Orthostatic hypotension is defined as the reduction of systolic blood pressure of at least 20 mmHg or the dropping of diastolic blood pressure of at least 10 mmHg within 3 minutes of standing compared to baseline values. Recent studies suggest a change in reference values to 30 mmHg in diabetic patients and hypertensive subjects with clinostatic systolic blood pressure higher than 160 mmHg, as this would more accurately estimate the probability of autonomic neuropathy in those populations.
Multiple system atrophy is a neurodegenerative disorder characterised by parkinsonian features, cerebellar ataxia, and autonomic failure. In a recent consensus, reference values for the diagnosis of orthostatic hypotension in multiple system atrophy have been upgraded to 30 mmHg in systolic blood pressure or 15 mmHg in diastolic blood pressure, within 3 minutes of standing . Orthostatic hypotension can be divided into neurogenic and non neurogenic forms. Neurogenic forms are caused by a primitive damage to autonomic nervous system.
Non neurogenic forms involve organs or systems regulating metabolic homeostasis and hemodynamics of the organism; in other instances, they may also be determined by external factors, such as the use of drugs, alcohol and other substances.
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