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Cerebral Blood Flow Velocity After Hyperventilation-Induced Vasoconstriction in Hypertensive Patients Lorenzo S. Malatino, MD; Salvatore Bellofiore, MD, PhD; Maria P. Costa, MD; Giuseppa Lo Manto, MD; Francesco Finocchiaro, MD; and Giuseppe U. Di Maria, MD 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 CO2 partial pressure were recorded at baseline, during 2-minute hyperventilation, and every 30 seconds up to 5 minutes after hyperventilation. Results: End-tidal CO2 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. (Stroke 1992;23:1728-1732) KEY WORDS • cerebral blood flow • hypertension • hyperventilation • vasoconstriction

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n hypertensive patients without neurological disorders, cerebrovascular resistance is elevated to maintain a resting cerebral blood flow (CBF) of the same magnitude as that in normotensive subjects.1 On the other hand, it is well recognized that in individuals with chronic hypertension, the CBF autoregulation curve is shifted to the right compared with that of normotensive individuals.1 The steady-state cerebrovascular reactivity to CO2 has been shown to be similar in hypertensive and normotensive subjects.2 However, the interference of arterial hypertension with the timecourse of CBF velocity recovery and the recovery of hyperventilation-induced hypocapnia has not yet been investigated. Our aim in the present study was to assess the dynamics of CBF velocity changes after hypocapniainduced vasoconstriction in patients with untreated From the Istituto di Clinica Medica (L.S.M., M.P.C., G. Lo M.), Istituto di Malattie Respiratorie (S.B., G.U. Di M), and Istituto di Neurologia (F.F.), University of Catania, Catania, Italy. Address for reprints: Dr. L.S. Malatino, Istituto di Clinica Medica "L. Condorelli," Universita di Catania, c/o Ospedale Vittorio Emanuele, Via Plebiscito 628, 95124 Catania, Italy. Received January 15, 1992; final revision received July 6, 1992; accepted August 17, 1992.

essential hypertension compared with normotensive control subjects. Subjects and Methods Sixteen hypertensive patients and 10 normotensive control subjects entered the study. Individual anthropometric data and arterial blood pressure values are reported in Table 1. Patients with mild-to-moderate essential hypertension belonged to stage I or II of the World Health Organization classification and showed no concurrent illness, including respiratory tract disorders. Antihypertensive drugs were withdrawn 4 weeks before the study. Patients were not allowed to smoke or to drink beverages containing xanthines for at least 24 hours before the study. The study was approved by the hospital ethics committee, and each subject gave informed consent. Study Protocol The study was performed in a single-blind fashion. Subjects lay in the supine position, and after 5 minutes of adaptation, CBF velocity in the middle cerebral artery (MCA) was measured bilaterally. Subjects were admitted to the study only if the difference between right and left CBF velocity values was less than 15% of

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Malatino et al

Cerebral Blood Flow Velocity in Hypertension

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TABLE 1. Individual Anthropometric Data and Arterial Blood Pressure Values of Hypertensive Patients and Nonnotensfae Control Subjects

Age Subject

(years)

Hypertensive patients 1 53 2 3 4

52

5

46 62

36 39

6 7 8

42 51

9

46

10 11

34 56 41

12

39 29 53 42

13 14 15

16 Mean±SE 45±2 Normotensive isubjects 1

30 36 38

2 3 4 5 6 7

43 50

8

60 31 31 42±4

43 62

9 10

Mean±SE

Height (cm)

Weight (kg)

F M M F M M F F F F

160

165 168 154 154

80 90 82 79 76 88 68 70 95 58

M

166

80

M M M M M

160 175 180 167 178

56 78 97 69 84

168±2

78±3*

178 166 174

72 76 67 80 61 70 88

Sex

M M M M F M M F F F

178 173 167 169 170

174 159 171

185 150 163 157

168±3

Arterial blood pressure (ramHg) 165/102 180/101 164/103 163/102 187/117 168/101 187/117 207/113 173/101 172/106 162/107 179/109 150/100 162/107 160/100 165/106 171±4/106±l

56 50 53 67±4

130/80 125/70 125/70 126/75 125/67 110/65 125/70 120/67 116/76 114/68 122±2/71±2

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

The aim of our study was to evaluate by transcranial Doppler ultrasonography the dynamics of blood flow velocity changes in the middle cerebral artery...
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