Arterial Blood Pressure Variability Research Articles

Study on the hydrodynamic mechanisms of the radial arterial blood pressure variation in response to arm elevation

Objective: To analyze the mechanism of invasive blood pressure change in radial artery caused by arm elevation by observing pressure, velocity and diameter of radial artery. Methods: Twenty-six hemodynamically stable hepatobiliary surgery patients admitted to the intensive care unit from June to December 2018 after general anesthesia in Tsinghua Changgung Hospital were selected. When the arm was raised, the invasive blood pressure was recorded, and the inner diameter and blood flow velocity of the radial artery were measured by Doppler ultrasound. The data following a normal distribution were compared with paired t test. Results: After arm elevation for 30 s, systolic blood pressure of radial artery decreased and diastolic blood pressure increased significantly((107±16) mmHg vs (120±17) mmHg, (75±6) mmHg vs (71±9) mmHg, t=25.0, -12.6, both P<0.05), but there was no significant difference in mean arterial pressure ((87±10) mmHg vs (87±11) mmHg, t=1.1, P>0.05). The peak velocity, end-diastolic velocity and resistance index of the radial artery increased significantly, and the transverse and longitudinal inner diameters of the radial artery decreased significantly after the arm was elevated for 30 s (t=-63.4, -14.6, -22.5, 31.4, 25.3, all P<0.01). Conclusions: Kinetic pressure compensation and vascular resistance compensation may be the main mechanism of radial artery pressure change when the arm is elevated. Arm elevation can be used as a vascular resistance response test clinically.

Continuous Monitoring of Cerebral Autoregulation in Children Supported by Extracorporeal Membrane Oxygenation: A Pilot Study.

Cerebral autoregulation (CA) impairment may pose a risk factor for neurological complications among children supported by extracorporeal membrane oxygenation (ECMO). Our first objective was to investigate the feasibility of CA continuous monitoring during ECMO treatment and to describe its evolution over time. The second objective was to analyze the association between CA impairment and neurological outcome. Observational prospective study. Twenty-nine children treated with veno-arterial or veno-venous ECMO in the PICU of Nantes University Hospital, France, and the PICU of the IRCCS Giannina Gaslini Institute in Genoa, Italy. A correlation coefficient between the variations of regional cerebral oxygen saturation and the variations of mean arterial blood pressure (MAP) was calculated as an index of CA (cerebral oxygenation reactivity index, COx). A COx > 0.3 was considered as indicative of autoregulation impairment. COx-MAP plots were investigated allowing determining optimal MAP (MAPopt) and limits of autoregulation: lower (LLA) and upper (ULA). Neurological outcome was assessed by the onset of an acute neurological event (ANE) after ECMO start. We included 29 children (median age 84days, weight 4.8kg). MAPopt, LLA, and ULA were detected in 90.8% (84.3-93.3) of monitoring time. Mean COx was significantly higher during day 1 of ECMO compared to day 2 [0.1 (0.02-0.15) vs. 0.01 (-0.05 to 0.1), p = 0.002]. Twelve children experienced ANE (34.5%). The mean COx and the percentage of time spent with a COx > 0.3 were significantly higher among ANE+ compared to ANE- patients [0.09 (0.01-0.23) vs. 0.04 (-0.02 to 0.06), p = 0.04 and 33.3% (24.8-62.1) vs. 20.8% (17.3-23.7) p = 0.001]. ANE+ patients spent significantly more time with MAP below LLA [17.2% (6.5-32.9) vs. 5.6% (3.6-9.9), p = 0.02] and above ULA [13% (5.3-38.4) vs. 4.2% (2.7-7.4), p = 0.004], respectively. CA assessment is feasible in pediatric ECMO. The first 24h following ECMO represents the most critical period regarding CA. Impaired autoregulation is significantly more severe among patients who experience ANE.

Comparison of Pressure Reactivity Index and Mean Velocity Index to Evaluate Cerebrovascular Reactivity During Induced Arterial Blood Pressure Variations in Severe Brain Injury.

To compare the assessment of cerebral autoregulation by cerebrovascular reactivity indices based on intracranial pressure (Pressure Reactivity Index, PRx) and on transcranial Doppler (Mean Velocity Index, Mx) during controlled variations of arterial blood pressure in severe brain injury. Primary outcome was the agreement between both cerebrovascular reactivity indices measured by the Bland-and-Altman method. Secondary outcomes were the association of cerebrovascular reactivity indices with arterial blood pressure variation, and the comparison of optimal cerebral perfusion pressures determined by both indices. All consecutive comatose (Glasgow Coma Scale < 8) patients from the surgical intensive care unit of Bicetre Hospital who had an acute brain injury on computerized tomography and needed vasopressor support were prospectively included. Step-by-step arterial pressure variations using vasopressors were performed to compare PRx and Mx and to calculate optimal cerebral perfusion pressure (CPPopt). 15 patients were included. Mean difference between both indices measured by Bland-and-Altman plot was -0.07 (IC 95% [-1.02 to 0.87]). Mx was significantly associated with arterial pressure variation (one-way ANOVA test, p=0.007), whereas PRx was not (p=0.44). Optimal cerebral perfusion pressure calculated with PRx and Mx was respectively 11 and 15mmHg higher than the mean perfusion pressure prescribed. Optimal cerebral perfusion pressure calculation was possible in all cases. Cerebral vasoreactivity indices calculated with intracranial pressure or transcranial Doppler show only moderate agreement. Both indices nonetheless suggest substantially higher optimal cerebral perfusion pressure than those currently provided by international guidelines.

The Effects of Gradual Change in Head Positioning on the Relationship between Systemic and Cerebral Haemodynamic Parameters in Healthy Controls and Acute Ischaemic Stroke Patients.

(1) Background: Larger blood pressure variability (BPv) in the first 3 h post-stroke onset increases pathophysiological effects such as infarct size, and leads to greater risk of disability, comorbidities and mortality at 90 days. However, there is limited information on the relationship between systemic and cerebral haemodynamic and variability parameters. (2) Objectives: This study determined the effect of a gradual change in head position (GHP) on cerebral blood flow velocity variability (CBFVv) and mean arterial blood pressure variability (MABPv), in healthy controls and acute ischaemic stroke (AIS) patients. Methods: CBFVv and MABPv were expressed as standard deviation (SD) and coefficient of variation. A total of 16 healthy controls (mean age 57 ± 16 years) were assessed over two visits, 12 ± 8 days apart, and 15 AIS patients (mean age 69 ± 8.5 years) were assessed over three visits (V1: 13.3 ± 6.9 h, V2: 4.9 ± 3.2 days and V3: 93.9 ± 11.5 days post-stroke). (3) Results: In response to GHP, MABPv does not initially increase, but over time MABPv showed a significant increase in response to GHP in AIS (visits 2 and 3) and controls (visit 2). Additionally, in response to GHP in AIS, CBFVv increased in the affected hemisphere. Lastly, in AIS, a significant correlation between CBFVv and MABPv, assessed by SD, was seen in the unaffected hemisphere, whereas this relationship was not demonstrated in the affected hemisphere. (4) Conclusions: To our knowledge, this is the first study to analyse the relationship between CBFVv and MABPv. Shedding light on the effect of head position on the relationship between cerebral blood flow and blood pressure is important to improve our understanding of the underlying effects of cerebral autoregulation impairment. This early mechanistic study provides evidence supporting supine head positioning in healthy controls and stroke patients, through demonstration of a reduction of MABPv and increase in CBFVv.

Low Variability of Blood Pressure Predicts Abnormal Electroencephalogram in Infants with Hypoxic Ischemic Encephalopathy.

This study aimed to evaluate the role of an objective physiologic biomarker, arterial blood pressure variability, for the early identification of adverse short-term electroencephalogram (EEG) outcomes in infants with hypoxic-ischemic encephalopathy (HIE). In this multicenter observational study, we analyzed blood pressure of infants meeting these criteria: (1) neonatal encephalopathy determined by modified Sarnat exam, (2) continuous mean arterial blood pressure (MABP) data between 18 and 27 hours after birth, and (3) continuous EEG performed for at least 48 hours. Adverse outcome was defined as moderate-severe grade EEG at 48 hours. Standardized signal preprocessing was used; the power spectral density was computed without interpolation. Multivariate binary logistic regression was used to identify which MABP time and frequency domain metrics provided improved predictive power for adverse outcomes compared with standard clinical predictors (5-minute Apgar score and cord pH) using receiver operator characteristic analysis. Ninety-one infants met inclusion criteria. The mean gestational age was 38.4 ± 1.8 weeks, the mean birth weight was 3,260 ± 591 g, 52/91 (57%) of infants were males, the mean cord pH was 6.95 ± 0.21, and 10/91 (11%) of infants died. At 48 hours, 58% of infants had normal or mildly abnormal EEG background and 42% had moderate or severe EEG backgrounds. Clinical predictor variables (10-minute Apgar score, Sarnat stage, and cord pH) were modestly predictive of 48 hours EEG outcome with area under curve (AUC) of 0.66 to 0.68. A composite model of clinical and optimal time- and frequency-domain blood pressure variability had a substantially improved AUC of 0.86. Time- and frequency-domain blood pressure variability biomarkers offer a substantial improvement in prediction of later adverse EEG outcomes over perinatal clinical variables in a two-center cohort of infants with HIE. · Early outcome prediction in HIE is suboptimal.. · Patterns in blood pressure physiology may be predictive of short-term outcomes.. · Early time- and frequency-domain measures of blood pressure variability predict short-term EEG outcomes in HIE infants better than perinatal factors alone..

Amplified Flow Imaging (aFlow): A Novel MRI-Based Tool to Unravel the Coupled Dynamics Between the Human Brain and Cerebrovasculature.

With each heartbeat, periodic variations in arterial blood pressure are transmitted along the vasculature, resulting in localized deformations of the arterial wall and its surrounding tissue. Quantification of such motions may help understand various cerebrovascular conditions, yet it has proven technically challenging thus far. We introduce a new image processing algorithm called amplified Flow (aFlow) which allows to study the coupled brain-blood flow motion by combining the amplification of cine and 4D flow MRI. By incorporating a modal analysis technique known as dynamic mode decomposition into the algorithm, aFlow is able to capture the characteristics of transient events present in the brain and arterial wall deformation. Validating aFlow, we tested it on phantom simulations mimicking arterial walls motion and observed that aFlow displays almost twice higher SNR than its predecessor amplified MRI (aMRI). We then applied aFlow to 4D flow and cine MRI datasets of 5 healthy subjects, finding high correlations between blood flow velocity and tissue deformation in selected brain regions, with correlation values r = 0.61 , 0.59, 0.52 for the pons, frontal and occipital lobe ( ). Finally, we explored the potential diagnostic applicability of aFlow by studying intracranial aneurysm dynamics, which seems to be indicative of rupture risk. In two patients, aFlow successfully visualized the imperceptible aneurysm wall motion, additionally quantifying the increase in the high frequency wall displacement after a one-year follow-up period (20%, 76%). These preliminary data suggest that aFlow may provide a novel imaging biomarker for the assessment of aneurysms evolution, with important potential diagnostic implications.

Neuronal Networks in Hypertension: Recent Advances.

Neurogenic hypertension is associated with excessive sympathetic nerve activity to the kidneys and portions of the cardiovascular system. Here we examine the brain regions that cause heightened sympathetic nerve activity in animal models of neurogenic hypertension, and we discuss the triggers responsible for the changes in neuronal activity within these regions. We highlight the limitations of the evidence and, whenever possible, we briefly address the pertinence of the findings to human hypertension. The arterial baroreflex reduces arterial blood pressure variability and contributes to the arterial blood pressure set point. This set point can also be elevated by a newly described cerebral blood flow-dependent and astrocyte-mediated sympathetic reflex. Both reflexes converge on the presympathetic neurons of the rostral medulla oblongata, and both are plausible causes of neurogenic hypertension. Sensory afferent dysfunction (reduced baroreceptor activity, increased renal, or carotid body afferent) contributes to many forms of neurogenic hypertension. Neurogenic hypertension can also result from activation of brain nuclei or sensory afferents by excess circulating hormones (leptin, insulin, Ang II [angiotensin II]) or sodium. Leptin raises blood vessel sympathetic nerve activity by activating the carotid bodies and subsets of arcuate neurons. Ang II works in the lamina terminalis and probably throughout the brain stem and hypothalamus. Sodium is sensed primarily in the lamina terminalis. Regardless of its cause, the excess sympathetic nerve activity is mediated to some extent by activation of presympathetic neurons located in the rostral ventrolateral medulla or the paraventricular nucleus of the hypothalamus. Increased activity of the orexinergic neurons also contributes to hypertension in selected models.

Short-term water deprivation does not increase blood pressure variability or impair neurovascular function in healthy young adults.

High dietary salt increases arterial blood pressure variability (BPV) in salt-resistant, normotensive rodents and is thought to result from elevated plasma [Na+] sensitizing central sympathetic networks. Our purpose was to test the hypothesis that water deprivation (WD)-induced elevations in serum [Na+] augment BPV via changes in baroreflex function and sympathetic vascular transduction in humans. In a randomized crossover fashion, 35 adults [17 female/18 male, age: 25 ± 4 yr, systolic/diastolic blood pressure (BP): 107 ± 11/60 ± 7 mmHg, body mass index: 23 ± 3 kg/m2] completed two hydration protocols: a euhydration control condition (CON) and a stepwise reduction in water intake over 3 days, concluding with 16 h of WD. We assessed blood and urine electrolyte concentrations and osmolality, resting muscle sympathetic nerve activity (MSNA; peroneal microneurography; 18 paired recordings), beat-to-beat BP (photoplethysmography), common femoral artery blood flow (Doppler ultrasound), and heart rate (single-lead ECG). A subset of participants (n = 25) underwent ambulatory BP monitoring during day 3 of each protocol. We calculated average real variability as an index of BPV. WD increased serum [Na+] (141.0 ± 2.3 vs. 142.1 ± 1.7 mmol/L, P < 0.01) and plasma osmolality (288 ± 4 vs. 292 ± 5 mosmol/kg H2O, P < 0.01). However, WD did not increase beat-to-beat (1.9 ± 0.4 vs. 1.8 ± 0.4 mmHg, P = 0.24) or ambulatory daytime (9.6 ± 2.1 vs. 9.4 ± 3.3 mmHg, P = 0.76) systolic BPV. Additionally, sympathetic baroreflex sensitivity (P = 0.20) and sympathetic vascular transduction were not different after WD (P = 0.17 for peak Δmean BP following spontaneous MSNA bursts). These findings suggest that, despite modestly increasing serum [Na+], WD does not affect BPV, arterial baroreflex function, or sympathetic vascular transduction in healthy young adults.

Outcomes of endovascular treatment of renal arterial stenosis in transplanted kidneys.

ABSTRACTObjective To evaluate the effectiveness and outcomes of endovascular treatment of TRAS with PTA.Materials and Methods We searched our prospectively collected database looking at cases of TRAS between January 2005-December 2011. CCT was the gold-standart for diagnosis of TRAS. Parameters analysed comprised technical aspects, arterial blood pressure variation, and renal function. A minimum follow-up of 24 months was considered.Results Of the 2221 renal transplants performed in the selected period, 22 (0.9%) patients were identified with TRAS. Fourteen (63.6%) were male and mean age was 377±14.8years (12-69). Kidney graft was from deceased donnors in 20 (80%) cases. On doppler evaluation, mean blood flow speed after transplantation, at TRAS diagnosis and after TAP was 210.6±99.5, 417±122.7 and 182.5±81.6mL/sec, respectively (p<0.001). For SBP and DBP, there was a significant difference between between pre-intervention and all post-treatment time points (p<0.001). After 1 month of the procedure, there was stabilization of the Cr level with a significant difference between mean Cr levels along time (p<0.001). After a mean follow-up of 16±4.2 (3-24) months, overall success rate was 100%.Conclusions Endovascular treatment with PTA/stenting is a safe and effective option for managing TRAS, ensuring the functionality of the graft and normalization of blood pressure and renal function.

Closed-loop modeling of the heart-rate reflex for improved diagnosis and monitoring of Mild Cognitive Impairment.

Analysis of beat-to-beat spontaneous cerebral hemodynamic data has yielded predictive dynamic models of cerebral hemodynamics and has shown previously that patients with Mild Cognitive Impairment (MCI) exhibit significantly reduced cerebral vasomotor reactivity to CO2 relative to cognitively normal control subjects [1]. The present work examines the heart-rate reflex (HRR) dynamics of 46 MCI patients compared to 20 control subjects, using closed-loop modeling of HRR under resting conditions of spontaneous variations of arterial blood pressure (baroreflex) and end-tidal CO2 (chemoreflex). These subject-specific predictive dynamic models are obtained via the methodology of Principal Dynamic Modes [2] and allow the computation of model-based markers of baroreflex and chemoreflex function. We found that the chemoreflex gain is significantly weakened in MCI patients relative to controls (p=0.0086), while the baroreflex is not significantly affected. These findings offer another tool for diagnosis and monitoring of MCI (via model-based markers), when used in conjunction with current methods.

Gender Difference of the Relationship between Arterial Stiffness and Blood Pressure Variability in Participants in Prehypertension.

Aim. The association of pressure load with elasticity in vascular system has not been studied fully. We proposed a hypothesis whether gender could modify the association of blood pressure variability (BPV) and arterial stiffness assessed by carotid-femoral pulse wave velocity (CF-PWV) in prehypertensive patients. Methods. 24h ambulatory blood pressure monitoring (24h-ABPM) and CF-PWV were measured in 723 participants with prehypertension. Univariate and multivariate regression analyses of these clinical and biological parameters were performed in total population, male and female. Results. A total of 723 participants (mean age 59.76 ± 12.37years, male 329 and female 394) were enrolled into the study. Compared with female, body mass index (BMI), fasting plasma glucose (FPG), uric acid (UA), and homocysteine (HCY) were significantly higher (all p < 0.05). Arterial stiffness (CF-PWV, male versus female, 10.89 ± 2.50 versus 10.33 ± 2.13 m/s, p=0.004) and BPVs (male versus female, 24 h SBPV 13.2 ± 5.11 versus 13.03 ± 5.20; 24 h DBPV 10.34 ± 3.87 versus 9.64 ± 3.59; N SBPV 11.90 ± 6.60 versus 10.94 ± 4.79; N DBPV 9.64 ± 5.87 versus 8.20 ± 4.48, all p<0.05) were higher in male. Multivariable linear regression analysis showed that 24 h BPV were linearly and positively related to CF-PWV in total population (24h SBPV, B=0.033; 24 h DBPV, B=0.035, both P<0.05) and female (24h SBPV, B=0.041; 24h DBPV, B=0.067, both P<0.05) independent of traditional risk factors and medications. Conclusion. BPV was independently associated with arterial stiffness in total population and the relation was modified by gender. 24 h BPVs in prehypertensive patients were useful to identify the early arterial stiffness. Clinical Trials Registration. This trial was registered with Clinical Trials.gov Identifier: NCT02569268.

Arterial blood pressure variability in pregnant women with placental insufficiency

Arterial blood pressure variability in pregnant women with placental insufficiency

Изучение питания и состава тела пациентов с диппинг- и нондиппинг-вариантами суточной регуляции артериального давления при артериальной гипертензии

Изучение питания и состава тела пациентов с диппинг- и нондиппинг-вариантами суточной регуляции артериального давления при артериальной гипертензии

A quantitative model of relation between respiratory-related blood pressure fluctuations and the respiratory sinus arrhythmia

In order to propose an interpretation of recent experimental findings concerning short-term variability of arterial blood pressure (ABP), heart rate variability (HRV), and their dependence on body posture, we develop a qualitative dynamical model of the short-term cardiovascular variability at respiratory frequency (HF). It shows the respiratory-related blood pressure fluctuations in relation to the respiratory sinus arrhythmia (RSA). Results of the model-based analysis show that the observed phenomena may be interpreted as buffering of the respiratory-related ABP fluctuations by heart rate (HR) fluctuations, i.e., the respiratory sinus arrhythmia. A paradoxical enhancement (PE) of the fluctuations of the ABP in supine position, that was found in experiment, is explained on the ground of the model, as an ineffectiveness of control caused by the prolonged phase shift between the the peak of modulation of the pulmonary flow and the onset of stimulation of the heart. Such phasic changes were indeed observed in some other experimental conditions. Up to now, no other theoretical or physiological explanation of the PE effect exists, whereas further experiments were not performed due to technical problems. Better understanding of the short-term dynamics of blood pressure may improve medical diagnosis in cardiology and diseases which alter the functional state of the autonomous nervous system.Graphical A simple mathematical model of cardiorespiratory dynamics. A novel class of mathematical models of blood pressure dynamics in humans allows to represent respiratory modulation of Arterial Blood Pressure. The model shows how the phase shift in neural control of the heart rate may produce Paradoxic Enhancement of respiratory Blood Pressure fluctuations. Observed in experiment. The model has many options for further development.

Effects of vagotomy on cardiovascular and heart rate variability alterations following chronic normobaric hypoxia in adult rabbits

Backgroundchronic hypoxia increases basal ventilation and pulmonary vascular resistance, with variable changes in arterial blood pressure and heart rate, but it’s impact on heart rate variability and autonomic regulation have been less well examined. We studied changes in arterial blood pressure, heart rate and heart rate variability (HRV) in rabbits subjected to chronic normobaric hypoxia (CNH; PB ~ 719 mmHg; FIO2 ~ 9.2%) for 14 days and assess the effect of autonomic control by acute bilateral vagal denervation.Resultsexposure to CNH stalled animal weight gain and increased the hematocrit, without affecting heart rate or arterial blood pressure. Nevertheless, Poincaré plots of the electrocardiographic R–R intervals showed a reduced distribution parallel to the line of identity, which interpreted as reduced long-term HRV. In the frequency domain, CNH reduced the very-low- (< 0.2 Hz) and high-frequency components (> 0.8 Hz) of the R–R spectrograms and produced a prominent component in the low-frequency component (0.2–0.5 Hz) of the power spectrum. In control and CNH exposed rabbits, bilateral vagotomy had no apparent effect on the short- and long-term HRV in the Poincaré plots. However, bilateral vagotomy differentially affected higher-frequency components (> 0.8 Hz); reducing it in control animals without modifying it in CNH-exposed rabbits.ConclusionsThese results suggest that CNH exposure shifts the autonomic balance of heart rate towards a sympathetic predominance without modifying resting heart rate or arterial blood pressure.

Role of arterial stiffness and blood pressure variability in the definition of SHATS (systemic hemodynamic atherothrombotic syndrome)

BackgroundCV risk exponentially increases as the number of damaged organs increases The Systemic Hemodynamic Atherosclerotic Syndrome (SHATS) represents a novel conceptualization of the CV continuum focusing on simultaneous multi-organ alteration. This is the first study operationally defining SHATS and aimed at identifying its determinants.MethodsLeft Ventricular Hypertrophy (echocardiography), Common Carotid Artery plaque and increased thickness (ultrasound), and Chronic Kidney Disease (estimated Glomerular Filtration Rate) indexed selective target organ damage. SHATS was operationally defined as their simultaneous presence in a patient. PWV was measured by Sphygmocor® and BP variability by 24 h ABPM.ResultsSHATS affected 19.9% of the 367 studied subjects. Subjects with SHATS had a similar prevalence in diabetes mellitus, but a greater prevalence of very stiff artery (84.9 vs 64.3 %, p < 0.01) and use of antihypertensive medications. In the presence of similar office BP, SHATS was associated with higher 24 h SBP and lower 24 h DBP (a greater pulsatile pressure!), reduced nighttime SBP fall, and a twofold greater prevalence of reverse dipper status (48.2 vs 20.2 %, p < 0.001). BMI (positive correlation) and DBP (negative correlation) were the only traditional CV risk factors significantly associated with the odds of having SHATS. Very stiff artery and BP variability were significant independent determinants of SHATS, with highly predictive accuracy.ConclusionSHATS, the simultaneous damage of multiple target organs, may easily operationally defined. Very stiff artery and BP variability represent key factors for SHATS. The present results support the hypothesis of SHATS as a systemic condition, needing further characterization.

Non-invasive determination of reference arterial blood pressure indices of healthy Alsatian and Boerboel dogs

In order to evaluate and manage Boerboels and Alsatians under critical and emergency care, knowledge of ranges and causes of variability of normal arterial blood pressure (ABP) indices is desirable. The systolic arterial pressure (SAP), diastolic arterial pressure (DAP) and mean arterial pressure (MAP) of 30 healthy dogs were evaluated with human sphygmomanometer and neonatal cuff. The age, sex, breed, weight, height, weight to height ratio (WTH), of each dog was recorded. The mean and range of ABP values for Alsatians and Boerboels were similar to those of some other breeds. There were no age, breed and sex differences in ABP indices of dogs. The coefficient of variations and ranges of DAP and MAP were significantly higher than SAP measurements. In all dogs, SAP was influenced by breed and interaction of breed and sex when all confounders were controlled. The WTH and sex were found to independently influence SAP in presence of confounders. In Alsatian, WTH and sex interaction influenced all pressures in presence of confounders. The DAP was significantly influenced by heart rate and WTH in presence and absence of confounders respectively. Although age did not influence ABP in all dogs, it influenced SAP and DAP in females and Boerboel. The absence of age, sex, and breed differences in ABP of dogs may be due to multiple interactions between these factors. The human sphygmomanometer has the best precision for SAP measurements and WTH may be used as canine’s body mass index (BMI) because of its influence on ABP.Keywords: Blood pressure, dogs, breed, sex, age, oscillometry

Cerebral autoregulation in migraine with aura: A case control study.

Migraine with aura is independently associated with increased risk of ischemic stroke, especially in younger subjects. This association might be related to an impairment of cerebral autoregulation, which normally maintains cerebral blood flow independent of arterial blood pressure variations. Patients aged 30-55, fulfilling ICHD-3 beta criteria for migraine with aura, were prospectively enrolled and compared with gender- and age-matched healthy controls without a history of migraine. Patients and controls with a history of stroke or any disease potentially impairing cerebral autoregulation were excluded. We assessed cerebral autoregulation with two different methods: Transfer function analysis, and the correlation coefficient index Mx. The transfer function phase and gain reflect responses of cerebral blood flow velocities to relatively fast fluctuations of arterial blood pressure, whereas Mx also reflects responses to slower arterial blood pressure fluctuations. A total of 22 migraine with aura patients (median age [IQR]: 39.5 [12.5] years) and 22 controls (39 [9.75] years) were included. Transfer function parameters and Mx were not different between patients and controls. However, Mx was inversely correlated with age in patients (ρ = -0.567, p = 0.006) and not in controls (ρ = -0.084, p = 0.509). Mx was also inversely correlated with migraine with aura duration (ρ = -0.617, p = 0.002), suggesting improvement of cerebral autoregulation efficiency with disease duration. Cerebral autoregulation did not differ between patients and controls aged 30-55. However, cerebral autoregulation efficiency was strongly correlated with migraine with aura duration. Further studies in younger patients are needed to determine whether cerebral autoregulation is impaired early in the course of disease. NCT02708797.

Blood Pressure Coefficient of Variation and Its Association With Cardiac Surgical Outcomes.

Multiple studies completed in the ambulatory nonsurgical setting show a significant association between short- and long-term blood pressure variability and poor outcomes. However, perioperative blood pressure variability outcomes have not been well studied, especially in the cardiac surgical setting. In this study, we sought to assess whether systolic and mean arterial blood pressure variability were associated with 30-day mortality and in-hospital renal failure in patients undergoing cardiac surgery requiring cardiopulmonary bypass. Furthermore, blood pressure variability has not been evaluated specifically during each phase of surgery, namely in the pre-, intra- and postbypass phases; thus, we aimed also to assess whether outcomes were associated with phase-specific systolic and mean arterial blood pressure variability. All patients undergoing cardiac surgery from January 2008 to June 2014 were enrolled in this retrospective, single-center study. Demographic, intraoperative, and postoperative outcome data were obtained from the institution's Society of Thoracic Surgery database and Anesthesia Information Management System. Systolic and mean arterial blood pressure variability were assessed using the coefficient of variation (CV). The primary outcomes were 30-day mortality and in-hospital renal failure in relation to the entire duration of a case, while the secondary outcomes assessed phase-specific surgical periods. In an effort to control the family-wise error rate, P values <.0125 were considered significant for the primary outcomes. Of the 3687 patients analyzed, 2.7% of patients died within 30 days of surgery and 2.8% experienced in-hospital renal failure. After adjusting for significant covariates, we found a statistically significant association between increasing CV for systolic blood pressure (CVSBP) and 30-day mortality and in-hospital renal failure. For every 0.10 increase in CVSBP, there was a 150% increase in the odds of death (odds ratio, 2.50; 95% confidence interval, 1.60-3.92; P < .0001) and there was a 104% increase in odds of experiencing renal failure (odds ratio, 2.04; 95% confidence interval, 1.33-3.14; P = .001). The association with mortality was driven primarily by the prebypass period, because the association between CVSBP and mortality during the prebypass phase was significant (P = .01), and not during the postbypass phase (P = .08). There was no significant association between CV for mean arterial blood pressure and either death or renal failure during any period of surgery, including the bypass phase. Increasing systolic blood pressure variability was associated with 30-day mortality and development of renal failure, with surgery phase-specific relationships observed. Further research is required to determine how to prospectively detect blood pressure variability and elucidate opportunities for intervention.

Muscle blood content and muscle oxygen saturation in response to head down and head up tilt

As microgravity alters blood distribution and flow in muscle tissue, in the present study, blood content and oxygen saturation in extremity muscles were evaluated by an analogous body tilting model. For this purpose, the supine resting posture was compared with successive head down tilt (HDT) and head up tilt (HUT) in ten well trained male volunteers. Muscle oxygen saturation and total hemoglobin content were measured using near infrared spectroscopy sensors attached on the gastrocnemius, vastus lateralis and biceps brachii muscles of each body side. Simultaneously, continuous and noninvasive recordings of arterial blood pressure and heart rate variability were performed. The test protocol consisted of the following stages (5 min each): supine, 6o HDT, 15o HDT, 30o HDT, supine, 6o HUT, 15o HUT, and 30o HUT postures in successive order. The evolution of the rhythmic components in the recorded time series were analyzed by wavelet based multiscale time-frequency distributions, and synchronization between measurement sites by wavelet phase synchronization indexing. A support vector machine (SVM) algorithm was employed for classification of posture in relation to muscle total hemoglobin content or oxygen saturation. Increasing or decreasing gravitational impact due to the posture changes resulted in significant increases or decreases of total hemoglobin content in the muscles, but showed no linear relation to muscle oxygen saturation. This effect was stronger pronounced as the respective extremity part was located more centrifugal to the body tilting axis. Blood pressure and heart rate did not influence muscle oxygen saturation. The two major rhythmic components in the cardiovascular system, the 0.1 Hz and respiratory rhythm, were only weakly displayed in the muscle oxygen saturation time series. Oscillations of muscle oxygen saturation in the very low frequency band displayed left-right synchrony. SVM was able to classify postural changes of muscle blood content with good accuracy but not those of muscle oxygen saturation. These results imply that muscle oxygen saturation during acute postural changes may be mainly regulated by neural drive to the micro-vascular circulation and not by systemic cardiovascular kinetics.