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The Journal of Maternal-fetal &... Dec 2023Baroreflex is a regulatory mechanism that slows the fetal heart rate. This study aimed to investigate the effects of lipopolysaccharide (LPS)-induced endotoxemia on...
OBJECTIVE
Baroreflex is a regulatory mechanism that slows the fetal heart rate. This study aimed to investigate the effects of lipopolysaccharide (LPS)-induced endotoxemia on fetal baroreceptor sensitivity in preterm fetal sheep.
METHODS
The changes in fetal baroreceptor sensitivity were measured in seven chronically instrumented preterm fetal sheep. Fetal baroreceptor sensitivity was measured in three phases: (A) control phase, defined as the 24 h before the first injection of LPS; (B) acute phase, defined as the 24 h between the first and second injections of LPS; and (C) fetal acidosis phase, defined as the time from the second LPS injection until intrauterine fetal death. Histological examinations of the fetal membrane and umbilical cord were also conducted.
RESULTS
Each fetus developed metabolic acidosis after the second injection of LPS. The fetuses died 24.7 (SD = 6.1) hours after the second injection of LPS. Both the umbilical cord and fetal membranes showed histological evidence of severe inflammation. In total, 163 fetal baroreceptor measurements were performed in this experiment (A, = 77 times; B, = 60 times; C, = 26 times). Fetal baroreceptor sensitivity showed significant differences in all three phases (A: 2.7 [SD = 0.2]; B: 2.5 [SD = 0.2]; and C: 1.5 [SD = 0.2]). Post hoc tests showed that baroreceptor sensitivity in the acidosis phase had decreased significantly compared to that in the control and acute phases (<.001 and =.002, respectively).
CONCLUSIONS
Fetal baroreceptor sensitivity decreased during fetal acidosis induced by LPSs.
Topics: Pregnancy; Female; Humans; Sheep; Animals; Lipopolysaccharides; Pressoreceptors; Fetus; Inflammation; Fetal Diseases; Acidosis; Heart Rate, Fetal
PubMed: 36443245
DOI: 10.1080/14767058.2022.2150392 -
Bioelectromagnetics Oct 2022Mounting evidence suggests enhanced blood pressure (BP) variability (BPV) independent role in cardiovascular (CV) damage. The goal was to estimate the effect of the...
Mounting evidence suggests enhanced blood pressure (BP) variability (BPV) independent role in cardiovascular (CV) damage. The goal was to estimate the effect of the carotid baroreceptor (CB) magnetic stimulation on sudden high BP elevation. Mean femoral arterial BP (MAP), heart rate (HR), baroreflex sensitivity (BRS), and ear lobe skin microcirculatory blood flow, by microphotoelectric plethysmography (MPPG), were simultaneously recorded in conscious rabbits sedated by pentobarbital intravenous (i.v.) infusion (5 mg/kg/h) after 40 min CB exposure to 350 mT static magnetic field (SMF), by Nd -Fe -B magnets (n = 14), or sham magnets exposure (n = 14). BRS was assessed from HR and MAP responses to abrupt hypotension induced by i.v. bolus injections of nitroprusside (Ni) and abrupt MAP elevation (MAP ) by i.v. bolus of phenylephrine (Ph). Beat-to-beat BPV was estimated by MAP standard deviation. SMF CB exposure significantly increased BRS (74.5 ± 17.8%, P < 0.001) and microcirculation (23.8% ± 11.0%, P = 0.039); decreased MAP (-5.7 ± 1.7%, P < 0.014) and phenylephrine-induced MAP (-19.1%, P = 0.043). MAP positively correlated with resting MAP (r = 0.342, P = 0.0383) and MAP SD (r = 0.383, P = 0.0194), and inversely with BRS (r = -0.47, P = 0.0156). SMF CB exposure enhanced the nitroprusside, which acts by releasing nitric oxide (NO), vasodilatory effect. This indicates arterial baroreflex to improve vessel sensitivity to NO, which is a new physiology with BP buffering effect. A positive correlation of MAP SD to phenylephrine BP ramps suggests a causal relationship and BPV prognostic significance to forecast abrupt BP elevation. Mechano/baroreceptor magneto-sensing property proposed to be the basic physiology by which SMFs boost CV autonomic regulation with potential implementation in high CV risk labile arterial hypertensive disease. © 2022 Bioelectromagnetics Society.
Topics: Animals; Rabbits; Pressoreceptors; Blood Pressure; Microcirculation; Nitroprusside; Hypertension; Phenylephrine; Magnetic Fields
PubMed: 36403257
DOI: 10.1002/bem.22425 -
Vascular Apr 2024The bilateral presentation of Carotid Body Tumors (CBT) is rare; the surgical resection of these masses remains the mainstay management due to the malignant potential....
OBJECTIVE
The bilateral presentation of Carotid Body Tumors (CBT) is rare; the surgical resection of these masses remains the mainstay management due to the malignant potential. We aim to describe, classify, and quantify baroreceptor failure (BRF) after the surgical management of patients with bilateral CBT to better understand the clinical consequences.
METHODS
Retrospective review of patients that underwent bilateral CBT resection to assess the changes in baroreceptor function. We describe the clinical events associated to BRF after surgery, baseline patient's demographics, characteristics, comorbidities. Additionally, clinical and a quantitative evaluation of baroreceptor sensitivity were conducted using the Composite Autonomic Severity Score (CASS).
RESULTS
From 1986 to 2020, a total 146 CBT resections were performed in 132 patients in our institution. Tumors were removed bilaterally in staged procedures in seven patients with a mean age of 61 years (Standard Deviation 11), six (85%) were females, and there was no family history of paragangliomas. The clinical presentation were palpable masses in 5 (71%), and odynophagia in 2 (29%) cases; malignant histopathology following surgery was found in one case. BRF occurred in one patient after unilateral CBT resection, consisting of bradycardia and a 40 s asystole that was not previously associated to BR sensitivity. Three (43%) patients presented BRF in the immediate postoperative period of the contralateral CBT excision, consisting of volatile hypertensive crisis in two cases, and supraventricular tachycardia in one. All the patients developed (100%) chronic baroreceptor sensitivity symptoms consisting in syncope, vertigo and fatigue in 4 (57%), tachycardia in 2 (28%), and orthostatic headache in one (14%). Autonomic testing showed mixed sympathetic and parasympathetic failure in five (71%), severe sympathetic failure in 1 (14%), and parasympathetic dysfunction in one patient (14%).
CONCLUSIONS
Postoperative autonomic assessment confirmed BRF in all studied patients that underwent staged bilateral CBT resection with mixed, sympathetic, and parasympathetic dysfunction. Further studies are necessary to evaluate the incidence and physiological mechanisms of these sequelae to anticipate possible complications and offer the appropriate perioperative management.
Topics: Humans; Carotid Body Tumor; Female; Male; Middle Aged; Retrospective Studies; Aged; Treatment Outcome; Baroreflex; Pressoreceptors; Risk Factors; Blood Pressure; Heart Rate
PubMed: 36394214
DOI: 10.1177/17085381221140167 -
American Journal of Hypertension Feb 2023The rates of uncontrolled hypertension, along with downstream cardiovascular outcomes, has been worsening in this country. Despite the plethora of antihypertensive...
BACKGROUND
The rates of uncontrolled hypertension, along with downstream cardiovascular outcomes, has been worsening in this country. Despite the plethora of antihypertensive medications on the market, the prevalence of resistant hypertension (RH) is estimated to be 13.7%. Therefore in addition to increased clinical education and focus on lifestyle management of hypertension and medication compliance, new therapies are needed to address this rise in hypertension.
METHODS
A systematic review of the available medical literature was performed to identify emerging treatment options for RH.
RESULTS
Six different pharmacologic classes and 2 procedural interventions were identified as being appropriate for review in this paper. The pharmacologic classes to be explored are non-steroidal mineralocorticoid receptor antagonists, aminopeptidase A inhibitors, dual endothelin antagonists, aldosterone synthetase inhibitors, atrial natriuretic peptide inhibitors, and attenuators of hepatic angiotensinogen. Discussion of procedural interventions to lower blood pressure will focus on renal denervation and devices that increase carotid baroreceptor activity.
CONCLUSIONS
Promising medication and procedural interventions are being developed and studied to expand our treatment arsenal for patients with uncontrolled essential hypertension and RH.
Topics: Humans; Hypertension; Antihypertensive Agents; Blood Pressure; Kidney; Pressoreceptors
PubMed: 36201204
DOI: 10.1093/ajh/hpac111 -
Naunyn-Schmiedeberg's Archives of... Dec 2022Cardiac autonomic neuropathy is a prominent feature of endotoxemia. Given the defensive role of the cholinergic pathway in inflammation, we assessed the roles of central...
Cardiac autonomic neuropathy is a prominent feature of endotoxemia. Given the defensive role of the cholinergic pathway in inflammation, we assessed the roles of central homomeric α7 and heteromeric α4β2 nAChRs in arterial baroreceptor dysfunction caused by endotoxemia in rats. Endotoxemia was induced by i.v. administration of lipopolysaccharides (LPS, 10 mg/kg), and baroreflex activity was measured by the vasoactive method, which assesses reflex chronotropic responses to increments (phenylephrine, PE) or decrements (sodium nitroprusside, SNP) in blood pressure. Shifts caused by LPS in PE/SNP baroreflex curves and associated decreases in baroreflex sensitivity (BRS) were dose-dependently reversed by nicotine (25-100 μg/kg, i.v.). The nicotine effect disappeared after intracisternal administration of methyllycaconitine (MLA) or dihydro-β-erythroidine (DHβE), selective blockers of α7 and α4β2 receptors, respectively. The advantageous effect of nicotine on BRS was replicated in rats treated with PHA-543613 (α7-nAChR agonist) or 5-iodo-A-85380 (5IA, α4β2-nAChRs agonist) in dose-dependent fashions. Conversely, the depressed BRS of endotoxic rats was improved after combined, but not individual, treatments with PHA and 5IA. Central α7 and α4β2 nAChR activation underlies the nicotine counteraction of arterial baroreflex dysfunction induced by endotoxemia. Moreover, the contribution of these receptors depends on the nature of the reflex chronotropic response (bradycardia vs. tachycardia).
Topics: Rats; Animals; Nicotine; Endotoxemia; Endotoxins; alpha7 Nicotinic Acetylcholine Receptor; Lipopolysaccharides; Pressoreceptors; Receptors, Nicotinic; Nicotinic Agonists; Nicotinic Antagonists
PubMed: 36100757
DOI: 10.1007/s00210-022-02289-1 -
Clinical and Experimental Rheumatology Oct 2022Systemic sclerosis (SSc) is an autoimmune disease characterised by diffuse vasculopathy and fibrosis of skin and visceral organs. Moreover, autonomic dysfunction is also...
OBJECTIVES
Systemic sclerosis (SSc) is an autoimmune disease characterised by diffuse vasculopathy and fibrosis of skin and visceral organs. Moreover, autonomic dysfunction is also suggested as an important step during the multifactorial SSc pathogenesis. Baroreceptors are responsible for maintaining blood pressure by means of autonomic system modulation. Considering that autonomic dysfunction and arteriosclerosis can both reduce baroreceptor sensitivity (BRS), in this cross-sectional study we investigated BRS in SSc patients.
METHODS
Twenty-one SSc patients (mean age 55±10 years, 18 females) and 147 age/sex-matched healthy controls were recruited for the study. BRS (ms/mmHg) was measured by a Finapres® Midi device (Finapres Medical Systems, Amsterdam, The Netherlands). Other parameters were measured: blood pressure, heart rate, heart rate variability triangular index (HRVI), intima-media thickness (IMT), carotid distensibility and pulse wave velocity (PWV).
RESULTS
BRS was significantly lower in SSc patients compared to controls (6.3±3.3 vs. 10.7±6.8 ms/mmHg; p=0.004). IMT was comparable between SSc and controls, whereas carotid distensibility was lower in SSc (20.1±7.6 vs. 26.6±13.3 KPa-1·10-3; p=0.02) and PWV higher in SSc (8.4±1.3 vs. 7.1±1.1 m/sec; p=0.01). Furthermore, HRVI was lower in SSc (4.5±2.1 vs. 7.5±2.8; p<0.001). BRS impairment was independent from age and carotid distensibility in SSc patients, suggesting that BRS dysfunction could be only partially a consequence of SSc vasculopathy.
CONCLUSIONS
BRS was reduced in SSc patients compared with healthy controls. This finding could represent a SSc-related alteration involving the autonomic system, besides being the mere consequence of sclerodermic vasculopathy.
Topics: Female; Humans; Middle Aged; Aged; Pressoreceptors; Pulse Wave Analysis; Carotid Intima-Media Thickness; Cross-Sectional Studies; Carotid Arteries; Scleroderma, Systemic; Vascular Diseases
PubMed: 35916301
DOI: 10.55563/clinexprheumatol/4j6028 -
Linear and nonlinear identification of the carotid sinus baroreflex in the very low-frequency range.Physiological Reports Jul 2022Since the arterial baroreflex system is classified as an immediate control system, the focus has been on analyzing its dynamic characteristics in the frequency range...
Since the arterial baroreflex system is classified as an immediate control system, the focus has been on analyzing its dynamic characteristics in the frequency range between 0.01 and 1 Hz. Although the dynamic characteristics in the frequency range below 0.01 Hz are not expected to be large, actual experimental data are scant. The aim was to identify the dynamic characteristics of the carotid sinus baroreflex in the frequency range down to 0.001 Hz. The carotid sinus baroreceptor regions were isolated from the systemic circulation, and carotid sinus pressure (CSP) was changed every 10 s according to Gaussian white noise with a mean of 120 mmHg and standard deviation of 20 mmHg for 90 min in anesthetized Wistar-Kyoto rats (n = 8). The dynamic gain of the linear transfer function relating CSP to arterial pressure (AP) at 0.001 Hz tended to be greater than that at 0.01 Hz (1.060 ± 0.197 vs. 0.625 ± 0.067, p = 0.080), suggesting that baroreflex control was largely maintained at 0.001 Hz. Regarding nonlinear analysis, a second-order Uryson model predicted AP with a higher R value (0.645 ± 0.053) than a linear model (R = 0.543 ± 0.057, p = 0.025) or a second-order Volterra model (R = 0.589 ± 0.055, p = 0.045) in testing data. These pieces of information may be used to create baroreflex models that can add a component of autonomic control to a cardiovascular digital twin for predicting acute hemodynamic responses to treatments and tailoring individual treatment strategies.
Topics: Animals; Arterial Pressure; Baroreflex; Blood Pressure; Carotid Sinus; Pressoreceptors; Rats; Rats, Inbred WKY; Sympathetic Nervous System
PubMed: 35859325
DOI: 10.14814/phy2.15392 -
Scientific Reports Jul 2022Carotid baroreceptor stimulation has been clinically explored for antihypertensive benefits, but neuromodulation of aortic baroreceptor afferents remains unexplored for...
Carotid baroreceptor stimulation has been clinically explored for antihypertensive benefits, but neuromodulation of aortic baroreceptor afferents remains unexplored for potential translation into the clinic. Published studies have used supramaximal stimulations, which are unphysiological and energy inefficient. The objective of the present study was to identify optimal low-charge nerve stimulation parameters that would provide a clinically-relevant (20-30 mmHg) decrease in mean arterial pressure (MAP) in anesthetized spontaneously hypertensive rats. Stimulations of 20 s were delivered to the left aortic depressor nerve (ADN) of these rats using low ranges of pulse amplitudes (≤ 0.6 mA), widths (≤ 0.5 ms) and frequencies (≤ 5 Hz). We also assessed the effects of continuous (20 s) versus intermittent (5 s ON/3 s OFF and 5 s ON/3 s OFF for 20 s) stimulation on MAP, heart rate (HR), mesenteric (MVR) and femoral (FVR) vascular resistance using low (5 Hz) and high (15 Hz) frequencies. Lower pulse amplitudes (0.2 mA) produced 9 ± 2 to 18 ± 2 mmHg decreases in MAP. Higher pulse amplitudes (0.4 mA) produced a median MAP reduction of 28 ± 4 mmHg at 0.2 ms and 5 Hz, with no added benefit seen above 0.4 mA. Continuous and intermittent low frequency stimulation at 0.4 mA and 0.2 ms produced similar sustained decreases in MAP, HR, MVR and FVR. Continuous high frequency stimulation at 0.4 mA and 0.2 ms produced larger reductions in MAP, HR, MVR and FVR compared with all low frequency and/or intermittent high frequency stimulations. We conclude from these findings that "low intensity intermittent" electrical stimulation is an effective alternate way for neuromodulation of the aortic baroreceptor afferents and to evoke a required restoration of MAP levels in spontaneously hypertensive rats. This approach enables low energy consumption and markedly lowers the excessive decreases in MAP and hemodynamic disturbances elicited by continuous high-charge injection protocols.
Topics: Animals; Aorta; Blood Pressure; Electric Stimulation; Heart Rate; Hypertension; Pressoreceptors; Rats; Rats, Inbred SHR
PubMed: 35851099
DOI: 10.1038/s41598-022-15761-y -
Autonomic Neuroscience : Basic &... Sep 2022A reciprocal relationship between the baroreflex and cerebral autoregulation (CA) has been demonstrated at rest and in response to acute hypotension. We hypothesized... (Review)
Review
A reciprocal relationship between the baroreflex and cerebral autoregulation (CA) has been demonstrated at rest and in response to acute hypotension. We hypothesized that the reciprocal relationship between cardiac baroreflex sensitivity (BRS) and CA would be maintained during sustained central hypovolemia induced by lower body negative pressure (LBNP), and that the strength of this relationship would be greater in subjects with higher tolerance to this stress. Healthy young adults (n = 51; 23F/28M) completed a LBNP protocol to presyncope. Subjects were classified as high tolerant (HT; completion of -60 mmHg LBNP stage, ≥20-min) or low tolerant (LT; did not complete -60 mmHg LBNP stage, <20-min). R-R intervals (RRI), systolic arterial pressure (SAP), mean arterial pressure (MAP), and middle cerebral artery velocity (MCAv) were measured continuously. Cardiac BRS was calculated in the time domain (ΔHR/ΔSAP) and frequency domain (RRI-SAP low frequency (LF) transfer function gain), and CA was calculated in the time domain (ΔMCAv/ΔMAP) and frequency domain (MAP-mean MCAv LF transfer function gain). There was a moderate relationship between cardiac BRS and CA for the group of 51 subjects in both the time (R = -0.54, P < 0.0001) and frequency (R = 0.61, P < 0.001) domains; there was a stronger relationship in the HT group (R = 0.73) compared to the LT group (R = 0.31) in the frequency domain (P = 0.08), but no difference between groups in the time domain (HT: R = -0.73 vs. LT: R = -0.63; P = 0.27). These findings suggest that an interaction between BRS and CA may be an important compensatory mechanism that contributes to tolerance to simulated hemorrhage in young healthy adults.
Topics: Blood Pressure; Heart Rate; Hemorrhage; Homeostasis; Humans; Lower Body Negative Pressure; Pressoreceptors; Young Adult
PubMed: 35716525
DOI: 10.1016/j.autneu.2022.103007 -
Respiratory Physiology & Neurobiology Sep 2022Cough, the main airway defensive process, is modulated by multiple sensory inputs from the respiratory system and outside of it. This modulation is one of the mechanisms... (Review)
Review
Cough, the main airway defensive process, is modulated by multiple sensory inputs from the respiratory system and outside of it. This modulation is one of the mechanisms that contributes to the sensitization of cough pathways at the peripheral and/or central level via neuroplasticity and it manifests most often as augmented coughing. Cardiorespiratory coupling is an important mechanism responsible for a match between oxygenation and cardiac output and bidirectional relationships exist between respiration and cardiovascular function. While the impact of cough with the robust swings of the intrathoracic pressure on haemodynamic parameters and heart electrophysiology are well characterized, little is known about the modulation of cough by haemodynamic parameters - mainly the blood pressure. Some circumstantial findings from older animal studies and more recent sophisticated analysis confirm that baroreceptor stimulation and unloading alters coughing evoked in experiments. Clinical relevance of such findings is not presently known.
Topics: Animals; Baroreflex; Blood Pressure; Cardiac Output; Cough; Heart Rate; Pressoreceptors; Respiration
PubMed: 35595217
DOI: 10.1016/j.resp.2022.103921