Clinical Physiology of Circulation

Chief Editor

Leo A. Bockeria, MD, PhD, DSc, Professor, Academician of Russian Academy of Sciences, President of Bakoulev National Medical Research Center for Cardiovascular Surgery


Reactivity of cerebral and systemic hemodynamics to orthostasisin young men with arterial hypertension

Authors: D.V. Kuznetsova, V.P. Kulikov

Company:
Altayskiy State Medical University of the Ministry of Health of the Russian Federation, pr. Lenina, 40, Barnaul, 656038, Russia

Link: Clinical Physiology of Blood Circulaiton. 2013; (): -

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Abstract

Objective of the study – is to determine the characteristics of the response of cerebral blood flow and systemic hemodynamics to orthostasis in young men with arterial hypertension. Material and methods. Active orthostatic test was performed in 14 patients with arterial hypertension and 13 healthy young men. We used the method of transcranial Doppler ultrasound to measure blood flow velocity in middle cerebral arteries on both sides, and systolic and diastolic blood pressure and pulse rate were measured using the method of continuous non-invasive “beat-to-beat” blood pressure measurement. Capnographic monitoring was performed during the experiment. The initial (for the first 30 seconds) and prolonged (for 10 min of orthostasis) orthostatic reactions were assessed. The criteria for initial orthostatic hypotension were defined as a fall of at least 20 mmHg in diastolic blood pressure and/or 40 mmHg in systolic blood pressure. Results. The study of initial orthostatic reactions has shown the considerable reduction of diastolic blood pressure in young men with hypertension in comparison with healthy young men (fall of 26 (22.3; 32.3) and 19,1 (15.9; 25.3) mmHg respectively, р=0,0082). Initial orthostatic hypotension in patients with arterial hypertension is observed significantly more often than in healthy young men (in 79 and 31% of cases respectively, р=0.021). The dynamics of cerebral blood flow changes was similar in patients with arterial hypertension and in healthy people. More prolonged reduction of diastolic blood pressure and cerebral blood flow velocity in young men with arterial hypertension in comparison with healthy men was revealed in the study of enduring orthostatic reactions. Hypocapnia throughout orthostasis was observed in both groups. Conclusion. The reaction of systemic hemodynamics to active orthostatic load in patients with arterial hypertension is characterized by diastolic hypotension and increased incidence of initial orthostatic hypotension. During prolonged orthostasis the cerebral blood flow velocity decreases in both groups, and we suppose that hypocapnia can be one of the causes of this response. Preservation of cerebral autoregulation was observed in patients with arterial hypertension in the studies of initial orthostatic reactions, however the effectiveness of autoregulation during prolonged orthostasis is decreased.

References

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