Arterial Blood Pressure Measurements Research Articles

Cardiovascular responses to low-level transcutaneous vagus nerve stimulation.

The aim was to determine cardiovascular responses to an arbitrary protocol of transcutaneous low-level vagus nerve electrical stimulation (tVNS). Study was performed in 15 male volunteers, mean age 23years. Data were collected during two sessions - sham stimulation (no stimulation) and stimulation. Each session included one-hour resting phase followed by 15-min autonomic nervous system testing phase (Valsalva, deep breathing, wet-cold face tests), all in supine position. The right tragus stimulation parameters were: 20Hz, constant current at sensation threshold, 1ms rectangular pulse width. The ECG, noninvasive arterial blood pressure and thoracic impedance cardiography measurements were recorded and analyzed continuously with the Task Force® Monitor (CNSystems Medizintechnik GmbH, Graz, Ver. 2.2.10.0). t-Test for paired samples, paired Wilcoxon signed-rank, and one-way ANOVA for repeated measurements were carried out. P<0.05 was considered significant. We demonstrated significant reductions of left ventricular contractility and output parameters, a trend for heart rate reduction, and resulting beneficial reduction of left ventricular work load. However, significant increases of blood pressure and total peripheral resistance were recognized, possibly as a reflex response. It seems that our tVNS protocol has a potential for cardiac autonomic modulation. This gives us opportunity to advance our stimulation parameters with participant-specific adjustments. Further studies are however needed to prove the therapeutic potential of such approach in different patient groups.

Telemetric data collection should be standard in modern experimental cardiovascular research

Cardiovascular (CV) health is often expressed by changes in heart rate and blood pressure, the physiological record of which may be affected by moving, anaesthesia, handling, time of day and many other factors in rodents. Telemetry measurement minimises these modulations and enables more accurate physiological recording of heart rate and blood pressure than non-invasive methods. Measurement of arterial blood pressure by telemetry requires implanting a catheter tip into the artery. Telemetry enables us to sample physiological parameters with a high frequency continuously for several months. By measuring the pressure in the artery using telemetry, we can visualize pressure changes over a heart cycle as the pressure wave. From the pressure wave, we can subtract systolic, diastolic, mean and pulse pressure. From the beat-to-beat interval (pressure wave) and the RR' interval (electrocardiogram), we can derive the heart rate. From beat-to-beat variability, we can evaluate the autonomic nervous system's activity and spontaneous baroreflex sensitivity and their impact on CV activity. On a long-term scale, circadian variability of CV parameters is evident. Circadian variability is the result of the circadian system's activity, which synchronises and organises many activities in the body, such as autonomic and reflex modulation of the CV system and its response to load over the day. In the presented review, we aimed to discuss telemetry devices, their types, implantation, set-up, limitations, short-term and long-term variability of heart rate and blood pressure in CV research. Data collection by telemetry should be, despite some limitations, standard in modern experimental CV research.

The Potential protective role of astaxanthin on doxorubicin-induced cardiac toxicity in rats

Abstract Background and Aim of Work Doxorubicin (DOX) is one of the most commonly used effective anticancer drugs, through its inhibition of topoisomerase II, DNA replication and repair. In addition, DOX leads to generation of semiquinone free radicals and oxygen free radicals which attack DNA and oxidize DNA bases. However, the clinical use of doxorubicin is limited by its adverse effects such as cardiotoxicity, which is acute and occurs within 2-3 days of its administration. Recently, the potential health benefits of Astaxanthin were investigated, however, the protective effect of astaxanthin supplementation on cardiac dysfunction induced by Doxorubicin is not clearly investigated. The aim of the present study is directed to investigate the possible role of astaxanthin (xanthophyll carotenoid) in protection against DOX- induced cardiac toxicity, and to elucidate the underlying mechanism(s). Materials and Methods Animals used were 47 adult male albino rats, which were randomly allocated into four groups. Control group(C): received 0.1ml/100gm BW i.p. saline injections for 7 successive days. DOX-treated group: received 0.1ml/100gm BW i.p. saline injections for 7 successive days, followed by a single i.p. injection of DOX, 20 mg/kg i.p. on the 7th day. ATX-treated group: received 40mg/kg/day BW i.p. ATX injections for 7 successive days. ATX+DOX treated group: received 40mg/kg/day BW i.p. ATX injections for 7 successive days, followed by a single i.p. injection of DOX, 20 mg/kg i.p. on the 7th day. At the end of the study, the overnight fasted rats were subjected to final arterial blood pressure measurement. Rats were then weighed and anaesthetized with 40 mg/kg B.W i.p. thiopental sodium. Then, ECG was recorded, blood samples were collected from abdominal aorta and centrifuged. The resulting plasma was used for measurement of plasma cardiac Troponin I (cTnI) and plasma Cytochrome C. The heart was subjected to In vitro study of isolated hearts perfused in langendorff preparation. Hearts and ventricles were weighed. The left ventricle was then stored at -80οC for later determination of cardiac tissue iron. Statistical Analysis was made using 1-way ANOVA for difference between means of different groups. Ethics Committee The study protocol was approved by the Research Ethical Committee of Faculty o fMedicine Ain Shams University (Reference No. FWA00017585). Results The systolic blood pressure was increased significantly in the DOX treated group compared to the control group. All of the systolic, diastolic and mean arterial blood pressures were significantly decreased in the ATX +DOX treated group compared to the DOX treated group. Heart rate was significantly increased in the ATX +DOX treated group compared to the control group, and compared to the DOX treated group. PT and PT/LVW were significantly increased in the ATX +DOX group compared to both of the DOX group and the control group. In addition, PT and PT/LVW were significantly increased in the ATX-treated group compared to the DOX group. The TPT was prolonged in the DOX group compared to the control group and this prolongation was statistically significant in pre-ischemia and 5 minutes after reperfusion of the isolated hearts, and was significantly shortened in the ATX-treated group and ATX +DOX group compared to the DOX. Also, TPT was significantly shortened in the ATX-treated and in the in the ATX +DOX groups compared to the control group. HRT was significantly prolonged in the DOX group compared to the control group. However, HRT was significantly shortened in the ATX-treated and ATX +DOX groups compared to the DOX group, and in the ATX +DOX group compared to the control group. The MFR and MFR/LVW were significantly decreased in the DOX group compared to the control group. However, the MFR was significantly increased in each of the ATX-treated group and ATX +DOX group when each was compared to the DOX group. Moreover, MFR was significantly increased in the ATX +DOX group compared to the control group. Each of plasma cardiac Troponin, plasma Cytochrome C and Cardiac Tissue Iron were significantly increased in the DOX group compared to the control group, and all were significantly decreased in the ATX-treated group when compared to DOX group, and in the ATX +DOX group when compared to the DOX group. No significant changes were detected in body weight, heart weights and ECG parameters between the different studied groups. Conclusion Doxorubicin produces acute cardiotoxic effects and impairs systolic and diastolic cardiac functions, which is due to increased oxidative stress, mitochondrial instability and iron accumulation in the cardiac tissue. Astaxanthin exerts a major cardioprotective activities against DOXinduced cardiotoxicity, probably due to its major antioxidant and iron chelation properties.

Neutrophil-to-lymphocyte ratio in patients with white-coat hypertension

Introduction: White coat hypertension (WCH), a distinct phenotype of hypertension, is defined as elevated office blood pressure (BP) measurements during repeat visits with normal out-of-office BP measurements. The association of WCH with cardiovascular risk remains unclear; however, current data support an association between untreated WCH and the risk for cardiovascular events, cardiovascular mortality, and all-cause mortality. Increased inflammatory processes may explain the underlying pathophysiology of the increased risk for cardiovascular events in WCH; therefore, we evaluated the neutrophil-to-lymphocyte ratio (NLR) of patients with WCH compared with matched normotensive controls. &#x0D; Material and Method: Forty-five eligible subjects with WCH and 45 age, sex, and BMI matched healthy and normotensive subjects were included in the study. The subjects were assessed by office arterial BP and 24-hour ambulatory BP measurements. An automated blood count analyzer measured the NLR values. &#x0D; Results: The mean NLR in the patients-with-WCH group was significantly higher than that in the control group (2.67±0.27 vs. 2.46±0.34, p

Blood-pressure–waveform monitoring without interruptions due to changes in arterial compliance: The use of the vibrational and volume-clamp methods

The arterial–blood-pressure (ABP) waveform can be monitored by the volume-clamp method. The photoplethysmography (PPG) signal is measured and clamped at maximum arterial compliance (PPGcmax) by controlling the external pressure (EP) with a cuff. PPGcmax is determined by the volume-oscillometric method though ABP measurement is regularly interrupted. To overcome this drawback, the vibrational method superimposes high-frequency vibrations on EP and measures the PPG response to estimate the “vibrational” compliance (Cv) and the PPGcmax. This method, though, has never been validated or implemented simultaneously with the volume-clamp method because the control has always been unstable. We implemented a custom-made device with a novel control system, monitoring stability and adapting the gain at high frequencies, plus lower-amplitude EP vibrations. We compared, in eleven volunteers, the EP at PPGcmax determined by the volume-oscillometric and the vibrational methods. Both exhibited a good linear correlation (r2 >0.92) and Bland-Altman agreement (95% confidence interval <15 mmHg). Moreover, in three volunteers, the vibrational and volume-clamp methods were implemented together while experimentally changing the ABP and/or Cv without manifesting control-system instability. Cv measured with the vibrational method could be used by the volume-clamp method to measure the ABP waveform without any interruptions due to changes in arterial compliance.

Plasmatic Dimethylarginines in Dogs With Myxomatous Mitral Valve Disease.

Plasmatic dimethylarginines, asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA) are considered biomarkers of endothelial and renal dysfunction, respectively, in humans. We hypothesize that plasmatic concentration of dimethylarginines in dogs with myxomatous mitral valve disease (MMVD) is influenced by heart disease stage. Eighty-five client-owned dogs with MMVD, including 39, 19, and 27 dogs in ACVIM stages B1, B2, and C+D, respectively, and a control group of 11 clinically healthy dogs were enrolled. A prospective, multicentric, case-control study was performed. Each dog underwent a complete clinical examination, arterial blood pressure measurement, thoracic radiography, six-lead standard electrocardiogram, transthoracic echocardiography, CBC, biochemical profile, and urinalysis. Plasmatic concentration of dimethylarginines was determined through high-performance liquid chromatography coupled with tandem mass spectrometry. Median ADMA was significantly increased in dogs of group C+D (2.5 μmol/L [2.1–3.0]) compared to those of group B1 (1.8 μmol/L [1.6–2.3]; p < 0.001) and healthy dogs (1.9 μmol/L [1.7–2.3]; p = 0.02). Median SDMA was significantly increased in dogs of group C+D (0.7 μmol/L [0.5–0.9]) compared to those of groups B1 (0.4 μmol/L [0.3–0.5]; p < 0.001), B2 (0.4 μmol/L [0.3–0.6]; p < 0.01), and the control group (0.4 μmol/L [0.35–0.45]; p = 0.001). In the final multivariable analysis, ADMA and SDMA were significantly associated with left atrium to aorta ratio (p < 0.001), and creatinine (p < 0.001), respectively. Increased plasmatic concentrations of dimethylarginines suggest a possible role as biomarkers of disease severity in dogs with decompensated MMVD.

Acute hypervolemic hemodilution combined with controlled hypotension to minimize blood loss during operations of spine fusion: remifentanil versus magnesium sulfate

BackgroundBlood loss is one of the major problems during operations of spine fusion. Several blood-conservative measures were applied to reduce the incidence of blood loss—among them, acute hypervolemic hemodilution (AHH) and controlled hypotension (CH). This study was designed to detect the effect of combination of AHH with CH induced by remifentanil versus magnesium sulfate on the volume of blood loss, allogeneic blood transfusion, hemodynamics, coagulation, and electrolytes during operations for spine fusion which are risky operations with high incidence of blood loss and blood transfusion. Sixty patients scheduled for posterior fusion of the spine were randomly allocated into three groups of 20 patients each (group I (AHH), group II (AHH combined with remifentanil-based CH), and group III (AHH combined with magnesium sulfate-based CH)). Estimated blood loss and total volume of packed red blood cells (PRBCS) transfused were recorded. Arterial blood pressure (ABP) and heart rate (HR) measures were recorded. Blood samples were obtained for the detection of hemoglobin (Hb) and hematocrit (HCT).ResultsEstimated blood loss, percentage blood loss, and intraoperative RBC transfusion units were significantly high in group I in relation to group II and group III (Table 2). Cardiac output was significantly higher in group I in relation to group II and group III at 10, 15, 30, 45, and 60 min after start of AHH. MBP and HR results were significantly high in group I in comparison with group II and group III at 30, 45, 60, and 90 min and 2 and 3 h after start of study drugs. CVP results were significantly high in group I in relation to group II and group III at 15, 30, 45, 60, and 90 min after start of AHH. PTT was significantly increased in the three study groups in comparison with baseline inside each group after AHH.ConclusionCombination of AHH with CH induced by remifentanil or magnesium sulfate was associated with reduction in estimated blood loss, and total volume of PRBCS transfused. There was no significant difference between hemodynamic parameters with the use of remifentanil or magnesium sulfate except that SBP, DBP, and MBP results were significantly high with magnesium sulfate at 15 min after drug infusion. There was significant increase in PT and PTT after AHH that was not reflected by significant blood oozing from the operative field, or by difficulty in hemostasis.

A Comparison of Deep Learning Techniques for Arterial Blood Pressure Prediction

Continuous vital signal monitoring is becoming more relevant in preventing diseases that afflict a large part of the world’s population; for this reason, healthcare equipment should be easy to wear and simple to use. Non-intrusive and non-invasive detection methods are a basic requirement for wearable medical devices, especially when these are used in sports applications or by the elderly for self-monitoring. Arterial blood pressure (ABP) is an essential physiological parameter for health monitoring. Most blood pressure measurement devices determine the systolic and diastolic arterial blood pressure through the inflation and the deflation of a cuff. This technique is uncomfortable for the user and may result in anxiety, and consequently affect the blood pressure and its measurement. The purpose of this paper is the continuous measurement of the ABP through a cuffless, non-intrusive approach. The approach of this paper is based on deep learning techniques where several neural networks are used to infer ABP, starting from photoplethysmogram (PPG) and electrocardiogram (ECG) signals. The ABP was predicted first by utilizing only PPG and then by using both PPG and ECG. Convolutional neural networks (ResNet and WaveNet) and recurrent neural networks (LSTM) were compared and analyzed for the regression task. Results show that the use of the ECG has resulted in improved performance for every proposed configuration. The best performing configuration was obtained with a ResNet followed by three LSTM layers: this led to a mean absolute error (MAE) of 4.118 mmHg on and 2.228 mmHg on systolic and diastolic blood pressures, respectively. The results comply with the American National Standards of the Association for the Advancement of Medical Instrumentation. ECG, PPG, and ABP measurements were extracted from the MIMIC database, which contains clinical signal data reflecting real measurements. The results were validated on a custom dataset created at Neuronica Lab, Politecnico di Torino.

Noninvasive continuous arterial pressure monitoring during anesthesia induction in patients undergoing cardiac surgery.

Objective:In this study we compared noninvasive arterial pressure measurement using ClearSight™ vascular-unloading-technique (Edwards Lifesciences Corp, Irvine, CA) with invasive arterial pressure measurement during induction of anesthesia undergoing mayor cardiac surgery.Design:Prospective, monocentric.Setting:University hospital.Participants:54 patients undergoing mayor cardiac surgery.Interventions:During induction all patients were simultaneously monitored with invasive (reference method) and noninvasive arterial pressure measurement (test-method) over a mean time period of 27 minutes.Measurements and Main Results:We observed slightly lower systolic and mean arterial pressures noninvasive than invasive. For systolic arterial pressure the mean of the differences was -18,05 mmHg (p < 0,05, SD ±16,78 mmHg), the mean arterial pressure MAP -5,47 mmHg (p < 0,05, SD ±11,08 mmHg) and for diastolic pressure -1,09 mmHg (p < 0,05, SD±11,15 mmHg),. The mean of the differences in heartrate was 1,15 (p < 0,05, SD±6,9 mmHg). When considering all measured values of the invasively measured MAP and the ClearSight ™ -MAP at the same timestamp over the recording interval, an almost identical progress can be seen that indicates a sufficient mapping of the hemodynamic changes. The percentage error for mean arterial, systolic and diastolic pressure measured by ClearSight™ amounts to 25,95 %, 26,77 % and 34,16 %, respectively.Conclusions:We conclude that ClearSight ™ is a good option for hemodynamic monitoring during induction of anesthesia. Taking into account the limitations, non-invasive arterial blood pressure measurement offers sufficient security to safely initiate anesthesia, especially when MAP is of particular interest. The use of non-invasive arterial blood pressure measurement with ClearSight ™ during induction of anesthesia in patients scheduled for major cardiac surgery is reliable and easy to use.

Perioperative Continuous Noninvasive Arterial Pressure Monitoring for Neuroendovascular Interventions: Prospective Study for Evaluation of the Vascular Unloading Technique

Blood pressure monitoring is crucial during neuroendovascular procedures. Intraoperative hemodynamic instability is associated with complications, which underscores the importance of continuous monitoring. Although direct measurement with an intra-arterial catheter is the gold standard for determining arterial pressure, it is costly, time-consuming, and associated with complications. The novel ClearSight system offers a noninvasive technique for monitoring arterial pressure via a finger cuff. This study compared noninvasive arterial pressure measurements with the gold standard method. Simultaneous recording of noninvasive and invasive arterial pressure was performed in patients undergoing neuroendovascular interventions. Both techniques were compared employing linear regression, Lin's correlation coefficient, Bland-Altman, and error grid analysis. The study enrolled 24 consecutive patients. The concordance correlation coefficient between both methods was 0.3526 (95% confidence interval [0.3134, 0.3906]) for mean arterial pressure and 0.4680 (95% confidence interval [0.4353, 0.4995]) and for systolic arterial pressure. The mean (SD) of the differences was 0.81 (17.86) mm Hg (95% limits of agreement [-52.52, 54.14]) for mean arterial pressure and 5.38 (14.64) mm Hg (95% limits of agreement [-45.12, 56.08]) for systolic arterial pressure. Error grid analysis demonstrated that the majority of measurements lie in regions with no or low risk for patients (mean arterial pressure, 71.0% and 24.4%; systolic arterial pressure, 59.2% and 25.8%). The ClearSight system provided accurate measurements of arterial blood pressure compared with invasive methods and within safe clinical parameters. This method may serve as a safe and reliable alternative for invasive blood pressure monitoring during neuroendovascular procedures.

Social and economic benefits of secondary prevention of arterial hypertension.

Arterial blood pressure is one of the main vital signs reflecting body functions and, at the same time, the most important functional parameter of the cardiovascular system. High blood pressure is the major modifiable cardiovascular risk factor. The aim of the study was assessment of the frequency of occurrence of cardiovascular risk factors, with particular consideration of arterial blood pressure. The study was conducted among 509 volunteers from Lublin in eastern Poland who participated in the prophylactic programme entitled 'White Sunday'. Standard measurements of blood pressure were performed using a TM-Z dial pressure gauge. The level of arterial blood pressure and socio-demographic parameters were analyzed. Hypertension was more frequently observed in the group of males than females. The age group especially vulnerable to abnormal blood pressure values were those aged 51-60. Isolated hypertension significantly more often occurred in the group of respondents who mentioned hypertension in an interview, compared to those who reported its absence. Among 367 persons who, in preliminary interview, did not declare hypertension, 60 cases of isolated arterial hypertension were noted (16.3%). From among respondents who declared absence of hypertension in an interview, the largest age group diagnosed with isolated arterial hypertension were those aged 61-70 (17.9%). Arterial hypertension is a civilisation disease which may be effectively prevented, simultaneously reducing the risk of premature death due to cardiovascular events, as well as reducing social and economic costs. International health organizations recommend the implementation of social screening programmes in order to diagnose high blood pressure and the promotion of routine measurements of arterial blood pressure.

Agreement between invasive and oscillometric arterial blood pressure measurement using a high-definition oscillometric device in normotensive New Zealand White rabbits using two different anaesthetic protocols

ObjectiveTo use American College of Veterinary Internal Medicine (ACVIM) criteria to evaluate a high-definition oscillometric (HDO) blood pressure monitoring device versus invasive blood pressure (IBP) measurement in normotensive rabbits anaesthetized with two different anaesthetic protocols. Study designProspective experimental study. AnimalsA group of 20 healthy adult New Zealand White rabbits weighing 4.36 ± 0.37 kg (mean ± standard deviation). Materials and methodsRabbits were premedicated with butorphanol 0.5 mg kg–1 and midazolam 0.5 mg kg–1 subcutaneously (SC, group BMA) or ketamine 25 mg kg–1 and medetomidine 0.4 mg kg–1 SC (group KM). Anaesthesia was induced with alfaxalone administered intravenously (group BMA) or isoflurane by face mask (group KM) and maintained with isoflurane in oxygen. IBP was measured from the central auricular artery. The cuff for the HDO monitor was placed distal to the left elbow and distal to the left tarsus. Agreement between invasive and HDO measurements was evaluated using Bland–Altman method. ResultsIn group KM there was better agreement between the HDO device and IBP when the cuff was placed on the thoracic limb, with 100% and 91% of the readings for mean (MAP) and diastolic arterial pressure (DAP), respectively, within 10 mmHg of the IBP measurements. The agreement, although worse, also met the ACVIM criteria for systolic arterial pressure (SAP; 53% of the readings within 10 mmHg). In group BMA, the device met the criteria with the cuff on the thoracic limb only, and only for MAP and DAP (73% and 75% of the measurements within 10 mmHg of the IBP, respectively) but not for SAP (12%). Conclusion and clinical relevanceThe HDO device met most of the ACVIM criteria for noninvasive blood pressure measurement in anaesthetized rabbits, specifically when the cuff was placed distal to the elbow and the anaesthetic protocol included ketamine and medetomidine.

STUDY OF MICROALBUMINURIA IN PATIENTS WITH NORMOGLYCEMIC HYPERTENSION

INTRODUCTION:Hypertension is one of the most important risk factors for cardiovascular disease. The incidence of microalbuminuria is more common among hypertensive patients, even in nondiabetic patients. Microalbuminuria is an independent predictor of cardiovascular morbidity and mortality in patients with essential hypertension. Therefore, current guidelines recommend routine screening of microalbuminuria in hypertensive patients to ensure appropriate interventions are initiated early in the disease process before progression to chronic kidney disease and/or renal failure. AIMS &amp; OBJECTIVES:This study is done to estimate the prevalence of microalbuminuria in patients with normoglycemic hypertension and to identify other variables associated with it. MATERIAL &amp; METHODS:In this study, we randomly selected 100 patients with essential hypertension based on inclusion and exclusion criteria. CBC, renal function test, 24-hour urine albumin excretion (UAE), Body mass index (BMI), and arterial blood pressure measurement were done among all selected patients. Data entry was done in Microsoft Ofce Excel and analysis was done using the software package Epi Info (Version 7.1.5) from CDC, Atlanta, U.S.A. OBSERVATIONS &amp; RESULTS: The study was conducted among 100 hypertensive patients out of which 74 were male and 24 were female. Out of 100 patients, microalbuminuria was present in 44 patients. Mean arterial pressure was found high among patients with microalbuminuria than patients without microalbuminuria. The presence of microalbumin in urine was found to increase with the increasing severity of hypertension. Mean body mass index and serum creatinine were found higher in the microalbuminuric group than the normoalbuminuric group. CONCLUSION:The incidence of microalbuminuria is more common among hypertensive patients, even in nondiabetic patients. The presence of microalbuminuria is an independent predictor of cardiovascular morbidity and mortality in patients with essential hypertension. Screening for microalbuminuria is a relatively simple process, should facilitate early vascular disease detection.

Comparison of urinary protein-to-creatinine ration, serum albumin, serum creatinine and systolic arterial blood pressure of glomerular injury cases in dogs with chronic kidney disease

This study aims at assessing the prevalence of glomerular alterations in dogs with chronic kidney disease (CKD) and comparing the clinical and laboratory parameters. The tests conducted include a double-blind histopathological assay conducted by two pathologists, urine tests including inactive sediment, urinary protein-to-creatinine (UPC), serum albumin and serum creatinine, as well as measurement of the systolic arterial blood pressure. The prevalence of glomerular injuries was determined and the predominant injury was compared with a group comprised of the remaining injuries. The study included 24 dogs with CKD. The results revealed a predominance of membranous glomerular alterations 17/24 (70,83%), followed by glomerulosclerosis 3/24 (12,50%), membranoproliferative injuries 2/24, glomerulocystic atrophy 1/24 and glomerular amyloidosis 1/24. Amyloidosis presented the highest UPC while the membranoproliferative injury presented the lowest mean concentration of serum albumin. Higher values in the UPC did not correspond with lower mean serum albumin values. Glomerulosclerosis presented the highest mean systolic blood pressure and glomerular atrophy presented the highest creatinine values. When comparing membranous injuries with a group comprised of the remaining injuries, the UPC did not present significant differences between the groups. Renal amyloidosis was included in the group with the lowest systolic arterial blood pressure values while membranoproliferative injury was included in the group with highest UPC. The group called “others” presented the highest creatinine value. Dogs with CKD may present several types of glomerular injuries with similar clinical and laboratory profiles. This study observed a predominance of membranous glomerular injuries, followed by membranoproliferative injuries, glomerulocystic atrophy and amyloidosis.

Noncanonical Thyroid Hormone Receptor α Action Mediates Arterial Vasodilation.

Hypothyroidism impairs cardiovascular health and contributes to endothelial dysfunction with reduced vasodilation. How 3,5,3'-triiodothyronine (T3) and its receptors are involved in the regulation of vasomotion is not yet fully understood. In general, thyroid hormone receptors (TRs) either influence gene expression (canonical action) or rapidly activate intracellular signaling pathways (noncanonical action). Here we aimed to characterize the T3 action underlying the mechanism of arterial vasodilation and blood pressure (BP) regulation. Mesenteric arteries were isolated from male rats, wild-type (WT) mice, TRα knockout (TRα 0) mice, and from knockin mice with a mutation in the DNA-binding domain (TRα GS). In this mutant, DNA binding and thus canonical action is abrogated while noncanonical signaling is preserved. In a wire myograph system, the isolated vessels were preconstricted with norepinephrine. The response to T3 was measured, and the resulting vasodilation (Δ force [mN]) was normalized to maximum contraction with norepinephrine and expressed as percentage vasodilation after maximal preconstriction with norepinephrine (%NE). Isolated vessels were treated with T3 (1 × 10-15 to 1 × 10-5 mol/L) alone and in combination with the endothelial nitric oxide-synthase (eNOS) inhibitor L-NG-nitroarginine methyl ester (L-NAME) or the phosphatidylinositol 3-kinase (PI3K) inhibitor wortmannin. The endothelium was removed to determine the contribution of T3 to endothelium-dependent vasodilation. The physiological relevance of T3-induced vasodilation was determined by in vivo arterial BP measurements in male and female mice. T3 treatment induced vasodilation of mesenteric arteries from WT mice within 2 minutes (by 21.5 ± 1.7%NE). This effect was absent in arteries from TRα 0 mice (by 5.3 ± 0.6%NE, P < .001 vs WT) but preserved in TRα GS arteries (by 17.2 ± 1.1%NE, not significant vs WT). Inhibition of either eNOS or PI3K reduced T3-mediated vasodilation from 52.7 ± 4.5%NE to 28.5 ± 4.1%NE and 22.7 ± 2.9%NE, respectively. Removal of the endothelium abolished the T3-mediated vasodilation in rat mesenteric arteries (by 36.7 ± 5.4%NE vs 3.5 ± 6.2%NE). In vivo, T3 injection led to a rapid decrease of arterial BP in WT (by 13.9 ± 1.9 mm Hg) and TRα GS mice (by 12.4 ± 1.9 mm Hg), but not in TRα 0 mice (by 4.1 ± 1.9 mm Hg). These results demonstrate that T3 acting through noncanonical TRα action affects cardiovascular physiology by inducing endothelium-dependent vasodilation within minutes via PI3K and eNOS activation.

Effects of circulatory arrest and cardiopulmonary bypass on cerebral autoregulation in neonatal swine

BackgroundCerebral autoregulation mechanisms help maintain adequate cerebral blood flow (CBF) despite changes in cerebral perfusion pressure. Impairment of cerebral autoregulation, during and after cardiopulmonary bypass (CPB), may increase risk of neurologic injury in neonates undergoing surgery. In this study, alterations of cerebral autoregulation were assessed in a neonatal swine model probing four perfusion strategies.MethodsNeonatal swine (n = 25) were randomized to continuous deep hypothermic cardiopulmonary bypass (DH-CPB, n = 7), deep hypothermic circulatory arrest (DHCA, n = 7), selective cerebral perfusion (SCP, n = 7) at deep hypothermia, or normothermic cardiopulmonary bypass (control, n = 4). The correlation coefficient (LDx) between laser Doppler measurements of CBF and mean arterial blood pressure was computed at initiation and conclusion of CPB. Alterations in cerebral autoregulation were assessed by the change between initial and final LDx measurements.ResultsCerebral autoregulation became more impaired (LDx increased) in piglets that underwent DH-CPB (initial LDx: median 0.15, IQR [0.03, 0.26]; final: 0.45, [0.27, 0.74]; p = 0.02). LDx was not altered in those undergoing DHCA (p > 0.99) or SCP (p = 0.13). These differences were not explained by other risk factors.ConclusionsIn a validated swine model of cardiac surgery, DH-CPB had a significant effect on cerebral autoregulation, whereas DHCA and SCP did not.ImpactApproximately half of the patients who survive neonatal heart surgery with cardiopulmonary bypass (CPB) experience neurodevelopmental delays. This preclinical investigation takes steps to elucidate and isolate potential perioperative risk factors of neurologic injury, such as impairment of cerebral autoregulation, associated with cardiac surgical procedures involving CPB.We demonstrate a method to characterize cerebral autoregulation during CPB pump flow changes in a neonatal swine model of cardiac surgery.Cerebral autoregulation was not altered in piglets that underwent deep hypothermic circulatory arrest (DHCA) or selective cerebral perfusion (SCP), but it was altered in piglets that underwent deep hypothermic CBP.

Current Age, but Not Age of Menopause, Is Associated with Blood Pressure Reactivity to Isometric Exercise in Postmenopausal Females

Hypertension (HTN) and cardiovascular disease (CVD) risks increase substantially after menopause, and literature suggests that the age at which menopause is completed contributes to this risk. Blood pressure (BP) reactivity to static fatiguing handgrip (HG) exercise can reveal existing HTN and may be valuable in predicting future risk for developing HTN. Thus, we aimed to determine if the age of menopause would contribute to greater BP reactivity during a static fatiguing HG in females. We hypothesized that cardiovascular reactivity would be positively related to age and inversely related to menopause age. METHODS: Participants laid supine throughout testing. Each participant performed a maximum voluntary contraction (MVC) of the hand followed by a 3-min. baseline rest (BL), then a continuous HG at 30% of MVC force to fatigue. Beat-to-beat BP and heart rate (HR) were recorded during BL and HG. Measures of systolic, diastolic, and mean arterial BP (SBP, DBP, and MAP, respectively) and HR were compared at the start, 25%, 50%, 75%, and end of each participant's fatiguing contraction. To further evaluate cardiovascular reactivity, baseline measures of BP and HR were also compared to peak responses. Statistical analyses included repeated-measures ANOVA and Pearson correlation, and results are presented as mean±SD. RESULTS: Eleven postmenopausal females (age 63±4 yrs.; range: 58-69 yrs.), with menopause age of 50±4 yrs. (range: 42-55 yrs.), completed all procedures. Average BL SBP and DBP were 135±14mmHg and 77±9mmHg, respectively. Systolic BP, DBP, MAP, and HR increased from BL throughout the fatiguing contraction (time effect: p≤0.001 for all). Peak values of BP and HR increased from BL (ΔSBP: 55±28mmHg; ΔDBP: 43±24mmHg; ΔMAP: 45±21mmHg; ΔHR: 29±14 bpm; p<0.001 for all tests). Age was correlated with peak increases in SBP, DBP, and MAP (r=0.71, p=0.014; r=0.76, p=0.006; r=0.78, p=0.005, respectively), but not with peak change in HR (p>0.05). Menopause age was not correlated with BP or HR reactivity (p>0.05 for all). CONCLUSION: Although age of menopause appears to be strongly linked to future risk of CVD, we did not observe a significant relationship between cardiovascular reactivity and age of menopause. Instead, findings from this study suggest that current age may provide a stronger indicator of exaggerated BP reactivity and potential increased risk for CVD in females.

Clinical performance of a machine-learning algorithm to predict intra-operative hypotension with noninvasive arterial pressure waveforms: A cohort study.

Intra-operative hypotension is associated with adverse postoperative outcomes. A machine-learning-derived algorithm developed to predict hypotension based on arterial blood pressure (ABP) waveforms significantly reduced intra-operative hypotension. The algorithm calculates the likelihood of hypotension occurring within minutes, expressed as the Hypotension Prediction Index (HPI) which ranges from 0 to 100. Currently, HPI is only available for patients monitored with invasive ABP, which is restricted to high-risk procedures and patients. In this study, the performance of HPI, employing noninvasive continuous ABP measurements, is assessed. The first aim was to compare the performance of the HPI algorithm, using noninvasive versus invasive ABP measurements, at a mathematically optimal HPI alarm threshold (Youden index). The second aim was to assess the performance of the algorithm using a HPI alarm threshold of 85 that is currently used in clinical trials. Hypotension was defined as a mean arterial pressure (MAP) below 65 mmHg for at least 1 min. The predictive performance of the algorithm at different HPI alarm thresholds (75 and 95) was studied. Observational cohort study. Tertiary academic medical centre. Five hundred and seven adult patients undergoing general surgery. The performance of the algorithm with invasive and noninvasive ABP input was similar. A HPI alarm threshold of 85 showed a median [IQR] time from alarm to hypotension of 2.7 [1.0 to 7.0] min with a sensitivity of 92.7 (95% confidence interval [CI], 91.2 to 94.3), specificity of 87.6 (95% CI, 86.2 to 89.0), positive predictive value of 79.9 (95% CI, 77.7 to 82.1) and negative predictive value of 95.8 (95% CI, 94.9 to 96.7). A HPI alarm threshold of 75 provided a lower positive predictive value but a prolonged time from prediction to actual hypotension. This study demonstrated that the algorithm can be employed using continuous noninvasive ABP waveforms. This opens up the potential to predict and prevent hypotension in a larger patient population. Clinical trials registration number NCT03533205.

An approach to early stage detection of atherosclerosis using arterial blood pressure measurements

Atherosclerosis is a pathological condition that develops gradually over the years and may eventually lead to a heart attack, a stroke, or a peripheral vascular disease, depending upon its site of occurrence in the human arterial network. We aim to detect this pathological condition in its early stage so that the necessary measures can be taken timely. To achieve this, a third-order nonlinear model of the cardiovascular system is considered, having states as systemic arterial and venous pressures along with the left ventricular volume. The available measurement signal is arterial blood pressure taken from the radial artery. This paper proposes the idea of online tracking of model parameters by utilizing an unscented Kalman filter (UKF) based framework that would help monitor the above-mentioned pathological condition. Furthermore, a classification approach has been presented, which carries out screening of subjects suffering from atherosclerotic cardiovascular diseases (CVDs) while utilizing estimates obtained from the UKF framework. It is observed that clinical quantities such as arterial compliance, systolic blood pressure, and ventricular elastance play an important role in the development of atherosclerosis. The classification results are quite encouraging. The proposed framework regularly monitors the atherosclerotic condition and has a potential for the early-stage screening of subjects suffering from atherosclerosis. With an increase in sedentary lifestyle in modern world, an early-stage screening of atherosclerotic cardiovascular diseases would be an important contribution to the healthcare and biomedical community.

POSSIBLE ROLE OF THE INVASIVE ARTERIAL BLOOD PRESSURE MEASUREMENT IN SEVERE RESISTANT HYPERTENSION AND GENERALISED ATHEROSCLEROSIS

Objective: In severe resistant hypertension, a generalised atherosclerosis with high arterial stiffness present significant challenge for clinicians to obtain the realistic non-invasive blood pressure measurements and adjust antihypertensive treatment successfully. Design and method: Several patients with generalised atherosclerosis and severe resistant hypertension of the renovascular and renoparenchymal aetiology were referred to our Excellence centre. After performing ambulatory blood pressure monitoring (ABPM) and testing for non-compliance, often we still don’t reach target blood pressure. Due to generally expressed atherosclerosis, daily oscillometer technique could not be reliable in these set of patients. Invasive arterial blood pressure measurements via intra-arterial radial line were recorded for 24-hours and the consecutive non-invasive blood pressure was measured on the ipsilateral arm by oscillatory method. Results: In 3 patients, hypertension was renovascular and renoparenchymal (serum creatinine 134–219 micromol/l, oGF CDK-EPI 47 ml/min). The blood pressure values obtained by oscillatory method ranged from 170/100 mmHg to 230/120 mmHg. Generalised atherosclerosis with obstructive coronary and carotid artery disease, stenosis of iliac arteries, a hemodynamically important renal artery stenosis and subclavian artery stenosis was present in all 3 patients; one had comorbid periaortitis. Two patients were treated with six and one with five antihypertensives in maximum doses, at least one being a diuretic, and with at least one antihypertensive drug exceeding maximum dose. The difference in blood pressure measurements by the invasive vs. non-invasive method ranged from -20/10 mmHg to -50/30 mmHg. In 2 patients, marked blood pressure elevations (+40/20 mmHg) were triggered by elevated sympathycotonus. At discharge, doses of antihypertensive drugs could be lowered or stayed in the same range and a short-acting anxiolytic was added. Conclusions: In patients with severe resistant hypertension and generalised atherosclerosis, after excluding non-adherence, invasive blood pressure technique could be helpful in determining the relative difference to non-invasive measurements and safely adjusting antihypertensive therapy.