Cardiovascular Autonomic Responses Research Articles

Low-dose fentanyl reduces pain perception, muscle sympathetic nerve activity responses, and blood pressure responses during the cold pressor test.

Our knowledge about how low-dose (analgesic) fentanyl affects autonomic cardiovascular regulation is primarily limited to animal experiments. Notably, it is unknown if low-dose fentanyl influences human autonomic cardiovascular responses during painful stimuli in humans. Therefore, we tested the hypothesis that low-dose fentanyl reduces perceived pain and subsequent sympathetic and cardiovascular responses in humans during an experimental noxious stimulus. Twenty-three adults (10 females/13 males; 27 ± 7 yr; 26 ± 3 kg·m-2, means ± SD) completed this randomized, crossover, placebo-controlled trial during two laboratory visits. During each visit, participants completed a cold pressor test (CPT; hand in ∼0.4°C ice bath for 2 min) before and 5 min after drug/placebo administration (75 μg fentanyl or saline). We compared pain perception (100-mm visual analog scale), muscle sympathetic nerve activity (MSNA; microneurography, 11 paired recordings), and beat-to-beat blood pressure (BP; photoplethysmography) between trials (at both pre- and postdrug/placebo timepoints) using paired, two-tailed t tests. Before drug/placebo administration, perceived pain (P = 0.8287), ΔMSNA burst frequency (P = 0.7587), and Δmean BP (P = 0.8649) during the CPT were not different between trials. After the drug/placebo administration, fentanyl attenuated perceived pain (36 vs. 66 mm, P < 0.0001), ΔMSNA burst frequency (9 vs. 17 bursts/min, P = 0.0054), and Δmean BP (7 vs. 13 mmHg, P = 0.0174) during the CPT compared with placebo. Fentanyl-induced reductions in pain perception and Δmean BP were moderately related (r = 0.40, P = 0.0641). These data provide valuable information regarding how low-dose fentanyl reduces autonomic cardiovascular responses during an experimental painful stimulus.

Cardiovascular autonomic responses during head-up tilt test in newly diagnosed type 2 diabetes.

Autonomic dysfunction is commonly observed in patients with long-standing type 2 diabetes. Previous studies have confirmed the value of both subjectively assessed symptoms and objective measurements of autonomic nervous system function in diagnosing cardiovascular autonomic neuropathy. However, the head-up tilt test (HUTT) has been rarely used to investigate cardiovascular autonomic responses in subjects with high risk ofnewly diagnosed type 2 diabetes (nT2D). To evaluate autonomic cardiovascular responses through passive orthostatic challenge along the diabetes continuum. The study population was stratified as normoglycemic (n = 16), prediabetes (n = 20), and nT2D (n = 20). The prevalence of orthostatic intolerance and autonomic cardiovascular responses was evaluated with the Task Force Monitor during a 30-min passive HUTT. Spectral indices of heart rate and blood pressure variability and baroreceptor effectiveness index (BEI) were calculated through the HUTT. BEI was obtained by the sequence method. There were no differences in the prevalence of orthostatic intolerance or in the indices of heart rate and blood pressure variability among the three groups of study. The BEI was attenuated in the nT2D group in supine rest and throughout HUTT compared with normoglycemic and prediabetes groups. The multivariable linear regression analysis showed that BEI was associated with fasting glucose (β = - 0.52, p <0.001) and HbA1c (β = - 0.57, p <0.001) independently of cardiovascular risk factors. Cardiovascular autonomic neuropathy, expressed as blunted BEI, is the only abnormal autonomic nervous test detected in nT2D, and it was independently associated with fasting glucose and HbA1c values.

A Wearable System for Heart Rate Recovery Evaluation with Real-Time Classification on Exercise Condition.

Heart rate recovery (HRR) is a convenient index to assess a cardiovascular autonomic function response to physical exercise. HRR monitoring during daily exercise can be an effective way to verify cardiorespiratory performance. Because HRR varies depending on exercise intensity and resting condition, an exercise condition needs to be acquired for a reliable HRR analysis. This study presents a wearable system for HRR evaluation with automatic labeling of exercise conditions using real-time activity classification. We developed an activity classification algorithm using two features from accelerometer sensor: an acceleration peak and an angle tilt peak. The classification algorithm was applied to a chest-attached wearable device with an embedded electrocardiogram sensor and accelerometer sensors. We classified daily activities such as running, walking, and postural transitions performed under supervised conditions. The wearable device system accurately detected activities with a sensitivity of 99.2 % and posture transitions with a sensitivity of 92 % and specificity of 93.3 % for seven healthy subjects. The proposed wearable system can help monitor HRR during exercise training by labeling the exercise condition simultaneously.

Association of Particulate Matter from Cooking Oil Fumes with Heart Rate Variability and Oxidative Stress.

Many studies have reported various cardiovascular autonomic responses to ambient particulate matter (PM) pollution, but few have reported such responses to occupational PM exposures. Even fewer have demonstrated a relationship between PM pollution and oxidative stress in humans. This panel study evaluates the association between occupational exposure to PM in cooking oil fumes (COFs), and changes in both heart rate variability (HRV) and oxidative stress responses in 54 male Chinese cooks. Linear mixed-effects regression models were adopted to estimate the strength of the association between PM and HRV. Participants’ pre- and post-workshift urine samples were analyzed for 8-hydroxy-2′-deoxyguanosine (8-OHdG) and malondialdehyde (MDA). Exposure to PM in COFs from 15 min to 2 h were associated with a decrease in HRV and an increase in heart rate among cooks. The urinary 8-OHdG levels of cooks were significantly elevated after workshift exposure to COFs. The levels of PM2.5, PM1.0, and particulate benzo(a)pyrene in COFs were all positively correlated with cross-workshift urinary 8-OHdG levels. Furthermore, the levels of benzo(a)pyrene in COFs were positively correlated with cross-workshift urinary MDA levels. The effects of COFs on HRV were independent of cross-workshift urinary 8-OHdG levels. Exposure to COFs leads to disturbed autonomic function and an increased risk of oxidative DNA injury among cooks in Chinese restaurants.

Controlled breathing and pain: Respiratory rate and inspiratory loading modulate cardiovascular autonomic responses, but not pain.

Slow, deep breathing (SDB) is a common pain self-management technique. Stimulation of the arterial baroreceptors and vagal modulation are suggested, among others, as potential mechanisms underlying the hypoalgesic effects of SDB. We tested whether adding an inspiratory load to SDB, which results in a stronger baroreceptor stimulation and vagal modulation, enhances its hypoalgesic effects. Healthy volunteers performed SDB (controlled at 0.1Hz) with and without an inspiratory threshold load. Controlled breathing (CB) at a normal frequency (0.23Hz) was used as an active control. Each condition lasted 90s, included an electrical pain stimulation on the hand, and was repeated four times in a randomized order. Pain intensity, self-reported emotional responses (arousal, valence, dominance), and cardiovascular parameters (including vagally-mediated heart rate variability) were measured per trial. A cover story was used to limit the potential effect of outcome expectancy. Pain intensity was slightly lower during SDB with load compared with normal-frequency CB, but the effect was negligible (Cohens d<0.2), and there was no other difference in pain intensity between the conditions. Heart rate variability was higher during SDB with/without load compared with normal-frequency CB. Using load during SDB was associated with higher heart rate variability, but less favorable emotional responses. These findings do not support the role of baroreceptor stimulation or vagal modulation in the hypoalgesic effects of SDB. Other mechanisms, such as attentional modulation, warrant further investigation.

Lateral Habenula Regulates Cardiovascular Autonomic Responses via the Serotonergic System in Rats.

The lateral habenula (LHb) plays essential roles in behavioral responses to stressful events. Stress is tightly linked to autonomic responses such as cardiovascular responses, yet how the LHb regulates these responses is not well understood. To address this issue, we electrically stimulated the LHb in rats, measured its effects on heart rate (HR) and mean arterial pressure (MAP), and investigated the neural circuits that mediate these LHb-induced cardiovascular responses via the autonomic nervous system. We observed that stimulation of the LHb induced bradycardia and pressor responses, whereas stimulation of the adjacent areas changed neither the HR nor the MAP. Bilateral vagotomy and administration of a muscarinic receptor antagonist suppressed the LHb stimulation effect on the HR but not on the MAP, whereas administration of a β-adrenoceptor antagonist partly attenuated the effect on the MAP but not on the HR. Thus, the LHb-induced cardiovascular responses of the HR and the MAP were likely caused by activations of the cardiac parasympathetic nerves and the cardiovascular sympathetic nerves, respectively. Furthermore, administration of a non-selective 5-HT receptor antagonist significantly attenuated the LHb stimulation effects on both the MAP and the HR. A 5-HT2 receptor antagonist also attenuated the LHb stimulation effects. A low dose of a 5-HT1A receptor antagonist enhanced the LHb stimulation effects, but a high dose of the drug attenuated them. 5-HT1B and 5-HT1D receptor antagonists as well as a 5-HT7 receptor antagonist did not affect the LHb stimulation effects. Taken together, our findings suggest that the LHb regulates autonomic cardiovascular responses at least partly through the serotonergic system, particularly via the 5-HT1A and 5-HT2 receptors.

Response of the Cardiac Autonomic Control to Exposure to Nanoparticles and Noise: A Cross-Sectional Study of Airport Ground Staff.

Airport activity causes the emission of particulate matter and noise, two environmental contaminants and potential health hazards, particularly for the personnel operating nearby taxiways. We explored the association between exposure to fine/ultrafine particles (UFPs) and noise with heart rate variability (HRV), an early indicator of cardiovascular autonomic response, among a sample of airport ground staff. Between May and June 2018, thirty-four male operators (mean age = 43 years and SD = 6.7) underwent personal monitoring of exposure to nanoparticles and noise, and HRV during their work activity. We conducted univariate and multivariate analysis to test the effect of UFP and noise exposure HRV. Total Lung Deposition Surface Area (LDSA) was significantly associated with a decrease in HRV Total Power and Triangular index (β = −0.038 p = 0.016 and β = −7.8 × 10−5, p = 0.042, respectively). Noise peak level showed an opposite effect, which was significant for Total Power (β = 153.03, p = 0.027), and for Triangular index (β = 0.362, p = 0.035). Further investigation is warranted to clarify the effect of the concurrent exposure to UFPs and noise on early changes of cardiac autonomic regulation.

Autonomic cardiovascular response during and after a graded exercise test in concussed athletes and healthy controls

Objective Dysfunction of the autonomic cardiovascular system after a concussion is known to cause exercise intolerance due to symptoms exacerbation. The aim of this study was to compare athletes with symptoms of a sport-related concussion and healthy controls with regard to their heart rate during a graded exercise test and their heart rate recovery during the 5 min cool-down after the graded exercise test. Methods Sport-related concussion patients ( N = 61; 31% female) and controls ( N = 16; 50% female) participated in a graded exercise test on a cycle ergometer followed by 5 min active cool-down. Based on the results of graded exercise tests they were divided into four groups: (1) patients who reached the symptom threshold and had to stop the graded exercise test (symptom threshold; N = 39; 33.3% female), (2) patients with symptoms who finished the graded exercise test (S; N = 16; 25% female), (3) patients without symptoms (NS; N = 6; 33.3% female), (4) controls ( N = 16; 50% female). Main outcome measures Heart rate, severity of headache and dizziness during graded exercise test, heart rate recovery (median (heart rate recoveries/maximal heart rate) ± median absolute deviation (MAD)) 30, 60 and 300 s after the start of cool-down. Results Heart rate recovery at 30 s was significantly slower in symptom (0.95 ± 0.01) compared to all other groups ( p &lt; 0.002; symptom threshold: 0.92 ± 0.02, NS: 0.91 ± 0.02, controls: 0.93 ± 0.02). Heart rate recovery at 60 s was significantly slower in symptom (0.90 ± 0.02) compared to the symptom threshold and controls ( p &lt; 0.041; 0.86 ± 0.03, 0.85 ± 0.04). Heart rate recovery at 300 s was significantly slower in symptom threshold (0.72 ± 0.05) compared to controls ( p = 0.003; 0.66 ± 0.02). Conclusions Heart rate measurements in athletes with symptoms of sport-related concussion should be continued during cool-down after the graded exercise test, as dysfunction of the autonomic cardiovascular system might manifest also during cool-down.

Preoperative regional scalp block versus intraoperative intravenous fentanyl for attenuating intraoperative surgical stress response to supratentorial craniotomy in adult patients under general anaesthesia

During brain tumour resection a lot of noxious stimuli are released resulting in a significant hemodynamic and stress response, its control is challenging during anaesthesia, and can be evaluated by monitoring blood pressure (BP), heart rate (HR) Attenuating autonomic cardiovascular responses to pain resulting from skull pinning, skin incision, and craniotomy are considered significant benefits of Regional Scalp Block (RSB) in addition to reducing postoperative analgesic requirements. This study aims to evaluate the effect of preoperative regional scalp block (RSB) versus intraoperative intravenous fentanyl for attenuating intraoperative surgical stress response to supratentorial craniotomy in adult patients under general anaesthesia. The study included 30 patients randomly distributed into two equal groups with 15 patients in each, Group A: Preoperative RSB was done after induction of general anaesthesia and before skull pinning, Group C: Control group: patients were given conventional intraoperative analgesia in the form of intravenous fentanyl with no block. This study included patients with Supratentorial brain tumours were admitted to Zagazig University Hospitals. Patients have been gathered over two years duration from march 2018 to march 2020. The results showed that there were highly significant differences between RSB group and control group. Preoperative RSB showed advantages over Standard analgesia in terms of better attenuation of stress response to pain in the form of heart rate and blood pressure intraoperatively, decrease opioid consumption, lower Visual Analogue Score (VAS), Preoperative RSB can be performed easily in a short time with very high success rate allowing better intraoperative control of haemodynamics, less postoperative pain. We recommend using preoperative RSB in supratentorial craniotomy as a gold standard in our hospital to get the advantages mentioned above.

Low dose ketamine reduces pain perception and blood pressure, but not muscle sympathetic nerve activity, responses during a cold pressor test.

Low dose ketamine is a leading medication used to provide analgesia in pre-hospital and hospital settings. Low dose ketamine is increasingly used off-label to treat conditions such as depression. In animals, ketamine stimulates the sympathetic nervous system and increases blood pressure, but these physiological consequences have not been studied in conscious humans. Our data suggest that low dose ketamine administration blunts pain perception and reduces blood pressure, but not muscle sympathetic nerve activity burst frequency, responses during a cold pressor test in healthy humans. These mechanistic, physiological results inform risk-benefit analysis for clinicians administering low dose ketamine in humans. Low dose ketamine is an effective analgesic medication. However, our knowledge of the effects of ketamine on autonomic cardiovascular regulation is primarily limited to animal experiments. Notably, it is unknown if low dose ketamine influences autonomic cardiovascular responses during painful stimuli in humans. We tested the hypothesis that low dose ketamine blunts perceived pain, and blunts subsequent sympathetic and cardiovascular responses during an experimental noxious stimulus. Twenty-two adults (10F/12M; 27±6years; 26±3kgm-2 , mean±SD) completed this randomized, crossover, placebo-controlled trial during two laboratory visits. During each visit, participants completed cold pressor tests (CPT; hand in ∼0.4°C ice bath for 2min) pre- and 5min post-drug administration (20mg ketamine or saline). We compared pain perception (100mm visual analogue scale), muscle sympathetic nerve activity (MSNA; microneurography, 12 paired recordings), and beat-to-beat blood pressure (BP; photoplethysmography) during the pre- and post-drug CPTs separately using paired, two-tailed t tests. For the pre-drug CPT, perceived pain (P = 0.4378), MSNA burst frequency responses (P = 0.7375), and mean BP responses (P = 0.6457) were not different between trials. For the post-drug CPT, ketamine compared to placebo administration attenuated perceived pain (P<0.0001) and mean BP responses (P = 0.0047), but did not attenuate MSNA burst frequency responses (P = 0.3662). Finally, during the post-drug CPT, there was a moderate relation between cardiac output and BP responses after placebo administration (r = 0.53, P = 0.0121), but this relation was effectively absent after ketamine administration (r = -0.12, P = 0.5885). These data suggest that low dose ketamine administration attenuates perceived pain and pressor, but not MSNA burst frequency, responses during a CPT.

The influence of low-intensity resistance training combined with neuromuscular electrical stimulation on autonomic activity in healthy adults: A randomized controlled cross-over trial

Background:Low-intensity resistance training (RT) combined with neuromuscular electrical stimulation (NMES) is one method of exercise to improve the deterioration of physical function. However, it is unclear whether low-intensity RT combined with NMES (RT + NMES) can be safely implemented.Objective:This study aimed to examine the influence of low-intensity RT + NMES on autonomic activity and cardiovascular responses in healthy adults.Methods:This study was an open-label, randomized controlled cross-over trial. The exercise intensity of isometric knee extension RT was set to 40% of the maximum voluntary contraction (peak torque). NMES was adjusted to a biphasic asymmetrical waveform with the frequency maintained at 50 Hz and a phase duration of 300 s. The difference in the change in autonomic activity and cardiovascular responses was compared by assessing heart rate variability, blood pressure, and heart rate during RT and .Results:Twenty healthy male college students (mean age years) participated in this study. The ratio of low- and high-frequency components of heart rate variability, systolic blood pressure, and heart rate increased during exercise in the RT and sessions (0.05). There were no significant differences in autonomic activity and cardiovascular responses throughout the sessions during RT and .Conclusion:In conclusion, our results demonstrated that low-intensity was safe and did not induce excessive autonomic and cardiovascular responses in healthy adults.

Influence of lower body compression garments on cardiovascular autonomic responses prior to, during and following submaximal cycling exercise.

The aim of the current study was to examine the impact of lower body compression garments (CG) on cardiac autonomic control of heart rate (HR) prior to, during and following submaximal exercise. Thirty (15 males, 15 females) healthy, active adults undertook consecutive 10-min stages of supine rest, moderate-intensity upright cycling and supine recovery while wearing either normal clothing (CONTROL) or normal clothing plus CG tights in a randomised order. Heart rate (HR) and rating of perceived exertion (RPE) were assessed every minute while cardiovascular autonomic responses were assessed during the final 5min of each stage via HR variability (HRV). The change in HR at 1-min (HRR1) and 2-min (HRR2) post-exercise and the time constant of HR recovery (HRtau) were assessed as indices of cardiac autonomic reactivation. Differences between variables were assessed via repeated measures ANOVA and corrected pairwise comparisons. Compared to rest, exercise resulted in a reduction of HRV that was similar for CONTROL and CG. A main effect for condition was identified for one non-linear, long-term HRV variable only with a significantly lower value (61.4 ± 47.8 vs. 67.1 ± 50.2ms, p < 0.05) for CG compared to CONTROL. Cardiac autonomic reactivation (HRR1, 42.0 ± 16.8 vs. 45.5 ± 13.4bpm; HRR2, 58.9 ± 10.5 vs. 58.9 ± 8.2bpm; HRtau, 63.4 ± 22.3 vs. 65.1 ± 23.0s, p > 0.05) was comparable for CONTROL and CG. Lower body CG failed to alter most cardiac autonomic responses during rest, moderate-intensity exercise or recovery. Mechanisms for potential ergogenic benefits of CG remain to be characterised.

Heart rate variability in different intensities of static and dynamic exercises graded using similar heart rate

The intensity and the type of the cardiovascular responses differ depending on the exercise type and intensity and the muscle groups involved. However, the responses in static and dynamic exercises are hardly comparable since the protocol used for grading the intensity of these exercises are different. Thus, we compared the cardiovascular autonomic responses in dynamic and static exercises of same muscle groups at increasing intensities graded using similar heart rate. 32 subjects performed dynamic and static exercises of lower limbs at 50% (HR50max) and 60% (HR60max) of their maximum achievable heart rates. Continuous ECG was recorded for 2 min during the exercise. Target heart rate specific single beat R–R intervals were extracted from the recorded ECG, and heart rate variability was determined. A factorial two way analysis of variance was conducted on the influence of two independent variables (load and exercise type) on the heart rate variability during different manoeuvres with baseline values taken as covariates. Exercise load had a main effect on HFnu and RMSSD. HFnu increased (p = 0.001) while RMSSD decreased (p = 0.025) with an increase in the exercise load. Exercise type also had a main effect on RMSSD with RMSSD being higher in dynamic exercise (p = 0.028). With increased load, LFnu decreased in dynamic exercise but was maintained in static exercise. Time domain parameter RMSSD decreases with an increase in the exercise load indicating a decrease in vagal modulation of heart rate with an increase in exercise load. RMSSD is more in dynamic exercise compared with static exercise indicating higher vagal modulation in dynamic exercise. However, increase in HFnu with exercise load may be due to the influence of increased ventilation on heart rate modulation.

Increased blood pressure during the suggested immobilization test in Restless Legs Syndrome.

To investigate the relationship between sensory discomfort/motor component and cardiovascular autonomic response by continuous beat-to-beat blood pressure monitoring (CBPM) during the suggested immobilization test (SIT) in patients with restless legs syndrome (RLS). Thirty-two drug-free patients with primary RLS (10 men; mean age 60.29 ± 10.81 years) and 17 healthy controls (2 men; mean age 58.82 ± 11.86 years) underwent a 1-hour SIT starting at 8 pm with concomitant CBPM to measure the heart rate (HR) and systolic/diastolic blood pressure (SBP, DBP). In all subjects, the presence of sensory discomfort and motor component during the SIT (S-SIT+ and M-SIT+, respectively) was quantified. Mixed regression models were used to compare the SBP, DBP, and HR profiles during the SIT by taking into account the repeated measures (6 time periods of 10 minutes). In patients with S-SIT+ (n = 17), SBP (p < 0.0001), DBP (p = 0.0007), and HR (p = 0.03) increased during the SIT compared with other patients and controls. Seventeen patients had M-SIT+ (none among healthy controls). Classifying patients in 4 groups in function of the presence/absence of the SIT sensory and motor components revealed that SDB and DBP increased throughout the SIT in patients with S-SIT+, independently of the motor component (p < 0.0001 and p = 0.0008 for SBD; p < 0.0001 and p = 0.01 for DBP in the S-SIT+/M-SIT- and S-SIT+/M-SIT+ groups, respectively). During the SIT, BP concomitantly increased only in patients with RLS and sensory discomfort, with or without motor component. This highlights the link between evening sensory RLS symptoms, autonomic activation, and potential long-term cardiovascular consequences.

Cardiovascular autonomic responses in patients with Parkinson disease to pedunculopontine deep brain stimulation.

Dysautonomia can be a debilitating feature of Parkinson disease (PD). Pedunculopontine nucleus (PPN) stimulation may improve gait disorders in PD, and may also result in changes in autonomic performance. To determine whether pedunculopontine nucleus stimulation improves cardiovascular responses to autonomic challenges of postural tilt and Valsalva manoeuver, eight patients with pedunculopontine nucleus deep brain stimulation were recruited to the study; two were excluded for technical reasons during testing. Participants underwent head up tilt and Valsalva manoeuver with stimulation turned ON and OFF. Continuous blood pressure and ECG waveforms were recorded during these tests. In a single patient, local field potential activity was recorded from the implanted electrode during tilt. The fall in systolic blood pressure after tilt was significantly smaller with stimulation ON (mean - 8.3% versus - 17.2%, p = 0.044). Valsalva ratio increased with stimulation from median 1.15 OFF to 1.20 ON (p = 0.028). Baroreflex sensitivity increased during Valsalva compared to rest with stimulation ON versus OFF (p = 0.028). The increase in baroreflex sensitivity correlated significantly with the mean depth of PPN stimulating electrode contacts. This accounted for 89% of its variance (r = 0.943, p = 0.005). PPN stimulation can modulate the cardiovascular system in patients with PD. In this study, it reduced the postural fall in systolic blood pressure during head-up tilt and improved the cardiovascular response during Valsalva, presumably by altering the neural control of baroreflex activation.

Quantifying acute physiological biomarkers of transcutaneous cervical vagal nerve stimulation in the context of psychological stress

BackgroundStress is associated with activation of the sympathetic nervous system, and can lead to lasting alterations in autonomic function and in extreme cases symptoms of posttraumatic stress disorder (PTSD). Vagal nerve stimulation (VNS) is a potentially useful tool as a modulator of autonomic nervous system function, however currently available implantable devices are limited by cost and inconvenience. ObjectiveThe purpose of this study was to assess the effects of transcutaneous cervical VNS (tcVNS) on autonomic responses to stress. MethodsUsing a double-blind approach, we investigated the effects of active or sham tcVNS on peripheral cardiovascular and autonomic responses to stress using wearable sensing devices in 24 healthy human participants with a history of exposure to psychological trauma. Participants were exposed to acute stressors over a three-day period, including personalized scripts of traumatic events, public speech, and mental arithmetic tasks. ResultstcVNS relative to sham applied immediately after traumatic stress resulted in a decrease in sympathetic function and modulated parasympathetic/sympathetic autonomic tone as measured by increased pre-ejection period (PEP) of the heart (a marker of cardiac sympathetic function) of 4.2 ms (95% CI 1.6–6.8 ms, p < 0.01), decreased peripheral sympathetic function as measured by increased photoplethysmogram (PPG) amplitude (decreased vasoconstriction) by 47.9% (1.4–94.5%, p < 0.05), a 9% decrease in respiratory rate (−14.3 to −3.7%, p < 0.01). Similar effects were seen when tcVNS was applied after other stressors and in the absence of a stressor. ConclusionWearable sensing modalities are feasible to use in experiments in human participants, and tcVNS modulates cardiovascular and peripheral autonomic responses to stress.

Role of vasopressin V1 antagonist in the action of vasopressin on the cooling-evoked hemodynamic perturbations of rats

We aimed to investigate the role of arginine vasopressin (AVP) acting via the AVPV1 receptor in the autonomic cardiovascular responses to cold stress (CS). The study was conducted on adult male Sprague-Dawley rats with telemetry transmitters implanted to monitor heart rate (HR) and systolic blood pressure (SBP) throughout the experiment course. Rats were divided into four groups and were given, respectively, saline (control group), AVPV1 antagonist (V1880) alone, and V1880 following the removal of sympathetic outflows using hexamethonium (HEX+V1880) or guanethidine (GUA + V1880). Rats were subjected to the CS stimuli (rapid immersion of the rat's limbs into 4 °C water). Hemodynamic responses were recorded at baseline (PreCS), during CS, and after CS. Data analysis was performed using descriptive methods and spectral and cross-spectral analysis of blood pressure variability (BPV) and heart rate variability (HRV). Key results showed that at PreCS, inhibition of AVPV1 increases SBP and HR as well as very-low-frequency BPV and low-frequency BPV, which is attenuated by hexamethonium (effect on SBP only) and guanethidine (effect on both SBP and HR). HEX+V1880 results in increased high-frequency BPV and attenuated very-low-frequency HRV, while GUA + V1880 results in increased high-frequency HRV and attenuated very-low-frequency HRV. During CS, we observed that SBP and HR, as well as very-low-frequency BPV and low-frequency BPV, were similar in the control group and the group with AVPV1 inhibition, while AVPV1 inhibition results in attenuated high-frequency BPV. Furthermore, we observed that changes produced by AVPV1 inhibition alone were affected differently by HEX+V1880 and GUA + V1880, particularly in low-frequency HRV and very-low-frequency HRV. The results support that AVPV1 mediates autonomic cardiovascular responses at both baseline and CS stimuli conditions are associated with central mechanism engagement.

Ovarian failure induced by 4-vinylcyclohexene diepoxide worsens the autonomic cardiovascular response to chronic unpredictable stress in rats

AimsAfter menopause, women are more responsive to stress and more prone to exhibit hypertension, which elevates the risk of cardiac diseases. This vulnerability is due, in part, to the decline of ovarian steroids plasma levels. The 4-vinylciclohexane diepoxide (VCD) causes a gradual depletion of ovarian follicles causing loss of the normal ovarian function and a hormonal profile comparable to menopause in humans. We aimed to verify whether the ovarian failure (OF) worsens the cardiovascular autonomic response to stress. Main methodsRats were treated with VCD (160 mg/kg) or oil for 15 days, exposed to chronic unpredictable stress (CUS) for 10 days and studied 80 and 180 days after VCD treatment. Key findings80 days after VCD-treatment, stressed rats showed increased sympathetic nerve activity, reduced parasympathetic activity and an increase in the overall spontaneous baroreflex sensitivity (BRS). 180 days after VCD treatment, BRS was impaired and the vascular sympathetic activity was increased, independently of stress exposure. SignificanceNeither 80 nor 180 days after the onset of VCD-treatment the hypertensive effects of stress were enhanced in rats. However, OF led to a worsening on different aspects of the cardiovascular response to stress, which can cause cardiovascular complications when associated with ovarian aging.

Characteristics of cardiovascular responses to an orthostatic challenge in trained spinal cord-injured individuals

BackgroundWe investigated cardiovascular responses to an orthostatic challenge in trained spinal cord-injured (SCI) individuals compared to able-bodied (AB) individuals.MethodsA total of 23 subjects participated, divided into three groups: seven were trained as spinal cord-injured (Tr-SCI) individuals, seven were able-bodied individuals trained as runners (Tr-AB), and nine were untrained able-bodied individuals (UnTr-AB). We measured the cardiovascular autonomic responses in all three groups during each 5-min head-up tilt (HUT) of 0°, 40°, and 80°. Stroke volume (SV), heart rate (HR), and cardiac output (Qc) as cardiovascular responses were measured by impedance cardiography. Changes in deoxyhemoglobin (∆[HHb]) and total hemoglobin (∆[Hbtot]) concentrations of the right medial gastrocnemius muscle were measured using near-infrared spectroscopy (NIRS).ResultsAs the HUT increased from 0° to 80°, Tr-SCI group showed less change in SV at all HUT levels even if HR increased significantly. Mean arterial pressure (MAP) also did not significantly increase as tilting increased from 0° to 80°. Regarding peripheral vascular responses, the alterations of ∆[Hbtot] from 0° to 80° were less in Tr-SCI group compared to AB individuals.ConclusionThere is a specific mechanism whereby blood pressure is maintained during a HUT in Tr-SCI group with the elicitation of peripheral vasoconstriction and the atrophy of the vascular vessels in paraplegic lower limbs, which would be associated with less change in SV in response to an orthostatic challenge.

THUR 120 Postprandial hypotension in MSA and PD with autonomic failure

IntroductionPostprandial hypotension is often reported in Parkinson’s disease with autonomic failure (PD+AF) and Multiple System Atrophy (MSA). However there has been no study directly comparing this feature between these two disorders. The aim of this study was to evaluate cardiovascular autonomic responses before and after standard liquid meal ingestion in PD+AF and MSA.MethodsPatients underwent a liquid meal challenge using a previously described protocol. Blood pressure (BP) and heart rate (HR) were measured at intervals. All participants remained supine for 45 min after the liquid meal ingestion. They underwent 10 min head-up tilt (HUT) to 60° before and 45 min after the meal.Results22 MSA and 11 PD+AF patients were identified. Supine post-prandial hypotension was significantly more common in PD+AF compared to MSA (73% vs 36%; p&lt;0.05). Both groups had orthostatic hypotension during pre-meal tilt, with no significant difference in BP and HR when tilted post-meal between PD+AF and MSA (p&gt;0.05).ConclusionDespite the similar degree of orthostatic hypotension on supine and HUT, postprandial hypotension is more commonly present in patients with PD+AF compared to MSA. The increased tendency to post-prandial hypotension even while supine reflects the nature of post-ganglionic sympathetic denervation in PD.