Reduction In Total Peripheral Resistance Research Articles

Preserved hemodynamics in breast cancer survivors not a function of cancer, but fitness

Introduction: One in eight U.S. women will develop breast cancer (BC), and cardiovascular disease is the second leading cause of death among survivors. Improving cardiorespiratory fitness (CRF) and increasing physical activity (PA) reduces risk of adverse cardiovascular events among the general population without BC. Specifically, improved heart rate recovery (HRR) and hemodynamic modulation established through greater PA are traditional methods of risk assessment for cardiovascular disease that may be beneficial for BC survivors. Purpose: The purpose of this study was to examine HRR and hemodynamic adjustments following a maximal test of CRF among active and inactive BC survivors compared to women without a BC diagnosis. Methods: Twenty-two BC survivors were separated into active (n=11, 48±9 yrs, 24.8±3 kg/m2, 373±172 min/wk) and inactive (n=11, 51±9 yrs, 26.1±3 kg/m2, 52±68 min/wk) groups and compared to 18 active women without BC (48±9 yrs, 25.3±5 kg/m2, 327±178 min/wk) based on the Paffenberger PA Questionnaire. Mean arterial pressure (MAP), cardiac output (CO), total peripheral resistance (TPR), and stroke volume (SV) were measured before and 5 minutes after after a cycle ergometry test of CRF (expressed as VO2peak) using an oscillometric device. Continuous heart rate was assessed using a three-lead ECG throughout and following the test to calculate the slow phase (Peak exercise [VO2peak] to 2-min post) of HRR. Results: Active BC survivors demonstrated similar HRR from peak exercise (-52±15 bpm) compared to active individuals without BC (-46±12 bpm), both of which were greater than the HRR observed in non-active BC survivors (-38±12 bpm; p for interaction=0.05). We found a significant relationship between CRF and HRR for the three groups (VO2peak, active BC survivors: 32.6±4 mL/kg·min-1; inactive BC survivors: 20.9±3 mL/kg·min-1; active controls: 29.5±6 mL/kg·min-1; r=0.38, p=0.01). Likewise, inactive BC survivors experienced a blunted change in SV following a maximal CRF test, compared to active BC survivors and control counterparts (%ΔSV [mL/min], active BC survivors: 32.7%; inactive BC survivors: 23.5%; active controls: 39.3%; p for interaction≤0.001). Active BC survivors (before: 1.32±0.1 mmHg/L·min-1, after: 1.13±0.2 mmHg/L·min-1) experienced a greater reduction in TPR following the maximal CRF test compared to their inactive BC survivors (before: 1.23±0.2 mmHg/L·min-1, after: 1.18±0.14 mmHg/L·min-1) and active individuals without BC (before: 1.20±0.2 mmHg/L·min-1, after: 1.16±0.12 mmHg/L·min-1; p for interaction=0.03). MAP was not different between the 3 groups ( p for interaction≥0.05). Conclusion: Physically active BC survivors exhibit preserved cardiac autonomic and hemodynamic control following maximal exercise, similar to active individuals without BC. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The effect of isometric exercise training on arterial stiffness: A randomized crossover controlled study.

Isometric exercise training (IET) is an effective intervention for the management of resting blood pressure (BP). However, the effects of IET on arterial stiffness remain largely unknown. Eighteen unmedicated physically inactive participants were recruited. Participants were randomly allocated in a cross-over design to 4 weeks of home-based wall squat IET and control period, separated by a 3-week washout period. Continuous beat-to-beat hemodynamics, including early and late systolic (sBP 1 and sBP 2, respectively) and diastolic blood pressure (dBP) were recorded for a period of 5 min and waveforms were extracted and analyzed to acquire the augmentation index (AIx) as a measure of arterial stiffness. sBP 1 (-7.7 ± 12.8 mmHg, p = 0.024), sBP 2 (-5.9 ± 9.9 mmHg, p = 0.042) and dBP (-4.4 ± 7.2 mmHg, p = 0.037) all significantly decreased following IET compared to the control period. Importantly, there was a significant reduction in AIx following IET (-6.6 ± 14.5%, p = 0.02) compared to the control period. There were also adjacent significant reductions in total peripheral resistance (-140.7 ± 65.8 dynes·cm-5, p = 0.042) and pulse pressure (-3.8 ± 4.2, p = 0.003) compared to the control period. This study demonstrates an improvement in arterial stiffness following a short-term IET intervention. These findings have important clinical implications regarding cardiovascular risk. Mechanistically, these results suggest that reductions in resting BP following IET are induced via favorable vascular adaptations, although the intricate details of such adaptations are not yet clear.

Skin Vascular Resistance Decreases during 5-HT-Induced Hypotension in the Rat.

A recognized vasodilator, the infusion of 5-hydroxytryptamine (5-HT, serotonin) decreases blood pressure through the reduction of total peripheral resistance in the rat. It is not clear which vascular beds/tissues are responsible for this fall. We hypothesized that an increase in blood flow within the skin, measured as an elevated temperature (T) in the thermoregulatory tail and paws, enables at least part of 5-HT-induced reduction in blood pressure through active vasodilation. The temperature of thermoregulatory regions of the skin of an anesthetized male, Sprague Dawley rats were measured using a Optris PI640 thermal camera. The blood pressure of the animal and the temperature of each paw and four locations along the tail (TL1-4) were recorded before, during, and after the infusion of 5-HT at a rate of 25 mg/min into a femoral vein. Contrary to our hypothesis, the temperature of the paws and tail was stable before and during 5-HT infusion and actually increased during the 15-min recovery period. This finding suggests that hyperemia of the skin circulation is not necessary for the fall in blood pressure observed with infused 5-HT, but that a reduction in cutaneous vascular resistance plays a part in the fall in total peripheral resistance.

Abstract P356: Cutaneous Vasodilation May Contribute To 5-ht-induced Hypotension In The Rat

5-hydroxytryptamine (5-HT, serotonin) is well-recognized to have vasodilator properties. For example, infusion of 5HT at low rates into rats decreases blood pressure acutely and chronically through reduction of total peripheral resistance. We recently showed that vasodilation in the hindquarters contributes to this fall in peripheral resistance. The hindquarter in the rat is mostly made up of skeletal muscle but also includes skin. Therefore, we hypothesized that an increase in blood flow in the skin, measured as an elevated temperature (T) in the thermoregulatory tail and paws, could contribute in part to 5-HT-induced reduction in blood pressure and hindquarters vasodilation. The temperature of thermoregulatory organs in the skin of anesthetized male, Sprague Dawley rats were measured using a Optris PI640 thermal camera. Blood pressure (from a radiotelemeter) and temperature of each paw and four locations along the tail (TL1-4) were recorded for 20 minutes before, during, and after infusion of 5-HT at a rate of 25 μg/min into the femoral vein. With this infusion protocol, the mean arterial blood pressure of rats fell over 30 mm Hg. However, the temperature of the paws (~29-32 o C) and tail (32 o at base, 25 o C at tip) were stable before and during 5-HT infusion, suggesting that flow was maintained, vs reduced, during this time. T increased during the 15-minute recovery time in all tail sections (base = from 32 o to 34 o C; tip from 23.5 o to 25.5 o C). Because the skin circulation exhibits only weak autoregulation, our results suggests that 5-HT infusion causes vasodilation of glabrous skin in the rat but without causing hyperemia. This could play a part in 5-HT induced hypotension.

Mechanisms for blood pressure reduction following isometric exercise training: a systematic review and meta-analysis.

Isometric exercise training (IET) is established as an effective antihypertensive intervention. Despite this, the physiological mechanisms driving blood pressure (BP) reductions following IET are not well understood. Therefore, we aimed to perform the first meta-analysis of the mechanistic changes measured following IET. PubMed, Cochrane library and SPORTDiscus were systematically searched for randomized controlled trials published between January 2000 and December 2021 reporting the effects of IET on resting BP and at least one secondary mechanistic parameter following a short-term intervention (2-12 weeks). Eighteen studies with a pooled sample size of 628 participants were included in the final analysis. IET produced significant reductions in resting systolic and diastolic BP of 9.35 mmHg (95% confidence interval [CI] = -7.80 to -10.89, P < 0.001) and 4.30 mmHg (CI = -3.01 to -5.60, P < 0.001), respectively. Mechanistically, IET produced a statistically significant reduction in resting heart rate (mean difference [MD]: -1.55 bpm, CI = -0.14 to -2.96, P = 0.031) and a significant increase in stroke volume (MD: 6.35 ml, CI = 0.35 to 12.60, P = 0.038), with no significant change in cardiac output. Conversely, total peripheral resistance (TPR) significantly decreased following IET (MD: -100.38 dyne s -1 cm 5 , CI = -14.16 to -186.61, P = 0.023), with significant improvements in the low frequency to high frequency heart rate variability ratio (MD: -0.41, CI = -0.09 to -0.73, P = 0.013) and baroreceptor reflex sensitivity (MD: 7.43 ms/mmHg, P < 0.001). This work demonstrates that a reduction in TPR, potentially mediated through enhanced autonomic vasomotor control, is primarily responsible for BP reductions following IET. Furthermore, this novel analysis suggests wall squat interventions to be the most effective IET mode, with clinically relevant differences in BP reductions compared to handgrip and leg extension IET; although future direct comparative research is required.

15‐Days of Therapeutic Mild Intermittent Hypoxia Improves Cardiovascular, Upper Airway and Motor Limb Function in Participants with Motor Incomplete Spinal Cord Injury and Severe Obstructive Sleep Apnea

IntroductionRepeated exposure to mild intermittent hypoxia (MIH) with sustained hypercapnia improves cardiovascular control in able‐bodied individuals with obstructive sleep apnea. Thus, we aimed to investigate if this treatment can improve cardiovascular function in individuals with motor incomplete spinal cord injuries (SCI). In addition, treatment with MIH improves cortical excitability, as well as, upper airway muscle and limb motor function. Consequently, we also explored if MIH improves upper airway motor function and walking endurance in individuals with motor incomplete SCI with concurrent sleep apnea.MethodsTwo individuals (age 51.0 ± 8.5) with traumatic motor incomplete SCI (T8, C6) and untreated severe obstructive sleep apnea (apnea hypopnea index 53.7 ± 34.0 events/hour) were treated with MIH for 15 days while receiving in‐home continuous positive airway pressure (CPAP) treatment. The MIH protocol consisted of twelve 2‐minute hypoxic exposures (PETO2 ≍ 50 mmHg) with PETCO2 maintained 2 mmHg above baseline. Therapeutic CPAP and the active critical closing pressure were measured before and after the 15‐day exposure period. In addition, blood pressure was measured over 24‐hours before and after the MIH protocol. Beat‐to‐beat blood pressure was measured during baseline (i.e. normoxia) prior to exposure to MIH on day 1 and day 15. Walking endurance was measured on the first and last day of the protocol prior to MIH exposure. Due to the small sample, Cohen’s D effect sizes are presented.Results24‐hour systolic (SBP), diastolic (DBP) and mean arterial (MAP) blood pressure (unit – mmHg) was reduced following 15 days of MIH (SBP: 131.4 ± 8.5 vs 113.4 ± 9.3, d= 2.0, DBP: 82.3 ± 1.4 vs 75.5 ± 3.9, d= 2.6, MAP: 98.5 ± 1.84 vs 88.0 ± 0.5, d= 9.04). Beat‐to‐beat blood pressure was also reduced following MIH (SBP: 135.3 ± 10.0 vs 116.9 ± 21.5, d= 1.2, DBP: 87.3 ± 0.46 vs 75.6 ± 3.1, d= 6.6, MAP 107.1 ± 0.4 vs 91.3 ± 7.0, d= 4.4). Additionally, an increase in indirect measures of cardiac output at rest (77.6 ± 39.9 vs 84.9 ± 30.2 L/min, d = 0.9) with concurrent reductions in total peripheral resistance (1.3 ± .7 vs 0.6 ± 0.1 mmHg*s/mL, d = 1.8) were found on the day 15. A reduction in therapeutic CPAP (11.0 ± 1.4 vs 9.0 ± 1.4 cmH2O, d= 1.4) and the critical closing pressure (4.5 ± 0.7 vs ‐0.6 ± 1.9 cmH2O, d = 3.9) was also evident following MIH. Lastly, walking endurance (155.8 ± 151.1 vs 240.5 ± 208.0 meters, d = 0.33) and walking velocity (0.4 ± 0.4 vs 0.7 ± 0.6 meters/second, d = 0.33) increased on day 15 compared to day 1.ConclusionFollowing 15 days of therapeutic MIH (i) blood pressure was reduced (ii) upper airway patency was improved and (iii) walking endurance and velocity increased in two individuals with motor incomplete SCI, hypertension and concurrent obstructive sleep apnea.

Global Reach 2018: sympathetic neural and hemodynamic responses to submaximal exercise in Andeans with and without chronic mountain sickness.

Andeans with chronic mountain sickness (CMS) and polycythemia have similar maximal oxygen uptakes to healthy Andeans. Therefore, this study aimed to explore potential adaptations in convective oxygen transport, with a specific focus on sympathetically mediated vasoconstriction of nonactive skeletal muscle. In Andeans with (CMS+, n = 7) and without (CMS-, n = 9) CMS, we measured components of convective oxygen delivery, hemodynamic (arterial blood pressure via intra-arterial catheter), and autonomic responses [muscle sympathetic nerve activity (MSNA)] at rest and during steady-state submaximal cycling exercise [30% and 60% peak power output (PPO) for 5 min each]. Cycling caused similar increases in heart rate, cardiac output, and oxygen delivery at both workloads between both Andean groups. However, at 60% PPO, CMS+ had a blunted reduction in Δtotal peripheral resistance (CMS-, -10.7 ± 3.8 vs. CMS+, -4.9 ± 4.1 mmHg·L-1·min-1; P = 0.012; d = 1.5) that coincided with a greater Δforearm vasoconstriction (CMS-, -0.2 ± 0.6 vs. CMS+, 1.5 ± 1.3 mmHg·mL-1·min-1; P = 0.008; d = 1.7) and a rise in Δdiastolic blood pressure (CMS-, 14.2 ± 7.2 vs. CMS+, 21.6 ± 4.2 mmHg; P = 0.023; d = 1.2) compared with CMS-. Interestingly, although MSNA burst frequency did not change at 30% or 60% of PPO in either group, at 60% Δburst incidence was attenuated in CMS+ (P = 0.028; d = 1.4). These findings indicate that in Andeans with polycythemia, light intensity exercise elicited similar cardiovascular and autonomic responses compared with CMS-. Furthermore, convective oxygen delivery is maintained during moderate-intensity exercise despite higher peripheral resistance. In addition, the elevated peripheral resistance during exercise was not mediated by greater sympathetic neural outflow, thus other neural and/or nonneural factors are perhaps involved.NEW & NOTEWORTHY During submaximal exercise, convective oxygen transport is maintained in Andeans suffering from polycythemia. Light intensity exercise elicited similar cardiovascular and autonomic responses compared with healthy Andeans. However, during moderate-intensity exercise, we observed a blunted reduction in total peripheral resistance, which cannot be ascribed to an exaggerated increase in muscle sympathetic nerve activity, indicating possible contributions from other neural and/or nonneural mechanisms.

Acute cardiac autonomic and haemodynamic responses to leg and arm isometric exercise.

Acute cardiovascular responses following a single session of isometric exercise (IE) have been shown to predict chronic adaptations in blood pressure (BP) regulation. It was hypothesised that exercises which recruit more muscle mass induce greater reductions in BP compared to exercises using smaller muscle mass. To test this hypothesis, the current study aimed to compare the acute haemodynamic and autonomic responses to a single session of isometric wall squat (IWS) and isometric handgrip (IHG) training. Twenty-six sedentary participants performed a single IWS and IHG session in a randomised cross-over design, with training composed of 4 × 2-min contractions, with 2-min rest, at 95 HRpeak and 30% MVC respectively. Haemodynamic and cardiac autonomic variables were recorded pre, during, immediately post, and 1-h post-exercise, with the change from baseline for each variable used for comparative analysis. During IWS exercise, there was a significantly greater increase in systolic BP (P < 0.001), diastolic BP (P < 0.001), mean BP (P < 0.001), heart rate (P < 0.001), and cardiac output (P < 0.001), and a contrasting decrease in baroreflex effectiveness index (BEI) and cardiac baroreceptor sensitivity (cBRS). In the 10-min recovery period following IWS exercise, there was a significantly greater reduction in systolic BP (P = 0.005), diastolic BP (P = 0.006), mean BP (P = 0.003), total peripheral resistance (TPR) (P < 0.001), BEI (P = 0.003), and power spectral density (PSD-RRI) (P < 0.001). There were no differences in any variables between conditions 1-h post exercise. Isometric wall squat exercise involving larger muscle mass is associated with a significantly greater post-exercise hypotensive response during a 10-min recovery window compared to smaller muscle mass IHG exercise. The significantly greater reduction in TPR may be an important mechanism for the differences in BP response.

Cardiac autonomic reactivity to acute ingestion of glucose and fructose in healthy subjects

Context: Excess intake of fructose in the form of soft drinks and corn syrup is increasing and considered as an interest of community health. The effects on the cardiovascular system due to acute intake of these sugars have not well-studied in humans. Animal studies show a clear relation between ingestion of simple sugar and pathogenesis of hypertension and metabolic disorders. Ingestion of glucose increases cardiac output (CO) without change in blood pressure (BP) and reduces total peripheral resistance (TPR). Fructose increases heart rate (HR), BP, and CO without reduction in TPR. Aims: This study aimed to evaluate the cardiac autonomic reactivity by HR variability (HRV) of basal and after ingestion of water, glucose, and fructose. Settings and Design: Randomized crossover study. Subjects and Methods: The study included 30 healthy both-gender subjects of age 18–24 years. In three separate sessions, HRV responses to one of the three test drinks were measured. (1) plain water, (2) 60 g glucose, and (3) 60 g fructose. Each drink is made up of 500 ml solution by addition of water. Statistical Analysis Used: Analysis was performed by two-way ANOVA. Results: Fructose ingestion showed decreased RR interval (RRI) (696.8 ± 102.7), increased Low frequency power (LF)/High frequency power (HF) (0.94 ± 0.2) compared to glucose (RRI: 747.0 ± 75.1, LF/HF: 0.89 ± 0.3) and water (RRI: 877.1 ± 107.0, LF/HF: 0.84 ± 0.1). Conclusions: Acute consumption of these simple sugars may result in different cardiac autonomic responses, fructose stimulating decreased vagal response.

Left ventricular mechanical, cardiac autonomic and metabolic responses to a single session of high intensity interval training.

High-intensity interval training (HIIT) produces significant health benefits. However, the acute physiological responses to HIIT are poorly understood. Therefore, we aimed to measure the acute cardiac autonomic, haemodynamic, metabolic and left ventricular mechanical responses to a single HIIT session. Fifty young, healthy participants completed a single HIIT session, comprising of three 30-s maximal exercise intervals on a cycle ergometer, interspersed with 2-min active recovery. Cardiac autonomics, haemodynamics and metabolic variables were measured pre-, during and post-HIIT. Conventional and speckle tracking echocardiography was used to record standard and tissue Doppler measures of left ventricular (LV) structure, function and mechanics pre- and post-HIIT. Following a single HIIT session, there was significant post-exercise systolic hypotension (126 ± 13 to 111 ± 10mmHg, p < 0.05), parallel to a significant reduction in total peripheral resistance (1640 ± 365 to 639 ± 177dyne⋅s⋅cm5, p < 0.001) and significant increases in baroreceptor reflex sensitivity and baroreceptor effectiveness index (9.2 ± 11 to 24.8 ± 16.7ms⋅mmHg-1 and 41.8 ± 28 to 68.8 ± 16.2, respectively) during recovery compared to baseline. There was also a significant increase in the low- to high-frequency heart rate variability ratio in recovery (0.7 ± 0.48 to 1.7 ± 1, p < 0.001) and significant improvements in left ventricular global longitudinal strain (- 18.3 ± 1.2% to - 29.2 ± 2.3%, p < 0.001), and myocardial twist mechanics (1.27 ± 0.72 to 1.98 ± 0.72°·cm-1, p = 0.028) post-HIIT compared to baseline. A single HIIT session is associated with acute improvements in autonomic modulation, haemodynamic cardiovascular control and left ventricular function, structure and mechanics. The acute responses to HIIT provide crucial mechanistic information, which may have significant acute and chronic clinical implications.

Pulsatile load and wasted pressure effort are reduced following an acute bout of aerobic exercise.

Following aerobic exercise, sustained vasodilation and concomitant reductions in total peripheral resistance (TPR) result in a reduction in blood pressure that is maintained for two or more hours. However, the time course for postexercise changes in reflected wave amplitude and other indices of pulsatile load on the left ventricle have not been thoroughly described. Therefore, we tested the hypothesis that reflected wave amplitude is reduced beyond an hour after cycling at 60% V̇o2peak for 60 min. Aortic pressure waveforms were derived in 14 healthy adults (7 men, 7 women; 26 ± 3 yr) from radial pulse waves acquired via high-fidelity applanation tonometry at baseline and every 20 min for 120 min postexercise. Concurrently, left ventricle outflow velocities were acquired via Doppler echocardiography and pressure-flow analyses were performed. Aortic characteristic impedance (Zc), forward (Pf) and backward (Pb) pulse wave amplitude, reflected wave travel time (RWTT), and wasted pressure effort (WPE) were derived. Reductions in aortic blood pressure, Zc, Pf, and Pb were all sustained postexercise whereas increases in RWTT emerged from 60 to 100 min post exercise (all P < 0.05). WPE was reduced by ∼40% from 40 to 100 min post exercise (all P < 0.02). Stepwise multiple regression analysis revealed that the peak ΔWPE was associated with ΔRWTT (β = -0.57, P = 0.003) and ΔPb (β = 0.52, P = 0.006), but not Δcardiac output, ΔTPR, ΔZc, or ΔPf. These results suggest that changes in pulsatile hemodynamics are sustained for ≥100 min following moderate intensity aerobic exercise. Moreover, decreased and delayed reflected pressure waves are associated with decreased left ventricular wasted effort after exercise.NEW & NOTEWORTHY We demonstrate that pulsatile load on the left ventricle is diminished following 60 min of moderate intensity aerobic exercise. During recovery from exercise, the amplitude of the forward and backward traveling pressure waves are attenuated and the arrival of reflected waves is delayed. Thus, the work imposed upon the left ventricle by reflected pressure waves, wasted pressure effort, is decreased after exercise.

Pathophysiology of streptokinase-induced hypotension in acute myocardial infarction: a systematic review of clinical evidence.

IntroductionDespite the common occurrence of streptokinase-induced hypotension among patients with acute myocardial infarction, the underlying pathophysiology remains obscure and poorly understood. Our study aimed to pool clinical evidence on the potential mechanism of streptokinase-induced hypotension through a systematic review of the literature.Material and methodsWe conducted literature search from Medline, Scopus and Web of Science on clinical studies related to streptokinase-induced hypotension.ResultsOur search yielded 972 citations. After removal of duplicates, 878 articles were screened for eligibility, of which 856 papers were excluded due to various reasons. Of the remaining 22 articles retrieved with full texts, eight relevant articles were selected for final analysis. Three themes emerged as the proposed mechanisms of streptokinase-induced hypotension, including (i) reduction in total peripheral resistance, (ii) complement activation, and (iii) dismissal of hypotheses involving other intermediaries.ConclusionsOur findings suggest that the underlying mechanism of streptokinase-induced hypotension lies primarily in the reduction in total peripheral resistance.

Vascular effects of aqueous Crocus sativus petals’ extract in the hypertensive rats

Background and Aim: Crocus sativus (C. sativus) petals attenuates smooth muscle tension and blood pressure in control animals. However the antihypertensive effect and its mechanisms haven’t been recognized. This study investigates the antihypertensive effects of C. sativus petals’ aqueous extract in hypertensive rats and also responses of the rat isolated perfused mesenteric bed. Materials and Methods: The interventional experimental study was performed on 20 male rats (divided to 5 and 15 rats for in vivo and in vitro studies respectively). Hypertension was induced by DOCA-salt injection (20 mg/kg, twice weekly, for 5 weeks, S.C) and water was replaced by NaCl (1%). Five weeks later, animals were anaesthetized with sodium thiopental (30 mg intraperitoneal). Then systemic arterial blood pressure was measured by cannulation of carotid artery following administration of different doses of aqueous extract of C. sativus. Isolated mesenteric beds precontracted with KCl (40 mM), and the tension was measured in presence of different concentrations of the aqueous extract. Finally, various doses of C. sativus extract were applied after incubation by L-NAME or indomethacin. The mesentry was perfused with pump and the recordings were done by physiograph. Results: Mean arterial blood pressure in hypertensive rats was 231±6 mmHg. Administration of aqueous extracts of C. sativus reduced the blood pressure in a dose–dependent manner. In mesenteric beds preparation, addition of C. sativus reduced the contractile effects of KCl. Incubation with L-NAME but not indomethacin abolished hypotension effect of the extract. Conclusion: It was proposed that the antihypertensive effects of C. sativus petals’ extract are through the reduction in total peripheral resistance following nitric oxide production.

Safety, hemodynamic effects, and detection of acute xenon inhalation: rationale for banning xenon from sport.

This study aimed to quantify the sedative effects, detection rates, and cardiovascular responses to xenon. On 3 occasions, participants breathed xenon (FiXe 30% for 20 min; FiXe 50% for 5 min; FiXe 70% for 2 min) in a nonblinded design. Sedation was monitored by a board-certified anesthesiologist. During 70% xenon, participants were also verbally instructed to operate a manual value with time-to-task failure being recorded. Beat-by-beat hemodynamics were measured continuously by ECG, photoplethysmography, and transcranial Doppler. Over 48 h postadministration, xenon was measured in blood and urine by gas chromatography-mass spectrometry. Xenon caused variable levels of sedation and restlessness. Task failure of the self-operating value occurred at 60-90 s in most individuals. Over the first minute, 50% and 70% xenon caused a substantial reduction in total peripheral resistance (P < 0.05). All dosages caused an increase in cardiac output (P < 0.05). By the end of xenon inhalation, slight hypertension was observed after all three doses (P < 0.05), with an increase in middle cerebral artery velocity (P < 0.05). Xenon was consistently detected, albeit in trace amounts, up to 3 h after all three doses of xenon inhalation in blood and urine with variable results thereafter. Xenon inhalation caused sedation incompatible with self-operation of a breathing apparatus, thus causing a potential life-threatening condition in the absence of an anesthesiologist. Yet, xenon can only be reliably detected in blood and urine up to 3 h postacute dosing.NEW & NOTEWORTHY Breathing xenon in dosages conceivable for doping purposes (FiXe 30% for 20 min; FiXe 50% for 5 min; FiXe 70% for 2 min) causes an initial rapid fall in total peripheral resistance with tachycardia and thereafter a mild hypertension with elevated middle cerebral artery velocity. These dose duration intervals cause sedation that is incompatible with operating a breathing apparatus and can only be detected in blood and urine samples with a high probability for up to ~3 h.

Circulatory responses at the onset of handgrip exercise in patients with Parkinson's disease.

What is the central question of this study? The initial circulatory response to isometric exercise in young healthy subjects is thought to be cholinergically mediated. Do patients with Parkinson's disease, a specific population known to present cholinergic dysfunction, present impairment in these initial circulatory responses? What is the main finding and its importance? The initial reduction in total peripheral resistance was absent in patients with Parkinson's disease and in older subjects, which augmented the pressor response at the onset of isometric handgrip exercise. Given that cholinergic mechanisms play an important role in the circulatory responses at the onset of isometric exercise in humans, our data suggest that cholinergic mechanisms might be compromised with ageing. Physical exercise has been used as coping strategy for Parkinson's disease (PD). Thus, a better understanding of circulatory responses to exercise in this population is warranted. During the onset of isometric handgrip (IHG) exercise there is an increase in blood pressure (BP) and a reduction in the total peripheral resistance (TPR) in young subjects. This immediate reduction of TPR is thought to be mediated by a cholinergic mechanism. Given that PD also affects cholinergic neurons, we hypothesized that patients with PD would present blunted circulatory responses at the onset of IHG exercise. Mean BP, stroke volume, heart rate, cardiac output and TPR were measured during performance of 20s of IHG at 40% maximal voluntary contraction in 12 patients with PD (66±2years old, 171±7cm, 74±7kg), 11 older subjects (65±9years old, 171±7cm, 74±10kg) and 10 young subjects (21±1years old, 178±6cm, 79±9kg). Isometric handgrip elicited an augmented BP increase in patients with PD and older subjects at 10 and 20s compared with young subjects. However, the BP augmentation was lower at 20s in patients with PD. The IHG-induced reduction in TPR was attenuated in patients with PD and older subjects compared with young subjects. Our results show that the circulatory responses at the onset of IHG are impaired in patients with PD and older subjects. Overall, these findings suggest that the cholinergic mechanism might be compromised with ageing.

Haemodynamic changes during prone positioning in anaesthetised chronic cervical myelopathy patients.

Background and Aims:Anaesthetised patients, when positioned prone, experience hypotension and reduction in cardiac output. Associated autonomic dysfunction in cervical myelopathy patients predisposes them to haemodynamic changes. The combined effect of prone positioning and autonomic dysfunction in anaesthetised patients remains unknown.Methods:Thirty adult chronic cervical myelopathy patients, aged 18-65 years with Nurick grade ≥2 were recruited in this prospective observational study. Heart rate, mean blood pressure, cardiac output, stroke volume, total peripheral resistance and stroke volume variation were measured using NICOM® monitor. Data were collected in supine before anaesthetic induction (baseline), 2 minutes after induction, 2 minutes after intubation, before and after prone positioning and every 5 minutes thereafter until skin incision. Repeated measures analysis of variance (ANOVA) was used to analyse the haemodynamic parameters across the time points. Bivariate Spearman's correlation was used to find factors associated with blood pressure changes. A P value <0.05 was kept significant.Results:Cardiac output during the entire study period remained stable (P = 0.186). Sixty percent of the patients experienced hypotension. At 15 and 20 minutes after prone positioning, mean blood pressure decreased (P = 0.001), stroke volume increased (P = 0.001), and heart rate and total peripheral resistance decreased (P < 0.001, P = 0.001, respectively). These changes were significant when compared to pre-prone position values. Number of levels of spinal cord compression positively correlated with the incidence of hypotension.Conclusion:Cervical myelopathy patients experienced hypotension with preserved cardiac output in prone position due to a reduction in total peripheral resistance. Hypotension correlated with the number of levels of spinal cord compression.

Continuous Cardiac Autonomic and Hemodynamic Responses to Isometric Exercise.

Elevated arterial blood pressure (BP) is associated with autonomic dysfunction and impaired hemodynamic control mechanisms. Isometric exercise (IE) training has been demonstrated effective at reducing BP; however, the continuous cardiovascular responses during IE are underinvestigated. We hypothesized that reflex autonomic cardiovascular control is an important mediator in reducing BP. To test our hypothesis, we investigated continuous cardiac autonomic modulation and baroreceptor reflex sensitivity (BRS) in response to IE. Twenty-five prehypertensive participants performed a single IE wall squat training session. Total power spectral density (PSD) of HR variability (HRV) and associated low-frequency (LF) and high-frequency (HF) power spectral components were recorded in absolute (ms) and normalized units (nu) before, during, and after an IE session. HR was recorded via electrocardiography and BRS via the sequence method. Continuous BP was recorded via the vascular unloading technique and stroke volume via impedance cardiography. Total peripheral resistance was calculated according to Ohm's law. During IE, there were significant reductions in HRV (P < 0.05) and BRS (P < 0.05) and significant increases in HR (P < 0.001), systolic, diastolic, and mean BP (all P < 0.001). In recovery from IE, HRV (P < 0.001), HFnu (P < 0.001), and BRS (P < 0.001) significantly increased with a significant decrease in LFnu (P < 0.001) and LF:HF ratio (P < 0.001), indicative of predominant parasympathetic over sympathetic activity. This autonomic response was associated with a significant reduction in systolic (23.2 ± 18.1 mm Hg, P < 0.001), diastolic (18.7 ± 16.9 mm Hg, P < 0.001), and mean (15.8 ± 15.5 mm Hg, P < 0.001) BP, below baseline and a significant reduction in total peripheral resistance (P < 0.001). A single IE session is associated with improved cardiac autonomic modulation and hemodynamic cardiovascular control in prehypertensive males. These acute responses may be mechanistically linked to the chronic reductions in resting BP reported after IE training interventions.

Safety, Detection and Hemodynamic Effects of Acute Xenon Inhalation

PURPOSE: Xenon is an inhalation anesthetic, which has the potential to increase plasma erythropoietin, red cell mass and thus endurance performance. This study aimed to describe the sedative effects, detection rates and cardiovascular responses of an open circuit breathing system to deliver increasing concentrations of Xenon. METHODS: On three occasions, participants breathed increasing concentrations of xenon (Xenon, 30% for 20 min; Xenon, 50% for 5 min; Xenon, 70% for 2 min and oxygen, 21% with balance Nitrogen) in a non-blinded design. Xenon inhalation has been completed in 6 (30%), 5 (50%) and 4 (70%) subjects to date. The level of sedation was monitored by a board certified anesthesiologist (Richmond Agitation and Sedation Scale (RASS). Over 48 hours post administration, Xenon was measured in blood and urine by gas chromatography-mass spectrometry. All reported beat-by-beat hemodynamics were measured continuously by photoplethysmography (Nexfin; BMEYE, Netherlands) for 10 minutes prior to and throughout xenon administration. RESULTS: Xenon caused variable levels of sedation and restlessness between subjects (e.g. 50% xenon RAAS, -2, briefly awakens to voice to +2 frequent nonpurposeful movements), with the greatness symptoms occurring at 50 and 70%. Xenon was detected, albeit in trace amounts, up to 6 hours post xenon inhalation in blood (e.g. 30% 6 hours post, 2.2±2.7 nmol/mL) and urine (e.g. 30% 1.5±0.82 nmol/mL) in all subjects. Over the first minute, xenon cause a substantial reduction in total peripheral resistance ([INCREMENT]2.7±0.49,mmHg·L·min), which caused a reflex increase in cardiac output ([INCREMENT]2.7±0.54, L·min). By the end of xenon inhalation, hypertension was observed after all three dosages (MAP: 30%, [INCREMENT]7±11; 50% [INCREMENT]12±2; 70%, [INCREMENT]19±5 mmHg). CONCLUSIONS: We show that three different conceivable dosages of xenon inhalation cause a level of sedation incompatible with self-operation of breathing apparatus and a persistent hypertensive state. Dispute begin acute (<5 mins), high dosages (50 and 70%) of xenon caused near anesthesia and thus could present a life threatening condition in the absence of an anesthesiologist. Xenon can be reliability detected in blood and urine up to 6 hours post dosing. These studies were supported in part by funding from the Partnership for Clean Competition Research Collaborative.

Cardiac hemodynamics before, during and after elective cesarean section under spinal anesthesia in low-risk women

The aim of this study was to describe maternal central hemodynamic parameters before and during delivery as well at the early puerperium in healthy women undergoing elective cesarean section (CS) at term. The noninvasive Cardiac System (NICaS, NI Medical, Petah-Tikva, Israel) is a regional impedance device that measures cardiac output (CO) and its derivatives with a good correlation with the gold standard Swan-Ganz catheter. We performed a prospective longitudinal study of healthy women with a singleton pregnancy at term. Maternal hemodynamic parameters were assessed by the NICaS at six time points: a few minutes before undergoing an elective CS, immediately after receiving spinal anesthesia, immediately after delivery of the fetus and placenta, after abdominal fascia closure, and within 24 to 36 and 48 to 72 h postpartum. Sixty-one consenting women were recruited during the study period (January 2015 to June 2015). Baseline (pre-CS) mean arterial pressure (MAP) was 87.7±7.9 mm Hg, baseline CO was 7.5±1.7 l per min and baseline total peripheral resistance (TPR) was 994±301 dyne × s per cm5. After spinal anesthesia CO significantly increased by 13%, no significant changes were observed in MAP or TPR. Immediately after delivery, a nadir for all parameters was reached: MAP and TPR were significantly reduced by 8% and 26%, respectively (comparing to pre-CS), and CO further increased by 9% (24% comparing to pre-CS). After fascia closure, partial recoveries of all parameters were observed. Twenty-four to thirty-six hours postpartum MAP returned to pre-CS values, while CO and TPR reached -9% and +11% comparing to baseline, respectively. None of the parameters differed significantly between 24 to 36 and 48 to 72 h postpartum. Significant hemodynamic changes (reduction of TPR and increase of CO) take place at the time of delivery of fetus and placenta. Knowledge of normal hemodynamic values using a reliable noninvasive technique during various stages of pregnancy and the postpartum period is feasible, and might assist clinicians in assessing the level of patient deviation from expected cardiac performance, especially in high-risk women.

Cardiovascular responses to sugary drinks in humans: galactose presents milder cardiac effects than glucose or fructose.

There is increasing interest into the potentially beneficial effects of galactose for obesity and type 2 diabetes management as it is a low-glycemic sugar reported to increase satiety and fat mobilization. However, fructose is also a low-glycemic sugar but with greater blood pressure elevation effects than after glucose ingestion. Therefore, we investigated here the extent to which the ingestion of galactose, compared to glucose and fructose, impacts upon haemodynamics and blood pressure. In a randomized cross-over study design, 9 overnight-fasted young men attended 3 separate morning sessions during which continuous cardiovascular monitoring was performed at rest for at least 30min before and 120min after ingestion of 500mL of water containing 60g of either glucose, fructose or galactose. These measurements included beat-to-beat systolic and diastolic blood pressure, heart rate deduced by electrocardiography, and stroke volume derived by impedance cardiography; these measurements were used to calculate cardiac output and total peripheral resistance. Ingestion of galactose, like glucose, led to significantly lesser increases in systolic, diastolic and mean blood pressure than fructose ingestion (p<0.05). Furthermore, the increase in cardiac output and reduction in total peripheral resistance observed after ingestion of glucose were markedly lower after galactose ingestion (p<0.01). Galactose thus presents the interesting characteristics of a low-glycemic sugar with mild cardiovascular effects. Further studies are warranted to confirm the clinical relevance of the milder cardiovascular effects of galactose than other sugars for insulin resistant obese and/or diabetic patients with cardiac insufficiency.