Instantaneous orthostatic hypotension in children and adolescents: a new entity of orthostatic intolerance

Association of adolescent postural tachycardia syndrome classifications with anxiety: a cross sectional study

BACKGROUND

Postural tachycardia syndrome (POTS), a subset of orthostatic dysregulation, has been reported to be associated with anxiety. POTS can be classified into two forms based on the degree of tachycardia during orthostasis. Reportedly, POTS with decreased orthostatic heart rate increase is associated with suppressed cardiac parasympathetic activity and increased sympathetic activity in the supine position. In this study, the relationship between the two types of POTS and anxiety was evaluated in terms of autonomic function.

METHODS

Fifty-two patients (23 male, age 10-15 years) who were diagnosed with POTS at the Department of Pediatrics, Osaka Medical and Pharmaceutical University from 2019 to 2021, completed a standing test and were accordingly classified into a Su group, with tachycardia from the supine position and a low heart rate increase on standing, a SI group, with a high heart rate increase during standing. They then completed the State-Trait Anxiety Scale for Children (STAIC) questionnaire. Autonomic function was assessed by frequency analysis (MemCalc method) based on heart rate, blood pressure changes, heart rate and blood pressure variability during the orthostatic test.

RESULTS

Patients in the Su group had higher trait anxiety and state anxiety, lower cardiac parasympathetic activity (RR-HF) in the supine position, and greater variability in cardiac parasympathetic activity during orthostasis than were found for patients in the SI group. The Su group had a greater decrease in cardiac index on standing than that of the SI group.

CONCLUSIONS

The Su group results may be partly attributed to chronically low venous return. We also found that patients in the Su group had low parasympathetic activity in the supine position, which may interact with the anxiety-prone characteristics of these patients. Therefore, it seems necessary to consider both physical and psychosomatic treatment approaches for patients with POTS.

A framework to simplify paediatric syncope diagnosis

This paper aims to improve the diagnosis of syncope and transient loss of consciousness (TLOC) in children. Diagnostic problems stem, first, from some causes spanning various disciplines, e.g. cardiology, neurology and psychiatry, while the most common cause, vasovagal syncope, is not embraced by any specialty. Second, clinical variability is huge with overlapping signs and symptoms. Third, the approach to TLOC/syncope of the European Society of Cardiology (ESC) is underused in childcare. We explain the ESC guidelines using an additional paediatric literature review. Classification of TLOC and syncope is hierarchic and based on history taking. Loss of consciousness (LOC) is defined using three features: abnormal motor control including falling, reduced responsiveness and amnesia. Adding a < 5 min duration and spontaneous recovery defines TLOC. TLOC simplifies diagnosis by excluding long LOC (e.g. some trauma, intoxications and hypoglycaemia) and focussing on syncope, tonic-clonic seizures and functional TLOC. Syncope, i.e. TLOC due to cerebral hypoperfusion, is divided into reflex syncope (mostly vasovagal), orthostatic hypotension (mostly initial orthostatic hypotension in adolescents) and cardiac syncope (arrhythmias and structural cardiac disorders). The initial investigation comprises history taking, physical examination and ECG; the value of orthostatic blood pressure measurement is unproven in children but probably low. When this fails to yield a diagnosis, cardiac risk factors are assessed; important clues are supine syncope, syncope during exercise, early death in relatives and ECG abnormalities.  Conclusions: In adults, the application of the ESC guidelines reduced the number of absent diagnoses and costs; we hope this also holds for children. What is Known: • Syncope and its mimics are very common in childhood, as they are at other ages. • Syncope and its mimics provide considerable diagnostic challenges. What is New: • Application of the hierarchic framework of transient loss of consciousness (TLOC) simplifies diagnosis. • The framework stresses history-taking to diagnose common conditions while keeping an eye on cardiac danger signs.

Prevalence of Pediatric and Adolescent Balance Disorders: Analysis of a Mono-Institutional Series of 472 Patients

(1) Background: To assess the prevalence and frequency distribution of balance disorders in children and adolescents to delineate the planning of a targeted clinical and instrumental diagnostic work-up; (2) Methods: Retrospective analysis of the clinical documentation of patients under 18 years suffering from balance disorders from 2010 to 2019. Detailed collection of clinical history, accurate clinical examination, including both nystagmus and vestibulospinal signs examinations, and specific instrumental testing were the basis of the diagnostic process. (3) Results: A total of 472 participants were included in the study. Vestibular loss (26.1%) was the most frequent cause of vertigo in children, followed by vestibular migraine (21.2%) and benign paroxysmal positional vertigo (10.2%). In 1.1% of patients, the cause of vertigo remained undefined; (4) Conclusions: The diagnostic process applied was effective in understanding the cause of balance disorders in most cases and prevents more complex and expensive investigations reserved for only a few selected cases.

Supine Parasympathetic Withdrawal and Upright Sympathetic Activation Underly Abnormalities of the Baroreflex in Postural Tachycardia Syndrome: Effects of Pyridostigmine and Digoxin

[Figure: see text].

Cerebral Autoregulation During Active Standing Test in Juvenile Patients with Instantaneous Orthostatic Hypotension

Instantaneous orthostatic hypotension (INOH) is one of the main types of orthostatic dysregulation in children and adolescents. In patients with INOH arterial pressure drops considerably after active standing and is slow to recover. We investigated changes in cerebral oxygenation in the bilateral prefrontal cortex during an active standing test in juvenile INOH patients to evaluate changes in cerebral oxygen metabolism. We enrolled 82 INOH patients (mean age 13.8 ± 2.2 years, 52 mild and 30 severe patients) at Nihon University Itabashi Hospital from October 2013 to April 2018. We measured cerebral oxygenated hemoglobin, deoxygenated hemoglobin, and total hemoglobin levels in the bilateral prefrontal cortex using near-infrared spectroscopy during an active standing test. In severe INOH patients, cerebral oxygenation of the right prefrontal cortex remained constant when blood pressure dropped; however, de-oxy-Hb significantly increased. These findings confirm that there is asymmetrical autoregulation between the right and left prefrontal cortex.

Sleep education in primary school prevents future school refusal behavior

BACKGROUND

Sleep disorders, along with extreme difficulty in awakening, are one of the main causes of school refusal. The accumulation of chronic sleep deprivation accompanied by a late-night lifestyle is considered the basic inciting factor.

METHODS

From 2007, we initiated a sleep education program (Min-Iku) in Fukui, Japan, with the aim of improving pupil lifestyle and preventing future school refusal. All grade 1-6 Miyake-primary school (M-PS) pupils participated in this program and gave their informed consent. The Min-Iku included (i) implementation of a "daily life rhythm survey" by recording the sleep-wake rhythm in a table for 14 days; (ii) evaluation of the sleep table according to the classifications A-D; (iii) interviews of stage D children and their guardians; (iv) lectures on the importance of daily life rhythms for parents and teachers; and (v) 45 min classwork for all participating pupils.

RESULTS

In 2007, 10% of M-PS graduates developed school refusal behavior after entering Kaminaka junior high school (K-JHS). The incidence of school refusal, however, decreased each year after the implementation of the Min-Iku program and finally reached 0 by 2012. The sleep onset time of pupils improved each year, with the most common sleep time reaching 9:30 p.m. on both weekdays and holidays. With an earlier sleep time, the night-time sleep duration was significantly extended (P < 0.001 vs 2007 data).

CONCLUSION

The Min-Iku program for primary school pupils successfully achieved a more routine night-time sleep pattern and a regular life rhythm, which prevented school refusal during the subsequent JHS years.

Increased Endogenous Sulfur Dioxide Involved in the Pathogenesis of Postural Tachycardia Syndrome in Children: A Case-Control Study

Background

The pathogenesis of postural tachycardia syndrome (POTS) remains unclear. This study aimed to explore the changes and significance of sulfur dioxide (SO₂) in patients with POTS.

Methods

The study included 31 children with POTS and 27 healthy children from Peking University First Hospital between December 2013 and October 2015. A detailed medical history, physical examination results, and demographic characteristics were collected. Hemodynamics was recorded and the plasma SO₂was determined.

Results

The plasma SO₂was significantly higher in POTS children compared to healthy children (64.0 ± 20.8 μmol/L vs. 27.2 ± 9.6 μmol/L, respectively, P < 0.05). The symptom scores in POTS were positively correlated with plasma SO₂levels (r = 0.398, P < 0.05). In all the study participants, the maximum heart rate (HR) was positively correlated with plasma levels of SO₂(r = 0.679, P < 0.01). The change in systolic blood pressure from the supine to upright (ΔSBP) in POTS group was smaller than that in the control group (P < 0.05). The ΔSBP was negatively correlated with baseline plasma SO₂levels in all participants (r = -0.28, P < 0.05). In the control group, ΔSBP was positively correlated with the plasma levels of SO₂(r = 0.487, P < 0.01). The change in HR from the supine to upright in POTS was obvious compared to that of the control group. The area under curve was 0.967 (95% confidence interval: 0.928-1.000), and the cutoff value of plasma SO₂ level >38.17 μmol/L yielded a sensitivity of 90.3% and a specificity of 92.6% for predicting the diagnosis of POTS.

Conclusions

Increased endogenous SO₂levels might be involved in the pathogenesis of POTS.

Vertigo in children; a narrative review of the various causes and their management

Vertigo is a not an uncommon symptom in children, but often the treating doctors are unsure of the diagnosis and the management of these cases. This narrative review of the literature discusses the brief etiopathology, the clinical manifestations and the management algorithm of most of the conditions causing vertigo in children. The relevant information has been condensed into a table for the perusal of the readers, which would assist in the appropriate management of these children.

Noninvasive beat-to-beat finger arterial pressure monitoring during orthostasis: a comprehensive review of normal and abnormal responses at different ages

Over the past 30 years, noninvasive beat-to-beat blood pressure (BP) monitoring has provided great insight into cardiovascular autonomic regulation during standing. Although traditional sphygmomanometric measurement of BP may be sufficient for detection of sustained orthostatic hypotension, it fails to capture the complexity of the underlying dynamic BP and heart rate responses. With the emerging use of noninvasive beat-to-beat BP monitoring for the assessment of orthostatic BP control in clinical and population studies, various definitions for abnormal orthostatic BP patterns have been used. Here, age-related changes in cardiovascular control in healthy subjects will be reviewed to define the spectrum of the most important abnormal orthostatic BP patterns within the first 180 s of standing. Abnormal orthostatic BP responses can be defined as initial orthostatic hypotension (a transient systolic BP fall of >40 mmHg within 15 s of standing), delayed BP recovery (an inability of systolic BP to recover to a value of >20 mmHg below baseline at 30 s after standing) and sustained orthostatic hypotension (a sustained decline in systolic BP of ≥20 mmHg occurring 60-180 s after standing). In the evaluation of patients with light-headedness, pre(syncope), (unexplained) falls or suspected autonomic dysfunction, it is essential to distinguish between normal cardiovascular autonomic regulation and these abnormal orthostatic BP responses. The prevalence, clinical relevance and underlying pathophysiological mechanisms of these patterns differ significantly across the lifespan. Initial orthostatic hypotension is important for identifying causes of syncope in younger adults, whereas delayed BP recovery and sustained orthostatic hypotension are essential for evaluating the risk of falls in older adults.

Characteristics of headaches in Japanese elementary and junior high school students: A school-based questionnaire survey

PURPOSE

Few studies have investigated pediatric headaches in Japan. Thus, we examined the lifetime prevalence and characteristics of headaches among elementary and junior high school students in Japan.

METHODS

In this school-based study, children aged 6-15years completed a questionnaire based on the diagnostic criteria of the International Classification of Headache Disorders-3β to assess headache characteristics and related disability.

RESULTS

Of the 3285 respondents, 1623 (49.4%) experienced headaches. Migraine and tension-type headaches (TTH) were reported by 3.5% and 5.4% of elementary school students, respectively, and by 5.0% and 11.2% of junior high school students. Primary headaches increased with age. Compared with TTH sufferers, the dominant triggers in migraine sufferers were hunger (odds ratio=4.7), sunny weather (3.3), and katakori (neck and shoulder pain) (2.5). Compared with TTH, migraine caused higher headache-related frustration (P=0.010) as well as difficulty concentrating (P=0.017). Migraine-related disability was greater among junior high school students (feeling fed up or irritated, P=0.028; difficulty concentrating, P=0.016). TTH-related disability was also greater among junior high school students (feeling fed up or irritated, P=0.035). Approximately half of the students who complained of headache-related disability were not receiving medical treatment.

CONCLUSION

This is the first detailed study of headaches in Japanese children to include elementary school students. Nearly 50% of the school children reported headaches and the disruption of daily activities caused by migraine was higher among junior high students than elementary school students.

Autonomic nervous system function in adolescent migraineurs

BACKGROUND

Migraine is a common and disabling neurological disorder. Studies on the relationship between migraine and the autonomic nervous system (ANS) have been inconclusive. Moreover, pediatric studies are extremely limited. Therefore, the present study investigated interictal ANS function in adolescent migraineurs.

METHODS

We studied 21 patients with migraine and 26 healthy controls. Beat-to-beat blood pressure (BP) and heart rate (HR) were non-invasively and continuously measured in the supine and standing positions. ANS function was evaluated on power spectral analysis of HR variability and diastolic BP (DBP) variability.

RESULTS

Heart rate and systolic BP were not different between the two groups in either the supine or standing position. DBP did not differ between groups in the standing position, but was significantly higher in migraineurs in the supine position. The vasoconstrictor index was significantly higher in migraineurs. High-frequency (HF) RR interval variability (RR-HF) and the ratio of the low-frequency (LF) to HF component of RR interval variability (RR-LF/HF) were not different between the two groups in both positions. The LF component of DBP variability (DBP-LF) in the supine position was significantly lower in migraineurs, while DBP-LF during standing in migraineurs was significantly higher than in controls.

CONCLUSION

Migraineurs have significantly lower sympathetic vasomotor activity in the supine position, while sympathetic vasomotor activity was hyperresponsive during standing.

Recent advances in the understanding of the mechanisms underlying postural tachycardia syndrome in children: practical implications for treatment

Postural tachycardia syndrome is defined by a heart rate increment of 40 beats/minute (bpm) (or a heart rate that exceeds 125 bpm) within 10 minutes of change from the supine position to an upright position in the absence of obvious orthostatic hypotension. There are multiple pathophysiological mechanisms that underlie postural tachycardia syndrome, including peripheral denervation, β-receptor supersensitivity, hypovolaemia, and impaired muscle pump. Some children afflicted with postural orthostatic tachycardia syndrome and hypovolaemic dysregulation have been found to have perturbed renin-angiotensin-aldosterone profile, disturbed vascular endothelial function, and abnormal vasodilation. The hyperadrenergic state in some postural tachycardia syndrome patients is likely a driver for orthostatic tachycardia. Other mechanisms include the presence of treatable autonomic neuropathies. An understanding of these pathophysiological mechanisms might be helpful for the effective treatment of postural tachycardia syndrome.

Detecting initial orthostatic hypotension: a novel approach

Our purpose, by modification of standard bedside tilt-testing, was to search for lesser known but important initial orthostatic hypotension (IOH), occurring transiently within the first 30 seconds of standing, heretofore only detectable with sophisticated continuous photoplethysmographic monitoring systems, not readily available in most medical facilities. In screened outpatients over 60 years of age, supine blood pressure (BP) parameters were recorded. To achieve readiness for immediate BP after standing, the cuff was re-inflated prior to standing, rather than after. Immediate, 1-, and 3-minute standing BPs were recorded. One hundred fifteen patients were studied (mean age, 71.1 years; 50.5% male). Eighteen (15.6%) had OH, of whom 14 (12.1%) had classical OH, and four (3.5%) had IOH. Early standing BP detection time was 20.1 ± 5.3 seconds. Immediate transient physiologic systolic BP decline was detected in non-OH (-8.8 ± 9.9 mm Hg; P < .0001). In contrast to classical OH (with lesser but persistent orthostatic BP decrements), IOH patients had immediate mean orthostatic systolic/diastolic BP change of -32.8 (±13.8) mm Hg/-14.0 (±8.5) mm Hg (P < .02), with recovery back to baseline by 1 minute. Two of the four IOH patients had pre-syncopal symptoms. For the first time, using standard inflation-deflation BP equipment, immediate transient standing physiologic BP decrement and IOH were demonstrated. This preliminary study confirms proof of principle that manual BP cuff inflation prior to standing may be useful and practical in diagnosing IOH, and may stimulate direct comparative studies with continuous monitoring systems.

Comparable accuracy of micro-electromechanical blood flowmetry-based analysis vs. electrocardiography-based analysis in evaluating heart rate variability

BACKGROUND

Because the conventional evaluation of autonomic nervous system (ANS) function inevitably uses long-lasting uncomfortable electrocardiogram (ECG) recording, a more simplified and comfortable analysis system has been sought for this purpose. The feasibility of using a portable micro-electromechanical system (MEMS) blood flowmeter to analyze heart rate variability (HRV) for evaluating ANS function was thus examined.

METHODS AND RESULTS

Measurements of the R-R interval (TRR) derived from an ECG, simultaneously with the pulse wave interval (TPP) derived from a MEMS blood flowmeter, in 8 healthy subjects was performed and resultant HRV variables in time and frequency domains were compared. The TRR- and TPP-derived variables were strongly correlated (coefficients of regression for low frequency (LF), high frequency (HF), and LF/HF of 1.1, 0.66, and 0.35, respectively; corresponding coefficients of determination of 0.92, 0.63, and 0.91, respectively (P<0.01)). In addition, the values of LF, HF, and LF/HF, as analyzed using TPP, changed significantly from the supine to the standing position in another 6 subjects.

CONCLUSIONS

Miniaturized-MEMS blood flowmetry can be used to perform HRV analysis for the evaluation of ANS function, which is as accurate as analysis based on ECG within comparable tolerances. As MEMS blood flowmetry can more easily and comfortably record physiological variables for longer durations than ECG recording, and can further capture skin blood flow information, this device has great potential to be used in a wider area of physiological analyses.

Orthostatic Dysregulation during Postural Change on the Dental Chair and Intraoperative Monitoring by Heart Rate Variability Analysis

This is the first case report of orthostatic dysregulation (OD) manifested during postural change on the dental chair and intraoperatively monitored by heart rate variability (HRV) analysis. OD-associated autonomic dysfunction is induced by postural changes and easily leads to disturbance in circulatory dynamics; however, most dental practices have not yet realized the importance of managing OD. We measured autonomic activity in a patient with OD during dental therapy and assessed the clinical significance of HRV analysis for OD. The patient was a 17-year-old Japanese female. She was diagnosed with impacted wisdom teeth and had no previous history of a distinct systemic disease. A surgical procedure to extract the teeth was safely performed under both local anesthesia and sedation with nitrous oxide and midazolam. After the surgery, her postural change to sitting induced orthostatic hypotension. HRV variables showed parasympathetic dominance due to the upright position. Subsequently, her posture was returned to supine, and atropine sulfate administration for the immediate treatment of OD returned her blood pressure to normal levels. HRV variables showed relative sympathetic dominance due to an atropine-derived parasympathetic blockade. HRV analysis revealed OD-associated autonomic dysfunction and should become a standard tool for safe and secure dental management of OD.

Variant cardiovascular regulation in children with postural tachycardia syndrome

BACKGROUND

Postural tachycardia syndrome (POTS) manifests as marked tachycardia while standing. We noticed two forms of circulatory response to orthostatic stress in POTS. We investigated cardiovascular and autonomic nervous response to orthostatic stress in the two forms.

METHODS

We studied 79 patients with POTS and 38 healthy control subjects (Ct). Beat-to-beat blood pressure (BP) and heart rate (HR) were non-invasively and continuously measured in the supine and standing positions. Autonomic nervous function was evaluated on power spectral analysis of HR variability and diastolic BP variability. We divided the subjects into two groups: standing-induced tachycardia (SI group; increase in HR ≥35 beats/min) and supine tachycardia (Su group; standing HR ≥115 beats/min with standing-induced HR increase <35 beats/min).

RESULTS

The Su group had higher supine BP and HR compared with the other groups, indicating dominant sympathetic control of the heart in the supine position. While rising, the SI group had a higher increase in HR than the Ct group, indicating excessive withdrawal of vagal tone. The Su group had a smaller increase in HR and a greater decrease of systolic BP and cardiac index by standing compared with the SI group. These results suggest that compensatory mechanisms of sympathetic function during standing failed in the Su group, probably because of exhaustion by the nearly maximum effort to generate sympathetic drive even in the supine position with low central blood volume.

CONCLUSION

There is a difference between the two types of POTS, in the balance of resting autonomic function and hemodynamic response to standing.

Postural tachycardia syndrome in children and adolescents

Postural tachycardia syndrome is a chronic condition with frequent symptoms of orthostatic intolerance or sympathetic activation and excessive tachycardia while standing, without significant hypotension. Orthostatic symptoms include dizziness, lightheadedness, blurring of vision, near faints, weakness in legs, poor concentration, nausea, and headaches. Somatic symptoms include fatigue, sleep disorder, widespread pain, abdominal pain, and menstrual irregularities. Psychological problems may overlap with physical complaints. This review discusses the normal physiology of orthostatic change, different pathophysiological mechanisms of postural tachycardia syndrome, including hypovolemia, venous pooling, autonomic neuropathy, and hyperadrenergic responses. In addition, an outline for management tailored to the patient's clinical syndrome is presented, along with concluding thoughts on future research needs.

Newly-identified symptoms of left renal vein entrapment syndrome mimicking orthostatic disturbance

BACKGROUND

In addition to the urinary abnormalities, symptoms of left renal vein entrapment between the aorta and superior mesenteric artery (left renal vein entrapment syndrome, LRVES) may include abdominal and flank pain as well as chronic fatigue. We investigated various LRVES symptoms in this study.

METHODS

In 53 pediatric LRVES patients treated at our department, 22 had a score of 5 points or higher on orthostasis. Initial evaluation of LRVES by abdominal ultrasonography showed a stenotic-to-prestenotic vein diameter ratio of 0.2 or less. Definitive diagnosis was made by computed tomography and magnetic resonance angiography. Cortisol, catecholamine (CA), and brain natriuretic peptide (BNP) were also measured.

RESULTS

The frequency of LRVES was 2.5 times higher in girls than in boys. Low or very low body mass indexes were seen in both sexes. The most common initial finding was urine abnormalities, followed by dizziness and malaise. In 6 patients, orthostasis precluded school attendance. Ten patients had orthostasis scores above 12. Patients unable to attend school had either low levels of plasma or urinary cortisol. Midodrine significantly decreased orthostasis scores. Some patients required treatment with fludrocortisone. Plasma CA, renin, and BNP levels were all normal.

CONCLUSIONS

Locally excessive venous pressure may cause reversible adrenal dysfunction with transitory Addisonian symptoms. Children with cryptogenic malaise or severe orthostasis should be evaluated for LRVES.

Relationship between the number of outpatient visits for hypotension in the springtime in Japan, extracted from clinical electronic records, and global solar radiation levels

Hypotension is commonly reported in springtime when health changes, such as autonomic imbalance, are common and its symptoms may cause difficulties in daily activities. In this study, medical data from 101 outpatient clinic attendees (mean age 43.9 years; 16 males) making their first visit for hypotension symptoms, were compared with meteorological data from the clinic's location. The main symptom of hypotension was giddiness on standing. The most common coexisting conditions were gastrointestinal; e.g. gastro-oesophageal reflux disorder and irritable bowel syndrome. The 7-day moving average of total global solar radiation correlated significantly with the 7-day moving average of the number of patients with hypotension. Discriminant analysis revealed an increase in hypotension consultations in the total global solar radiation moving average range 11-19 MJ/m(2), consistent with the local spring season. Guidance--such as wearing compression stockings during springtime--may help to reduce the occurrence of clinical hypotension in susceptible patients.

Lower limb-localized vascular phenomena explain initial orthostatic hypotension upon standing from squat

The cause(s) of initial orthostatic hypotension (transient fall in blood pressure within 15 s upon active rising) have not been established. We tested the hypothesis that this hypotension is due to local vascular phenomena in contracting leg muscles from the brief effort of standing up. Seventeen young healthy subjects (2 male and 15 female, 22.5 ± 1.0 years) performed an active rise from resting squat after a 10-s squat, a 1-min squat, or a 5-min squat. Beat-by-beat arterial blood pressure, cardiac output, heart rate, and stroke volume (Finometer finger photoplethysmography) and right common femoral artery blood flow (Doppler and Echo ultrasound) were recorded. Data are means ± SE. Quiet standing before squat represented baseline. Peak increases in lower limb and total vascular conductance (ml·min−1·mmHg−1) upon standing were not different within squat conditions (10-s squat, 50.0 ± 12.4 vs. 44.3 ± 5.0; 1-min squat, 54.7 ± 9.2 vs. 50.5 ± 4.5; 5-min squat, 67.4 ± 13.7 vs. 58.8 ± 3.9; all P > 0.574). Mean arterial blood pressure (in mmHg) fell to a nadir well below standing baseline in all conditions despite increases in cardiac output. The hypotension predicted by the increase in leg vascular conductance accounted for this hypotension [observed vs. predicted (in mmHg): 10-s squat, −17.1 ± 2.1 vs. −18.3 ± 5.5; 1-min squat, −22.0 ± 3.8 vs. −25.3 ± 4.9; 5-min squat, −28.3 ± 4.0 vs. −29.2 ± 6.7]. We conclude that rapid contraction induced dilation in leg muscles with the effort of standing, along with a minor potential contribution of elevated lower limb arterio-venous pressure gradient, outstrips compensatory cardiac output responses and is the cause of initial orthostatic hypotension upon standing from squat.

Orthostatic intolerance and the headache patient

Orthostatic intolerance (OI) refers to a group of clinical conditions, including postural orthostatic tachycardia syndrome (POTS) and neurally mediated hypotension (NMH), in which symptoms worsen with upright posture and are ameliorated by recumbence. The main symptoms of chronic orthostatic intolerance syndromes include light-headedness, syncope or near syncope, blurring of vision, headaches, problems with short-term memory and concentration, fatigue, intolerance of low impact exercise, palpitations, chest pain, diaphoresis, tremulousness, dyspnea or air hunger, nausea, and vomiting. This review discusses what is known about the pathophysiology of this disorder, potential treatments, and understanding its role in the patient with chronic headache pain.

Initial orthostatic hypotension in the young is attenuated by static handgrip

Initial orthostatic hypotension is common in children. Isometric handgrip increases arterial pressure, central blood volume, cardiac output, and total peripheral resistance. We show that in 14 subjects with initial orthostatic hypotension, isometric handgrip coupled with standing abolished symptoms of initial orthostatic hypotension and minimized decreases in blood pressure and cardiac output with standing.

Initial orthostatic hypotension is unrelated to orthostatic tolerance in healthy young subjects

The physiological challenge of standing upright is evidenced by temporary symptoms of light-headedness, dizziness, and nausea. It is not known, however, if initial orthostatic hypotension (IOH) and related symptoms associated with standing are related to the occurrence of syncope. Since IOH reflects immediate and temporary adjustments compared with the sustained adjustments during orthostatic stress, we anticipated that the severity of IOH would be unrelated to syncope. Following a standardized period of supine rest, healthy volunteers [ n = 46; 25 ± 5 yr old (mean ± SD)] were instructed to stand upright for 3 min, followed by 60° head-up tilt with lower-body negative pressure in 5-min increments of −10 mmHg, until presyncope. Beat-to-beat blood pressure (radial arterial or Finometer), middle cerebral artery blood velocity (MCAv), end-tidal Pco2, and cerebral oxygenation (near-infrared spectroscopy) were recorded continuously. At presyncope, although the reductions in mean arterial pressure, MCAv, and cerebral oxygenation were similar to those during IOH (40 ± 11 vs. 43 ± 12%; 36 ± 18 vs. 35 ± 13%; and 6 ± 5 vs. 4 ± 2%, respectively), the reduction in end-tidal CO2 was greater (−7 ± 6 vs. −4 ± 3 mmHg) and was related to the decline in MCAv ( R2 = 0.4; P < 0.05). While MCAv pulsatility was elevated with IOH, it was reduced at presyncope ( P < 0.05). The cardiorespiratory and cerebrovascular changes during IOH were unrelated to those at presyncope, and interestingly, there was no relationship between the hemodynamic changes and the incidence of subjective symptoms in either scenario. During IOH, the transient nature of physiological changes can be well tolerated; however, potentially mediated by a reduced MCAv pulsatility and greater degree of hypocapnic-induced cerebral vasoconstriction, when comparable changes are sustained, the development of syncope is imminent.

Quantitative study on cerebral blood volume determined by a near-infrared spectroscopy during postural change in children

AIM

To investigate changes in cerebral blood volume during standing in healthy children with or without abnormal cardiovascular responses.

METHODS

We studied 53 children (age, 10-15 years). Cerebral oxygenated haemoglobin (oxy-Hb) and deoxygenated Hb (deoxy-Hb) were non-invasively and continuously measured using near-infrared spectroscopy (NIRS) (NIRO 300, Hamamatsu Photomedics, Shizuoka, Japan) during active standing. Beat-to-beat arterial pressure was monitored by Portapres.

RESULTS

Of 49 children with complete data acquisition, 33 had a normal cardiovascular response to the test (Group I) and 16 showed an abnormal response (Group II); nine with instantaneous orthostatic hypotension, three with postural tachycardia syndrome, three with neutrally mediated syncope and one with delayed orthostatic hypotension. At the onset of standing, Group II showed a significantly larger fall of oxy-Hb than Group I did (-2.9 +/- 2.8 micromol/L vs. -6.4 +/- 7.2 micromol/L, respectively, p < 0.05). During min 1 to 7 of standing, with one exception, changes in oxy-Hb were normally distributed over the level of -4 micromol/L in Group I. Group II also showed a significantly marked decrease in oxy-Hb compared to Group I. Decreases in oxy-Hb were not correlated with blood pressure changes.

CONCLUSION

This study shows that precise change in cerebral blood volume caused by orthostatic stress can be determined by NIRS in children in a quantitative manner of NIRS. Children with abnormal circulatory responses to standing showed a significant reduction of oxy-Hb compared with normal counterparts, suggesting impairment of cerebral autoregulation in these children.

Japanese clinical guidelines for juvenile orthostatic dysregulation version 1

This clinical practice guideline provides recommendations for the assessment, diagnosis and treatment of school-aged children and juveniles with orthostatic dysregulation (OD), usually named orthostatic intolerance in USA and Europe. This guideline is intended for use by primary care clinicians working in primary care settings. The guideline contains the following recommendations for diagnosis of OD: (i) initial evaluation composed of including and excluding criteria, the assessment of no evidence of other disease including cardiac disease and so on; (ii) a new orthostatic test to determine four different subsets: instantaneous orthostatic hypotension, postural tachycardia syndrome, neurally mediated syncope and delayed orthostatic hypotension; (iii) evaluation of severity; and (iv) judgment of psychosocial background with the use of rating scales. The guideline also contains the following recommendations for treatment of OD on the basis of the result of an orthostatic test in addition to psychosocial assessment: (i) guidance and education for parents and children; (ii) non-pharmacological treatments; (iii) contact with school personnel; (iv) use of adrenoceptor stimulants and other medications; (v) strategies of psychosocial intervention; and (vi) psychotherapy. This clinical practice guideline is not intended as a sole source of guidance in the evaluation of children with OD. Rather, it is designed to assist primary care clinicians by providing a framework for decision making of diagnosis and treatments.

Effects of some beta-adrenoceptor antagonists on orthostatic hypotension in repeatedly cold- (SART-) stressed rats

Rats stressed by specific alternation of rhythm in temperature (SART) show various symptoms of disautonomia, increased pulse rates, continuous hypotension, and severe orthostatic hypotension (OH) when they are subjected to postural change. The OH symptoms are improved by muscarinic M2-receptor blockers. In the present study, effects of beta-adrenoceptor blocking agents on OH in SART-stressed rats were investigated. Anesthetized rats were restrained on a board in the supine position, and direct blood pressure and ECG were measured automatically using Fluclet Jr.2. Postural change was performed by raising the rat's head up to a 60 degrees angle for 4 min. Unstressed rats treated with hexamethonium showed large decrease in blood pressure, small reflex from the bottom of pressure and decreased tachycardia reflex, whereas isoproterenol showed little changes. In SART-stressed rats, isoproterenol alleviated the decrease in blood pressure in postural change, brought large reflex from the bottom of pressure and increased tachycardia reflex, whereas hexamethonium had little changes. Propranolol and atenolol induced the similar changes as those seen by hexamethonium. ICI-118,551, a selective beta2-adrenoceptor antagonist showed large reflex from the bottom of pressure and increased tachycardia reflex in stressed rats, whereas little changes in unstressed rats. In conclusion, it was suggested that the hypotension in OH manifestation time of rats reflects the state of peripheral blood vessels, and beta1-adrenoceptors played a role in compensatory tachycardia reflex and beta2-adrenoceptors in blood pressure reflex. The circulatory regulation in SART-stressed rats seems to be poorly functioning in nervous reflex in postural changes.

The postural tachycardia syndrome

Postural tachycardia syndrome (POTS) is a disorder of unknown etiology, and patients with this condition exhibit orthostatic intolerance (OI) and excessive tachycardia. Excessive tachycardia with POTS has been defined as a rapid (within 10 minutes) increase in heart rate by more than 30 beats per minute or a heart rate that exceeds 120 beats per minute. Patients with POTS can experience difficulty with daily routines such as housework, shopping, eating, and attending work or school. The possibility exists that all forms of OI, including POTS, result from central hypovolemia even without tachycardia. The clinical findings of POTS are observed in an increasing number of patients who are usually female and aged 15 to 50 years. Adults with POTS do not have hypotension, whereas children may exhibit hypotension. Many patients with POTS are intolerant of exercise. "Idiopathic" POTS must be distinguished from other conditions that can reduce venous return to the heart and produce similar signs and symptoms such as dehydration, anemia, or hyperthyroidism. Therapies for POTS are directed at relieving the central hypovolemia or at compensating for the circulatory dysfunctions that may cause this disorder. Treatments have resulted in varying degrees of success and are often used in combination with each other.

Initial orthostatic hypotension: review of a forgotten condition

Several studies have shown that standing up is a frequent (3-10%) trigger of loss of consciousness both in young and old subjects. An exaggerated transient BP (blood pressure) fall upon standing is the underlying cause. IOH (initial orthostatic hypotension) is defined as a transient BP decrease within 15 s after standing, >40 mmHg SBP (systolic BP) and/or >20 mmHg DBP (diastolic BP) with symptoms of cerebral hypoperfusion. It differs distinctly from typical orthostatic hypotension (i.e. BP decrease >20 mmHg SBP and/or >10 mmHg DBP after 3 min of standing) as the BP decrease is transient. Only continuous beat-to-beat BP measurement during an active standing-up manoeuvre can document this condition. As IOH is only associated with active rising, passive tilting is of no diagnostic value. The pathophysiology of IOH is thought to be a temporal mismatch between cardiac output and vascular resistance. The marked decrease of vascular resistance during rising is similar to that observed at the onset of leg exercise and is absent during head-up tilting. It is attributed to vasodilatation in the working muscle through local mechanisms. Standing up causes an initial increase in venous return through the effects of contraction of leg and abdominal muscles. The consequent sudden increase in right atrial pressure may contribute to the fall in systemic vascular resistance through a reflex effect. This review alerts clinicians and clinician scientists to a common, yet often neglected, condition that occurs only upon an active change of posture and discusses its epidemiology, pathophysiology and management.

Autonomic Function in Adolescents with Orthostatic Dysregulation Measured by Heart Rate Variability

We evaluated the responses of autonomic nervous system to transient positional changes and daily changes in orthostatic dysregulation (OD) patients in order to clarify the mechanisms underlying the appearance of symptoms. The control group consisted of 16 healthy adolescents (8 males and 8 females), and the OD group consisted of 25 adolescents (13 males and 12 females). Each subject underwent continuous electrocardiographic monitoring during the head-up tilt test, followed by electrocardiographic monitoring for 24 h. Low frequency power (LF) and high frequency power (HF) were calculated as indices of autonomic function. During 0-5 min in the standing position in the tilt test, HF was higher in the OD group than in the control group (180+/-110 ms(2) vs. 42.6+/-54.1 ms(2); p<0.05). The LF/HF ratio during standing for 15-20 min was higher in OD patients than in the controls (4.75+/-3.45 vs. 1.67+/-1.21; p<0.05). The 24 h analysis showed that HF during sleep was significantly lower in the OD patients than in the controls (516+/-290 ms(2) vs. 1,290+/-429 ms(2); p<0.05); the LF/HF ratios were consistently higher in the OD patients than in the controls (4.13+/-3.41 and 2.92+/-2.00 vs. 2.46+/-0.89 and 1.35+/-1.54 in waking and sleeping states, respectively; p<0.05). This study showed that OD patients have less variability of the parasympathetic nervous system as well as hyperactivity of the sympathetic nervous system. This autonomic dysfunction is responsible for the symptoms of OD.

Comparison of the active standing test and head-up tilt test for diagnosis of syncope in childhood and adolescence

We examined 51 children and adolescents with orthostatic symptoms using two orthostatic tests, the active standing test (the AS test) and head-up tilt test (HUT), and compared circulatory responses, autonomic function in addition to the induction rate of syncope during short-time orthostasis. Syncope was induced in eight patients with both tests, in only six patients with the AS test and in only one patient with HUT. The induction rate was significantly higher with the AS test (p<0.0001). In addition, the AS test is common and daily postural motion and does not require a tilt table. We calculated percent changes in systolic blood pressure at the initial drop (DeltaID-SBP), in systolic blood pressure (DeltaSBP), in diastolic blood pressure (DeltaDBP), in heart rate (DeltaHR), component coefficient variation LF/HF (DeltaLF/HF) from supine to upright. DeltaHR were significantly larger in fainters than in non-fainters with both tests, although there was no difference in DeltaSBP and in DeltaDBP. In six fainters only with the AS test, DeltaHR was significantly larger with the AS test than with HUT. With the AS test DeltaID-SBP were correlative with DeltaLF/HF, and DeltaLF/HF were correlative with DeltaHR, whereas these relations were not clear in HUT. These results indicated the AS test caused cardiac sympathetic activation associated with an initial pressure drop, and was more prone to induce syncope with a greater HR increase in some patients. We conclude the AS test is as potential as HUT as a diagnostic test for syncope.

Learning and memorization impairment in childhood chronic fatigue syndrome manifesting as school phobia in Japan

For the last 15 years, we have tried to understand the pathophysiology of childhood chronic fatigue syndrome (CCFS) in Japan. In this condition, two major symptoms are important: easy fatigability and disturbed learning and memorization. In CCFS patients we clinically evaluated autonomic nervous system function, circadian rhythm of hormonal secretion (melatonin, cortisol and 3-endorphin), core body temperature, and sleep-wake pattern. Most patients showed autonomic nervous system dysfunction and circadian rhythm disturbances, similar to those observed in jet lag. Radiological imaging studies (SPECT, Xe-CT, and MRS) revealed decreased blood flow in the frontal and thalamic areas, and accumulation of choline in the frontal lobe. We analyzed the relationship between the laboratory data and clinical symptoms in CCFS.

Transient orthostatic hypotension is common in adolescents

OBJECTIVES

We hypothesized that transient hypotension associated with the symptom of lightheadedness with standing is a common phenomenon in healthy adolescents but may be mistaken for orthostatic intolerance.

STUDY DESIGN

We studied 23 healthy adolescents, combining upright tilt to 70 degrees and to 35 degrees (in 12 patients) with continuous heart rate and blood pressure (BP) measurements. We measured peripheral blood flow and venous pressure in the arms and legs by using venous plethysmography.

RESULTS

Healthy subjects with normal vasoconstrictive responses to sustained upright tilt uniformly have a transient fall in BP during 70 degrees upright tilt that varies from almost undetectable to large decreases in BP easily exceeding the 20-mm Hg threshold for orthostatic hypotension. Large decreases are associated with short-lived symptoms of lightheadedness and are most marked in those with the largest calf blood flow. The higher the flow, the lower the BP falls. There is appropriate reflex tachycardia.

CONCLUSIONS

We conclude that transient orthostatic hypotension is common in many healthy adolescents, especially after prolonged recumbency, and is related to dependent vascular tone.

Impaired postural cerebral hemodynamics in young patients with chronic fatigue with and without orthostatic intolerance

OBJECTIVES

To measure postural changes in cerebral hemodynamics in young patients with chronic fatigue with and without orthostatic intolerance.

STUDY DESIGN

We studied 28 patients (age, 10 to 22 years) and 20 healthy control subjects (age, 6 to 27 years). Cerebral oxygenated hemoglobin (oxy-Hb) and deoxygenated Hb were noninvasively and continuously measured with near infrared spectroscopy during active standing. Beat-to-beat arterial pressure was monitored by Finapres.

RESULTS

Orthostatic intolerance determined by cardiovascular responses to standing was observed in 16 of 28 patients: instantaneous orthostatic hypotension in 8, delayed orthostatic hypotension in 2, and postural orthostatic tachycardia in 6. A rapid recovery of oxy-Hb by near infrared spectroscopy at the onset of active standing was not found in 15 of 16 patients with chronic fatigue and orthostatic intolerance and in 6 of 12 patients with chronic fatigue without orthostatic intolerance but only in 2 of 20 control subjects. Thirteen of 16 patients with orthostatic intolerance showed prolonged reduction in oxy-Hb during standing.

CONCLUSIONS

Impaired cerebral hemodynamics in patients with chronic fatigue syndrome and postural orthostatic tachycardia suggest a link between impaired cerebral oxygenation and chronic fatigue. However, this cannot explain the symptoms in patients meeting the criteria of chronic fatigue without orthostatic intolerance.

Orthostatic hypotension in pediatrics

Transient orthostatic hypotension is a common experience of many healthy adolescents and is the expected outcome of relatively dilated-dependent vascular tone. These children may experience brief symptoms of orthostatic intolerance when standing up rapidly, but they have no chronic symptoms or diseases. However, persistent orthostatic hypotension and chronic symptoms of orthostatic intolerance indicate postural tachycardia syndrome.

Initial orthostatic hypotension as a cause of recurrent syncope: a case report

A 60-year-old male patient with recurrent unexplained syncope on standing was studied. During continuous, noninvasive blood pressure (BP) recording with a Finapres device, an abnormally large and symptomatic initial decrease in systemic BP was documented. After 2 minutes of standing, BP had recovered. The transient decrease in BP was attributed to the use of a combination of antidepressants known to interfere with sympathetic function. This case shows the importance of continuous, noninvasive BP measurement on standing: routine intermittent BP recording would have missed the abnormality. In patients using medications such as antidepressants, initial transient hypotension should be considered as the cause of falls and syncope.

Inappropriate early hypotension in adolescents: a form of chronic orthostatic intolerance with defective dependent vasoconstriction

Instantaneous orthostatic hypotension (INOH) has been reported in children and adolescents as a new entity of orthostatic intolerance in children who underwent rapid standing as an orthostatic stress test. Children with INOH were discovered among patients presenting with symptoms of chronic orthostatic intolerance, which is often related to orthostatic tachycardia. We used head-up tilt table testing at 70 degrees to investigate children presenting with symptoms of chronic orthostatic intolerance. We compared 24 patients aged 12-17 y, with chronic orthostatic intolerance and symptoms for >or=3 mo, with 13 healthy normal control patients. We recorded continuous heart rate, blood pressure, and respiratory rate and used venous occlusion strain gauge plethysmography to measure calf and forearm blood flow while supine and calf blood flow during head-up tilt. Patients with chronic orthostatic intolerance fulfilled criteria for the postural orthostatic tachycardia syndrome. Postural orthostatic tachycardia syndrome patients were divided into two groups by the occurrence of INOH. Supine forearm and calf arterial resistance was decreased in patients with INOH (n = 8) compared with postural orthostatic tachycardia syndrome patients without INOH (n = 16) and compared with control (n = 13). Resting calf venous pressure was elevated, suggesting excess venous filling because of vasodilation. During early head-up tilt, calf blood flow increased markedly in INOH, less in No-INOH, postural orthostatic tachycardia syndrome patients and least in control patients. Flow was temporally related to calf swelling and negatively correlated to hypotension. The data suggest that INOH occurs in patients with chronic orthostatic intolerance and orthostatic tachycardia and is related to rapid caudal blood flow when upright because of a vasoconstrictor defect.

Reflex vascular defects in the orthostatic tachycardia syndrome of adolescents

Dependent pooling occurs in postural orthostatic tachycardia syndrome (POTS) related to defective vasoconstriction. Increased venous pressure (Pv) >20 mmHg occurs in some patients (high Pv) but not others (normal Pv). We compared 22 patients, aged 12–18 yr, with 13 normal controls. Continuous blood pressure and strain-gauge plethysmography were used to measure supine forearm and calf blood flow, resistance, venous compliance, and microvascular filtration, and blood flow and swelling during 70° head-up tilt. Supine, high Pv had normal resistance in arms (26 ± 2 mmHg · ml−1 · 100 ml · min) and legs (34 ± 3 mmHg · ml−1 · 100 ml · min) but low leg blood flow (1.5 ± 0.4 ml · 100 ml−1 · min−1). Supine leg Pv (30 ± 2 vs. 13 ± 1 mmHg in control) exceeded the threshold for edema (isovolumetric pressure = 19 ± 3 mmHg). Supine, normal Pv had high blood flow in arms (4.1 ± 0.2 vs. 3.5 ± 0.2 ml · 100 ml−1 · min−1 in control) and legs (3.8 ± 0.4 vs. 2.7 ± 0.3 ml · 100 ml−1 · min−1 in control) with low resistance. With tilt, calf blood flow increased steadily in POTS with high Pv and transiently increased in normal Pv. Calf volume increased in all POTS patients. Arm blood flow increased in normal Pv only with forearm maintained at heart level. These data suggest that there are (at least) two subgroups of POTS characterized by high Pv and low flow or normal Pv and high flow. These may correspond to abnormalities in local or baroreceptor-mediated vasoconstriction, respectively.

The relation between lower limb pooling and blood flow during orthostasis in the postural orthostatic tachycardia syndrome of adolescents

OBJECTIVES

Postural orthostatic tachycardia syndrome (POTS) is characterized by symptoms of lightheadedness, fatigue, and signs of edema, acrocyanosis, and exaggerated tachycardia within 10 minutes of upright posture. Our objective was to determine how vascular properties contribute to the pathophysiology of POTS in adolescents.

STUDY DESIGN

We compared 11 patients aged 13 to 18 years with 8 members of a control group, recording continuous heart rate and blood pressure and using strain-gauge plethysmography to measure forearm and calf blood flow and to estimate venous pressure while the subjects were supine. Calf blood flow and size change were measured during 70 degrees head-up tilt.

RESULTS

Resting calf venous pressure was higher in the POTS group compared with the control group. Resting resistance was decreased in both the forearm (15 +/- 2 vs 30 +/- 4) and calf (27 +/- 2 vs 42 +/- 5) in the POTS group. Calf blood flow 60 seconds after tilt increased from 1.9 +/- 0.4 mL/100 mL/min to 6.6 +/- 2.3 mL/100 mL/min in the POTS group but only by half in the control group. Flow remained elevated in the POTS group but decreased to 70% baseline in the control group. Calf volume increased twice as much in the POTS group compared with the control group over a shorter time (13 vs 30 minutes).

CONCLUSIONS

Lower resistance at baseline reflects a defect in arterial vasoconstriction in POTS, further exacerbated during upright posture.

Vascular perturbations in the chronic orthostatic intolerance of the postural orthostatic tachycardia syndrome

Chronic orthostatic intolerance is often related to the postural orthostatic tachycardia syndrome (POTS). POTS is characterized by upright tachycardia. Understanding of its pathophysiology remains incomplete, but edema and acrocyanosis of the lower extremities occur frequently. To determine how arterial and venous vascular properties account for these findings, we compared 13 patients aged 13-18 yr with 10 normal controls. Heart rate and blood pressure were continuously recorded, and strain-gauge plethysmography was used to measure forearm and calf blood flow, venous compliance, and microvascular filtration while the subject was supine and to measure calf blood flow and calf size change during head-up tilt. Resting venous pressure was higher in POTS compared with control (16 vs. 10 mmHg), which gave the appearance of decreased compliance in these patients. The threshold for edema formation decreased in POTS patients compared with controls (8.3 vs. 16.3 mmHg). With tilt, early calf blood flow increased in POTS patients (from 3.4 +/- 0.9 to 12.6 +/- 2.3 ml. 100 ml(-1). min(-1)) but did not increase in controls. Calf volume increased twice as much in POTS patients compared with controls over a shorter time of orthostasis. The data suggest that resting venous pressure is higher and the threshold for edema is lower in POTS patients compared with controls. Such findings make the POTS patients particularly vulnerable for edema fluid collection. This may signify a redistribution of blood to the lower extremities even while supine, accounting for tachycardia through vagal withdrawal.