Abstract
Orthostatic challenge produced by upright posture may lead to syncope if the cardiovascular system is unable to maintain adequate brain perfusion. This review outlines orthostatic intolerance related to the aging process, long-term bedrest confinement, drugs, and disease. Aging-associated illness or injury due to falls often leads to hospitalization. Older patients spend up to 83% of hospital admission lying in bed and thus the consequences of bedrest confinement such as physiological deconditioning, functional decline, and orthostatic intolerance represent a central challenge in the care of the vulnerable older population. This review examines current scientific knowledge regarding orthostatic intolerance and how it comes about and provides a framework for understanding of (patho-) physiological concepts of cardiovascular (in-) stability in ambulatory and bedrest confined senior citizens as well as in individuals with disease conditions [e.g., orthostatic intolerance in patients with diabetes mellitus, multiple sclerosis, Parkinson's, spinal cord injury (SCI)] or those on multiple medications (polypharmacy). Understanding these aspects, along with cardio-postural interactions, is particularly important as blood pressure destabilization leading to orthostatic intolerance affects 3–4% of the general population, and in 4 out of 10 cases the exact cause remains elusive. Reviewed also are countermeasures to orthostatic intolerance such as exercise, water drinking, mental arithmetic, cognitive training, and respiration training in SCI patients. We speculate that optimally applied countermeasures such as mental challenge maintain sympathetic activity, and improve venous return, stroke volume, and consequently, blood pressure during upright standing. Finally, this paper emphasizes the importance of an active life style in old age and why early re-mobilization following bedrest confinement or bedrest is crucial in preventing orthostatic intolerance, falls and falls-related injuries in older persons.
Highlights
In most persons, the hemodynamic and neurovascular responses to orthostatic challenge produced by standing up are adequate to stabilize arterial blood pressure and to maintain cerebral blood flow after standing
Rehabilitation post-stroke could benefit from combination of mobile monitoring of the autonomic and cardiovascular systems with effective physical therapy interventions to ensure that older persons are protected from muscle wasting and muscle loss after stroke
Future sit-tostand protocols that include Muscle sympathetic nerve activity (MSNA) evaluation, by which the magnitude and timing of sympathetic responses could be measured, could be carried out to clarify the relationship between MSNA and HRV. All these aspects are important in the asssement of orthostatic intolerance risk in patients during hospitalization and upon discharge
Summary
The hemodynamic and neurovascular responses to orthostatic challenge produced by standing up are adequate to stabilize arterial blood pressure and to maintain cerebral blood flow after standing. Some of these include deconditioning in the cardiovascular, skeletal and neuromuscular systems as well as potential deficits in brain function and structure (Grogorieva and Kozlovskaia, 1987; Leblanc et al, 1990; Traon et al, 1998; Perhonen et al, 2001; Pisot et al, 2008; Lipnicki and Gunga, 2009; Rittweger et al, 2009; Dolenc and Petric, 2013; Marusic et al, 2014, 2016; Li et al, 2015; Cassady et al, 2016) Further complicating this situation is the fact that orthostatic intolerance incidence is markedly accelerated with intravascular instrumentation (Stevens, 1966) or with increased heat stress (Crandall, 2000), and is greater in taller persons (Ludwig and Convertino, 1994) and in anxiety states (Smith et al, 1994). Countermeasures can include cognitive training (Goswami et al, 2015) and nutritional supplementation (Muscaritoli et al, 2017)—with and without physical activity—in mitigating orthostatic intolerance
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