p = 0.001 and p < 0.001). There was no significant correlation between Mxa and BRS in patients with CV, neither during nor before vasospasm. In patients without CV, a significant, although moderate correlation was found between BRS and Mxa (rS = 0.31; p = 0.040), with higher BRS being associated with worse CA. Multiple linear regression analysis showed a significant worsening of BRS after aSAH in patients with CV (Rp = −0.42; p < 0.001).Conclusions: Inverse compensatory correlation between BRS and CA was lost in patients who developed CV after aSAH, both before and during vasospasm. The impact of these findings on the prognosis of aSAH should be investigated in larger studies.

Heart rate variability and the dawn of complex physiological signal analysis: methodological and clinical perspectives

2021 ◽  
Vol 379 (2212) ◽  
Author(s):  
J. Philip Saul ◽  
Gaetano Valenza
Keyword(s):  
Heart Rate ◽  
Heart Rate Variability ◽  
Linear Models ◽  
Linear Time ◽  
Venous Pressure ◽  
Autonomic Nerve ◽  
Physiological Signal ◽  
Arterial Blood ◽  
Challenges And Opportunities ◽  
The Impact

Spontaneous beat-to-beat variations of heart rate (HR) have intrigued scientists and casual observers for centuries; however, it was not until the 1970s that investigators began to apply engineering tools to the analysis of these variations, fostering the field we now know as heart rate variability or HRV . Since then, the field has exploded to not only include a wide variety of traditional linear time and frequency domain applications for the HR signal, but also more complex linear models that include additional physiological parameters such as respiration, arterial blood pressure, central venous pressure and autonomic nerve signals. Most recently, the field has branched out to address the nonlinear components of many physiological processes, the complexity of the systems being studied and the important issue of specificity for when these tools are applied to individuals. When the impact of all these developments are combined, it seems likely that the field of HRV will soon begin to realize its potential as an important component of the toolbox used for diagnosis and therapy of patients in the clinic. This article is part of the theme issue 'Advanced computation in cardiovascular physiology: new challenges and opportunities'.

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