A review of orthostatic blood pressure regulation and its association with mood and cognition

Aims  

This paper will review literature that examines the psychological and neuropsychological correlates of orthostatic blood pressure regulation.     

Ambulatory blood pressure in patients with Parkinson's disease without and with orthostatic hypotension

Non-invasive ambulatory recordings of blood pressure and heart rate were performed using a Spacelabs device during day and night periods in patients with Parkinson's disease with (n = 19) or without orthostatic hypotension (n = 19). In patients with orthostatic hypotension, the average systolic and diastolic blood pressure during the night (137 ± 5/80 ± 3 mmHg) was higher (p < 0.05) than during the day period (121 ± 3/76 ± 2 mmHg). In patients without orthostatic hypotension, a decrease in blood pressure was recorded during the nocturnal period. In patients with orthostatic hypotension, the blood pressure variability was higher (p < 0.05) during the day (systolic: 14.6 ± 1.3%; diastolic: 16.5 ± 1.0%) than during the night (systolic: 9.1 ± 0.8%; diastolic: 10.8 ± 1.1%). The blood pressure load (percentage of values above 140/90 mmHg) during the night was significantly higher than during the day for both systolic (41.2 ± 8.1 vs. 19.6 ± 4.7%) and diastolic blood pressure (24.9 ± 6.9 vs. 16.3 ± 4.9%). There was a decrease in heart rate in both groups during the night. A fall of 25 mmHg or more in systolic blood pressure after meals occurred in ten patients with orthostatic hypotension and in one patient without orthostatic hypotension. These results indicate that orthostatic hypotension in Parkinson's disease is associated with specific modifications of ambulatory blood pressure including loss of circadian rhythm of blood pressure, increased diurnal blood pressure variability and post-prandial hypotension.     

Association of orthostatic blood pressure with the symptoms of orthostatic hypotension and cognitive impairment in patients with multiple system atrophy

The degree and frequency of orthostatic hypotension (OH) are high in patients with multiple system atrophy (MSA); however, the association of orthostatic blood pressure (BP) with the symptoms of OH and cognitive impairment in these patients remains unclear. The aim of this study was to clarify whether absolute BP and/or changes in BP during standing are related to OH symptoms and cognitive impairment in patients with MSA. Thirty-two patients with MSA were examined using the head-up tilt and cognitive function tests. OH symptoms were evaluated using a patient-reported scale. The results were compared with those for 15 age- and sex-matched healthy controls. Seventeen of the 32 (53.1%) patients had OH, with eight of them exhibiting OH symptoms, which were related to the absolute BP value at 60° tilt. However, OH symptoms were not related to the degree of decrease in BP during the tilt test, and they were frequently observed in patients with a mean BP of <80 mmHg at 60° tilt (sensitivity, 67%; specificity, 91%). Cognitive dysfunction assessed by the Mini-Mental State Examination (MMSE; ≤ 26) was also associated with a low mean BP at 60° tilt (odds ratio, 1.32; 95% confidence interval, 1.04–1.67; p = 0.02). The upright BP value is associated with OH symptoms and the MMSE score in patients with MSA. Thus, careful observation of OH symptoms can enable early management of BP and the detection of cognitive impairment in these patients.     

A prospective study of orthostatic blood pressure in diabetic patients

To clarify whether orthostatic blood pressure is affected by the type of diabetes, cardiac autonomic neuropathy, and the duration of diabetes, orthostatic blood pressure (passive 90° tilt) was evaluated in 102 patients with insulin dependent diabetes mellitus (IDDM), 51 patients with non-insulin dependent diabetes mellitus (NIDDM), and in 238 control subjects in a first study followed up after 8 to 17 years. The heart rate reaction during deep breathing (E/I ratio) and to tilt (acceleration and brake indices) assessed cardiac autonomic function. In the first study, the lowest systolic blood pressure (LSBP) and the lowest diastolic blood pressure (LDBP) after tilt were significantly lower in IDDM patients compared with NIDDM patients (p<0.001 for LSBP and p<0.05 for LDBP) and controls (p<0.001). LDBP was, however, also significantly lower (p<0.05) in NIDDM patients than in controls. Hence, although most severe in IDDM, LDBP was disturbed in both types of diabetes. In IDDM, a low E/I ratio was associated with disturbed orthostatic blood pressure. At follow-up examinations, orthostatic blood pressure deteriorated in NIDDM but not in IDDM patients. In conclusion, LSBP and LDBP were impaired in IDDM patients compared with NIDDM and control subjects; however, LDBP was also impaired in NIDDM patients compared with controls. When the duration of diabetes increased, orthostatic blood pressure deteriorated in NIDDM but not in IDDM patients.     

Psychophysical assessment of visual acuity in infants with visual disorders

The measurement of visual acuity is an essential part of the eye examination of adults, but is rarely attempted in infants being examined for presumed or known eye disease. We have used a preferential looking technique to test visual acuity of infants attending a hospital eye clinic. Serial measurements of acuity of infants attending a hospital eye clinic. Serial measurements of acuity in infants with certain eye diseases can provide examples of the effects of visual deprivation on the developing human visual system. Amongst 14 cases of monocular visual form deprivation in early life, there were 9 infants who had monocular occlusion as therapy for esotropia; 3 infants who had unilateral opacities of the ocular media; and 2 infants who had unilateral eyelid closure from infection or burns. Despite differences in exact mode of deprivation, the effects on visual acuity were similar. There was a reduction of visual acuity in the deprived eye and a simultaneous increase in acuity of the non-deprived eye. These effects of monocular deprivation were not permanent. Recovery occurred with reverse deprivation or by simple cessation of the deprivation. Of 10 children with binocular visual form deprivation, there were 5 who had bilateral congenital cataracts and 5 who had bilateral uncorrected high refractive errors. Infants with cataract surgery before 2 months of age showed normal early development of visual acuity. A 4-6 month delay before treatment resulted in reduced acuity, but recovery subsequently occurred.(ABSTRACT TRUNCATED AT 250 WORDS)     

Evaluation of circadian variation of blood pressure by ambulatory blood pressure monitoring in an elderly diabetic population with or without orthostatic hypotension

Orthostatic hypotension is frequently observed in the elderly population and has been previously identified as a significant risk factor for increased mortality. The link between this condition and increased mortality could be due to an abnormal circadian pattern of blood pressure. The absence of a physiological nocturnal decrease in blood pressure is termed the non-dipping pattern. This abnormality is relatively frequent in elderly people suffering from orthostatic hypotension, but its prevalence in the diabetic geriatric population is unknown. The purpose of this study is to compare blood pressure profiles on ambulatory blood pressure monitoring (ABPM) in a sample of elderly diabetic subjects suffering from orthostatic hypotension with those without postural hypotension. One hundred and ninety-eight patients were recruited by mail. The presence or absence of orthostatic hypotension was determined. They all subsequently underwent ABPM. One hundred and thirty-one of our subjects (68%) suffered from orthostatic hypotension; of these, 76% had a non-dipping pattern on ABPM, compared with 74% of the subjects not suffering from orthostatic hypotension (P?=?NS). This study thus demonstrates the high prevalence of orthostatic hypotension in an elderly diabetic population. On the other hand, we could not demonstrate a correlation between the non-dipping pattern and the presence of orthostatic hypotension. This is in contrast with previous work done in a non-diabetic elderly population. Further studies are needed to determine the effect of diabetes on blood pressure.     

The relationship between performance-based visual acuity screening,self-reported visual acuity,and neuropsychological performance

Despite frequent cautions in the literature concerning the importance of visual acuity in neuropsychological testing, there are few published empirical investigations of what constitutes "sufficient" visual acuity, nor are there published guidelines for performance-based visual screening techniques. The current study attempted to validate the utility of a visual acuity screening technique by examining individuals with varying visual ability on neuropsychological measures. Results revealed declines on neuropsychological measures associated with reduced visual acuity, as well as discrepancies between self-reported and measured visual acuity, with neuropsychological performance being more closely related to a performance-based measure of visual acuity than to self-reported visual acuity. Clinical implications are discussed.     

Charles Bonnet syndrome and visual acuity

A 61–year–old patient suffered from Charles Bonnet syndrome (CBS) while his visual acuity declined, whereas CBS subsided after he became blind. These findings suggest that reduction of visual acuity (dynamic or acute impairment) has a greater impact on the onset of CBS than low visual acuity (static or chronic impairment) per se in some patients. They may also explain why patients with low visual acuity do not always suffer from CBS. Although further studies are required, the present case highlights the importance of the differentiation between lowering and low visual acuity in the etiology of CBS.     

Effects of dietary salt on orthostatic tolerance, blood pressure and baroreceptor sensitivity in patients with syncope

This study had three main objectives: to examine in patients presenting with unexplained syncope the relationship between orthostatic tolerance and dietary salt intake; to examine in patients with relative low baseline salt excretion the effect of salt loading on both orthostatic tolerance and blood pressure; and to examine the relationship between dietary salt intake and the sensitivity of the baroreceptor reflex. In 178 patients with unexplained syncope we determined 24-hour urinary sodium excretion, supine arterial blood pressure, carotid cardiac baroreceptor sensitivity (neck suction) and tolerance to orthostatic stress (head-up tilt and lower body suction). Those with low salt excretions and poor orthostatic tolerance were given salt supplements and reassessed after three months. Baseline studies revealed that patients with sodium excretions < 170 mmol/day had significantly lower orthostatic tolerance than those with higher excretions. Salt loading caused a small but significant increase in mean pressure and significant increases in orthostatic tolerance and baroreceptor sensitivity. Improved orthostatic tolerance was seen in 68 of 98 (69 %) patients in whom salt was given. These patients had significantly greater changes in baroreceptor sensitivity than those failing to improve. These results confirm the benefits of salt loading patients with posturally-related syncope. Incidence of hypertension following salt in these patients is relatively uncommon but it is advisable to monitor the effects on blood pressure. Received: 5 July 2001, Accepted: 8 March 2002     

Changes in visual acuity associated with shunt failure

OBJECT: The object of this article was to report on a retrospective analysis of the clinical findings in a series of patients with changes in visual acuity associated with shunt failure. METHODS AND RESULTS: Over a 10-year period, 350 patients underwent revisions for shunt failure. The clinical course of patients who demonstrated changes in visual acuity (VA) before or during hospitalization were reviewed; follow-up was achieved using outpatient records and telephone calls with physicians, family, or caregivers. Six patients (4 male) ranging in age from 2.5 years to 40 years demonstrated changes in vision associated with shunt failure. The youngest patient lapsed into coma before transfer and showed bilateral occipital lobe infarctions on the CT scan. Three patients had no complaints referable to the visual system prior to revision. Two patients with symptoms lasting more than 21 days showed unequivocal signs of increased intracranial pressure. Serial CT scans remained unchanged in 2 patients. A 3rd patient showed questionable progression in ventricular volume, while another patient's ventricles dilated after a period of 48-72 h. Four patients demonstrated a pattern of aqueductal stenosis, long-term shunting without revision, small ventricles, and poor outpatient follow-up. Four patients showed partial or complete recovery following revision. CONCLUSIONS: Changes in vision are uncommon and can be an isolated finding associated with shunt failure. Patients with aqueductal stenosis, long-term shunting without revision, and small, potentially non-compliant ventricles may be at risk of this complication. Misdiagnosis or inadequate follow-up places these patients at additional risk, but rapid revision can result in partial or complete recovery.     

A quantitative analysis of head movement behaviour during visual acuity assessment under prosthetic vision simulation

In most current vision prosthesis designs, head movement is the sole director of visual gaze and scanning due to the head-mounted nature of the camera. Study of this unnatural behaviour may provide insight into improved prosthesis designs and rehabilitation procedures. In this paper, we conducted a psychophysical study to investigate the characteristics of head movements of normally sighted subjects undergoing a visual acuity task in simulated prosthetic vision (SPV). In 12 na?ve, untrained subjects, we recorded spontaneous changes in the amount of head movements during SPV sessions compared to control (normal vision) sessions. The observed behaviour continued to be refined until five or six sessions of practice. Increased head movement velocity was shown to be correlated to improved visual acuity performance, up to 0.3 logMAR, an equivalent of detecting details at half the physical size compared to complete deprivation of head movements. We postulate that visual scanning can as much as double the spatial frequency information in prosthetic vision. Increased head movement velocity observed when subjects were attempting smaller test items and for low-pass filtering schemes with higher cut-off frequencies may be further evidence that higher frequency content may be available through visual scanning, unconsciously driving subjects to increase head movement velocity.     

Reliability of orthostatic beat-to-beat blood pressure tests: implications for population and clinical studies

Objective

To assess the test–retest reliability of orthostatic beat-to-beat blood pressure responses to active standing and related clinical definitions of orthostatic hypotension.

Methods

A random sample of community-dwelling older adults from the pan-European Survey of Health, Ageing and Retirement in Europe, Ireland underwent a health assessment that mimicked that of the Irish Longitudinal Study on Ageing. An active stand test was performed using continuous blood pressure measurements. Participants attended a repeat assessment 4–12 weeks after the initial measurement. A mixed-effects regression model estimated the reliability and minimum detectable change while controlling for fixed observer and time of day effects.

Results

A total of 125 individuals underwent repeat assessment (mean age 66.2 ± 7.5 years; 55.6% female). Mean time between visits was 84.3 ± 23.3 days. There was no significant mean difference in heart rate or blood pressure recovery variables between the first and repeat assessments. Minimum detectable change was noted for changes from resting values in systolic blood pressure (26.4 mmHg) and diastolic blood pressure (13.7 mmHg) at 110 s and for changes in heart rate (10.9 bpm) from resting values at 30 s after standing. Intra-class correlation values ranged from 0.47 for nadir values to 0.80 for heart rate and systolic blood pressure values measured 110 s after standing.

Conclusion

Continuous orthostatic beat-to-beat blood pressure and related clinical definitions show low to moderate reliability and substantial natural variation over a 4–12-week period. Understanding variation in measures is essential for study design or estimating the effects of orthostatic hypotension, while clinically it can be used when evaluating longer term treatment effects.

     

Contrast sensitivity and visual acuity in patients with Alzheimer's disease

Alzheimer's disease is a disorder which is typified by a deterioration in cognition and a range of behavioural problems which result in a loss of functional ability and often necessitate transfer to residential care. This article looks at a growing body of research which is revealing the presence of changes in vision, particularly contrast sensitivity and acuity. We discuss the possible pathological basis for such deficits, and examine the possibility that such changes in vision may impact on the behavioural and functional outcomes of the demented individual.     

Developmental plasticity of mouse visual acuity

Monocular deprivation in mice between postnatal days 19 and 32 has been reported to significantly shift ocular dominance within the binocular region of primary visual cortex; however, it is not known whether visual deprivation in mice during this physiologically defined critical period also results in amblyopia, as it does in other mammals. We addressed this uncertainty by psychophysically assessing in adulthood (postnatal day 70 or older) the grating acuity of normal and monocularly deprived mice, using the Visual Water Task. The visual acuity of mice tested with their nondeprived eyes was equivalent to that of normal mice ( approximately 0.5 cycles/degree); however, acuity measured with eyes monocularly deprived of vision transiently between postnatal days 19 and 32 was reduced by over 30% ( approximately 0.31 cycles/degree). Identical binocular deprivation produced a significant, but smaller, decrease in acuity ( approximately 0.38 cycles/degree). The effects of monocular and binocular deprivation were long lasting and occurred only if visual deprivation occurred between postnatal days 19 and 32. These data indicate that the deleterious effects of early visual deprivation on visual acuity in mice are similar to those reported in other mammals, and together with electrophysiological evidence of ocular dominance plasticity, suggest that the mechanisms of mouse visual plasticity are fundamentally the same as that in other mammals. Therefore, the mouse is probably a good model for investigating the basic cellular and molecular mechanisms underlying visual developmental plasticity and amblyopia.     

Beyond visual acuity: new and complementary tests of visual function

Visual acuity is an essential component of the routine ophthalmic examination and the most common measure of visual function. There is increasing recognition, however, of the need to evaluate visual function beyond the limited extent afforded by visual acuity. The primary objective of this article is to introduce a variety of new and lesser-used techniques for measuring visual function that complement visual acuity assessment, each of which has been shown to detect visual dysfunction in patients with normal visual acuity.     

The Schellong test: detecting orthostatic blood pressure and heart rate changes in German-speaking countries

Clinical Autonomic Research -     

Experience-dependent plasticity of visual acuity in rats

Rats have become a popular model for investigating the mechanisms underlying ocular dominance plasticity; however, no quantitative assessment of the effects of visual deprivation on behavioural acuity has been reported in this species. We measured the spatial acuity of monocularly and binocularly deprived rats with a visual discrimination task. The average spatial acuity of normal rats and rats deprived of vision after postnatal day 40 was approximately 1 cycle/degree. Monocular deprivation up to postnatal day 40 resulted in a 30% decrease in acuity and there was no recovery after 8 months. Identical binocular deprivation produced a comparable but significantly smaller reduction in acuity. The deleterious effects of monocular and binocular deprivation on visual acuity indicate that the development of cortical receptive field properties related to spatial tuning are affected by both monocular and binocular deprivation. The similarities in the effects of visual deprivation on visual acuity between rats and other mammals confirm that rats are a good model system for studying the cellular and molecular mechanisms underlying experience-dependent visual plasticity.     

In-air visual acuity of the bottlenose dolphin

Using the method of constant stimuli, horizontal black and white line gratings were presented to a bottlenose dolphin in a successive discrimination task. Over a constant viewing distance of 2.8 m, a minimal visual angle of 18 min of arc was obtained. This value is poorer than that reported for pinnipeds, but comparable to functions reported for the antelope, elephant, and clawless otter.