Altered Autonomic Responses Research Articles

Effects of acute hyperoxia on autonomic function and coronary tone in patients with peripheral artery disease.

Numerous studies have shown that oxidative stress plays an important role in peripheral artery disease (PAD). Prior reports suggested autonomic dysfunction in PAD. We hypothesized that responses of the autonomic nervous system and coronary tone would be impaired in patients with PAD during exposure to acute hyperoxia, an oxidative stressor. In 20 patients with PAD and 16 healthy, sex- and age-matched controls, beat-by-beat heart rate (HR, from ECG) and blood pressure (BP, with Finometer) were recorded for 10 min during room air breathing and 5 min of hyperoxia. Cardiovagal baroreflex sensitivity and HR variability (HRV) were evaluated as measures of autonomic function. Transthoracic coronary echocardiography was used to assess peak coronary blood flow velocity (CBV) in the left anterior descending coronary artery. Cardiovagal baroreflex sensitivity at rest was lower in PAD than in healthy controls. Hyperoxia raised BP solely in the patients with PAD, with no change observed in healthy controls. Hyperoxia induced an increase in cardiac parasympathetic activity assessed by the high-frequency component of HRV in healthy controls but not in PAD. Indices of parasympathetic activity were lower in PAD than in healthy controls throughout the trial as well as during hyperoxia. Hyperoxia induced coronary vasoconstriction in both groups, while the coronary perfusion time fraction was lower in PAD than in healthy controls. These results suggest that the response in parasympathetic activity to hyperoxia (i.e., oxidative stress) is blunted and the coronary perfusion time is shorter in patients with PAD.NEW & NOTEWORTHY Patients with peripheral artery disease (PAD) showed consistently lower parasympathetic activity and blunted cardiovagal baroreflex sensitivity compared with healthy individuals. Notably, hyperoxia, which normally boosts parasympathetic activity in healthy individuals, failed to induce this response in patients with PAD. These data suggest altered autonomic responses during hyperoxia in PAD.

Symptoms Associated With Exercise Intolerance and Resting Heart Rate Following Mild Traumatic Brain Injury.

People may experience a myriad of symptoms after mild traumatic brain injury (mTBI), but the relationship between symptoms and objective assessments is poorly characterized. This study sought to investigate the association between symptoms, resting heart rate (HR), and exercise tolerance in individuals following mTBI, with a secondary aim to examine the relationship between symptom-based clinical profiles and recovery. Prospective observational study of adults aged 18 to 65 years who had sustained mTBI within the previous 7 days. Symptoms were assessed using the Post-Concussion Symptom Scale, HR was measured at rest, and exercise tolerance was assessed using the Buffalo Concussion Bike Test. Symptom burden and symptom-based clinical profiles were examined with respect to exercise tolerance and resting HR. Data from 32 participants were assessed (mean age 36.5 ± 12.6 years, 41% female, 5.7 ± 1.1 days since injury). Symptom burden (number of symptoms and symptom severity) was significantly associated with exercise intolerance ( P = .002 and P = .025, respectively). Physiological and vestibular-ocular clinical profile composite groups were associated with exercise tolerance ( P = .001 and P = .014, respectively), with individuals who were exercise intolerant having a higher mean number of symptoms in each profile than those who were exercise tolerant. Mood-related and autonomic clinical profiles were associated with a higher resting HR (>80 bpm) ( P = .048 and P = .028, respectively), suggesting altered autonomic response for participants with symptoms relating to this profile. After adjusting for age and mechanism of injury (sports- or non-sports-related), having a higher mood-related clinical profile was associated with persisting symptoms at 3 months postinjury (adjusted odds ratio = 2.08; 95% CI, 1.11-3.90; P = .013). Symptom-based clinical profiles, in conjunction with objective measures such as resting HR and exercise tolerance, are important components of clinical care for those having sustained mTBI. These results provide preliminary support for the concept that specific symptoms are indicative of autonomic dysfunction following mTBI.

Diurnal and nocturnal cardiovascular variability and heart rate arousal response in idiopathic hypersomnia

ObjectivesAutonomic nervous system dysfunction has been described in narcolepsy with cataplexy affecting sympathetic functions. In this study we analyzed whether altered diurnal and nocturnal cardiovascular control is present in idiopathic hypersomnia (IH). MethodsFourteen drug-free patients aged 26.2 ± 7 years and 14 age-matched controls were examined. Clinical data, 24-h polysomnography, heart rate (HR) variability, and the HR response to spontaneous arousal were available. ResultsSleep macrostructure was comparable between controls and patients, with the latter having significantly longer sleep time, a higher number of sleep cycles (p < 0.0001), and low sleep efficiency (p < 0.01). The HR variability indices did not differ between groups, except for the rise of high frequency (HF) and HFnu in patients (p < 0.05) associated with blunted sympathetic indices (p < 0.01). These parasympathetic alterations were present for light, slow wave, and rapid eye-movement sleep and persisted for all sleep cycles. Compared to controls, the HR arousal response was significantly higher (p < 0.01) in patients starting before the arousal onset and persisting into the post-arousal period. ConclusionsIn IH patients a dysfunction of the parasympathetic activity during awake and sleep and an altered autonomic response to arousals are present. These findings suggest an impaired parasympathetic function that may explain some vegetative symptoms present in this type of central hypersomnia.

Autonomic response to valsalva maneuver in patients of cervical spondylosis

Background- Cervical spondylosis(CS) is a broad term which describes the age related chronic disc degeneration which starts in the intervertebral disc with osteophyte formation and lead to physiological degenerative cascade that contributes to biomechanical changes that result in neural and vascular compression. Autonomic balance in the body can be influenced from this compression. Aim and objectives- The aim of this study was to assess the autonomic balance in response to stress in patients of cervical spondylosis. Material and methods- Heart rate variability (HRV) was recorded during valsalva maneuver(VM) and recovery period, in two groups comprising of thirty patients with CS and thirty healthy age and sex matched controls. The results were analysed in time and frequency domains by using student t-test (significance level at p<0.05). Observations and Results- There was an inefficient autonomic response during the period of stress, with increased sympathetic tone during the recovery period. Dicussion - HRV is as a simple, non-invasive measure of the autonomic activity which analyses beat to beat variation in the heart rate and VM further improves the sensitivity of its interpretation. Conclusion - CS patients have an altered autonomic response to stress and a higher sympathetic tone than controls.

Altered cardiovascular and baroreflex response to air jet stress in dexamethasone programed rat (LB738)

Raised gestational glucocorticoid may program hypertension in the offspring, although the data are inconsistent. The pathophysiological mechanisms may be due to altered autonomic responses to stress. We compared the cardiovascular and autonomic responses to air jet stress in rats programed by maternal injection of dexamethasone (DEX, 0.2 mg/kg) at gestational days E15 and E16 with control rats. At 6 months, offspring were implanted with a telemetry blood pressure (BP) transmitter. BP, heart rate (HR), and spontaneous baroreflex gain (sBRG) were recorded at rest and during exposure to a series of puffs of air directed at the face. There was a trend towards a higher resting mean BP in DEX rats than controls (97.6±4.9 v 84.1±2.5 mmHg, n=6, P=0.06), although there was no difference in systolic BP (109.7±5.5 v 104.7±1.3 mmHg, P=0.45). This was accompanied by a lower heart rate (260±9 v 302±13 bpm, P&lt;0.05) and sBRG (1.5±0.2 v 2.3±0.2 ms/mmHg, P&lt;0.05) in DEX rats. Air jet stress increased BP and HR in both groups, however the BP increase was greater in DEX (initial increase 22.2±3.7 vs 8.3±3.9 mmHg, P&lt;0.05). Stress reduced sBRG in control but not DEX rats (by 0.86±0.14 vs 0.01±0.3 ms/mmHg). Our results show that DEX programmed rats have altered cardiovascular and baroreflex responses to airjet stress.

The October issue of Medical Express

MedicalExpress is happy to announce the coming of its 5 issue, October 2014. This is where we move ahead towards accomplishing one more of our goals, which is to publish in continuous flow: following this editorial you have the first three original research articles of volume 1(5). Others will follow, as their processing becomes complete. The most significant piece of news at the time of writing is that MedicalExpress has now acquired the necessary credentials and has formally applied for indexation in SciELO, the Brazilian based Scientific Electronic Library Online. We expect to have news on this development before the end of this year. Our previous, 4 issue, dated August 2014, came out en bloc in July 11th. The 11 titles therein (8 original research articles, 3 reviews) were processed as shown in Table 1. We are moving towards our average goal of 10 articles per issue; our initial response time has remained quite steady whereas our interval between acceptance and publication has fallen to 44 days in the fourth issue. We expect to publish 11 articles in October totalizing 48 in the first five issues (9.6 articles per issue). The table does not show time from submission to publication, because this statistic includes time controlled by authors, not by the journal. The August issue was the largest, so far, with three reviews, seven original research papers and one rapid communication. Oliveira et al reviewed present state of the art technology for cerebrospinal shunt circuitry with emphasis on the development of last generation valves. Iuamoto et al reviewed available reports on the viability of islet allotransplantation in rats and the amelioration of survival with the use of the latest immunosuppressive agents. Campos reviews recent recommendations concerning the use of Chondroprotective agents in osteoarthritic patients and makes a strong case for their use despite negative recommendations by learned international rheumatologic institutions Gotfryd et al retrospectively evaluated back pain in adolescent idiopathic scoliosis and conclude that spinal arthrodesis is efficient for patients with Cobb angles greater than 45 degrees. Andreia Silva et al retrospectively analyzed immunophenotype of lung granulomas in HIV and in non-HIV associated tuberculosis and concluded that the advent of AIDS changed the immunological profile, probably because of CD4 þ lymphocyte depletion. Valenti et al examined the effect of cigarette smoke on the general activity and anxiety of rats and found that exposure to smoke affetcs their performace in open field tests. Tavares et al evaluated the pattern of ambulatory blood pressure monitoring in children with dilated cardiomyopathy and found (a) that arterial pressure is similar to that in normal children, but (b) that cardiopathic children with low ejection fraction exhibited a lower dipping pattern. Gomes et al described and tested a new protocol of regular aerobic training and its effect as an anxiolytic for panic disorder and concluded that the protocol is safe and potentially useful. Plassa et al examined cardiac autonomic responses to musical stimulation with a baroque piece by Pachelbel and report that subjects with affinity to classical music exhibited altered autonomic responses, whereas subjects with no affinity remained unaffected. Coqueiro et al examined the relation between anthropometric indicators and serum triglycerides and conclude that the best indicators differ between men and women; for both sexes, body mass index, calf circumference and triceps skinfold thickness were found to be the best predictors. Koike et al described an ingenious new technique for evaluating aortic valve function in rats with experimental aortic valve insufficiency. The new technique allows for acute and chronic evaluation of cardiac function following the placement of the lesion. Once again we invite readers to submit their research to MedicalExpress. We provide quality revision and speed of publication second to few in the world, second to none in Brazil.

Cardiac defense in response to imminent threat in women with multiple trauma and severe PTSD

Posttraumatic stress disorder (PTSD) arises as a long-term result of exposure to trauma and brings with it an altered autonomic response to potentially threatening stimuli. The present study investigates the dynamic sequence of cardiac defense in women with and without PTSD. An acoustic noise of 0.5-s duration and 105 dB was used to elicit the cardiac defense reaction. The stimulus was repeated three times. Within the PTSD sample, respondents who suffered from more severe PTSD showed a higher heart rate at rest, a higher baseline, and a greater response. Compared to the healthy subjects, the PTSD group showed an elevated heart rate from 6 s to 25 s following the presentation of the first stimulus. There was evidence of habituation in the PTSD group and hints of differential effects on the cardiac defense of traumatic experiences with a high proximity of danger.

Heart rate complexity in response to upright tilt in persons with Down syndrome

People with Down syndrome (DS) show altered autonomic response to sympatho-excitation. Cardiac autonomic modulation may be examined with heart rate (HR) complexity which is associated uniquely with cardiovascular risk. This study examined whether the response of HR complexity to passive upright tilt differs between persons with and without DS and whether potential between-group differences in this response are accounted for by differences in body mass index (BMI). The electrocardiogram of 16 persons with DS (8 women, 8 men) and 16 persons without DS (8 women, 8 men) was recorded during 10 min of supine rest and 10 min of upright tilt. For each participant, 550 continuous, steady state, and ectopy-free R-R intervals under each condition were analyzed. Dependent variables were approximate entropy, correlation dimension, StatAv, and the mean R-R interval. In response to tilt, changes in approximate entropy and correlation dimension were reduced in participants with DS (p<0.05). These differences were explained by higher BMI in participants with DS. StatAv increased in persons with DS (p < 0.05) and stayed the same in those without DS even when controlling for BMI. The response of R-R interval did not differ between groups. None of the variables differed between groups at rest. Therefore, people with DS show smaller decrease in HR complexity in response to upright tilt than people without DS partially due to their higher BMI. Resting HR complexity does not differ between persons with and without DS. These results may have implications for cardiovascular risk in people with DS.

Analysis of heart rate variability: a useful tool to evaluate autonomic tone in the anesthetized patient?

HE discovery of general anesthesia is one of the most important advancements in medicine within the last century. Unfortunately, it is impossible to perform anesthesia adequately , without altering autonomic nervous system tone. Coping with altered autonomic responses is made possible by continuous monitoring of changes in vital signs, including blood pressure and heart rate, and by fine-tuning anesthetic depth, and correcting imbalances in autonomic tone with pharmacological agents. Because anesthesia blunts autonomic reflexes without abolishing them, most interventions to correct autonomic imbalance are followed by reflex responses, leading to fluctuations in vital signs. Intraoperative variations in blood pressure and heart rate have taught experienced anesthesiologists to practice patience and moderation in the correction of vital signs, and to avoid unnecessary pharmacological interventions to “correct the correction”. The lag time between step changes in drug concentration, and changes in vital signs, reflects the degree of hyster esis between changes in autonomic balance at the end-organ level, and the delays in pharmacological responses to correct the imbalance. Measurements of changes in autonomic tone, therefore, offer the possibility of correcting the dysfunction more rapidly, before the end-organ changes occur in higher-risk patient populations. The issue of clinical relevance for anesthesiologists is, whether or not this can in fact, be achieved without invasive monitoring of autonomic nerve impulses. It was first observed by Hales, 1 that the time interval between successive heart beats can be extracted in a series of numbers, whose variability can be studied; hence the origin of the misleading term “heart rate variability”. This term is misleading, because it is not the variability in heart rate per se, but rather, variability of the time intervals between cardiac contractions, that

Feeding and colonic distension provoke altered autonomic responses in irritable bowel syndrome

Objective. Alterations in autonomic balance, detectable by heart rate variability (HRV) analysis, have been shown to occur after a meal in patients with irritable bowel syndrome (IBS). There are few data on changes in sympathovagal responses in IBS to other forms of enteric stimulation such as colonic distension. The aim of this study was to determine the effects of colonic balloon distension on HRV in the fasting and the postprandial state in healthy subjects and in IBS patients. Material and methods. Eight IBS patients and 8 age- and gender-matched healthy subjects underwent unsedated descending colonic distension before and after a 1000 kcal liquid meal. Low- (LF) and high-frequency (HF) HRV band values obtained from 2-min ECG segments recorded before and during distension were compared between groups, and between fasting and postprandial states. A visual analogue scale was used to determine sensation during colonic distension. Results. HF values decreased significantly with feeding in IBS patients (p=0.01), but not in healthy subjects. The low-to-high frequency (LF/HF) ratio was significantly higher postprandially in IBS patients (p=0.02) and, additionally, was decreased (p<0.01) with colonic distension in the fed state, independently of colonic sensitivity or distending volume. Moreover, changes in the LF/HF ratio with distension in the fed versus the fasting state were negatively correlated in IBS patients but positively correlated in healthy subjects (both p<0.05). Conclusions. IBS patients demonstrated altered autonomic responses to feeding and colonic distension. Further studies should determine whether these alterations could explain the postprandial exacerbation of symptoms in IBS.

BEHAVIOR, PAIN PERCEPTION, AND THE EXTREMELY LOW-BIRTH WEIGHT SURVIVOR

This article explores the literature concerning responses to pain of both premature and term-born newborn infants, the evidence for short-term and long-term effects of pain, and behavioral sequelae in individuals who have experienced repeated early pain in neonatal life as they mature. There is no doubt that pain causes stress in babies and this in turn may adversely affect long-term neurodevelopmental outcome. Although there are methods for assessing dimensions of acute reactivity to pain in an experimental setting, there are no very good measures available at the present time that can be used clinically. In the clinical setting repeated or chronic pain is more likely the norm rather than infrequent discrete noxious stimuli of the sort that can be readily studied. The wind-up phenomenon suggests that, exposed to a cascade of procedures as happens with clustering of care in the clinical setting in an attempt to provide periods of rest for stressed babies, an infant may in fact perceive procedures that are not normally viewed as noxious, as pain. Pain exposure during lifesaving intensive medical care of ELBW neonates may also affect subsequent reactivity to pain in the neonatal period, but behavioral differences are probably not likely to be clinically significant in the long term. Prolonged and repeated untreated pain in the newborn period, however, may produce a relatively permanent shift in basal autonomic arousal related to prior NICU pain experience, which may have long-term sequelae. In the long run, the most significant clinical effects of early pain exposure may be on neurodevelopment, contributing to later attention, learning, and behavior problems in these vulnerable children. Although there is considerable evidence to support a variety of adverse effects of early pain, there is less information about the long-term effects of opiates and benzodiazepines on the developing central nervous system. Current evidence reviewed suggests that judicious use of morphine for adjustment to mechanical ventilation may ameliorate the altered autonomic response. It may be very important, however, to distinguish stress from pain. Animal evidence suggests that the neonatal brain is affected differently when exposed to morphine administered in the absence of pain than in the presence of pain. Pain control may be important for many reasons but overuse of morphine or benzodiazepines may have undesirable long-term effects. This is a rapidly evolving area of knowledge of clear relevance to clinical management likely to affect long-term outcomes of high-risk children.