Cerebral blood flow velocity after hyperventilation-induced vasoconstriction in hypertensive patients.

Abstract

Background and Purpose:The aim of our study was to evaluate by transcranial Doppler ultrasonography the dynamics of blood flow velocity changes in the middle cerebral artery during and after hypocapniainduced vasoconstriction in untreated essential hypertensive patients.Methods: Sixteen hypertensive patients (10 men and six women, 29-62 years of age) and 10 healthy control subjects (six men and four women, 30-62 years of age) were studied. Patients with mild-tomoderate essential hypertension (mean±SE blood pressure, 171/106±3/2 mm Hg) belonged to stage I or II of the World Health Organization classification. Mean blood flow velocity in the middle cerebral artery, arterial blood pressure, and end-tidal CO 2 partial pressure were recorded at baseline, during 2-minute hyperventilation, and every 30 seconds up to 5 minutes after hyperventilation.Results: End-tidal CO 2 partial pressure values overlapped in the two groups throughout the study. Baseline values of mean blood flow velocity in hypertensive patients were similar to those in normotensive subjects (mean±SE values, 64.7±3.9 cm/sec versus 58.6±3.7 cm/sec). A similar fall in mean blood flow velocity was observed in hypertensive patients and normotensive subjects (43.2±2.8% versus 46.7+3.6%). Mean blood flow velocity reverted to baseline more quickly in hypertensive patients: 1.5 minutes after hyperventilation, mean blood flow velocity was 60.7±3.1% and 84.9±1.8% of control in normotensive subjects and hypertensive patients, respectively. No changes in arterial blood pressure were observed in either group throughout the study.Conclusions: This study demonstrates that the recovery of blood flow velocity in the middle cerebral artery after hyperventilation is faster in hypertensive patients than in normal subjects, thus providing further evidence that chronic hypertension is associated with changes in the dynamics of cerebral blood vessel reactivity.

Hypertension Impairs Vascular Reactivity in the Pediatric Brain

“…8,9 Both hypertrophy and remodeling of the cerebral artery walls have been proposed as the mechanisms behind this adjustment, resulting in wall thickening, luminal narrowing, and decreased compliance of the vessels. 19,20 Furthermore, in both adult and adolescent hypertensive patients, studies have demonstrated abnormal responses of the cerebral vessels to hypercapnia 10,11,21 and hypocapnia, 22,23 presumably as a result of increased arteriolar vascular resistance. We hypothesize that hypertension has similar effects on the small vessels in children, resulting in increased cerebrovascular resistance and decreased compliance, thereby explaining the decreased hypercapnic reactivity.…”

Hypocapnia Induced by Involuntary Hyperventilation during Mental Arithmetic Reduces Cerebral Blood Flow Velocity

“…In our previous study (Szirmai et al 2005), in which we described the correlation between blood flow velocity and central frequency of EEG, we found that during cognitive tests, after a transitory increase, blood flow velocity returned almost to the initial level, despite increasing blood pressure and heart rate. These observations suggested analogy with the physiological effect of hyperventilation induced vasoconstriction (Malatino et al 1992), because temporary decrease of flow velocity could not be explained by the metabolic-and/or neurogenic theory of cerebral blood flow regulation. We presumed that the unexpected decrease of blood flow velocity was due to hypocapnia evoked by hyperventilation, and that this systemic effect interfered with the local cerebral circulatory changes induced by cognitive processes.…”

Antihypertensive Efficacy and Vasoprotective Properties of a New Combination of Beta-Blocker, Bisoprolol (2,5/5 Mg) and Diuretic, Hydrochlorothiazide (6,25 Mg)

“…В литературе данные о цереброваскулярной реак-тивности при АГ малочисленны и противоречивы [10,13,15,20]. Так, Н. Маеdа и соавт.…”

“…[15] (пробы с гипервентиляцией, с задержкой дыхания и с приемом нитроглицерина), а также L. Маlatino и соавт. [20] (проба с гипервенти-ляцией) не обнаружили значимых различий цереб-роваскулярной реактивности при АГ без сердечно-со-судистых осложнений и в контроле. До настоящего времени практически не изучено влияние антигипертензивных препаратов отдельных групп и фиксированных комбинаций на церебровас-кулярную реактивность.…”