Phenylephrine alters phase synchronization between cerebral blood velocity and blood pressure in ME/CFS with orthostatic intolerance.

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) with orthostatic intolerance (OI) is characterized by neurocognitive deficits perhaps related to upright hypocapnia and loss of cerebral autoregulation (CA). We performed N-back neurocognition testing and calculated the phase synchronization index (PhSI) between arterial pressure (AP) and cerebral blood velocity (CBV) as a time-dependent measurement of cerebral autoregulation in 11 control (mean age = 24.1 yr) and 15 patients with ME/CFS (mean age = 21.8 yr). All patients with ME/CFS had postural tachycardia syndrome (POTS). A 10-min 60° head-up tilt (HUT) significantly increased heart rate (109.4 ± 3.9 vs. 77.2 ± 1.6 beats/min, P < 0.05) and respiratory rate (20.9 ± 1.7 vs. 14.2 ± 1.2 breaths/min, P < 0.05) and decreased end-tidal CO2 (ETCO2; 33.9 ± 1.1 vs. 42.8 ± 1.2 Torr, P < 0.05) in ME/CFS versus control. In ME/CFS, HUT significantly decreased CBV compared with control (-22.5% vs. -8.7%, P < 0.005). To mitigate the orthostatic CBV reduction, we administered supplemental CO2, phenylephrine, and acetazolamide and performed N-back testing supine and during HUT. Only phenylephrine corrected the orthostatic decrease in neurocognition by reverting % correct n = 4 N-back during HUT in ME/CFS similar to control (ME/CFS = 38.5 ± 5.5 vs. ME/CFS + PE= 65.6 ± 5.7 vs. Control 56.9 ± 7.5). HUT in ME/CFS resulted in increased PhSI values indicating decreased CA. Although CO2 and acetazolamide had no effect on PhSI in ME/CFS, phenylephrine caused a significant reduction in PhSI (ME/CFS = 0.80 ± 0.03 vs. ME/CFS + PE= 0.69 ± 0.04, P < 0.05) and improved cerebral autoregulation. Thus, PE improved neurocognitive function in patients with ME/CFS, perhaps related to improved neurovascular coupling, cerebral autoregulation, and maintenance of CBV.NEW & NOTEWORTHY We evaluated cognitive function before and after CO2, acetazolamide, and phenylephrine, which mitigate orthostatic reductions in cerebral blood velocity. Neither CO2 nor acetazolamide affected N-back testing (% correct answers) during an orthostatic challenge. Only phenylephrine improved upright N-back performance in ME/CFS, as it both blocked hyperventilation and increased CO2 significantly compared with those untreated. And only phenylephrine resulted in improved PSI values in both ME/CFS and control while upright, suggesting improved cerebral autoregulation.

Double-Balloon Catheter-Mediated Transarterial Chemotherapy Delivery in a Swine Model: A Mechanism Recruiting the Vasa Vasorum for Localized Therapies.

PURPOSE: Treatment of hypovascular tumors, such as pancreatic adenocarcinoma, is challenging owing to inefficient drug delivery. This report examines the potential mechanism of localized drug delivery via transarterial microperfusion (TAMP) using a proprietary adjustable double-balloon occlusion catheter in a porcine model. MATERIALS AND METHODS: Adult Yorkshire swine (N = 21) were used in the Institutional Animal Care & Use Committee-approved protocols. The RC-120 catheter (RenovoRx, Los Altos, California) was positioned into visceral, femoral, and pulmonary arteries with infusion of methylene blue dye, gemcitabine, or gold nanoparticles. Transmural delivery was compared under double-balloon occlusion with and without side-branch exclusion, single-balloon occlusion, and intravenous delivery. Intra-arterial pressure and vascular histologic changes were assessed. RESULTS: Infusion with double-balloon occlusion and side-branch exclusion provided increased intra-arterial pressure in the isolated segment and enhanced perivascular infusate penetration with minimal vascular injury. Infusates were predominantly found in the vasa vasorum by electron microscopy. CONCLUSIONS: TAMP enhanced transmural passage mediated by localized increase in arterial pressure via vasa vasorum.

Sulforaphane Improves Redox Homeostasis and Right Ventricular Contractility in a Model of Pulmonary Hypertension.

ABSTRACT: Pulmonary arterial hypertension (PAH) is characterized by increased pulmonary vascular resistance (PVR), imposing overload on the right ventricle (RV) and imbalance of the redox state. Our study investigated the influence of treatment with sulforaphane (SFN), found in cruciferous vegetables, on RV remodeling and redox homeostasis in monocrotaline (MCT)-induced PAH. Male Wistar rats were separated into 4 groups: control (CTR); CTR + SFN; MCT; and MCT + SFN. PAH induction was implemented by a single dose of MCT (60 mg/kg intraperitoneally). Treatment with SFN (2.5 mg/kg/day intraperitoneally) started on the seventh day after the MCT injection and persisted for 2 weeks. After 21 days of PAH induction, echocardiographic, hemodynamic, and oxidative stress evaluation was performed. The MCT group showed an increase in RV hypertrophy, RV systolic area, RV systolic, mean pulmonary artery pressure, and PVR and exhibited a decrease in the RV outflow tract acceleration time/ejection time ratio, RV fractional shortening, and tricuspid annular plane systolic excursion compared to CTR ( P < 0.05). SFN-treated PAH attenuated detrimental changes in tricuspid annular plane systolic excursion, mean pulmonary artery pressure, and PVR parameters. Catalase levels and the glutathione/Glutathione disulfide (GSSG) ratio were diminished in the MCT group compared to CTR ( P < 0.05). SFN increased catalase levels and normalized the glutathione/GSSG ratio to control levels ( P < 0.05). Data express the benefit of SFN treatment on the cardiac function of rats with PAH associated with the cellular redox state.

Hypotension During Vasopressor Infusion Occurs in Predictable Clusters: A Multicenter Analysis.

Background: Published evidence indicates that mean arterial pressure (MAP) below a goal range (hypotension) is associated with worse outcomes, though MAP management failures are common. We sought to characterize hypotension occurrences in ICUs and consider the implications for MAP management. Methods: Retrospective analysis of 3 hospitals' cohorts of adult ICU patients during continuous vasopressor infusion. Two cohorts were general, mixed ICU patients and one was exclusively acute spinal cord injury patients. "Hypotension-clusters" were defined where there were ≥10 min of cumulative hypotension over a 60-min period and "constant hypotension" was ≥10 continuous minutes. Trend analysis was performed (predicting future MAP using 14 min of preceding MAP data) to understand which hypotension-clusters could likely have been predicted by clinician awareness of MAP trends. Results: In cohorts of 155, 66, and 16 ICU stays, respectively, the majority of hypotension occurred within the hypotension-clusters. Failures to keep MAP above the hypotension threshold were notable in the bottom quartiles of each cohort, with hypotension durations of 436, 167, and 468 min, respectively, occurring within hypotension-clusters per day. Mean arterial pressure trend analysis identified most hypotension-clusters before any constant hypotension occurred (81.2%-93.6% sensitivity, range). The positive predictive value of hypotension predictions ranged from 51.4% to 72.9%. Conclusions: Across 3 cohorts, most hypotension occurred in temporal clusters of hypotension that were usually predictable from extrapolation of MAP trends.

KV7.1 channel blockade inhibits neonatal renal autoregulation triggered by a step decrease in arterial pressure.

KV7 channels, the voltage-gated K+ channels encoded by KCNQ genes, mediate heterogeneous vascular responses in rodents. Postnatal changes in the functional expression of KV7 channels have been reported in rodent saphenous arteries, but their physiological function in the neonatal renal vascular bed is unclear. Here, we report that, unlike adult pigs, only KCNQ1 (KV7.1) out of the five members of KCNQ genes was detected in neonatal pig renal microvessels. KCNQ1 is present in fetal pig kidneys as early as day 50 of gestation, and the level of expression remains the same up to postnatal day 21. Activation of renal vascular smooth muscle cell (SMC) KV7.1 stimulated whole cell currents, inhibited by HMR1556 (HMR), a selective KV7.1 blocker. HMR did not change the steady-state diameter of isolated renal microvessels. Similarly, intrarenal artery infusion of HMR did not alter mean arterial pressure, renal blood flow, and renal vascular resistance in the pigs. An ∼20 mmHg reduction in mean arterial pressure evoked effective autoregulation of renal blood flow, which HMR inhibited. We conclude that 1) the expression of KCNQ isoforms in porcine renal microvessels is dependent on kidney maturation, 2) KV7.1 is functionally expressed in neonatal pig renal vascular SMCs, 3) a decrease in arterial pressure up to 20 mmHg induces renal autoregulation in neonatal pigs, and 4) SMC KV7.1 does not control basal renal vascular tone but contributes to neonatal renal autoregulation triggered by a step decrease in arterial pressure.NEW & NOTEWORTHY KV7.1 is present in fetal pig kidneys as early as day 50 of gestation, and the level of expression remains the same up to postnatal day 21. KV7.1 is functionally expressed in neonatal pig renal vascular smooth muscle cells (SMCs). A decrease in arterial pressure up to 20 mmHg induces renal autoregulation in neonatal pigs. Although SMC KV7.1 does not control basal renal vascular resistance, its inhibition blunts neonatal renal autoregulation engendered by a step decrease in arterial pressure.

Oral L-Arginine (5 g/day) for 14 Days Improves Microcirculatory Function in Healthy Young Women and Healthy and Type 2 Diabetes Mellitus Elderly Women.

OBJECTIVE: The aim of this study was to investigate the effect of oral supplementation with L-arginine on serum biochemical profile, blood pressure, microcirculation, and vasoreactivity/endothelial function in young controls, and elderly women with and without type 2 diabetes mellitus (T2DM). METHODS: Healthy young (n = 25), healthy elderly (n = 25), and elderly women with type 2 diabetes mellitus (T2DME, n = 23, glycated Hb ≥6.4% and mean of 7.7 years for duration of the disease), aged 18-30 and older than 65 years, respectively, were included in the study. All patients underwent biochemical analysis (fasting glycemia and lipidogram), arterial blood pressure, nailfold videocapillaroscopy (capillary diameters, functional capillary density [FCD], peak red blood cell velocity [RBCVmax] after 1 min ischemia, time to reach peak RBCV [TRBCVmax]), and venous occlusion plethysmography (vasoreactivity), before and after 14 days of oral supplementation with L-arginine (5 g/day). RESULTS: L-Arginine did not change fasting glycemia and lipidogram, but it decreased systolic, diastolic, and mean arterial pressure in elderly women, increased RBCVmax in all groups, and did not decrease TRBCVmax in T2DME. Capillary diameters and FCD remained unchanged in all groups. L-Arginine improved vasoreactivity during reactive hyperemia and after sublingual nitroglycerin (0.4 mg) in all groups. CONCLUSION: L-Arginine supplementation (5g/day during 14 days) was able to improve vascular/microvascular health in the elderly women with or without T2DM.

Considerations for Inotrope and Vasopressor Use in Critically Ill Patients With Pulmonary Arterial Hypertension.

ABSTRACT: Pulmonary arterial hypertension (PAH) is a rare and progressive cardiopulmonary disease, characterized by pulmonary vasculopathy. The disease can lead to increase pulmonary arterial pressures and eventual right ventricle failure due to elevated afterload. The prevalence of PAH in patients admitted to the intensive care unit (ICU) is unknown, and pulmonary hypertension (PH) in the ICU is more commonly the result of left heart disease or hypoxic lung injury (PH due to left heart disease and PH due to lung diseases and/or hypoxia, respectively), as opposed to PAH. Management of patients with PAH in the ICU is complex as it requires a careful balance to maintain perfusion while optimizing right-sided heart function. A comprehensive understanding of the underlying physiology and underlying hemodynamics is crucial for the management of this population. In this review, we summarized the evidence for use of vasopressors and inotropes in the management of PH and extrapolated the data to patients with PAH. We strongly believe that the understanding of the hemodynamic consequences of inotropes and vasopressors, especially from data in the PH population, can lead to better management of this complex patient population.

Cardiac Output Assessments in Anesthetized Children: Dynamic Capnography Versus Esophageal Doppler.

BACKGROUND: The objective of this study was to compare esophageal Doppler cardiac output (COEDM) against the reference method effective pulmonary blood flow cardiac output (COEPBF), for agreement of absolute values and ability to detect change in cardiac output (CO) in pediatric surgical patients. Furthermore, the relationship between these 2 methods and noninvasive blood pressure (NIBP) parameters was evaluated. METHODS: Fifteen children American Society of Anesthesiology (ASA) I and II (median age, 8 months; median weight, 9 kg) scheduled for surgery were investigated in this prospective observational cohort study. Baseline COEPBF/COEDM/NIBP measurements were made at positive end-expiratory pressure (PEEP) 3 cm H2O. PEEP was increased to 10 cm H2O and COEPBF/COEDM/NIBP was recorded after 1 and 3 minutes. PEEP was then lowered to 3 cm H2O, and all measurements were repeated after 3 minutes. Finally, 20-µg kg-1 intravenous atropine was given with the intent to increase CO, and all measurements were recorded again after 5 minutes. Paired recordings of COEDM and COEPBF were examined for agreement and trending ability, and all parameters were analyzed for their responses to the hemodynamic challenges. RESULTS: Bias between COEDM and COEPBF (COEDM - COEPBF) was -17 mL kg-1 min-1 (limits of agreement, -67 to +33 mL kg-1 min-1) with a mean percentage error of 32% (95% confidence interval [CI], 25-37) and a concordance rate of 71% (95% CI, 63-80). The hemodynamic interventions caused by PEEP manipulations resulted in significant decrease in COEPBF absolute numbers (155 mL kg-1 min-1 [95% CI, 151-159] to 127 mL kg-1 min-1 [95% CI, 113-141]) and a corresponding relative decrease of 18% (95% CI, 14-22) 3 minutes after application of PEEP 10. No corresponding decreases were detected by COEDM. Mean arterial pressure showed a relative decrease with 5 (95% CI, 2-8) and 6% (95% CI, 2-10) 1 and 3 minutes after the application of PEEP 10, respectively. Systolic arterial pressure showed a relative decrease of 5% (95% CI, 2-10) 3 minutes after application of PEEP 10. None of the recorded parameters responded to atropine administration except for heart rate that showed a 4% relative increase (95% CI, 1-7, P = .02) 5 minutes after atropine. CONCLUSIONS: COEDM was unable to detect the reduction of CO cause by increased PEEP, whereas COEPBF and to a minimal extent NIBP detected these changes in CO. The ability of COEPBF to react to minor reductions in CO, before noticeable changes in NIBP are seen, suggests that COEPBF may be a potentially useful tool for hemodynamic monitoring in mechanically ventilated children.

The evolution of mean arterial pressure in critically ill patients on vasopressors before and during a trial comparing a specific mean arterial pressure target to usual care.

BACKGROUND: In randomized clinical controlled trials, the choice of usual care as the comparator may be associated with better clinician uptake of the study protocol and lead to more generalizable results. However, if care processes evolve to resemble the intervention during the course of a trial, differences between the intervention group and usual care control group may narrow. We evaluated the effect on mean arterial pressure of an unblinded trial comparing a lower mean arterial pressure target to reduce vasopressor exposure, vs. a clinician-selected mean arterial pressure target, in critically ill patients at least 65 years old. METHODS: For this multicenter observational study using data collected both prospectively and retrospectively, patients were recruited from five of the seven trial sites. We compared the mean arterial pressure of patients receiving vasopressors, who met or would have met trial eligibility criteria, from two periods: [1] at least 1 month before the trial started, and [2] during the trial period and randomized to usual care, or not enrolled in the trial. RESULTS: We included 200 patients treated before and 229 after trial initiation. There were no differences in age (mean 74.5 vs. 75.2 years; p = 0.28), baseline Acute Physiology and Chronic Health Evaluation II score (median 26 vs. 26; p = 0.47) or history of chronic hypertension (n = 126 [63.0%] vs. n = 153 [66.8%]; p = 0.41). Mean of the mean arterial pressure was similar between the two periods (72.5 vs. 72.4 mmHg; p = 0.76). CONCLUSIONS: The initiation of a trial of a prescribed lower mean arterial pressure target, compared to a usual clinician-selected target, was not associated with a change in mean arterial pressure, reflecting stability in the net effect of usual clinician practices over time. Comparing prior and concurrent control groups may alleviate concerns regarding drift in usual practices over the course of a trial or permit quantification of any change.

Time interval between alfentanil and rocuronium administration necessary to prevent rocuronium-induced withdrawal movement.

BACKGROUND: We aimed to determine the time interval between alfentanil and rocuronium administration, at a 50% probability of preventing pain-induced withdrawal movement from rocuronium injection (TimeAR50). METHODS: A total of 64 patients scheduled for general anesthesia were enrolled in this study (33 men and 31 women). Anesthesia was induced with target-controlled infusion of propofol, at an effect-site target concentration of 3 µg/mL. Then, alfentanil 15 µg/kg was injected for 30 s. After 60 s, rocuronium 0.6 mg/kg was administered to the first patient. The Dixon's up-and-down method was used to determine the time interval for each subsequent patient (interval of 5 s). Mean arterial pressure (MAP) and heart rate (HR) were recorded at three time points: T0, pre-induction; T1, before rocuronium injection; and T2, 1 min after rocuronium injection. RESULTS: The TimeAR50 ± standard deviation (SD) was 5.6 ± 3.7 s and 21.9 ± 5.6 s in the male and female patients, respectively. Based on the probit regression, the TimeAR50 was 4.7 s (95% confidence interval [CI], 1.2-7.6 s) and 20.3 s (95% CI, 7.7-26.1 s) in the male and female patients, respectively. The TimeAR95 was 10.6 s (95% CI, 7.7-25.3 s) and 35.0 s (95% CI, 28.1-95.5 s) in the male and female patients, respectively, with significantly higher values in females than in males (P < 0.001). Compared with the T0, MAP and HR decreased significantly at T1 and T2 in both groups. CONCLUSION: The TimeAR50 required for preventing rocuronium-induced withdrawal movement were 4.7 s and 20.3 s in male and female patients, respectively. TRIAL REGISTRATION: This study was registered with the Chinese Clinical Trials Registry on April 7, 2021 (URL: http://www.chictr.org.cn . Registry number: ChiCTR2100045137 ) .

Efficacy and safety of remimazolam tosylate in hysteroscopy: A randomized, single-blind, parallel controlled trial.

WHAT IS KNOWN AND OBJECTIVE: To compare the effectiveness and safety of remimazolam tosylate and propofol for hysteroscopy. METHODS: From November 2020 to June 2021, a total of 90 patients who underwent hysteroscopy were prospectively enrolled in this study. The patients were randomly assigned to three groups: propofol group (group A), low-dose remimazolam tosylate group (group B), and high-dose remimazolam tosylate group (group C), with 30 cases in each group. All cases received intravenous sufentanil 0.1ug/kg for analgesic preconditioning. Patients in group A were given 2 mg/kg propofol intravenously, and maintained at a rate of 5 mg/kg/h. Patients in groups B and C were given intravenous remimazolam tosylate 0.25 mg/kg. Group B was maintained with remimazolam tosylate at a rate of 0.48 mg/kg/h, while group C was at a rate of 0.6 mg/kg/h. The changes of heart rate (HR), mean arterial pressure (MAP) and saturation of peripheral oxygen (SpO2) were recorded after admission (T0), 1 min after anaesthesia (T1), dilation of the uterine cavity (T2), and the end of hysteroscopy (T3). In addition, Observer's Assessment of Alertness/Sedation Scale (OAA/S) at 1 min, 3 min, and 5 min after hysteroscopy, the incidence of adverse events, and the time from the end of the hysteroscopy to reach the discharge standard, were recorded. RESULTS AND DISCUSSION: The success rate of sedation in each group was 100%. After administration, the adverse event incidence in group A was significantly higher than that in groups B and C (p < 0.05, respectively). Compared with propofol, remimazolam tosylate did not cause injection pain, had less impact on haemodynamics and caused less respiratory depression. WHAT IS NEW AND CONCLUSION: Remimazolam tosylate and propofol have similar success rates for painless hysteroscopy, and both can provide safe and effective sedation. The safety of remimazolam tosylate for hysteroscopy appears to be better than that of propofol.

Bacillus anthracis edema toxin inhibits hypoxic pulmonary vasoconstriction via edema factor and cAMP-mediated mechanisms in isolated perfused rat lungs.

Bacillus anthracis edema toxin (ET) inhibited lethal toxin-stimulated pulmonary artery pressure (Ppa) and increased lung cAMP levels in our previous study. We therefore examined whether ET inhibits hypoxic pulmonary vasoconstriction (HPV). Following baseline hypoxic measures in isolated perfused lungs from healthy rats, compared with diluent, ET perfusion reduced maximal Ppa increases (mean ± SE percentage of maximal Ppa increase with baseline hypoxia) during 6-min hypoxic periods (FIO2 = 0%) at 120 min (16 ± 6% vs. 51 ± 6%, P = 0.004) and 180 min (11.4% vs. 55 ± 6%, P = 0.01). Protective antigen-mAb (PA-mAb) and adefovir inhibit host cell edema factor uptake and cAMP production, respectively. In lungs perfused with ET following baseline measures, compared with placebo, PA-mAb treatment increased Ppa during hypoxia at 120 and 180 min (56 ± 6% vs. 10 ± 4% and 72 ± 12% vs. 12 ± 3%, respectively, P ≤ 0.01) as did adefovir (84 ± 10% vs. 16.8% and 123 ± 21% vs. 26 ± 11%, respectively, P ≤ 0.01). Compared with diluent, lung perfusion with ET for 180 min reduced the slope of the relationships between Ppa and increasing concentrations of endothelin-1 (ET-1) (21.12 ± 2.96 vs. 3.00 ± 0.76 × 108 cmH2O/M, P < 0.0001) and U46619, a thromboxane A2 analogue (7.15 ± 1.01 vs. 3.74 ± 0.31 × 107 cmH2O/M, P = 0.05) added to perfusate. In lungs isolated from rats after 15 h of in vivo infusions with either diluent, ET alone, or ET with PA-mAb, compared with diluent, the maximal Ppa during hypoxia and the slope of the relationship between change in Ppa and ET-1 concentration added to the perfusate were reduced in lungs from animals challenged with ET alone (P ≤ 0.004) but not with ET and PA-mAb together (P ≥ 0.73). Inhibition of HPV by ET could aggravate hypoxia during anthrax pulmonary infection.NEW & NOTEWORTHY The most important findings here are edema toxin's potent adenyl cyclase activity can interfere with hypoxic pulmonary vasoconstriction, an action that could worsen hypoxemia during invasive anthrax infection with lung involvement. These findings, coupled with other studies showing that lethal toxin can disrupt pulmonary vascular integrity, indicate that both toxins can contribute to pulmonary pathophysiology during infection. In combination, these investigations provide a further basis for the use of antitoxin therapies in patients with worsening invasive anthrax disease.

Acute effects of electronic cigarettes on arterial pressure and peripheral sympathetic activity in young nonsmokers.

Electronic cigarettes (e-cigarettes) are marketed as an alternative to smoking for those who want to decrease the health risks of tobacco. Tobacco cigarettes increase heart rate (HR) and arterial pressure, while reducing muscle sympathetic nerve activity (MSNA) through sympathetic baroreflex inhibition. The acute effects of e-cigarettes on arterial pressure and MSNA have not been reported: our purpose was to clarify this issue. Using a randomized crossover design, participants inhaled on a JUUL e-cigarette containing nicotine (59 mg/mL) and a similar placebo e-cigarette (0 mg/mL). Experiments were separated by ∼1 mo. We recorded baseline ECG, finger arterial pressure (n = 15), and MSNA (n = 10). Subjects rested for 10 min (BASE) and then inhaled once every 30 s on an e-cigarette that contained nicotine or placebo (VAPE) for 10 min followed by a 10-min recovery (REC). Data were expressed as Δ means ± SE from BASE. Heart rate increased in the nicotine condition during VAPE and returned to BASE values in REC (5.0 ± 1.3 beats/min nicotine vs. 0.1 ± 0.8 beats/min placebo, during VAPE; P < 0.01). Mean arterial pressure increased in the nicotine condition during VAPE and remained elevated during REC (6.5 ± 1.6 mmHg nicotine vs. 2.6 ± 1 mmHg placebo, during VAPE and 4.6.0 ± 1.7 mmHg nicotine vs. 1.4 ± 1.4 mmHg placebo, during REC; P < 0.05). MSNA decreased from BASE to VAPE and did not restore during REC (-7.1 ± 1.6 bursts/min nicotine vs. 2.6 ± 2 bursts/min placebo, during VAPE and -5.8 ± 1.7 bursts/min nicotine vs. 0.5 ± 1.4 bursts/min placebo, during REC; P < 0.05). Our results show that acute e-cigarette usage increases mean arterial pressure leading to a baroreflex-mediated inhibition of MSNA.NEW & NOTEWORTHY The JUUL e-cigarette is the most popular e-cigarette in the market. In the present study, inhaling on a JUUL e-cigarette increased mean arterial pressure and heart rate, and decreased muscle sympathetic nerve activity (MSNA). In contrast, inhaling on a placebo e-cigarette without nicotine elicited no sympathomimetic effects. Although previous tobacco cigarette studies have demonstrated increased mean arterial pressure and MSNA inhibition, ours is the first study to report similar responses while inhaling on an e-cigarette. Listen to this article's corresponding podcast at @ https://ajpheart.podbean.com/e/aerosolized-nicotine-and-cardiovascular-control/.

Ivabradine augments high-frequency dynamic gain of the heart rate response to low- and moderate-intensity vagal nerve stimulation under ß-blockade.

Our previous study indicated that intravenously administered ivabradine (IVA) augmented the dynamic heart rate (HR) response to moderate-intensity vagal nerve stimulation (VNS). Considering an accentuated antagonism, the results were somewhat paradoxical; i.e., the accentuated antagonism indicates that an activation of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels via the accumulation of intracellular cyclic adenosine monophosphate (cAMP) augments the HR response to VNS, whereas the inhibition of HCN channels by IVA also augmented the HR response to VNS. To remove the possible influence from the accentuated antagonism, we examined the effects of IVA on the dynamic vagal control of HR under ß-blockade. In anesthetized rats (n = 7), the right vagal nerve was stimulated for 10 min according to binary white noise signals between 0 and 10 Hz (V0-10), between 0 and 20 Hz (V0-20), and between 0 and 40 Hz (V0-40). The transfer function from VNS to HR was estimated. Under ß-blockade (propranolol, 2 mg/kg iv), IVA (2 mg/kg iv) did not augment the asymptotic low-frequency gain but increased the asymptotic high-frequency gain in V0-10 (0.53 ± 0.10 vs. 1.74 ± 0.40 beats/min/Hz, P < 0.01) and V0-20 (0.79 ± 0.14 vs. 2.06 ± 0.47 beats/min/Hz, P < 0.001). These changes, which were observed under a minimal influence from sympathetic background tone, may reflect an increased contribution of the acetylcholine-sensitive potassium channel (IK,ACh) pathway after IVA, because the HR control via the IK,ACh pathway is faster and acts in the frequency range higher than the cAMP-mediated pathway.NEW & NOTEWORTHY Since ivabradine (IVA) inhibits hyperpolarization-activated cyclic nucleotide-gated channels, interactions among the sympathetic effect, vagal effect, and IVA can occur in the control of heart rate (HR). To remove the sympathetic effect, we estimated the transfer function from vagal nerve stimulation to HR under ß-blockade in anesthetized rats. IVA augmented the high-frequency dynamic gain during low- and moderate-intensity vagal nerve stimulation. Untethering the hyperpolarizing effect of acetylcholine-sensitive potassium channels after IVA may be a possible underlying mechanism.

Angiotensin II type 1 receptor mediates pulmonary hypertension and right ventricular remodeling induced by inhaled nicotine.

Use of electronic cigarettes is rapidly increasing among youth and young adults, but little is known regarding the long-term cardiopulmonary health impacts of these nicotine-containing devices. Our group has previously demonstrated that chronic, inhaled nicotine induces pulmonary hypertension (PH) and right ventricular (RV) remodeling in mice. These changes were associated with upregulated RV angiotensin-converting enzyme (ACE). Angiotensin II receptor blockers (ARBs) have been shown to reverse cigarette smoking-induced PH in rats. ACE inhibitor and ARB use in a large retrospective cohort of patients with PH is associated with improved survival. Here, we utilized losartan (an ARB specific for angiotensin II type 1 receptor) to further explore nicotine-induced PH. Male C57BL/6 mice received nicotine vapor for 12 h/day, and exposure was assessed using serum cotinine to achieve levels comparable to human smokers or electronic cigarette users. Mice were exposed to nicotine for 8 wk and a subset was treated with losartan via an osmotic minipump. Cardiac function was assessed using echocardiography and catheterization. Although nicotine exposure increased angiotensin II in the RV and lung, this finding was nonsignificant. Chronic, inhaled nicotine significantly increased RV systolic pressure and RV free wall thickness versus air control. These parameters were significantly lower in mice receiving both nicotine and losartan. Nicotine significantly increased RV internal diameter, with no differences seen between the nicotine and nicotine-losartan group. Neither nicotine nor losartan affected left ventricular structure or function. These findings provide the first evidence that antagonism of the angiotensin II type 1 receptor can ameliorate chronic, inhaled nicotine-induced PH and RV remodeling.NEW & NOTEWORTHY Chronic, inhaled nicotine causes pulmonary hypertension and right ventricular remodeling in mice. Treatment with losartan, an angiotensin II type 1 receptor antagonist, ameliorates nicotine-induced pulmonary hypertension and right ventricular remodeling. This novel finding provides preclinical evidence for the use of renin-angiotensin system-based therapies in the treatment of pulmonary hypertension, particularly in patients with a history of tobacco-product use.

Alamandine but not angiotensin-(1-7) produces cardiovascular effects at the rostral insular cortex.

Experiments aimed to evaluate the tissue distribution of Mas-related G protein-coupled receptor D (MrgD) revealed the presence of immunoreactivity for the MrgD protein in the rostral insular cortex (rIC), an important area for autonomic and cardiovascular control. To investigate the relevance of this finding, we evaluated the cardiovascular effects produced by the endogenous ligand of MrgD, alamandine, in this brain region. Mean arterial pressure (MAP), heart rate (HR), and renal sympathetic nerve activity (RSNA) were recorded in urethane anesthetized rats. Unilateral microinjection of equimolar doses of alamandine (40 pmol/100 nL), angiotensin-(1-7), angiotensin II, angiotensin A, and Mas/MrgD antagonist d-Pro7-Ang-1-7 (50 pmol/100 nL), Mas antagonist A779 (100 pmol/100 nL), or vehicle (0.9% NaCl) were made in different rats (n = 4-6/group) into rIC. To verify the specificity of the region, a microinjection of alamandine was also performed into intermediate insular cortex (iIC). Microinjection of alamandine in rIC produced an increase in MAP (Δ = 15 ± 2 mmHg), HR (Δ = 36 ± 4 beats/min), and RSNA (Δ = 31 ± 4%), but was without effects at iIC. Strikingly, an equimolar dose of angiotensin-(1-7) at rIC did not produce any change in MAP, HR, and RSNA. Angiotensin II and angiotensin A produced only minor effects. Alamandine effects were not altered by A-779, a Mas antagonist, but were completely blocked by the Mas/MrgD antagonist d-Pro7-Ang-(1-7). Therefore, we have identified a brain region in which alamandine/MrgD receptor but not angiotensin-(1-7)/Mas could be involved in the modulation of cardiovascular-related neuronal activity. This observation also suggests that alamandine might possess unique effects unrelated to angiotensin-(1-7) in the brain.

Activation of the carotid body increases directly recorded cardiac sympathetic nerve activity and coronary blood flow in conscious sheep.

Activation of the carotid body (CB) using intracarotid potassium cyanide (KCN) injection increases coronary blood flow (CoBF). This increase in CoBF is considered to be mediated by co-activation of both the sympathetic and parasympathetic nerves to the heart. However, whether cardiac sympathetic nerve activity (cardiac SNA) actually increases during CB activation has not been determined previously. We hypothesized that activation of the CB would increase directly recorded cardiac SNA, which would cause coronary vasodilatation. Experiments were conducted in conscious sheep implanted with electrodes to record cardiac SNA and diaphragmatic electromyography (dEMG), flow probes to record CoBF and cardiac output, and a catheter to record arterial pressure. Intracarotid KCN injection was used to activate the CB. To eliminate the contribution of metabolic demand on coronary flow, the heart was paced at a constant rate during CB chemoreflex stimulation. Intracarotid KCN injection resulted in a significant increase in directly recorded cardiac SNA frequency (from 24 ± 2 to 40 ± 4 bursts/min; P < 0.05) as well as a dose-dependent increase in mean arterial pressure (79 ± 15 to 88 ± 14 mmHg; P < 0.01) and CoBF (75 ± 37 vs. 86 ± 42 mL/min; P < 0.05). The increase in CoBF and coronary vascular conductance to intracarotid KCN injection was abolished after propranolol infusion, suggesting that the increased cardiac SNA mediates coronary vasodilatation. The pressor response to activation of the CB was abolished by pretreatment with intravenous atropine, but there was no change in the coronary flow response. Our results indicate that CB activation increases directly recorded cardiac SNA, which mediates vasodilatation of the coronary vasculature.

Indole-3-propionic acid, a tryptophan-derived bacterial metabolite, increases blood pressure via cardiac and vascular mechanisms in rats.

Recent evidence suggests that gut bacteria-derived metabolites interact with the cardiovascular system and alter blood pressure (BP) in mammals. Here, we evaluated the effect of indole-3-propionic acid (IPA), a gut bacteria-derived metabolite of tryptophan, on the circulatory system. Arterial BP, electrocardiographic, and echocardiographic (ECHO) parameters were recorded in male, anesthetized, 12-wk-old Wistar-Kyoto rats at baseline and after intravenous administration of either IPA or vehicle. In additional experiments, rats were pretreated with prazosin or pentolinium to evaluate the involvement of the autonomic nervous system in cardiovascular responses to IPA. IPA's concentrations were measured using ultra-high performance liquid chromatography tandem mass spectrometry. The reactivity of endothelium-intact and -denuded mesenteric resistance arteries was tested. Cells' viability and lactate dehydrogenase (LDH) cytotoxicity assays were performed on cultured cardiomyocytes. IPA increased BP with a concomitant bradycardic response but no significant change in QTc interval. The pretreatment with prazosin and pentolinium reduced the hypertensive response. ECHO showed increased contractility of the heart after the administration of IPA. Ex vivo, IPA constricted predilated and endothelium-denuded mesenteric resistance arteries and increased metabolic activity of cardiomyocytes. IPA increases BP via cardiac and vascular mechanisms in rats. Furthermore, IPA increases cardiac contractility and metabolic activity of cardiomyocytes. Our study suggests that IPA may act as a mediator between gut microbiota and the circulatory system.

Chronic ablation of TRPV1-sensitive skeletal muscle afferents attenuates the muscle metaboreflex.

Exercise intolerance is a hallmark symptom of cardiovascular disease and likely occurs via enhanced activation of muscle metaboreflex-induced vasoconstriction of the heart and active skeletal muscle which, thereby limits cardiac output and peripheral blood flow. Muscle metaboreflex vasoconstrictor responses occur via activation of metabolite-sensitive afferent fibers located in ischemic active skeletal muscle, some of which express transient receptor potential vanilloid 1 (TRPV1) cation channels. Local cardiac and intrathecal administration of an ultrapotent noncompetitive, dominant negative agonist resiniferatoxin (RTX) can ablate these TRPV1-sensitive afferents. This technique has been used to attenuate cardiac sympathetic afferents and nociceptive pain. We investigated whether intrathecal administration (L4-L6) of RTX (2 µg/kg) could chronically attenuate subsequent muscle metaboreflex responses elicited by reductions in hindlimb blood flow during mild exercise (3.2 km/h) in chronically instrumented conscious canines. RTX significantly attenuated metaboreflex-induced increases in mean arterial pressure (27 ± 5.0 mmHg vs. 6 ± 8.2 mmHg), cardiac output (1.40 ± 0.2 L/min vs. 0.28 ± 0.1 L/min), and stroke work (2.27 ± 0.2 L·mmHg vs. 1.01 ± 0.2 L·mmHg). Effects were maintained until 78 ± 14 days post-RTX at which point the efficacy of RTX injection was tested by intra-arterial administration of capsaicin (20 µg/kg). A significant reduction in the mean arterial pressure response (+45.7 ± 6.5 mmHg pre-RTX vs. +19.7 ± 3.1 mmHg post-RTX) was observed. We conclude that intrathecal administration of RTX can chronically attenuate the muscle metaboreflex and could potentially alleviate enhanced sympatho-activation observed in cardiovascular disease states.

V1a and V1b vasopressin receptors within the paraventricular nucleus contribute to hypertension in male rats exposed to chronic mild unpredictable stress.

Depression is an independent nontraditional risk factor for cardiovascular disease and mortality. The chronic unpredictable mild stress (CMS) rat model is a validated model of depression. Within the paraventricular nucleus (PVN), vasopressin (VP) via V1aR and V1bR have been implicated in stress and neurocardiovascular dysregulation. We hypothesized that in conscious, unrestrained CMS rats versus control, unstressed rats, PVN VP results in elevated arterial pressure (MAP), heart rate, and renal sympathetic nerve activity (RSNA) via activation of V1aR and/or V1bR. Male rats underwent 4 wk of CMS or control conditions. They were then equipped with hemodynamic telemetry transmitters, PVN cannula, and left renal nerve electrode. V1aR or V1bR antagonism dose-dependently inhibited MAP after VP injection. V1aR or V1bR blockers at their ED50 doses did not alter baseline parameters in either control or CMS rats but attenuated the pressor response to VP microinjected into PVN by ∼50%. Combined V1aR and V1bR inhibition completely blocked the pressor response to PVN VP in control but not CMS rats. CMS rats required combined maximally inhibitory doses to block either endogenous VP within the PVN or responses to microinjected VP. Compared with unstressed control rats, CMS rats had higher plasma VP levels and greater abundance of V1aR and V1bR transcripts within PVN. Thus, the CMS rat model of depression results in higher resting MAP, heart rate, and RSNA, which can be mitigated by inhibiting vasopressinergic mechanisms involving both V1aR and V1bR within the PVN. Circulating VP may also play a role in the pressor response.